Method of detecting cancer stem cell, method of screening cancer stem cell, and method of inhibiting cancer stem cell

This application is a divisional application of U.S. patent application Ser. No. 14/408,787, which was the National Stage of International Application No. PCT/JP2013/079650, filed Oct. 25, 2013, which claims the benefit of Japanese Patent Application No. 2012-236977, filed Oct. 26, 2012. All of these prior applications are incorporated herein by reference in their entirety.

The present invention relates to a cancer cell inhibitory drug, particularly to a cancer stem cell inhibitory drug, and a cancer stem-cell detection probe.

At present, as a general cancer therapy, e.g., radiation therapy, chemotherapy, immunotherapy and surgical (excision) therapy are mentioned. The chemotherapy is a method for suppressing cancer by use of an anticancer therapeutic agent made of various types of low-molecular compounds.

The therapy using an anticancer therapeutic agent is directed to reduce the size of a solid tumor. However, the most part of a tumor is occupied by differentiated cancer cells which no longer have a function as a cancer stem cell and it is pointed out in a general anticancer agent treatment that the differentiated cancer cells are only targeted to reduce the size thereof.

Cancer has cells having nature of stem cells, called cancer stem cells.

The cancer stem cells, which were first identified in 1997 in an acute myeloid leukemia, are now increasingly found in various types of cancers including solid cancers, and recently, a new way of thinking, called “cancer stem cell hypothesis” that cancer would be developed from cancer stem cells as an origin, has been proposed (NPL 1).

According to the hypothesis, even though the most part of cancer cells are killed or excised out by applying the aforementioned therapy, if a very small number of self-reproducible cancer stem cells remain, recurrence and metastasis conceivably occur. In short, it is considered that recurrence and metastasis are caused by the remaining small amount of cancer stem cells. Accordingly, if cancer stem cells can be targeted and completely eradicated, it is expected to develop a useful therapy for preventing metastasis and recurrence of cancer.

It is pointed out that some of the cancer stem cells acquire drug resistance to an anticancer therapeutic agent (NPL 2).

At present, as a low-molecular compound for use in detection of cancer stem cells and as a therapeutic agent, a compound containing radioactive Cu-ATSM is known (PTL 1). However, the radioactive compound may affect normal cells. Therefore, when a radioactive compound is used, safety becomes a matter of concern. In addition, it is also pointed out that cancer stem cells may develop strong resistance to radiation.

In the circumstances, it has been desired to develop a drug inhibiting cancer stem cells and a compound capable of detecting cancer stem cells.

Patent Literature

PTL 1: Japanese Patent Application Laid-Open No. 2010-013380

Non Patent Literature

NPL 1: Carcinogenesis, Vol. 26, p.p. 703-711, 2005

NPL 2: Nature Review Cancer, Vol. 5, p.p. 275-284, 2005

NPL 3: Journal of the American Chemical Society, Vol. 133, p.p. 6626-6635, 2011

NPL 4: Dye and Pigments, Vol. 71, p.p. 28-36, 2005

NPL 5: Organic & Biomolecular Chemistry, Vol. 9, p.p. 4199-4204, 2011

Technical Problem

Cancer stem cells have high resistance to radiation therapies and chemotherapies conventionally used and are causual cells from which cancer growth, recurrence and metastasis occur. Up to present, where cancer stem cells are present cannot be clearly detected. This was a issue remaining unsolved. To completely cure cancer, it has been strongly desired to detect cancer stem cells and develop a drug inhibiting cancer cells, in particular, cancer stem cells.

Solution to Problem

The present inventors intensively made studies with a view to solving the aforementioned problem. As a result, they found that a compound represented by the following general formula (1) has an inhibitory effect on cancer cells and is selectively taken into particularly cancer stem cells among the cancer cells and inhibits them. Based on the finding, the present invention was accomplished.

Furthermore, the compound of the present invention has a luminescence property. Owing to this, the position of cancer cells can be identified (determined) by detecting luminescence of the compound selectively taken into cancer cells. Based on the finding, the present inventors arrived at the present invention. Note that, in the specification, luminescence includes fluorescence and phosphorescence. Since the compound of the present invention is taken into particularly cancer stem cells in a high ratio, cancer stem cells can be selectively detected.

More specifically, the compound of the present invention contains a compound represented by general formula (1):

In general formula (1), R 1 and R 2 each independently represent an alkyl group, a carboxylalkyl group, an alkoxycarbonylalkyl group or an alkylcarbonyloxyalkyl group; R 3 to R 10 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a halogen atom, an alkoxysulfonyl group, a N-alkylsulfamoyl group, an alkyloxycarbonyl group, a carbamoyl group or a N-alkylcarbamoyl group; R 3 and R 4 , R 5 and R 6 , R 7 and R 8 , and R 9 and R 10 may be each independently cyclized to form a benzene ring; X 1 − represents an anionic group; Y 1 is a group including *1, *2 and *5 and represents any one of the followings: *1-S-*5-*2, *1-O-*5-*2, *1-C(—R 11 ,—R 12 )-*5-*2, and *1-*5-CH═CH-*2, where R 11 and R 12 each independently represent an alkyl group, and R 11 and R 12 may bind together to form a ring; Y 2 is a group including *3, *4 and *6 and represents any one of the followings:

*4=*6-S-*3, *4=*6-O-*3, *4=*6-C(—R 51 ,—R 52 )-*3, *4=*6-CH═CH-*3, and *4=CH—CH=*6-*3, where R 51 and R 52 each independently represent an alkyl group and R 51 and R 52 may bind together to form a ring; and a group including A to carbon atoms represented by *5 and *6 is represented by general formula (2) or (3).

(In general formula (2), R 13 to R 15 each independently represent a hydrogen atom, an alkyl group or an aryl group; and n represents an integer of 0 to 2, and in general formula (3), R 16 represents a hydrogen atom, a phenyl group, a thiol group, an alkoxy group, an aryloxy group or a halogen atom; and R 17 and R 18 each independently represent a hydrogen atom, an alkyl group or an alkyloxycarbonyl group).

Advantageous Effects of Invention

Owing to the compound provided by the present invention, growth suppression, cellular division suppression, metastasis suppression, functional inhibition and cytocidal action of cancer cells can be mediated even in sites where cancer cells are overlooked by surgical excision and hardly excised out. More specifically, the present invention provides a cancer cell inhibitory drug. Further, of the cancer cells, particularly against cancer stem cells, these effects are significantly exerted. Furthermore, cancer stem cells can be easily detected and the site of the cancer stem cells can be accurately determined. More specifically, the present invention provides a cancer stem-cell detection probe.

Now, embodiments of the present invention will be described below.

A cancer cell inhibitory drug of the present invention, particularly, a cancer stem-cell inhibitory drug which is selectively taken into cancer cells, particularly, into cancer stem cells, thereby inhibiting cancer stem cells, and a cancer stem-cell detection probe will be described; however, the present invention is not limited to these.

Cancer Cell Inhibitory Drug

The cancer cell inhibitory drug refers to a composition having functions of suppressing growth, cellular division, metastasis and function of cancer cells and killing cancer cells. Furthermore, cancer cells can be detected and observed by measuring luminescence of the compound of the present invention.

A compound according to the present invention contains a compound represented by general formula (1).

Regarding compound represented by general formula (1)

In general formula (1), R 1 and R 2 each independently represent an alkyl group, a carboxylalkyl group, an alkoxycarbonylalkyl group or an alkylcarbonyloxyalkyl group; R 3 to R 10 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a halogen atom, an alkoxysulfonyl group, a N-alkylsulfamoyl group, an alkyloxycarbonyl group, a carbamoyl group or a N-alkylcarbamoyl group; R 3 and R 4 , R 5 and R 6 , R 7 and R 8 , and R 9 and R 10 may be each independently cyclized to form a benzene ring; X 1 − represents an anionic group; Y 1 is a group including

*1, *2 and *5, and represents any one of the followings:

*1-S-*5-*2 (exemplified in compounds 1 to 12, 29, 39 and 42),

*1-O-*5-*2 (exemplified in compounds 13 to 19, 23, 28, 33, 38, 41, 44, 56 and 57),

*1-C(—R 11 ,—R 12 )-*5-*2 (exemplified in compounds 20 to 22, 24 to 27, 30 to 32, 37, 40, 43, 49 to 55 and 58), and

*1-*5-CH═CH-*2 (exemplified in compounds 34 to 36 and 45 to 48),

where R 11 and R 12 each independently represent an alkyl group, R 11 and R 12 may bind together to form a ring;

Y 2 is a group including *3, *4 and *6 and represents any one of the followings:

*4=*6-S-*3 (exemplified in compounds 1 to 12, 29, 34, 39 and 42),

*4=*6-O-*3 (exemplified in compounds 13 to 19, 23, 28, 33, 35, 38, 41, 44, 56 and 57),

*4=*6-C(—R 51 , —R 52 )-*3 (exemplified in compounds 20 to 22, 24 to 27, 30 to 32, 36, 37, 40, 43, 49 to 55 and 58),

*4=*6-CH═CH-*3 (exemplified in compounds 45, 47 and 48) and

*4=CH—CH═*6-*3 (exemplified in compound 46),

where R 51 and R 52 each independently represent an alkyl group and R 51 and R 52 may bind together to form a ring; and a group including A to carbon atoms represented by *5 and *6 is represented by general formula (2) or (3):

In general formula (2), R 13 to R 15 each independently represent a hydrogen atom, an alkyl group or an aryl group; and n represents an integer of 0 to 2, in general formula (3), R 16 represents a hydrogen atom, a phenyl group, a thiol group, an alkoxy group, an aryloxy group or a halogen atom; and R 17 and R 18 each independently represent a hydrogen atom, an alkyl group or an alkyloxycarbonyl group.

In general formula (1), examples of the alkyl group represented by R 1 and R 2 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (1), examples of the carboxylalkyl group represented by R 1 and R 2 include, but are not particularly limited to, a carboxylmethyl group, a carboxylethyl group and a carboxylpropyl group.

In general formula (1), examples of the alkoxycarbonylalkyl group represented by R 1 and R 2 include, but are not particularly limited to, a methoxycarbonylmethyl group, a methoxycarbonylethyl group, an ethoxycarbonylethyl group, a butoxycarbonylethyl group and a methoxycarbonylpropyl group; and examples of the alkylcarbonyloxyalkyl group include, but are not particularly limited to, a methylcarbonyloxymethyl group, an ethylcarbonyloxymethyl group, an ethylcarbonyloxyethyl group, an ethylcarbonyloxybutyl group and a propylcarbonyloxymethyl group.

In general formula (1), examples of the alkyl groups represented by R 3 to R 10 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (1), examples of the aryl groups represented by R 3 to R 10 include, but are not particularly limited to, a phenyl group, a 2-bromophenyl group, a 3-bromophenyl group, a 4-bromophenyl group, a 2-methoxyphenyl group, a 3-methoxyphenyl group, a 4-methoxyphenyl group, a 2-thiomethylphenyl group, a 3-thiomethylphenyl group, a 4-thiomethylphenyl group and a naphthyl group.

In general formula (1), examples of the alkoxy groups represented by R 3 to R 10 include, but are not particularly limited to, a methoxy group, an ethoxy group, a propoxy group and a butoxy group.

In general formula (1), examples of the halogen atoms represented by R 3 to R 10 include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

In general formula (1), examples of the alkoxysulfonyl groups represented by R 3 to R 10 include, but are not particularly limited to, a methoxysulfonyl group and an ethoxysulfonyl group.

In general formula (1), examples of the N-alkylsulfamoyl groups represented by R 3 to R 10 include, but are not particularly limited to, a N-methylsulfamoyl group, a N-ethylsulfamoyl group, a N,N-dimethylsulfamoyl group and a N,N-diethylsulfamoyl group.

In general formula (1), examples of the alkyloxycarbonyl groups represented by R 3 to R 10 include, but are not particularly limited to, a methyloxycarbonyl group, an ethyloxycarbonyl group, a propyloxycarbonyl group and a butyloxycarbonyl group.

In general formula (1), examples of the N-alkylcarbamoyl groups represented by R 3 to R 10 include, but are not particularly limited to, a N-methylcarbamoyl group, a N-ethylcarbamoyl group, a N,N-dimethylcarbamoyl group and a N,N-diethylcarbamoyl group.

R 3 to R 10 in general formula (1) each independently represent preferably a hydrogen atom, a halogen atom, a phenyl group or an alkoxy group, and more preferably a hydrogen atom or a phenyl group.

In general formula (1), examples of the anionic group represented by X 1 − include, but are not particularly limited to, a chloride ion, a bromide ion, an iodide ion, a sulfate ion, a nitrate ion, a methanesulfonate ion, a p-toluenesulfonate ion, a tetrafluoroborate ion and a hexafluorophosphate ion.

In general formula (1), examples of the alkyl groups represented by R 11 , R 12 , R 51 and R 52 in Y 1 and Y 2 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group and a 2-ethylhexyl group. R 11 and R 12 are favorably the same; however they may differ. R 51 and R 52 are favorably the same; however they may differ.

In general formula (1), R 11 and R 12 or R 51 and R 52 may bind together to form an aliphatic ring such as a cyclohexane ring and a cyclopentane ring.

In general formula (2), examples of the alkyl groups represented by R 13 to R 15 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (2), examples of the aryl groups represented by R 13 to R 15 include, but are not particularly limited to, a phenyl group, a 2-bromophenyl group, a 3-bromophenyl group, a 4-bromophenyl group, a 2-methoxyphenyl group, a 3-methoxyphenyl group, a 4-methoxyphenyl group, a 2-thiomethylphenyl group, a 3-thiomethylphenyl group and a 4-thiomethylphenyl group.

In general formula (3), examples of the thiol group represented by R 16 include a methanethiol group, a butanethiol group and a benzenethiol group. Alternatively, the thiol group represented by R 16 may be a phenylthio group.

In general formula (3), examples of the alkoxy group represented by R 16 include a methoxy group, an ethoxy group, a propoxy group and a butoxy group.

In general formula (3), examples of the aryloxy group represented by R 16 include a phenoxy group and a phenoxy group which may have a substituent.

In general formula (3), examples of the halogen atoms represented by R 16 include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

In general formula (3), examples of the alkyl groups represented by R 17 and R 18 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (3), examples of the alkyloxycarbonyl groups represented by R 17 and R 18 include, but are not particularly limited to, a methyloxycarbonyl group, an ethyloxycarbonyl group, a propyloxycarbonyl group and a butyloxycarbonyl group.

Regarding compound represented by general formula (4) As a favorable compound of the present invention, a compound represented by general formula (3) can be mentioned.

In general formula (4), R 19 and R 20 each independently represent an alkyl group, a carboxylalkyl group, an alkylcarbonyloxyalkyl group or an alkoxycarbonylalkyl group; and R 21 to R 28 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a halogen atom, an alkoxysulfonyl group, a N-alkylsulfamoyl group, an alkyloxycarbonyl group or a N-alkylcarbamoyl group. R 21 and R 22 , R 23 and R 24 , R 25 and R 26 and R 27 and R 28 may be each independently cyclized to form a benzene ring; R 29 to R 31 each independently represent a hydrogen atom, an alkyl group or an aryl group; and m represents an integer of 0 to 2. X 2 − represents an anionic group; and Y 3 and Y 4 each independently represent an oxygen atom, a sulfur atom or an alkylene group and the alkylene group may have a substituent being alkyl group. If the alkylene group has two or more substituents being alkyl groups, they may bind together to form an aliphatic ring.

In general formula (4), examples of the alkyl group represented by R 19 and R 20 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (4), examples of the carboxylalkyl group represented by R 19 and R 20 include, but are not particularly limited to, a carboxylmethyl group, a carboxylethyl group and a carboxylpropyl group.

In general formula (4), examples of the alkoxycarbonylalkyl group represented by R 19 and R 20 include, but are not particularly limited to, a methoxycarbonylmethyl group, a methoxycarbonylethyl group, an ethoxycarbonylethyl group, a butoxycarbonylethyl group and a methoxycarbonylpropyl group.

Examples of the alkylcarbonyloxyalkyl group include, but are not particularly limited to, a methylcarbonyloxymethyl group, an ethylcarbonyloxymethyl group, an ethylcarbonyloxyethyl group, an ethylcarbonyloxybutyl group and a propylcarbonyloxymethyl group.

In general formula (4), examples of the alkyl groups represented by R 21 to R 28 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (4), examples of the aryl groups represented by R 21 to R 28 include, but are not particularly limited to, a phenyl group, a 2-bromophenyl group, a 3-bromophenyl group, a 4-bromophenyl group, a 2-methoxyphenyl group, a 3-methoxyphenyl group, a 4-methoxyphenyl group, a 2-thiomethylphenyl group, a 3-thiomethylphenyl group, a 4-thiomethylphenyl group and a naphthyl group.

In general formula (4), examples of the alkoxy groups represented by R 21 to R 28 include, but are not particularly limited to, a methoxy group, an ethoxy group, a propoxy group and a butoxy group.

In general formula (4), examples of the halogen atoms represented by R 21 to R 28 include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

In general formula (4), examples of the alkoxysulfonyl groups represented by R 21 to R 28 include, but are not particularly limited to, a methoxysulfonyl group and an ethoxysulfonyl group.

In general formula (4), examples of the N-alkylsulfamoyl groups represented by R 21 to R 28 include, but are not particularly limited to, a N-methylsulfamoyl group, a N-ethylsulfamoyl group, a N,N-dimethylsulfamoyl group and a N,N-diethylsulfamoyl group.

In general formula (4), examples of the alkyloxycarbonyl groups represented by R 21 to R 28 include, but are not particularly limited to, a methyloxycarbonyl group, an ethyloxycarbonyl group, a propyloxycarbonyl group and a butyloxycarbonyl group.

In general formula (4), examples of the N-alkylcarbamoyl groups represented by R 21 to R 28 include, but are not particularly limited to, a N-methylcarbamoyl group, a N-ethylcarbamoyl group, a N,N-dimethylcarbamoyl group and a N,N-diethylcarbamoyl group.

R 21 to R 28 in general formula (4) each independently represent preferably a hydrogen atom, a halogen atom, a phenyl group or an alkoxy group, and more preferably a hydrogen atom or a phenyl group.

In general formula (4), examples of the alkyl groups represented by R 29 to R 31 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (4), examples of the aryl group represented by R 29 to R 31 include, but are not particularly limited to, a phenyl group, a 2-bromophenyl group, a 3-bromophenyl group, a 4-bromophenyl group, a 2-methoxyphenyl group, a 3-methoxyphenyl group, a 4-methoxyphenyl group, a 2-thiomethylphenyl group, a 3-thiomethylphenyl group and a 4-thiomethylphenyl group.

In general formula (4), examples of the anionic group represented by X 2 − include, but are not particularly limited to, a chloride ion, a bromide ion, an iodide ion, a sulfate ion, a nitrate ion, a methanesulfonate ion, a p-toluenesulfonate ion, a tetrafluoroborate ion and a hexafluorophosphate ion.

In general formula (4), Y 3 and Y 4 each independently represent an oxygen atom, a sulfur atom or an alkylene group and the alkylene group may have a substituent being alkyl group. If the alkylene group has two or more substituents being alkyl groups, they may bind together to form an aliphatic ring.

Examples of the alkylene group herein include, but are not particularly limited to, a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group and a 2-ethylhexylene group. Examples of the aliphatic ring to be formed include, but are not particularly limited to, a cyclohexane ring and a cyclopentane ring.

The compounds represented by general formula (4) in the present invention are mostly commercially available and can be purchased and also synthesized in the same manner as in known methods (for example, NPL-3).

In the above compounds (A) to (D), R 19 to R 31 , X 2 − , Y 3 , and Y 4 are the same as defined in R 19 to R 31 , X 2 − , Y 3 and Y 4 in compounds (A) to (D) in general formula (4). Furthermore, R in compound (A) represents an alkyl group such as a methyl group and an ethyl group.

More specifically, a compound represented by general formula (4) where m represents 0 is obtained by coupling compound (A), compound (C) and compound (D). A compound represented by general formula (4) where m represents 0 to 2 is obtained by coupling compound (B), compound (C) and compound (D).

Examples of the coupling method are not particularly limited. For example, a method of using compound (A) where m represents 0 will be described below as an embodiment.

The use amount of compound (C) in a coupling step relative to compound (A) (1 mole) is 0.1 to 1.2 times by mole, preferably 0.5 to 1.1 times by mole, and more preferably 0.8 to 1.0 times by mole.

The use amount of compound (D) in a coupling step relative to compound (A) (1 mole) is 0.1 to 2 times by mole, preferably 0.5 to 1.5 times by mole, and more preferably 0.8 to 1.2 times by mole.

The compound (C) and compound (D), which are not limited, may be the same or different; however, they are preferably the same compounds in view of process. The use amount of compound (C) and compound (D) relative to compound (A) (1 mole) when they are the same compounds, is 0.1 to 3 times by mole, preferably 0.5 to 2 times by mole, and more preferably 0.8 to 1.5 times by mole.

The coupling step can be performed in the absence of a solvent; however, it is favorably performed in the presence of a solvent. The solvent is not particularly limited as long as it is not involved in a reaction. Examples of the solvent include ester solvents such as methyl acetate, ethyl acetate, isopropyl acetate and butyl acetate; nitrile solvents such as acetonitrile, propionitrile and benzonitrile; aromatic solvents such as benzene, toluene, xylene, ethylbenzene, chlorobenzene and mesitylene; ether solvents such as diisopropyl ether, methyl-tert-butyl ether and tetrahydrofuran; alcohol solvents such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, butyl alcohol and diethylene glycol; ketone solvents such as acetone and methylethyl ketone; dimethylformamide (DMF), dimethylsulfoxide (DMSO), water and acetic acid. Preferably, alcohol solvents such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, butyl alcohol and diethylene glycol, water and acetic acid, and more preferably e.g., ethanol, iso-propyl alcohol and diethylene glycol and acetic acid are mentioned. Furthermore, two or more types of solvents can be used in combination and the mixing ratio of solvents used in combination can be determined at discretion.

The use amount of reaction solvent in the coupling step relative to compound (A) falls within the range of 0.1 to 1000 times by weight, preferably 0.5 to 500 times by weight, and more preferably 1.0 to 150 times by weight.

The reaction temperature in the coupling step falls within the range of −80 to 250° C., preferably −20 to 200° C., and more preferably 10 to 170° C. The reaction is generally completed within 24 hours.

In the coupling step, if an acid or a base is added as necessary, the reaction swiftly proceeds. The acid to be used is not particularly limited. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid; organic acids such as p-toluenesulfonic acid, formic acid, acetic acid, propionic acid, trifluoroacetic acid and acetic anhydride; strongly acidic ion exchange resins such as Amberlite (Rohm and Haas) and Amberlyst (Rohm and Haas); and inorganic acid salts such as ammonium formate and ammonium acetate. More preferably, an inorganic acid salt such as ammonium formate or ammonium acetate, and more preferably ammonium acetate is mentioned. The use amount of acid relative to compound (A) (1 mole) is 0.001 to 50 times by mole, preferably 0.01 to 10 times by mole, and more preferably 0.1 to 5 times by mole.

Specific examples of the base to be used in the coupling step include metal alkoxides such as potassium tert-butoxide, sodium tert-butoxide, sodium methoxide and sodium ethoxide; organic bases such as piperidine, pyridine, 2-methylpyridine, dimethylaminopyridine, diethylamine, triethylamine, isopropylethylamine, sodium acetate, potassium acetate, 1,8-diazabicyclo[5,4,0]undec-7-ene (hereinafter, simply referred to as DBU) and ammonium acetate; organic bases such as N-butyllithium and tert-butylmagnesium chloride; and inorganic bases such as sodium borohydride, metallic sodium, sodium hydride and sodium carbonate. Preferably, potassium tert-butoxide, sodium methoxide, sodium ethoxide, piperidine, dimethylaminopyridine, sodium acetate and ammonium acetate; and more preferably sodium methoxide, piperidine, sodium acetate and ammonium acetate are mentioned. The use amount of base as mentioned above relative to compound (A) (1 mole) is 0.1 to 20 times by mole, preferably 0.5 to 8 times by mole, and more preferably 1.0 to 4 times by mole.

After completion of the reaction, a reaction product is diluted with water or precipitated with an acid such as hydrochloric acid to obtain a compound represented by general formula (4).

To the obtained compound, isolation/purification methods generally used for organic compounds can be applied. For example, a reaction solution is acidified with an acid such as hydrochloric acid to precipitate a solid substance. The solid substrate is separated by filtration, neutralized with e.g., sodium hydroxide and concentrated to obtain a crude product. The crude product is further purified by e.g., recrystallization using e.g., acetone or methanol, or a column using silica gel. The crude product can be highly purified by employing these methods alone or in combination with two or more.

Regarding compound represented by general formula (5) As a preferable compound of the present invention, a compound represented by general formula (5) can be mentioned.

In general formula (5), R 34 and R 35 each independently represents an alkyl group, a carboxylalkyl group or an alkoxycarbonylalkyl group; and R 36 to R 43 each independently represent a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, a halogen atom, an alkoxysulfonyl group, a N-alkylsulfamoyl group, an alkyloxycarbonyl group or a N-alkylcarbamoyl group. R 36 and R 37 , R 38 and R 39 , R 40 and R 41 and R 42 and R 43 may be each independently cyclized to form a benzene ring. R 44 represents a hydrogen atom, a phenyl group, a thiol group, an alkoxy group, an aryloxy group or a halogen atom; and R 45 and R 46 each independently represent a hydrogen atom, an alkyl group or an alkylcarbonyloxy group. X 3 − represents an anionic group; and Y 5 and Y 6 each independently represent an oxygen atom, a sulfur atom or an alkylene group and the alkylene group may have substituents being alkyl groups which may bind together to form an aliphatic ring.

In general formula (5), examples of the alkyl group represented by R 34 and R 35 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (5), examples of the carboxylalkyl group represented by R 34 and R 35 include, but are not particularly limited to, a carboxylmethyl group, a carboxylethyl group and a carboxylpropyl group.

In general formula (5), examples of the alkoxycarbonylalkyl group represented by R 34 and R 35 include, but are not particularly limited to, a methoxycarbonylmethyl group, a methoxycarbonylethyl group, an ethoxycarbonylethyl group, a butoxycarbonylethyl group and a methoxycarbonylpropyl group; and in general formula (5), examples of the alkyl groups represented by R 36 to R 43 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (5), examples of the aryl groups represented by R 36 to R 43 include, but are not particularly limited to, a phenyl group, a 2-bromophenyl group, a 3-bromophenyl group, a 4-bromophenyl group, a 2-methoxyphenyl group, a 3-methoxyphenyl group, a 4-methoxyphenyl group, a 2-thiomethylphenyl group, a 3-thiomethylphenyl group, a 4-thiomethylphenyl group and a naphthyl group.

In general formula (5), examples of the alkoxy groups represented by R 36 to R 43 include, but are not particularly limited to, a methoxy group, an ethoxy group, a propoxy group and a butoxy group.

In general formula (5), examples of the halogen atoms represented by R 36 to R 43 include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

In general formula (5), examples of the alkoxysulfonyl groups represented by R 36 to R 43 include, but are not particularly limited to, a methyl sulfonate group and an ethyl sulfonate group.

In general formula (5), examples of the alkylsulfamoyl groups represented by R 36 to R 43 include, but are not particularly limited to, a monomethylamide sulfonate group, a monoethylamide sulfonate group, a dimethylamide sulfonate group and a diethylamide sulfonate group.

In general formula (5), examples of the alkylcarbonyloxyalkyl groups represented by R 36 to R 43 include, but are not particularly limited to, a methylcarbonyloxymethyl group, an ethylcarbonyloxymethyl group, an ethylcarbonyloxyethyl group, an ethylcarbonyloxybutyl group and a propylcarbonyloxymethyl group.

In general formula (5), examples of the N-alkylcarbamoyl groups represented by R 36 to R 43 include, but are not particularly limited to, a N-methylcarbamoyl group, a N-ethylcarbamoyl group, a N,N-dimethylcarbamoyl group and a N,N-diethylcarbamoyl group.

R 36 to R 43 in general formula (5) each independently represent preferably a hydrogen atom, a halogen atom, a phenyl group or an alkoxy group, and more preferably a hydrogen atom or a phenyl group.

In general formula (5), examples of the thiol group represented by R 44 include a mercaptomethyl group, a mercaptobutyl group and a mercaptophenyl group. Alternatively, the thiol group represented by R 44 may be a phenylthio group.

In general formula (5), examples of the alkoxy group represented by R 44 include a methoxy group, an ethoxy group, a propoxy group and a butoxy group.

In general formula (5), examples of the aryloxy group represented by R 44 include a phenoxy group and a phenoxy group which may have a substituent.

In general formula (5), examples of the halogen atom represented by R 44 include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

In general formula (5), examples of the alkyl group represented by R 45 and R 46 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (5), examples of the alkyloxycarbonyl groups represented by R 45 and R 46 include, but are not particularly limited to, a methyloxycarbonyl group, an ethyloxycarbonyl group, a propyloxycarbonyl group and a butyloxycarbonyl group.

In general formula (5), examples of the anionic group represented by X 3 − include, but are not particularly limited to, a chloride ion, a bromide ion, an iodide ion, a sulfate ion, a nitrate ion, a methanesulfonate ion, a p-toluenesulfonate ion, a tetrafluoroborate ion and a hexafluorophosphate ion.

In general formula (5), examples of the alkylene groups represented by Y 5 and Y 6 include, but are not particularly limited to, a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, a hexylene group and a 2-ethylenehexyl group. Examples of the alkyl group serving as a substituent of an alkylene group include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group and a butyl group.

The compounds represented by general formula (5) in the present invention are mostly commercially available and can be purchased and also synthesized in the same manner as in known methods (for example, NPL-4).

In compounds (E) to (G), R 35 to R 44 , X 3 − , Y 5 , and Y 6 are the same as defined in R 35 to R 44 , X 3 − , Y 5 , and Y 6 in compounds (E) to (G) in general formula (5).

More specifically, a compound represented by general formula (5) can be obtained by coupling compounds (E) to (G). Examples of the coupling method are not particularly limited. For example, a method described below is mentioned as an embodiment.

The use amount of compound (F) in a coupling step relative to compound (E) (1 mole) is 0.1 to 1.2 times by mole, preferably 0.5 to 1.1 times by mole, and more preferably 0.8 to 1.0 times by mole.

The use amount of compound (G) in a coupling step relative to compound (E) (1 mole) is 0.1 to 2 times by mole, preferably 0.5 to 1.5 times by mole, and more preferably 0.8 to 1.2 times by mole.

The compound (F) and compound (G), which are not limited, may be the same or different; however, they are preferably the same compounds in view of process. The use amount of compound (F) and compound (G) relative to compound (E) (1 mole) when they are the same compounds, is 0.1 to 3 times by mole, preferably 0.5 to 2 times by mole, and more preferably 0.8 to 1.5 times by mole.

The coupling step can be performed in the absence of a solvent; however, it is favorably performed in the presence of a solvent. The solvent is not particularly limited as long as it is not involved in a reaction. Examples of the solvent include ester solvents such as methyl acetate, ethyl acetate, isopropyl acetate and butyl acetate; nitrile solvents such as acetonitrile, propionitrile and benzonitrile; aromatic solvents such as benzene, toluene, xylene, ethylbenzene, chlorobenzene and mesitylene; ether solvents such as diisopropyl ether, methyl-tert-butyl ether and tetrahydrofuran; alcohol solvents such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, butyl alcohol and diethylene glycol; ketone solvents such as acetone and methylethyl ketone; dimethylformamide (DMF), dimethylsulfoxide (DMSO), water and acetic acid. Preferably, alcohol solvents such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, butyl alcohol and diethylene glycol, water and acetic acid, and more preferably e.g., ethanol, iso-propyl alcohol and diethylene glycol and acetic acid are mentioned. Furthermore, two or more types of solvents can be used in combination and the mixing ratio of solvents used in combination can be determined at discretion.

The use amount of reaction solvent in the coupling step relative to compound (E) falls within the range of 0.1 to 1000 times by weight, preferably 0.5 to 500 times by weight, and more preferably 1.0 to 150 times by weight.

The reaction temperature in the coupling step falls within the range of −80 to 250° C., preferably −20 to 200° C., and more preferably 10 to 170° C. The reaction is generally completed within 24 hours.

In the coupling step, if an acid or a base is added as necessary, the reaction swiftly proceeds. The acid to be used is not particularly limited. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid; organic acids such as p-toluenesulfonic acid, formic acid, acetic acid, propionic acid, trifluoroacetic acid and acetic anhydride; strongly acidic ion exchange resins such as Amberlite (Rohm and Haas) and Amberlyst (Rohm and Haas); and inorganic acid salts such as ammonium formate and ammonium acetate. More preferably, an inorganic acid salt such as ammonium formate or ammonium acetate, and more preferably ammonium acetate is mentioned. The use amount of acid relative to compound (E) (1 mole) is 0.001 to 50 times by mole, preferably 0.01 to 10 times by mole, and more preferably 0.1 to 5 times by mole.

Specific examples of the base to be used in the coupling step include metal alkoxides such as potassium tert-butoxide, sodium tert-butoxide, sodium methoxide and sodium ethoxide; organic bases such as piperidine, pyridine, 2-methylpyridine, dimethylaminopyridine, diethylamine, triethylamine, isopropylethylamine, sodium acetate, potassium acetate, 1,8-diazabicyclo[5,4,0]undec-7-ene (hereinafter, simply referred to as DBU) and ammonium acetate; organic bases such as N-butyllithium and tert-butylmagnesium chloride; and inorganic bases such as sodium borohydride, metallic sodium, sodium hydride and sodium carbonate. Preferably, potassium tert-butoxide, sodium methoxide, sodium ethoxide, piperidine, dimethylaminopyridine, sodium acetate and ammonium acetate; and more preferably sodium methoxide, piperidine, sodium acetate and ammonium acetate are mentioned. The use amount of base as mentioned above relative to compound (E) (1 mole) is 0.1 to 20 times by mole, preferably 0.5 to 8 times by mole, and more preferably 1.0 to 4 times by mole.

After completion of the reaction, a reaction product is diluted with water or precipitated with an acid such as hydrochloric acid to obtain a compound represented by general formula (5).

To the obtained compound, isolation/purification methods generally used for organic compounds can be applied. For example, a reaction solution is acidified with an acid such as hydrochloric acid to precipitate a solid substance. The solid substrate is separated by filtration, neutralized with e.g., sodium hydroxide and concentrated to obtain a crude product. Furthermore, the crude product is purified by e.g., recrystallization using e.g., acetone or methanol, or a column using silica gel. The crude product can be highly purified by employing these methods alone or in combination with two or more.

Regarding compound represented by general formula (6) As a preferable compound of the present invention, a compound represented by general formula (6) can be mentioned.

In general formula (6), R 49 and R 50 each independently represent an alkyl group, a carboxylalkyl group, an alkylcarbonyloxyalkyl group or an alkoxycarbonylalkyl group. X 4 − represents an anionic group.

In general formula (6), examples of the alkyl group represented by R 49 and R 50 include, but are not particularly limited to, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group and a hexyl group.

In general formula (6), examples of the carboxylalkyl group represented by R 49 and R 50 include, but are not particularly limited to, a carboxylmethyl group, a carboxylethyl group and a carboxylpropyl group.

In general formula (6), examples of the alkoxycarbonylalkyl group represented by R 49 and R 50 include, but are not particularly limited to, a methoxycarbonylmethyl group, a methoxycarbonylethyl group, an ethoxycarbonylethyl group, a butoxycarbonylethyl group and a methoxycarbonylpropyl group; and examples of the alkylcarbonyloxyalkyl group include, but are not particularly limited to, a methylcarbonyloxymethyl group, an ethylcarbonyloxymethyl group, an ethylcarbonyloxyethyl group, an ethylcarbonyloxybutyl group and a propylcarbonyloxymethyl group.

In general formula (6), examples of the anionic group represented by X 4 − include, but are not particularly limited to, a chloride ion, a bromide ion, an iodide ion, a sulfate ion, a nitrate ion and a methanesulfonate ion.

The compounds represented by general formula (6) in the present invention are mostly commercially available and can be purchased and also synthesized in the same manner as in known methods (for example, NPL-5).

In compounds (H) to (J), R 49 , R 50 and X 4 − are the same as defined in R 49 , R 50 and X 4 − in compounds (H) to (J) in general formula (6).

More specifically, a compound represented by general formula (6) can be obtained by coupling compounds (H) to (J). Examples of the coupling method is not particularly limited. For example, a method described below is mentioned as an embodiment.

The use amount of compound (I) in a coupling step relative to compound (H) (1 mole) is 0.1 to 1.2 times by mole, preferably 0.5 to 1.1 times by mole, and more preferably 0.8 to 1.0 times by mole.

The use amount of compound (J) in a coupling step relative to compound (H) (1 mole) is 0.1 to 2 times by mole, preferably 0.5 to 1.5 times by mole, and more preferably 0.8 to 1.2 times by mole.

The compound (I) and compound (J), which are not limited, may be the same or different; however, preferably the same compounds in view of process. The use amount of compound (I) and compound (J) relative to compound (H) (1 mole) when they are the same compounds, is 0.1 to 3 times by mole, preferably 0.5 to 2 times by mole, and more preferably 0.8 to 1.5 times by mole.

The coupling step can be performed in the absence of a solvent; however, it is favorably performed in the presence of a solvent. The solvent is not particularly limited as long as it is not involved in a reaction. Examples of the solvent include ester solvents such as methyl acetate, ethyl acetate, isopropyl acetate and butyl acetate; nitrile solvents such as acetonitrile, propionitrile and benzonitrile; aromatic solvents such as benzene, toluene, xylene, ethylbenzene, chlorobenzene and mesitylene; ether solvents such as diisopropyl ether, methyl-tert-butyl ether and tetrahydrofuran; alcohol solvents such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, butyl alcohol and diethylene glycol; ketone solvents such as acetone and methylethyl ketone; dimethylformamide (DMF), dimethylsulfoxide (DMSO), water and acetic acid. Preferably, alcohol solvents such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, butyl alcohol and diethylene glycol, water and acetic acid, and more preferably e.g., ethanol, iso-propyl alcohol and diethylene glycol and acetic acid are mentioned. Furthermore, two or more types of solvents can be used in combination and the mixing ratio of solvents used in combination can be determined at discretion.

The use amount of reaction solvent in the coupling step relative to compound (H) falls within the range of 0.1 to 1000 times by weight, preferably 0.5 to 500 times by weight, and more preferably 1.0 to 150 times by weight.

The reaction temperature in the coupling step falls within the range of −80 to 250° C., preferably −20 to 200° C., and more preferably 10 to 170° C. The reaction is generally completed within 24 hours.

In the coupling step, if an acid or a base is added as necessary, the reaction swiftly proceeds. The acid to be used is not particularly limited. Examples of the acid include inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid; organic acids such as p-toluenesulfonic acid, formic acid, acetic acid, propionic acid, trifluoroacetic acid and acetic anhydride; strongly acidic ion exchange resins such as Amberlite (Rohm and Haas) and Amberlyst (Rohm and Haas); and inorganic acid salts such as ammonium formate and ammonium acetate. More preferably, an inorganic acid salt such as ammonium formate or ammonium acetate, and more preferably ammonium acetate is mentioned. The use amount of acid relative to compound (H) (1 mole) is 0.001 to 50 times by mole, preferably 0.01 to 10 times by mole, and more preferably 0.1 to 5 times by mole.

Specific examples of the base to be used in the coupling step include metal alkoxides such as potassium tert-butoxide, sodium tert-butoxide, sodium methoxide and sodium ethoxide; organic bases such as piperidine, pyridine, 2-methylpyridine, dimethylaminopyridine, diethylamine, triethylamine, isopropylethylamine, sodium acetate, potassium acetate, 1,8-diazabicyclo[5,4,0]undec-7-ene (hereinafter, simply referred to as DBU) and ammonium acetate; organic bases such as N-butyllithium and tert-butylmagnesium chloride; and inorganic bases such as sodium borohydride, metallic sodium, sodium hydride and sodium carbonate. Preferably, potassium tert-butoxide, sodium methoxide, sodium ethoxide, piperidine, dimethylaminopyridine, sodium acetate and ammonium acetate; and more preferably sodium methoxide, piperidine, sodium acetate and ammonium acetate are mentioned. The use amount of base as mentioned above relative to compound (H) (1 mole) is 0.1 to 20 times by mole, preferably 0.5 to 8 times by mole, and more preferably 1.0 to 4 times by mole.

After completion of the reaction, a reaction product is diluted with water or precipitated with an acid such as hydrochloric acid to obtain a compound represented by general formula (6).

To the obtained compound, isolation/purification methods generally used for organic compounds can be applied. For example, a reaction solution is acidified with an acid such as hydrochloric acid to precipitate a solid substance. The solid substrate is separated by filtration, neutralized with e.g., sodium hydroxide and concentrated to obtain a crude product. Furthermore, the crude product is purified by e.g., recrystallization using e.g., acetone or methanol, or a column using silica gel. The crude product can be highly purified by employing these methods alone or in combination with two or more.

Now, compounds (1) to (60) will be shown below as preferable examples of the compounds according to the present invention; however, the present invention is not limited to the following examples.

The compounds of the present invention are favorably emitted by light upon irradiation with excitation light of 350 to 800 nm in wavelength.

The compounds of the present invention is characterized in that growth suppression, cellular division suppression, metastasis suppression, functional inhibition and cytocidal action of cancer cells are mediated by taking a compound selectively into the cancer cells. Further, cancer cells can be detected and observed by measuring luminescence of the compound of the present invention.

The compounds of the present invention may be used alone or in combination with two types or more for cancer inhibition, and may be used in combination with a known anti-cancer drug(s).

In the present invention, an effect is selectively exerted particularly on cancer stem cells among cancer cells.

Cancer Stem Cells

In the specification, the cancer stem cells refer to cancer cells having properties of the stem cells. The stem cells refer to cells having two functions, i.e., self-replication ability and pluripotency (ability to differentiate into various types of cells).

Applicable Cancer

Examples of the cancer to be inhibited by the compound of the present invention include, but are not particularly limited to Examples of the cancers include breast cancer, brain tumor, stomach cancer, prostatic cancer, pancreatic cancer, lung cancer, large bowel cancer, small intestine cancer, colon cancer, rectal cancer, esophagus cancer, duodenal cancer, tongue cancer, pharyngeal cancer, liver cancer, endometrium cancer, uterine cervix cancer, renal cancer, bile duct cancer, ovarian cancer, bladder cancer, skin cancer, blood vessel cancer, salivary gland cancer, thyroid cancer, parathyroid gland cancer, nasal cavity cancer, paranasal sinus cancer, penile cancer, infant solid cancer, malignant lymphoma, malignant melanoma, retina sarcoma, testicular tumor, myeloma, sarcoma, blood vessel fibroma and leukemia. Preferably, e.g., pancreatic cancer, prostatic cancer and leukemia are mentioned. Particularly, applicable cancers may include cancer stem cells or cells originated from cancer stem cells.

Test Subject

Examples of the subject used in a test for checking whether a compound of the present invention suppresses a cancer or not include, but are not particularly limited to, vertebral animals including bony fish such as Takifugu (Japanese pufferfish), Takifugu niphobles , green spotted pufferfish ( Tetraodon nigroviridis ), killifish and zebra fish, amphibians such as Xenopus , birds such as fowl and quail, and mammalians such as human, monkey, chimpanzee, calf, horse, pig, dog, cat, mouse, rat, guinea pig, hamster and rabbit; small animals such as rat, mouse and hamster; and large animals such as goat, pig, dog, cat, calf and horse, monkey, chimpanzee and human. Favorably, e.g., human, mouse, rat, dog and cat are mentioned.

When a compound of the present invention is used as a medicinal drug, various types of dosage forms can be selected depending upon the administration route. Examples of dosage forms that can be used include liquid, syrup, fine granule, granule, tablet, capsule, pasting medicine and drug delivery system (DDS) such as liposome.

The administration method of a compound of the present invention is not limited and oral or parenteral administration may be used. Examples of the administration method that can be used include exposure to a living body (e.g., liquid); administration such as oral, intravascular (through e.g., a vein or an artery), peroral, sublingual, intrarectal, intraperitoneal, dermal, subcutaneous, intracutaneous, intravesical, tracheal (via bronchia), intraocular and intranasal administrations; and injection, spray and application into ear or the like.

A compound of the present invention, if necessary, may contain pharmacologically or pharmaceutically acceptable additives such as a moisturizer, a surface tension moderator, a thickener, a pH moderator, a pH buffer, a preservative, an antibacterial agent, a sweetening agent, a flavor, a solubilizer, a solubilizing agent, a coating agent and a binder.

The dose of the compound of the present invention is appropriately determined depending upon a purpose for therapy or prophylaxis, and conditions such as sexuality, age, weight of a test subject, an administration route, and degree of a disease.

Transplant Model Animal

Generally, it is difficult to monitor behavior of metastatic cancer by culturing cells. Thus, in the present invention, in order to monitor behavior of metastatic cancer, particularly, a transplant model animal can be used.

Examples of the cancer-cell transplant model animal applicable to the present invention include, but are not particularly limited to, vertebral animals including bony fish such as Takifugu (Japanese pufferfish), Takifugu niphobles , green spotted pufferfish ( Tetraodon nigroviridis ), killifish and zebra fish, amphibians such as Xenopus , birds such as fowl and quail, mammalians such as human, monkey, chimpanzee, calf, horse, pig, dog, cat, mouse, rat, guinea pig, hamster and rabbit, and birds such as fowl and quail; small animals such as rat, mouse and hamster; and large animals such as goat, pig, dog, cat, calf and horse, monkey and chimpanzee. Favorably, e.g., mouse, rat, dog and cat are mentioned.

Of these, e.g., immunodeficiency mice and rats, are often generally used in an initial study. In this case, it is necessary to maintain an environment by use of e.g., a clean room in the period (usually, at least 3 to 6 months) during which the study is carried out. In addition, extraordinary labor cost for management during this period is required.

For the reason, among these biological samples, zebra fish is particularly preferably used in view of cost and speed (usually at least a week). Zebra fish has been recently and already recognized as a third model animal which comes next to mice and rats in the United States and the United Kingdom. It has been elucidated that, the entire genomic sequence of zebra fish has a 80% homology to that of a human and the number of genes of zebra fish is virtually the same as that of a human. Furthermore, development and structure of major organs/tissues are mutually quite resembled. Since a process from differentiation of a fertilized egg to formation of each part (organ such as heart, liver, kidney and digestive tube) can be observed through a transparent body, it is particularly preferable to use zebra fish (the inside of which can be observed non-invasively) for screening as a model animal.

Furthermore, zebra fish lay about 200 or more fertilized eggs per time. Since zebra fish having the same genetic background are obtained, zebra fish is advantageous for screening.

The method for administering a compound of the present invention is not particularly limited; however, a cancer cell inhibitory drug may be suspended in the form of a complex with an appropriate surfactant or in the form of an emulsion in breeding water. Alternatively, the cancer cell inhibitory drug may be mixed in feed or food and orally or parenterally (e.g., injection) administered.

Cancer Stem Cell Detection Probe

Since the compound of the present invention can be used for selective detection of cancer stem cells, it can be suitably used as a cancer stem-cell detection probe. More specifically, the present invention encompasses a cancer cell detection probe.

The ratio of the compound of the present invention particularly taken into cancer stem cells among the cancer cells is large. Thus, cancer stem cells can be selectively detected. Detection and confirmation of behavior of cancer stem cells by the present invention can be carried out all in vitro, ex vivo or in vivo.

A method for detecting, by use of a compound of the present invention, which is not particularly limited as long as it has no effect upon cancer stem cells, is a method for capturing state and change of a biological sample as an image. For example, visible light, near infrared light or infrared light is applied to cancer stem cells and an image is visually observed by e.g., a camera or CCD, namely, visible light observation, near infrared light observation and infrared light observation are mentioned. Alternatively, observation by a laser microscope; fluorescence observation in which excitation light is applied to a biological sample from an excitation-light source and fluorescence emitted from the biological sample is observed by a fluorescent endoscope or the like; observation by a fluorescent microscope; observation by a fluorescent endoscope; observation by a confocal fluorescence microscope; or observation by a multiphoton excitation fluorescence microscope is mentioned. Alternatively, narrow-band light observation; colight interference tomogram observation (OCT) or observation by a soft X ray microscope is mentioned. Particularly, fluorescence observation is favorable.

The wavelength of light for exciting a compound of the present invention varies depending upon the compound represented by general formula (1) and the wavelength of the excitation light is not particularly limited as long as a cancer cell detection probe of the present invention efficiently emits fluorescent light.

The wavelength is preferably, 200 to 1010 nm, more preferably 400 to 900 nm, and more preferably 480 to 800 nm. When light within a near infrared region is used, the wavelength that is used is preferably 600 to 1000 nm, and more preferably 680 to 900 nm, which is also excellent in permeability through a living body.

The source of excitation light for exciting a compound of the present invention is not particularly limited and various types of laser light sources can be used. Examples of these laser light sources include a dye laser light source, a semiconductor laser light source, an ion laser light source, a fiber laser light source, a halogen lamp, a xenon lamp and a tungsten lamp. Alternatively, if various types of optical filters are used, a favorable excitation wavelength can be obtained and fluorescence alone can be detected.

As described above, in the state where a compound of the present invention present within cancer stem cells is allowed to emit light by applying excitation light to an individual biological organism, if the cancer stem cells can be photographed, a luminescent site can be easily detected. Furthermore, if an image in light field, which is obtained by applying visible light, is combined with a fluorescent image, which is obtained by applying excitation light, with the help of an image processing unit, cancer stem cells can be more specifically observed. Furthermore, if a confocal microscope is used, a sectional optical image can be favorably obtained. Furthermore, a multiphoton excitation fluorescence microscope, since it is highly permeable to a deep portion and a spatial resolution, is favorably used for observing inside a tissue.

Now, the present invention will be more specifically described below by way of Examples. These are specific Examples for further deep understanding of the present invention and should not be construed as limiting the invention.

The compound provided by the present invention is useful as a cancer cell inhibitory drug. Furthermore, owing to the cancer cell inhibitory drug provided by the present invention, growth suppression, cellular division suppression, metastasis suppression, functional inhibition and cytocidal action of cancer cells, particularly cancer stem cells, can be mediated. In addition, cancer stem cells can be easily detected and the site of cancer stem cells can be accurately specified. The compound of the present invention is expected to widely contribute to the medical industry.