Ruthenium complexes for treating cancer which comprises cancer stem cells

1. A method of treating cancer, where the cancer is a cancer comprising cancer stem cells which comprises contacting said cancer stem cells with a pharmaceutical composition comprising a therapeutically effective amount of a ruthenium complex of formula (I)

wherein

N 1 —N 1 —N 1 represents an N,N,N-tridentate aza-aromatic ligand;

N 2 —N 2 represents an N,N-bidentate aza-aromatic ligand;

X is OH 2 ;

Y − is a monovalent anion; and

n is 2,

wherein the method increases c-MYC protein expression,

wherein the therapeutically effective amount is effective to reduce tumorigenicity in cancer stem cells without being cytotoxic to differentiated cancer cells.

2. The method according to claim 1 , wherein N 1 —N 1 —N 1 is selected from the group consisting of:

wherein each group R′ is independently selected from hydrogen, optionally substituted C 1 -C 6 alkyl, optionally substituted C 6 -C 14 aryl, optionally substituted 5- to 10-membered heteroaryl, and halogen.

3. The method according to claim 1 , wherein N 2 —N 2 is selected from the group consisting of:

wherein each group R′ is independently selected from hydrogen, optionally substituted C 1 -C 6 alkyl, optionally substituted C 6 -C 14 aryl, optionally substituted 5- to 10-membered heteroaryl, and halogen.

4. The method according to claim 1 , wherein N 1 —N 1 —N 1 is

where each group R′ is independently selected from hydrogen, optionally substituted C 1 -C 6 alkyl, optionally substituted C 6 -C 14 aryl, optionally substituted 5- to 10-membered heteroaryl, and halogen.

5. The method according to claim 1 , wherein the ruthenium complex has the following formula:

wherein

X is OH 2 ;

Y − is a monovalent anion; and

n is 2.

6. The method according to claim 1 , wherein the ruthenium complex is

wherein Y − is a monovalent anion.

7. The method according to claim 1 , wherein the cancer is selected from the group consisting of breast cancer, lung cancer, colon cancer, prostate cancer, ovarian cancer, pancreatic cancer, cervical cancer, and kidney cancer carcinoma.

8. The method according to claim 7 , wherein the cancer is pancreatic adenocarcinoma.

9. A method of treating cancer, where the cancer is a cancer comprising cancer stem cells, which comprises contacting said cancer stem cells with a pharmaceutical composition comprising a therapeutically effective amount of a conjugate comprising:

a ruthenium complex of formula (I), as defined in claim 1 , and

an ABCG2 substrate or an anti-tumor drug,

wherein the method increases c-MYC protein expression, and

wherein the therapeutically effective amount is effective to reduce tumorigenicity in cancer stem cells without being cytotoxic to differentiated cancer cells.

10. The method according to claim 9 , where the ABCG2 substrate is selected from the group consisting of imatinib, gefitinib, flavopirodol, topotecan, irinotecan, SN-38, mitoxantrone, cimetidine, prazosin, statins, zidovudine, estrone, 17β-estradiol, protoporphyrin IX, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine, amsacrine, asparaginase, azathioprine, bisantrene, bleomycin, busulfan, capecitabine, carboplatin, carmustine, chlorambucil, cisplatin, cladribine, clofarabine, cyclophosphamide, cytarabine, dacarbazine, dactinomycin, daunorubicin, docetaxel, doxorubicin, epirubicin, etoposide, flavopiridol, fludarabine, fluorouracil, gemcitabine, idarubicin, ifosfamide, irinotecan, hydroxyurea, leucovorin, liposomal daunorubicin, liposomal doxorubicin, lomustine, chlormethine, melphalan, mercaptopurine, mesna, methotrexate, mitomycin, mitoxantrone, oxaliplatin, paclitaxel, pemetrexed, pentostatin, procarbazine, satraplatin, streptozotocin, tegafur-uracil, temozolomide, teniposide, thioguanine, thiotepa, treosulfan, topotecan, vinblastine, vincristine, vindesine, SN-38, vinorelbine, riboflavin, D-luciferin, rhodamine 123, pheophorbide a, BODIPY-prazosin, and Hoechst 33342.

11. The method according to claim 9 , where the ABCG2 substrate is riboflavin.

12. The method according to claim 9 , where the ruthenium complex is a complex of formula (I′)

wherein

X is OH 2 ;

Y − is a monovalent anion; and

n is 2.

13. The method according to claim 9 , where the conjugate comprises a linker covalently bound to the ruthenium complex and to the ABCG2 substrate or to the anti-tumor drug.

14. The method according to claim 9 , wherein the cancer is selected from the group consisting of breast cancer, lung cancer, colon cancer, prostate cancer, ovarian cancer, pancreatic cancer, cervical cancer, and kidney cancer carcinoma.

15. The method according to claim 1 , wherein the pharmaceutical composition comprising said therapeutically effective amount of a ruthenium complex of formula (I) further comprises another therapeutic agent.

16. The method according to claim 15 , wherein said therapeutic agent is an anti-tumor drug.

17. The method according to claim 1 , wherein said increase in c-MYC protein expression is an increase in the dark.

18. The method according to claim 9 wherein the pharmaceutical composition comprising said therapeutically effective amount of the conjugate further comprises another therapeutic agent.

19. The method according to claim 17 , wherein said therapeutic agent is an anti-tumor drug.

20. The method of claim 15 , wherein the pharmaceutical composition is a combination of two dosage forms.

21. The method of claim 15 , wherein the pharmaceutical composition is formulated for simultaneous, separate, or sequential administration.

22. The method of claim 18 , wherein the pharmaceutical composition is a combination of two dosage forms.

23. The method of claim 18 , wherein the pharmaceutical composition is formulated for simultaneous, separate, or sequential administration.