Advanced melanoma poses a major therapeutic challenge, and despite the development of recent promising therapeutic agents, resistance to treatment remains a problem. Until recently, despite low response rates, alkylating agents dacarbazine and temozolomide (TMZ) were the standard of care for the treatment of advanced melanoma. The cytotoxic effects of these agents relies upon the formation of alkylated base lesions such as O⁶-methylguanine (O⁶MeG), which is repaired by a protein implicated in TMZ resistance called O⁶-methylguanine-DNA methyltransferase (MGMT). Failure to resolve such alkylated bases results in DNA replication-associated double-strand breaks (DSBs). The type 1 insulin-like growth factor receptor (IGF-1R) mediates a number of characteristics common to cancers, including proliferation and survival, and evidence suggests it may also contribute to resistance to many anticancer agents. The aims of this study were to test whether melanoma cells could be sensitized to TMZ by small molecule IGF1R inhibitors, and to explore the mechanism of any chemosensitization. This study found an association between basal IGF1R phosphorylation and in vitro TMZ resistance in seven MGMT-proficient melanoma cell lines, suggesting that IGF1R activation may be linked with TMZ resistance. Furthermore, IGF1R inhibition caused dose-dependent sensitization of melanoma cells to TMZ, regardless of BRAF mutation status. This reduction in cell survival was not accompanied by an increase in apoptosis, but rather Chk2 activation and an accumulation of cells in the G2/M phase of the cell cycle, suggesting a possible effect of IGF1R inhibition on DNA repair. IGF1R depletion was found to increase MGMT protein levels and activity, but this effect was not seen in IGF1R inhibited cells. In addition, IGF1R inhibition was not epistatic with MGMT inhibition, and IGF1R inhibition reduced survival of TMZ treated MGMT-null cells. This suggested that TMZ sensitization by IGF1R inhibition was independent of MGMT. IGF1R inhibition did however cause an increase in the accumulation of TMZ-induced RPA foci, and delay in resolution of RAD51 foci. Together with the finding that IGF1R inhibition reduced survival in PARP inhibited melanoma cells, these results suggested that IGF1R inhibition influenced DSB repair by homologous recombination. Finally, the combination of IGF1R inhibition with TMZ was tested in a mouse model and was found to be tolerable. TMZ or IGF-1R inhibitor alone caused minor reduction in melanoma xenograft growth rates (rate reduction by 13% and 25% respectively), while combination treatment caused supra-additive growth delay (72%) that was significantly different from other treatment groups (p<0.05). The findings of this study suggest IGF1R inhibition as a possible option in overcoming alkylating drug resistance in melanoma.

No / Novel 1- and 1,4-substituted chloroethylaminoanthraquinones with DNA binding and alkylating properties along with their respective hydroxyethylaminoanthraquinone intermediates were synthesized. Selected chloroethylaminoanthraquinones were shown to cross-link DNA and alkylate guanines (at low nM concentration) with a preference for reaction sites containing 5'-PyG. A compound (Alchemix) with the bis-chloroethyl functionality confined to one side chain alkylated but did not cross-link DNA. All the 1,4-disubstituted chloroethylaminoanthraquinones were potently cytotoxic (nM IC50s) against cisplatin-resistant ovarian cancer cell lines.

No / A novel series of 1,4-disubstituted aminoanthraquinones were prepared by ipso-displacement of 1,4-difluoro-5,8-dihydroxyanthraquinones by hydroxylated piperidinyl- or pyrrolidinylalkyl-amino side chains. One aminoanthraquinone (13) was further derivatized to a chloropropyl-amino analogue by treatment with triphenylphosphine-carbon tetrachloride. The compounds were evaluated in the A2780 ovarian cancer cell line and its cisplatin-resistant variants (A2780/ cp70 and A2780/MCP1). The novel anthraquinones were shown to possess up to 5-fold increased potency against the cisplatin-resistant cells compared to the wild-type cells. Growth curve analysis of the hydroxyethylaminoanthraquinone 8 in the osteosarcoma cell line U-2 OS showed that the cell cycle is not frozen, rather there is a late cell cycle arrest consistent with the action of a DNA-damaging topoisomerase II inhibitor. Accumulative apoptotic events, using time lapse photography, indicate that 8 is capable of fully engaging cell cycle arrest pathways in G2 in the absence of early apoptotic commitment. 8 and its chloropropyl analogue 13 retained significant activity against human A2780/cp70 xenografted tumors in mice.