Abstract 4737: New platinum (Pt)-based anticancer agents, bearing a PtN2SO coordination core, for treating advanced melanoma

Abstract

Abstract The aim of this project is to demonstrate the potential utility of a new series of platinum (Pt) compounds having a PtN2SO coordination core in treating advanced melanoma. There is currently an unsatisfied medical need for a more effective treatment of advanced melanoma, which is notorious for its prominent resistance to conventional chemotherapeutic drugs due to elevated DNA repair capacity and dysregulation of cancer apoptotic pathways. Platinum (Pt)-based anticancer drugs, exemplified by cisplatin, are key component in combination chemotherapy. They bind to DNA and form mainly the DNA-Pt bifunctional crosslink, subsequently leading to apoptosis to mediate cell death. A series of new Pt(II) compounds possessing a bidentate ligand modified from oxaliplatin has been synthesized, with one of the oxygen ligating atom substituted for a sulfur atom (resulting in a PtN2SO coordination core structure). This novel design is to minimize competition from protein and other bionucleophiles for the Pt drug but maximize drug-DNA interaction. We hypothesize that the unique features of the new PtN2SO compounds may make them good candidates for treating advanced melanoma by (i) overcoming DNA repair-mediated drug resistance; and (ii) generating excess reactive oxygen species (ROS) to selectively trigger apoptosis in melanoma cells. The new compounds were found to be more cytotoxic than cisplatin in a panel of human and mouse melanoma cell lines. Importantly, the new compounds were also found to be minimally affected by Pt resistance, which is presumably caused by the formation of unique DNA-Pt monoadduct and reduced DNA repair. DNA-platination study in melanoma cell lines revealed that the new PtN2SO compounds are able to form more DNA-Pt adducts and there was less repair than treatment with cisplatin. The new compounds were also found to cause a greater induction of the MAPKs (p38, JNK and ERK) than cisplatin to mediate apoptosis. On the other hand, at equipotent concentration, some of the new Pt compounds were found to generate more ROS than cisplatin as indicated by a general fluorescent dye-based oxidative stress indicator. Interestingly, the cytotoxicity of the new compounds were blocked to a greater extent than cisplatin by ROS scavengers, suggesting a more prominent role played by ROS in mediating the cytotoxicity of the new compounds. Our study thus advocates further investigation of the new PtN2SO compounds in treating advanced melanoma. Citation Format: Kenneth K.W. To, Peace Chong, Steve C.F. Au-Yeung. New platinum (Pt)-based anticancer agents, bearing a PtN2SO coordination core, for treating advanced melanoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4737.