Abstract 1120: Chronopharmacology of cisplatin: role of the circadian rhythm in modulating cisplatin-induced toxicity in melanoma mouse model

Abstract

Abstract Purpose: The goal of this research is to highlight novel and divergent molecular mechanisms of the circadian system in modulating the response of cisplatin therapy against melanoma tumors. Cisplatin is one of the most commonly used chemotherapeutic drugs in treating a variety of tumors including cancers of ovaries, testis, lungs, blood and solid tumors of the head and neck, and is more recently under clinical trials for potential application in melanoma tumors. However, the major limitation of cisplatin as a chemotherapeutic drug is its tumor resistance and nephrotoxicity. Hence, improving the effectiveness and reducing the toxicities associated with cisplatin therapy are desirable outcomes. Studies on human models have shown decreased renal and blood toxicity by time-of-the-day. Consequently, our project seeks to study the chronopharmacological effects and understand the mechanisms that have been successfully demonstrated in human models. We hypothesize a mechanistic, circadian rhythm-based cause for these outcomes. Experimental Design: Studies were done on B16F10 melanoma mouse models of wild-type and circadian disrupted Per1/2 -/- animals treated with 3 doses of 5 mg/kg cisplatin in the morning (7 AM) and evening (5 PM). Animal weights and tumor sizes were measured regularly post-treatment. Upon sacrifice, tissues (skin, kidney, and tumor) were harvested and analyzed for cisplatin-induced toxicities and DNA damage responses using H & E staining, western blot, and KIM-1 and immuno-slot blot assays. Results: Weight measurements show a clock-regulated response to cisplatin toxicity. AM-treated wild-type animals showed significant weight loss compared to PM-treated wild-type animals. This treatment time differential is lost in the Per1/2 -/-. On a molecular level, kidney tissue DNA samples showed clock-controlled cisplatin-DNA repair activity in wild-type animals compared to Per1/2 -/-. These initial findings strongly suggest that nephrotoxicity and DNA damage response function might be regulated by the circadian rhythm. Conclusions: These findings indicate a possible mechanism for the chronopharmacology of cisplatin in minimizing the toxicity associated with it and reveal a target for future study of additional mechanistic causes of circadian dosing changes in cisplatin and other genotoxic stress-mediated anti-cancer agents. Citation Format: Panshak Dakup, Kenneth Porter, Rajendra Gajula, Shobhan Gaddameedhi. Chronopharmacology of cisplatin: role of the circadian rhythm in modulating cisplatin-induced toxicity in melanoma mouse model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1120. doi:10.1158/1538-7445.AM2017-1120