Abstract 3938: Altered nucleotide excision repair gene expression after cisplatin treatment in melanoma

Abstract

Abstract Melanoma incidence rates in Australia are the highest in the world. Two of the hallmark features of melanoma are the development of disease as a result of chronic repeated ultraviolet (UV) radiation exposure and the limited efficacy of cisplatin in treatment. These features have one commonality; both result in large helix distorting DNA damage that is recognised and repaired by the DNA repair system, nucleotide excision repair (NER). The aim of this study was to examine the expression of NER gene transcripts in melanoma cell lines treated with cisplatin. One melanocyte, three primary melanoma (MM200, IgR3, Me4405) and two metastatic melanoma (Mel-RM and Sk-Mel-28) cell lines were used for this study. The cells were treated with cisplatin (10μg/mL) and RNA was harvested at 0, 6 and 24 hours after treatment. Thirteen NER gene transcripts were measured by semi-quantitative real-time PCR. The relative expression of each gene was calculated and t-tests were used to identify significantly altered expression in melanoma compared to melanocytes and between timepoints. The genes involved in the global genome repair (GGR) DNA damage recognition pathway; XPC, DDB1 and DDB2 (XPE) showed significantly decreased relative expression (RE) in the melanomas compared to the melanocytes, 24 hours after cisplatin treatment. In contrast, the genes involved in the transcription coupled repair (TCR) DNA damage recognition pathway, ERCC8 (CSA) and ERCC6 (CSB) showed low RE in all cell lines at all time points. Furthermore, the genes involved in the convergent NER pathway revealed no significant change in RE 24 hours after cisplatin treatment in the melanomas, however, an increase in RE was seen in the melanocytes. Overall, the basal expression levels of all genes investigated were greater in the melanoma cell lines compared to the melanocytes. The GGR DNA damage recognition arm of the NER pathway is essential to maintain genomic stability through the identification of helix distorting DNA adducts arising from UV radiation and genotoxic chemicals. The findings from this study revealed reduced GGR transcript levels 24 hours after cisplatin treatment. This finding may be the first step towards identifying the biological mechanisms underlying the limited efficacy of cisplatin in melanoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3938.