Abstract 3821: Interaction and cross-resistance of cisplatin and pemetrexed in malignant pleural mesothelioma cell lines

Abstract

Abstract Background: Malignant pleural mesothelioma (MPM) is one of the most lethal cancers with a rapidly increasing incidence worldwide. Although cisplatin and pemetrexed are recognized as key drugs, and their combination chemotherapy is a standard therapy for MPM, their drug-to-drug interactions, cross-resistance, and resistance mechanisms are not well understood. Methods: The interaction between cisplatin and pemetrexed was evaluated by colonogenic assays followed by isobologram analysis in 4 human MPM cell lines. The cell lines were exposed to the agents using a stepwise dose-escalation method to establish drug-resistant sublines. Thymidylate synthase (TS) mRNA expression was evaluated by RT-PCR, and gene expression profiles were assessed by cDNA microarray analysis and gene ontology analysis using Ingenuity Pathway Analisis (IPA) in the drug-resistant sublines. Results: Cisplatin and pemetrexed had synergistic effects in 3 cell lines and an additive effect in the fourth cell line. The former 3 cell lines showed similar sensitivity to pemetrexed in the parental cells and their cisplatin-resistant sublines, whereas the fourth cell line exhibited cross-resistance. In contrast, cisplatin had diverse effects on pemetrexed-resistant sublines. High TS expression did not correlate with natural pemetrexed resistance and its elevatedexpression correlated with acquired pemetrexed resistance in 2 sublines. Microarray analysis disclosed that the genes which related to “cellular development”,” small molecule biochemistry,” “cellular movement,” “cell death, and “cellular growth and proliferation” affected drug-resistant mechanisms deeply, and that this tendency was common to cisplatin-resistant sublines and pemetrexed-resistant sublines. Conclusion: Cisplatin and pemetrexed showed synergistic activity and no cross-resistance in 3 of the 4 MPM cell lines, suggesting the clinical relevance of their combination chemotherapy. TS expression did not necessarily correlate with pemetrexed resistance. Multiple mechanisms of molecular and cellular functions may underlie acquired resistance to cisplatin and pemetrexed in MPM. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3821. doi:1538-7445.AM2012-3821