Abstract 3515: Combined effects of leptomycin B and doxorubicin on lung cancer

Abstract

Abstract To develop novel molecularly targeted therapy has become an important focus of research efforts in lung cancer treatment. Our previous study has shown leptomycin B (LMB), by blocking chromosome maintenance region 1 (CRM1), significantly inhibits cell proliferation in lung cancer cells in a p53-dependent manner. These results suggest the potential use of LMB as a new therapeutic regimen for lung cancer treatment. On the other hand, doxorubicin (DOX) is one of the most effective anticancer agents, which induces p53 activation and nuclear accumulation. The objective of this study is to determine the combinative cytotoxic and molecular effects of LMB and DOX on lung adenocarcinoma cell line, A549. Cells were treated with DOX alone, pre-treatment of DOX/LMB and subsequent treatment of LMB/DOX, or DOX and LMB simultaneously. Cell viability was measured by the MTT assay. The inhibitory effects of DOX on A549 were dose and time-dependent (P<0.001). The 50% inhibitory concentrations (IC50s) of DOX at 24, 48, and 72 h were 60.0, 2.2, and 1.7 µM, respectively. The pre-treatment of 0.5 µM DOX for 24 h significantly improved the cytotoxic effects of LMB on A549 cells at 48 h (P<0.05). The resulting IC50 of LMB was decreased more than 2 fold after pre-treatment of DOX (4.4 nM) as compared to that of LMB alone (10.6 nM). However, the pre-treatment of LMB and the simultaneous treatment of DOX and LMB did not change the cytotoxic effects of either treatment of LMB or DOX. p21 and survivin are well-known p53 downstream genes that play important roles in cell cycle arrest and/or apoptosis. The protein expression levels of these two genes were further analyzed by western blots. Our results showed that the protein expression level of p21 was significantly increased while the protein expression level of survivin was significantly decreased in A549 cells treated with either pre-treatment of DOX and LMB or LMB alone in comparison with those of controls. Furthermore, these changes were more pronounced in pre-treatment of DOX and LMB group as compared to those of LMB alone group. Taken together, our data suggest that the combined therapy using an initial DOX treatment (through activating p53) and subsequent LMB treatment (through blocking the CRM1 function to accumulate activated p53 in the cellular nucleus), that lead to the activation of p53 downstream transcripted genes for cell cycle arrest and apoptosis, might be more effective as a new therapeutic strategy for lung cancer treatment. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3515. doi:10.1158/1538-7445.AM2011-3515