Abstract 2484: Gene expression profiling: p53 signaling pathway dependent anticancer effects of Leptomycin B on lung cancer

Proceedings: AACR 101st Annual Meeting 2010‐‐ Apr 17‐21, 2010; Washington, DC Leptomycin B (LMB), a metabolite of Streptomyces, is a specific and potent inhibitor of chromosome maintenance region 1 (CRM1), which mediates the nuclear export of p53. LMB and/or its derivatives are being considered as a novel class of cancer therapeutics. Our previous data showed that cell growth inhibitory effects of LMB were more pronounced in human lung cancer cell lines than the normal human bronchial epithelial cell line. In addition, the inhibitory effects varied among lung cancer cell lines with different p53 status. For instance, the inhibitory effect was more remarkable in p53 null/mutated cell lines like NCI-H358 than p53 wild-type cell lines like A549. The objectives of the present study were to evaluate the mechanism for p53-mediated tumor inhibitory effect of LMB and to identify the mechanistic difference in tumor inhibitory effect of LMB between lung cancer cells with p53 wild type (A549) and p53-null (NCI-H358) by profiling gene expression in human p53 signaling pathway. Cells were treated with 20 nM LMB or 0.1% ethanol vehicle control for 24 h. p53 and p21 protein expression levels were evaluated by Western blots. RNA was extracted and used to perform the RT2 Profiler™ PCR array for analyzing gene expression of 84 genes involved in human p53 signaling pathway. Treatment of cancer cells with LMB led to increased p53 protein expression in A549 but not NCI-H358. LMB treatment significantly altered p53-dependent transcription for 23 genes predominantly involved in apoptosis and cell cycle/proliferation in A549, including 13 down-regulated genes, such as CDC2, CDC25C, PRC1, and survivin, and 10 up-regulated genes, such as BTG2, MDM2, p21, and SESN1. These results suggested that the cell growth inhibition effects of LMB on A549 could be closely related to the CRM1-dependent p53 nuclear accumulation to induce cell cycle arrest and/or apoptosis. On the other hand, LMB treatment did not show strong modulating effects on p53-mediated genes in NCI-H358. In comparison to A549, some p53 regulated genes, such as BAX, CCNE2, HK2, MDM2, p21, and SESN1, had significantly different expression in NCI-H358. The more pronounced cell growth inhibitory effects of LMB on NCI-H358 as compared to A549 could result from signal transduction pathways other than p53. In addition, the p21 gene expression data were further confirmed by protein expression analyses, which showed selectively significant up-regulation in A549 while no change in NCI-H358 after LMB treatment. Collectively, these findings suggest the involvement of p53 in cellular response of A549 to LMB but not NCI-H358. The abilities of LMB to induce p53 protein expression and modulate its responsive genes that lead to cell growth inhibition and/or apoptosis may be useful in lung cancer treatment. The different cellular responses of cells with distinct p53 status suggest the importance of individualized therapy for lung cancer. 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 2484.