Abstract A64: NFκB-IκBα Interaction: A Mechanism of Resistance to Cisplatin in Non Small Cell Lung Cancer (NSCLC)

Abstract

Abstract Introduction: The purpose of this study was to investigate the role of the PI3K-NFκB pathway in resistance to cisplatin in Non-small cell lung cancer (NSCLC). This form of malignancy is the leading cause of cancer morbidity and mortality in the western world with a poor overall 5 year survival of <15%. The most effective systemic chemotherapy for NSCLC is cisplatin-based combination treatment. However, chemoresistance is a major therapeutic problem and understanding the mechanisms involved is critical to the development of new therapeutic intervention strategies. The PI3K/AKT/mTOR pathway signals through NFκB and plays an important role in NSCLC, representing a novel therapeutic target for overcoming cisplatin resistance. Methods: A panel of cisplatin resistant NSCLC cell lines (H460, SKMES1, A549) were developed in our laboratory. H460 parent & resistant cell lines were screened for changes in mRNA expression using the PI3K Profiler array (SABiosciences). Changes in gene expression were validated by QPCR and protein expression by Western blot and HCA. IκBα exons 3–5 were screened for mutations by sequencing. DHMEQ is an inhibitor of NFκB translocation. The effects of DHMEQ on NFκB translocation as well as on cell apoptosis and proliferation were assessed by HCA and BrdU assays. Results: An 11.99 fold increase in IκBα mRNA expression was identified in the cisplatin resistant H460 cells compared to parent cells. QPCR, Western blot and HCA confirmed this overexpression of IκBα. No mutations were identified in exons 3-5 of the IκBα gene. Inhibition of NFκB by DHMEQ led to significantly increased apoptosis and significantly decreased proliferation in cisplatin resistant cells versus parent cells. Conclusions: The transcription factor NFκB is involved in cell survival and regulates the transcription of its own inhibitor, IκBα. Both IκBα and NFκB were found to be upregulated in cisplatin resistant cells compared to cisplatin sensitive cells. Inhibiton of NFκB by the inhibitor DHMEQ succeeded in reducing resistant cell survival and proliferation. NFκB inhibition could represent a novel therapeutic strategy to overcome NSCLC resistance to cisplatin.