Abstract 4678: Silencing of TIMELESS induces growth suppression, apoptosis and enhanced cytotoxicity of cisplatin in H157 lung cancer cells

Background: TIMELSS (TIM) is a circadian clock gene in Drosophila, but its role in mammals in circadian clock systems is not well-understood. Mammalian TIM is involved in Chk1 activation and intra-S checkpoint through genotoxic stress (Unsal-Kaçmaz et.al, Molecular and Cellular Biology, 27(8), 3131-3142(2007)). TIM is also associated with doxorubicin-induced G2/M cell cycle arrest and TIM depletion sensitizes HCT116 colon cancer cells to doxorubicin-induced cytotoxicity (Yang et.al, Journal of Biological Chemistry, 285(5), 3030-3034(2010)). Mutations in TIM in breast cancer were reported (Sjöblom et.al, Science, 314(5797), 268-274(2006)). Methods and Findings: The mRNA expression levels of TIM in 17 non-small cell lung cancer (NSCLC) cell lines and 4 small cell lung cancer (SCLC) cell lines were analyzed by reverse transcriptase PCR. HCC44, H460, H157 (NSCLC), H146 and H740 (SCLC) expressed higher levels of TIM than cdk4/hTERT-immortalized normal human bronchial epithelial cell line HBEC4. Sequencing analysis of TIM revealed no mutation in 21 lung cancer cell lines. RNAi-mediated knockdown of TIM in H157 suppressed proliferation in WST-1 assay and clonogenic growth in liquid colony formation assay. Western blot analysis revealed increased level of cleaved caspase-3 after TIM-knockdown, suggesting that apoptosis was involved in growth inhibition. TIM-knockdown induced increased sensitivity to cisplatin in drug sensitivity assay using WST-1 (IC50 were 1.70μM and 0.91μM in TIM-knocked down H157 compared to 4.87μM in control). Conclusions: TIM inhibition causes growth suppression, apoptosis and enhanced cytotoxicity of cisplatin. Our results suggest that TIM inhibition has a potential utility in the treatment of lung cancer. 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 4678. doi:1538-7445.AM2012-4678