Abstract 1589: LKB1 overexpression regulates DNA repair pathway and sensitivity to radiation in LKB1 mutant non-small cell lung cancer cell lines .

Abstract

Abstract Background: LKB1 is a serine/threonine kinase which is mutated in 20-30% of non-small cell lung cancers (NSCLC).In general, DNA repair pathway activation leads cellular resistant to DNA damaging agents. The loss of LKB1 leads NSCLC to be more invasive and resistant to DNA damage based therapies. We hypothesize that loss of LKB1 may contribute to DNA damage response. We investigated LKB1- mediated signaling pathways by stably overexpressing LKB1 in its mutated NSCLC cell lines, A549 and H460. Methods: Expression of 139 proteins was analyzed by reverse phase protein array (RPPA) in LKB1 overexpressing cell lines along with the appropriate vector control lines. Differences in protein expression at baseline in clones with LKB1 versus clones with vector control were assessed by unpaired T-test with Welch's correction. Ionizing radiation sensitivity (reproductive cell death) was assessed by clonogenic cell survival assay (CSA). Results: LKB1 overexpression in A549 and H460 showed a significant downregulation of genes involved in DNA damage and repair pathway, such as RAD50 (1.4-fold relative expression, p< 0.05 and 1.5-fold relative expression p<0.02 respectively), XRCC1 (1.2-fold relative expression p<0.005 and 1.1-fold relative expression p<0.05, respectively), and DNA-PKCS (1.2-fold relative expression p≈0.067 and 1.2-fold relative expression p<0.01. Also, CSA showed that A549 with LKB1 overexpression led to enhanced sensitization of cells to radiation (DER = 2) which is in consistent with the downregulation of RAD50, XRCC1 and DNA-PKCS. Furthermore, expression of CHK2 and phosphorylation of CHK1 are downregulated, H460 with LKB1 overexpression showed a significant decreasing of CHK1 phosphorylation level (p<0.05). Conclusion: Our results suggest that LKB1 overexpression modulates DNA repair capacity through downregulation of RAD50, XRCC1, DNA-PKCS, CHK1 and CHK2. LKB1 loss may lead to the resistance to DNA damaging induced cell death. Citation Format: Chao Yang, Uma Giri, Maria Angelica Cortez, Jayanthi Gudikote, YouHong Fan, Lixia Diao, Lauren A. Byers, John V. Heymach. LKB1 overexpression regulates DNA repair pathway and sensitivity to radiation in LKB1 mutant non-small cell lung cancer cell lines . [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1589. doi:10.1158/1538-7445.AM2013-1589