Abstract 2332: Oncogenic mutant KRAS modulates EZH2 expression through MEK-ERK signaling by remodeling gene expression in NSCLC

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Abstract: Background. EZH2 overexpression occurs in lung cancer and is associated with a poor outcome. The mechanisms driving EZH2 expression in lung cancer are not fully understood. In this study, we investigated whether pharmacological disruption of signaling MEK-ERK pathway would affect EZH2 expression in a panel of NSCLC cell lines with and without KRAS mutation. Moreover, we analyzed the transcriptome expression following knockdown of EZH2 expression in NSCLC cell lines with different types of KRAS mutations. Methods. NSCLC cell lines were treated with different doses of MEK inhibitor AZD6244 (0, 0.5 and 1μM) and the expressions of EZH2, MEK and MAPK were determined by Western-blots. Cell lines were transfected with gene-specific EZH2 siRNA and control siRNA. Gene expression profiling was performed using the Illumina Human HT-12 v 4.0 platform. Functional pathway analysis was conducted using the software Ingenuity Pathways Analysis. Result. We found that pharmacological disruption of signaling MEK-ERK pathways with AZD6244 decreases the expression of MAPK p44/42 and phospho-MAPK p44/42 in all NSCLC cell lines analyzed wild-type and of KRAS mutant status. However, after AZD6244 treatment, EZH2 expression in NSCLC cell lines varied according to the KRAS mutation status: strong reduction only in NSCLC cell lines harboring GtoC mutation, a partial reduction in cells with GtoS and GtoR mutation, and no change in cell lines with GtoD or GtoV mutation and with wild-type KRAS. The gene expression analysis revealed that 3,235 genes were similarly regulated for mutant KRAS GtoC, GtoD and GtoV in NSCLC following EZH2 knockdown compared with KRAS wild-type (P < 0.05). Functional pathways analysis showed that EZH2 knockdown modulated differentially pathways commonly activated in cancer as growth factor signaling, molecular mechanism of cancer and cellular growth, proliferation and development, between cell lines that harbor mutant KRAS GtoC, GtoD or GtoV compared with KRAS wild-type. Conclusion. Our findings suggest that oncogenic mutant KRAS GtoC, GtoS and GtoR modulate EZH2 expression through MEK-ERK signaling contributing to changes of the expression of genes frequently altered in cancer (Grant support: 5 R01 CA155196 and P50CA70907) Citation Format: Erick M. Riquelme, Li Shen, Jing Wang, Carmen Behrens, John D. Minna, Ignacio I. Wistuba. Oncogenic mutant KRAS modulates EZH2 expression through MEK-ERK signaling by remodeling gene expression in NSCLC. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2332. doi:10.1158/1538-7445.AM2014-2332