Abstract 4643: EZH2 promote a malignant phenotype in lung adenocarcinoma and VEGF/VEGFR2 pathways mediates regulation of EZH2 through E2F3/HIF-1α and downregulation of miR-101.
Authors: Riquelme Erick M. , Berhens Carmen , Suraokar Milind , Wistuba Ignacio I. 
Published: August 2014

Background. EZH2 overexpression has been described in a wide variety of tumors, including lung cancer. EZH2 has been implicated in neoplastic transformation, tumor progression and activation of angiogenesis. The mechanisms associated with the regulation of EZH2 expression in lung cancer cells are mostly unknown. In this study, we investigated the role of EZH2 in cell proliferation/migration and response to chemotherapy in lung adenocarcinoma (LADCa) cell lines. Moreover, we studied the mechanisms of EZH2 regulation associated to the VEGF/VEGFR2 pathway expression.

Methods. LADCa cell lines were inhibited pharmacologically with different doses of DZNep (0, 2.5 and 5μM) and by knockdown of EZH2 by siRNA. EZH2, H3K27me3 and PARP-C expressions were determined by Western-blots (WB). Cisplatin and carboplatin sensitivity (IC50) and proliferation were determined by MTS assay. Cell migration was measured using Boyden chamber assay. After stimulation of cell lines with VEGF-A, EZH2, VEGFR-2, E2F3 and HIF-1α expression were determined using WBs, and EZH2 and miR-101 expressions were determined by quantitative PCR. To study the role of VEGFR-2 and HIF-1α in the regulation of EZH2, we examined the effect of knockdown VEGFR-2 and HIF-1α by siRNA.

Results. We found that inhibition with DZNep and knockdown by siRNA decreased the expression of EZH2, reduced H3K27me3 level, and increased PARP-C levels in LADCa cell lines. Treatment with DZNep and knockdown of EZH2 significantly increased sensitivity to cisplatin and carboplatin (p&lt;0.05) by MTS assay of LADCa cell lines. Knockdown of EZH2 reduced significantly cell proliferation and migration of LADCa cell lines (p&lt;0.05). VEGF stimulation induced expression of EZH2 and H3K27me3 levels. Concomitantly, we found that stimulation with VEGF induced expression of E2F3 and HIF-1α, and downregulation of miR-101. This phenomenon was observed only in LADCa cell lines expressing VEGFR-2, and not in cell lines with low or lack of expression of VEGFR-2. The increased expression of EZH2, E2F3 and HIF-1α, and the down-regulation of miR-101 in response to VEGF, were reduced by knocking down VEGFR-2 and to a lesser degree by knocking down HIF-1α in LADCa.

Conclusion. Our in vitro findings suggest that EZH2 overexpression may promote a more malignant phenotype of lung adenocarcinoma. The pharmacologic inhibition with DZNep and knockdown of EZH2 by siRNA increased sensitivity of LADCa cell lines to cisplatin and carboplatin, and reduced cell migration capabilities. Our results suggest that VEGF/VEGFR-2 axis plays a role in the regulation of EZH2 through E2F3/HIF-1α and miR-101 regulations. EZH2 is a potential therapeutic target in lung cancer that regulates the epigenome to overcome drug resistance. (Supported in part by grants DoD PROSPECT W81XWH-07-1-0306, NCI/UT Lung SPORE 5P50CA70907-11, and Becas Chile)

Citation Format: Erick M. Riquelme, Carmen Berhens, Milind Suraokar, Ignacio I. Wistuba. EZH2 promote a malignant phenotype in lung adenocarcinoma and VEGF/VEGFR2 pathways mediates regulation of EZH2 through E2F3/HIF-1α and downregulation of miR-101. [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 4643. doi:10.1158/1538-7445.AM2013-4643