Abstract 1714: EZH2Hig h and miR-101Lo w expressions are associated with chemoresistance and shorter survival in patients with lung adenocarcinoma who received adjuvant chemotherapy

Abstract

Abstract Background. EZH2 (a histone methyltransferase and part of the polycomb repressive complex-2) has been implicated in neoplastic transformation, tumor progression, and resistance to chemotherapy. Though EZH2 overexpression has been described in non-small cell lung cancer (NSCLC), there have been no functional studies reported. Recently, it has been demonstrated that miR-101 negatively regulates the expression of EZH2. In this study, we investigated the effect of EZH2 and miR-101 expression levels on the outcome of lung adenocarcinoma patients treated with surgery and adjuvant chemotherapy, and analyzed in vitro mechanisms associated with the role in chemoresistance and cell migration of lung adenocarcinoma. Methods. We analyzed EZH2 and miR-101 expression in RNA extracted from 151 lung adenocarcinoma tumors obtained from patients treated with surgery with (n=57) or without (n=94) platinum adjuvant therapy, and compared those data with patients’ overall survival (median follow-up 5.6 years). EZH2 and miR-101 expression levels were tested using Illumina mRNA arrays W6-6 V.3 and Agilent V3 human microRNA, respectively. We knockdown EZH2 expression in adenocarcinoma cell lines using small interfering RNA (siRNA). Cisplatin sensitivity (IC50) was determined by MTS assay. Cell migration was measured using Boyden chamber. Results. We found that, high EZH2 expression (p=0.007) and low miR101 (p=0.01) expression were significantly associated with worse overall survival in lung adenocarcinoma patients who received platinum adjuvant therapy, but not in patients who did not receive such therapy. Similar results (p=0.008) were observed when combined EZH2High/miR-101Low expression was examined. From a panel of 21 adenocarcinoma cell lines with known EZH2 gene/protein expression, we selected 4 cell lines: 2 with high EZH2 (H1993 and HCC1171), and 2 with low EZH2 (HCC461 and HCC193) expression. Knockdown of EZH2 using siRNA reduced cell migration of H1993 and HCC1171 cells (3.7-fold decrease and 1.7-fold, respectively, p<0.05), but not of HCC193 and HCC461 cells. Knockdown of EZH2 significantly decreased (p<0.05) the viability (by MTS assay) of cell lines H1993 and HCC1171 when treated with cisplatin, but not of HCC193 and HCC461 cells. Conclusion. Our in vitro findings suggest that EZH2 overexpression may promote a more malignant phenotype of lung adenocarcinoma, including increased chemoresistance and cell migration capabilities. Expression of EZH2 and miR-101 may represent a predictive marker of worse outcome in lung adenocarcinoma patients treated with surgery and adjuvant platinum chemotherapy. EZH2 is a potential target that regulates the epigenome to overcome drug resistance in lung cancer (Supported in part by grants DoD PROSPECT W81XWH-07-1-0306 and NCI/UT Lung SPORE 5P50CA70907-11, ER, Becas Chile program) 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 1714. doi:1538-7445.AM2012-1714