P2.01-092 PRMT5 is a Poor Prognostic Marker for NSCLC and Inhibition of PRMT5 Results in Increased Lung Cancer Sensitivity to Cisplatin and Radiotherapy

Abstract

Protein arginine methyltransferase 5 (PRMT5), a member of the protein arginine methyltransferase family, has important regulatory function in many cellular processes through epigenetic control of target gene expression. Because of its overexpression in a number of human cancers and its essential role in cell proliferation, transformation and cell cycle progression, PRMT5 has been recently proposed to function as an oncoprotein in cancer cells. In this study, we explore prognostic and predictive value of PRMT5 expression in lung cancer. Impact of PRMT5 inhibition in the setting of radiation therapy and platin-based chemotherapy was investigated. PRMT5 expression levels in lung tumors as well as their paired normal tissue obtained from TCGA public databases were compared. The impact of PRMT5 expression on lung cancer patient survival was investigated by using “Director’s challenge Consortium for the Molecular Classification of Lung Adenocarcoma” and JBR10 datasets. SiRNA designed to target PRMT5 was used to transiently knockdown (KD) PRMT5 expression in several lung cancer cell lines. Clonogenic survival assays of lung cancer cell lines with increasing doses of cisplatin or radiation were performed in cells with normal endogenous PRMT5 expression or in cells after siRNA knockdown. Impact of PRMT5 knockdown in cell cycle, apoptosis, DNA damage response was investigated through cell cycle analysis, Annexin/PI flow cytometry, ɣH2A foci measurements in lung cancer cells with normal or reduced PRMT5 expression. PRMT5 expression is significant higher in lung tumors compared to parired normal tissue in TCGA datasets (LUAD and LUSC) with p value ≤0.0001. Patients with high PRMT5 expression portend lower overall survival at 3 years (p=0.02) from director’s challenge lung cancer study. Patients with low PRMT5 expression had significantly better DFS at 5 years (p=0.3) if they received cisplatin while patients with high PRMT5 expression did not benefit from cisplatin treatment (p=0.7). In several lung cancer cell lines, we observed >90% PRMT5 KD in transiently transfected cells at 48 h and 72 h post transfection as verified by western blot analysis. This inhibition of PRMT5 activity achieved by transient KD lead to a significant decrease in colony survival after radiation and cisplatin. There is an increase of cell population in G1 arrest in PRMT5 transient KD cells. High PRMT5 expression is associated with worse survival in lung cancer patients. Inhibition of PRMT5 in lung cancer cells results in sensitization to cisplatin and radiotherapy,