Abstract 4436: Eukaryotic translation initiation factor 4 gamma 1 (EIF4G1) is upregulated modulates prostate cancer growth and proliferation
Authors: Jaiswal Praveen K. , Koul Sweaty , Shanmugam Prakash Srinivasan Timiri , Koul Hari K. 
Published: August 2018

Introduction: cap-dependent translation is necessary due to high protein requirement in cancer cells. An interaction between EIF4E and EIF4G is crucial for the formation of the EIF4F complex and initiation of cap-dependent translation. In the current study, we analyzed Human prostate cancer tissue microarray (TMA) and mRNA expression data in clinical datasets, and prostate tumor tissue from TRAMP (Transgenic Adenocarcinoma of the Mouse Prostate) model. We also assessed the functional role of EIF4G1 in commonly used PCa cell lines.

Methods: Human prostate cancer tissue microarray was used to analyze the EIF4G1 level in patient samples. mRNA expression data for EIF4G1 was analyzed from TCGA and Trento/Cornell/Broad clinical data sets. PCa cells viz. LNCaP, C4-2b, 22Rv1, DU145, PC3 and normal human prostate cell line RWPE-1 were used. For an in-vivo model of PCa, we used TRAMP and wild-type mouse. Loss of function studies was performed by using siRNA/shRNA. Real-time PCR and Western Blot analysis were used to quantitate the relative mRNA and protein levels respectively. Analysis of polysome was performed by sucrose density gradient fractionation. Polysome-to-Monosome (P/M) ratios were determined for global translation activity. Cell cycle, cell proliferation, cell migration and Clonogenic activity were measured by standard methods.

Results: Results from TMA analysis showed that protein levels of EIF4G1 are high in PCa as compared to normal prostate tissue, and there is a graded increase in EIF4G1 as the disease progresses. Results of our analysis of EIF4G1 expression in TCGA database revealed that increased expression of EIF4G1 positively correlated with higher tumor grade and stages (Gleason Score). Available data from Trento/Cornell/Broad clinical dataset revealed that 43% of castration-resistant prostate cancer (CRPC) patients have EIF4G1 mRNA up-regulation. PCa cells express a significantly higher level of EIF4G1 as compared to normal prostate cells. Similarly, prostate tumor tissue from TRAMP tissue showed higher EIF4G1 expression as compared to normal wild-type prostate tissue. Silencing of EIF4G1 causes G0/G1 cell cycle delay and decreases Cyclin D1 and p-Rb levels. There is a shift in polysome (P) to monosome (M) ratio with the siEIF4G1 knockdown in LNCaP and C4-2b. Loss of function studied by knockdown of EIF4G1 showed impaired Clonogenic activity as well as cell proliferation. Real-time PCR data suggests that EIF4G1 knockdown in LNCaP & C4-2b decreases the level of EMT markers such as N-Cadherin, Vimentin & Zeb1 and limits the cell migration in C4-2b cells.

Conclusions: Taken all together, our data indicate that EIF4G1 may function as an oncoprotein and is a novel target for intervention in PCa and CRPC.

Citation Format: Praveen K. Jaiswal, Sweaty Koul, Prakash Srinivasan Timiri Shanmugam, Hari K. Koul. Eukaryotic translation initiation factor 4 gamma 1 (EIF4G1) is upregulated modulates prostate cancer growth and proliferation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4436.