AKT3 promotes prostate cancer proliferation cells through regulation of Akt, B-Raf, and TSC1/TSC2.

Hui-Ping Lin,Jun-Yang Liou,Ying-Yu Kuo,Wun-Shaing Wayne Chang,Chieh Huo,John Wang,Hsing-Jien Kung,Chih-Pin Chuu,Chih-Ting Wang,Jen-Chih Tseng,Chung-Ho Chang,Yee-Jee Jan,Shyh-Chang Chen,Ching-Yu Lin,Shih Sheng Jiang,Tzu-Min Chan

doi:10.18632/oncotarget.4553

Abstract

The qRT-PCR analysis of 139 clinical samples and analysis of 150 on-line database clinical samples indicated that AKT3 mRNA expression level was elevated in primary prostate tumors. Immunohistochemical staining of 65 clinical samples revealed that AKT3 protein expression was higher in prostate tumors of stage I, II, III as compared to nearby normal tissues. Plasmid overexpression of AKT3 promoted cell proliferation of LNCaP, PC-3, DU-145, and CA-HPV-10 human prostate cancer (PCa) cells, while knockdown of AKT3 by siRNA reduced cell proliferation. Overexpression of AKT3 increased the protein expression of total AKT, phospho-AKT S473, phospho-AKT T308, B-Raf, c-Myc, Skp2, cyclin E, GSK3β, phospho-GSK3β S9, phospho-mTOR S2448, and phospho-p70S6K T421/S424, but decreased TSC1 (tuberous sclerosis 1) and TSC2 (tuberous Sclerosis Complex 2) proteins in PC-3 PCa cells. Overexpression of AKT3 also increased protein abundance of phospho-AKT S473, phospho-AKT T308, and B-Raf but decreased expression of TSC1 and TSC2 proteins in LNCaP, DU-145, and CA-HPV-10 PCa cells. Oncomine datasets analysis suggested that AKT3 mRNA level was positively correlated to BRAF. Knockdown of AKT3 in DU-145 cells with siRNA increased the sensitivity of DU-145 cells to B-Raf inhibitor treatment. Knockdown of TSC1 or TSC2 promoted the proliferation of PCa cells. Our observations implied that AKT3 may be a potential therapeutic target for PCa treatment.

Highlights

Prostate cancer (PCa) is one of the most common non-cutaneous carcinoma of men in Western countries, especially in United States
We demonstrated that AKT3 mRNA and protein expression was elevated in primary prostate tumors as compared to normal prostate www.impactjournals.com/oncotarget tissues
We discovered that the elevation of AKT3 promoted the proliferation of different prostate cancer cell lines via induction of AKT phosphorylation and B-Raf as well as the reduction of TSC1 and TSC2

Summary

Introduction

Prostate cancer (PCa) is one of the most common non-cutaneous carcinoma of men in Western countries, especially in United States. PTEN is a negative regulator for phosphoinositide 3-kinase (PI3K)-AKT signaling pathway [1]. Deletion of PTEN was observed in 40–70% of PCA patients, resulting in upregulation of PI3K-AKT signaling. PI3K-AKT signaling plays an important role in the survival of PCa cells [2,3,4]. AKT is a serine/threonine protein kinase regulating a variety of cellular responses. There are two phosphorylation sites on all AKT isoforms, the threonine 308 and serine 473 These two phosphorylation sites regulate the activity of AKT [9, 10]. The molecular mechanisms how AKT1 and AKT2 regulate proliferation and survival or prostate cancer cells has been extensively studied. The clinical significance of AKT3 is not clear and how AKT3 may promote prostate cancer cell proliferation is not understood

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Results

Conclusion