Bloom Syndrome Protein Activates AKT and PRAS40 in Prostate Cancer Cells

Kun Chen,Jiafu Zhao,Houqiang Xu

doi:10.1155/2019/3685817

Abstract

Purpose Prostate cancer (PC) is a common malignant tumor and a leading cause of cancer-related death in men worldwide. In order to design new therapeutic interventions for PC, an understanding of the molecular events underlying PC tumorigenesis is required. Bloom syndrome protein (BLM) is a RecQ-like helicase, which helps maintain genetic stability. BLM dysfunction has been implicated in tumor development, most recently during PC tumorigenesis. However, the molecular basis for BLM-induced PC progression remains poorly characterized. In this study, we investigated whether BLM modulates the phosphorylation of an array of prooncogenic signaling pathways to promote PC progression. Methods We analyzed differentially expressed proteins (DEPs) using iTRAQ technology. Site-directed knockout of BLM in PC-3 prostate cancer cells was performed using CRISPR/Cas9-mediated homologous recombination gene editing to confirm the effects of BLM on DEPs. PathScan® Antibody Array Kits were used to analyze the phosphorylation of nodal proteins in PC tissue. Immunohistochemistry and automated western blot (WES) analyses were used to validate these findings. Results We found that silencing BLM in PC-3 cells significantly reduced their proliferative capacity. In addition, BLM downregulation significantly reduced levels of phosphorylated protein kinase B (AKT (Ser473)) and proline-rich AKT substrate of 40 kDa (PRAS40 (Thr246)), and this was accompanied by enhanced ROS (reactive oxygen species) levels. In addition, we found that AKT and PRAS40 inhibition reduced BLM, increased ROS levels, and induced PC cell apoptosis. Conclusions We demonstrated that BLM activates AKT and PRAS40 to promote PC cell proliferation and survival. We further propose that ROS act in concert with BLM to facilitate PC oncogenesis, potentially via further enhancing AKT signaling and downregulating PTEN expression. Importantly, inhibiting the BLM-AKT-PRAS40 axis induced PC cell apoptosis. Thus, we highlight new avenues for novel anti-PC treatments.

Highlights

Prostate cancer (PC) is a common malignancy of prostate epithelial cells [1]
We found that Bloom syndrome protein (BLM) deletion inhibits PC cell proliferation via downregulating pAKT (Ser473) and pRAS40 (Thr246), which was accompanied by enhanced ROS production
We found that reductions in BLM expression in PC-3 cells were associated with increased ROS production and that these increases occurred in a dose-dependent manner (Figure 7(e))

Summary

Introduction

Prostate cancer (PC) is a common malignancy of prostate epithelial cells [1]. PC is the most common cancer affecting American males, with 221,000 newly diagnosed cases and 27,500 deaths reported in 2015 alone [2]. PC is a complex disease, and these genetic variants interact with environmental factors and dietary habits [5]. Chemotherapy drugs which target signaling pathways with a known association to PC tumor progression, including mTOR, PI3K-Akt, MAPK, AMPK, and p53 signaling, are used to induce PC cancer cell death. This is exemplified by BEZ235, a phosphatidylinositol-3-kinase (PI3K)/mammalian target of rapamycin (mTOR) inhibitor that blocks AKT phosphorylation (Thr308/Ser473) and can prevent breast [6, 7], glioma [8], and non-small-cell lung cancer growth [9, 10]. Combining BEZ235 with abiraterone acetate, which blocks cytochrome P450 17 alpha-hydroxylase

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