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

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, GSK3?, phospho-GSK3? 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.

SUBMITTER: Lin HP

PROVIDER: S-EPMC4694976 | biostudies-literature | 2015 Sep

REPOSITORIES: biostudies-literature

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

Lin Hui-Ping HP Lin Ching-Yu CY Huo Chieh C Jan Yee-Jee YJ Tseng Jen-Chih JC Jiang Shih Sheng SS Kuo Ying-Yu YY Chen Shyh-Chang SC Wang Chih-Ting CT Chan Tzu-Min TM Liou Jun-Yang JY Wang John J Chang Wun-Shaing Wayne WS Chang Chung-Ho CH Kung Hsing-Jien HJ Chuu Chih-Pin CP

Oncotarget 20150901 29

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 kn ...[more]

PMID: 26318033

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Project description:BACKGROUND:Signal regulatory protein β1 (SIRPB1) is a signal regulatory protein member of the immunoglobulin superfamily and is capable of modulating receptor tyrosine kinase-coupled signaling. Copy number variations at the SIRPB1 locus were previously reported to associate with prostate cancer aggressiveness in patients, however, the role of SIRPB1 in prostate carcinogenesis is unknown. METHODS:Fluorescence in situ hybridization and laser-capture microdissection coupled with quantitative polymerase chain reaction was utilized to determine SIRPB1 gene amplification and messenger RNA expression in prostate cancer specimens. The effect of knockdown of SIRPB1 by RNA interference in PC3 prostate cancer cells on cell growth in colony formation assays and cell mobility in wound-healing, transwell assays, and cell cycle analysis was determined. Overexpression of SIPRB1 in C4-2 prostate cancer cells on cell migration, invasion, colony formation and cell cycle progression and tumor take rate in xenografts was also determined. Western blot assay of potential downstream SIRPB1 pathways was also performed. RESULTS:SIRPB1 gene amplification was detected in up to 37.5% of prostate cancer specimens based on in silico analysis of several publicly available datasets. SIRPB1 gene amplification and overexpression were detected in prostate cancer specimens. The knockdown of SIRPB1 significantly suppressed cell growth in colony formation assays and cell mobility. SIRPB1 knockdown also induced cell cycle arrest during the G0 /G1 phase and enhancement of apoptosis. Conversely, overexpression of SIPRB1 in C4-2 prostate cancer cells significantly enhanced cell migration, invasion, colony formation, and cell cycle progression and increased C4-2 xenograft tumor take rate in nude mice. Finally, this study presented evidence for SIRPB1 regulation of Akt phosphorylation and showed that Akt inhibition could abolish SIRPB1 stimulation of prostate cancer cell proliferation. CONCLUSIONS:These results suggest that SIRPB1 is a potential oncogene capable of activating Akt signaling to stimulate prostate cancer proliferation and could be a biomarker for patients at risk of developing aggressive prostate cancer.

Project description:BackgroundThe signaling pathways imposing hormonal control over adipocyte differentiation are poorly understood. While insulin and Akt signaling have been found previously to be essential for adipogenesis, the relative importance of their many downstream branches have not been defined. One direct substrate that is inhibited by Akt-mediated phosphorylation is the tuberous sclerosis complex 2 (TSC2) protein, which associates with TSC1 and acts as a critical negative regulator of the mammalian target of rapamycin (mTOR) complex 1 (mTORC1). Loss of function of the TSC1-TSC2 complex results in constitutive mTORC1 signaling and, through mTORC1-dependent feedback mechanisms and loss of mTORC2 activity, leads to a concomitant block of Akt signaling to its other downstream targets.Methodology/principal findingsWe find that, despite severe insulin resistance and the absence of Akt signaling, TSC2-deficient mouse embryo fibroblasts and 3T3-L1 pre-adipocytes display enhanced adipocyte differentiation that is dependent on the elevated mTORC1 activity in these cells. Activation of mTORC1 causes a robust increase in the mRNA and protein expression of peroxisome proliferator-activated receptor gamma (PPARgamma), which is the master transcriptional regulator of adipocyte differentiation. In examining the requirements for different Akt-mediated phosphorylation sites on TSC2, we find that only TSC2 mutants lacking all five previously identified Akt sites fully block insulin-stimulated mTORC1 signaling in reconstituted Tsc2 null cells, and this mutant also inhibits adipogenesis. Finally, renal angiomyolipomas from patients with tuberous sclerosis complex contain both adipose and smooth muscle-like components with activated mTORC1 signaling and elevated PPARgamma expression.Conclusions/significanceThis study demonstrates that activation of mTORC1 signaling is a critical step in adipocyte differentiation and identifies TSC2 as a primary target of Akt driving this process. Therefore, the TSC1-TSC2 complex regulates the differentiation of mesenchymal cell lineages, at least in part, through its control of mTORC1 activity and PPARgamma expression.

Project description:Tuberous sclerosis complex (TSC) is an autosomal dominant neurogenetic disorder caused by mutations in one of two genes, TSC1 or TSC2, which encode the proteins hamartin and tuberin, respectively 123. Common features of TSC include intractable epilepsy, mental retardation, and autistic features. TSC is associated with specific brain lesions, including cortical tubers, subependymal nodules and subependymal giant cell astrocytomas. In addition, this disease frequently produces characteristic tumors, termed hamartomas, in the kidneys, heart, skin, retina, and lungs. Disease severity in TSC can be quite variable and is not determined by the primary mutation alone. In fact, there is often considerable variability in phenotype within single families, where all affected individuals carry the same mutation. Factors suspected to influence phenotype in TSC include the specific primary mutation, random occurrence of second-hit somatic mutations, mosaicism, "modifying genes", and environmental factors. In addition to these factors, we hypothesize that differences in mRNA expression from the non-mutated TSC allele, or possibly from the mutated allele, play a part in modifying disease severity. Common genetic variants that regulate mRNA expression have previously been shown to play important roles in human phenotypic variability, including disease susceptibility. A prediction based on this idea is that common regulatory variants that influence disease severity in TSC should be detectable in non-affected individuals.A PCR/primer extension assay was used to measure allele specific expression of TSC1 and TSC2 mRNAs in leukocytes isolated from normal volunteers. This assay can be used to measure "allelic expression imbalance" (AEI) in individuals by making use of heterozygous "marker" single nucleotide polymorphisms (SNPs) located within their mRNA.In this study we show for the first time that TSC1 and TSC2 genes exhibit allele-specific differences in mRNA expression in blood leukocytes isolated from normal individuals.These results support the possibility that allele-specific variation in TSC mRNA expression contributes to the variable severity of symptoms in TSC patients.

Dataset Information

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

Publications

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

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