Functional Genetic Variants In The MTORC1 Related Genes Contribute To Prostate Cancer Susceptibility And Clinical Outcomes

Prostate cancer is one of the most common malignancies in man worldwide. The morbidity of prostate cancer in China has increased rapidly during the past several years. The initiation and progression of prostate cancer has been considered a result of the interaction between genetic and environmental contributors. A number of single nucleotide polymorphisms by far have been defined as potential attributorsof prostate cancer; however, few concordant results have been reached because of the relativelysmalleffect size.It was evidently indicated that the PI3K/AKT/mTORsignaling pathway may play an important role in carcinogenesis in some tumor types, correlating with cell growth, proliferation, survival, and migration. The mammalian target of rapamycin complex 1(mTORC1), located in the downstream of the pathway and comprised with Raptor, mLST8, DEPTOR, PRAS40, and mTOR,was reported to be associated with carcinogenesis. In the past several years, reports about the associtions between polymorphisms in genes involved in the PI3K/AKT/mTOR signaling pathway and prostate cancer risk have been observed worldwide;however, no consensus was reached as expected.This is the first study to explore genetic variants in the mTORC1-related genes and their associations with prostate cancer susceptibility and clinical outcomes. We hypothesized that (1) genetic variants (i.e., SNPs) in the mTORC1-related genes are associated with prostate cancer susceptibility individually or jointly and that gene-gene/gene-enviornment interactions play important roles in the etiology; (2) functional genetic variants (i.e., SNPs) modulate prostate cancer susceptibility by certain biological mechanisms; (3) genetic variants (i.e., SNPs) in the mTORC1-related genes are associated with clinical outcomes in prostate cancer patients.Part I Associations between genetic variantsin the mTORC1-relatedgenes and prostate cancer susceptibilityTo explore the associations between genetic variation in the mTORC1-related genes and prostate cancer risk, we performed a large hospital-based case-control study with 1015primary prostate cancer cases and 1093 cancer-free controls. By genotyping the selected 16 candidate SNPs of mTORCl, we found thatthe mTOR-rs2536 [additive:1.34 (1.08-1.66), P=0.008; dominant:1.42 (1.13-1.78), P=0.003], mTOR-rs 1034528 [additive:1.21 (1.03-1.42), P=0.019; dominant:1.29 (1.07-1.55),P=0.007], and mTOR-rs2295080 [additive:0.80 (0.69-0.94), P=0.005; dominant:0.76 (0.64-0.92), P=0.003]was associated with risk of prostate cancer.Additionally, an association between RPTOR-rs 1062935 [additive:1.14 (1.01-1.29), P=0.0341; dominant:1.28 (1.06-1.56), P=0.0127] and prostate cancer risk was observed as well.The analysis of combined genotypes showed thatprostate cancer risk was increased in a dose-response manner with the increasing number of risk genotypes among the mTORC1-related genes. The analysis among the SNPs of mTORfound that the variant haplotypewas associated with a substantially altered risk for prostate cancer, compared with the most commonhaplotype. By using the logistic dominantmodel, we observed that prostate cancer risk was increased in a dose-response manner with the increasing number of risk genotypes ofthe mTOR genes, especially in subgroups of age≤69yrs, BMI≤25kg/m2, ever smoking, Gleason<7(3+4), and stage III+IV.Further multifactor dimensionality reduction (MDR) also showedhigh-order interactions among SNPs in the mTORC1-related genes; for example, the significant interaction effects were found between BMI and mTOR-rs2536 (P=0.0031), BMI and AKT1S1-rs2290774 (P=0.0496) and between DEPTOR-rs4871827 and RPTOR-rs 1062935 (P=0.0224).Taken together, although there were some limitations in the current study, our study provides evidence that SNPs in the mTORCl-related genes individually or jointly contribute to prostatecancer susceptibility in Chinese Han men and that gene-gene/gene-environment interactions may play important roles in prostate carcinogenesis.Part Ⅱ Functional analysis of mTOR 3 untranslated region genetic variants significantly associated with prostate cancer susceptibilityIn this study, we investigated biological effects of the mTOR-rs2536 SNP, located in the 3’untranslated region of mTOR gene,which was found to be significantly associated with prostate cancer risk. By usingthe HapMap genotyping and GENEVA geneexpression databases, we compared levels of mRNA expression by different genotype groups of this SNP and found that the mTORgenotype was associated with levels of mTORmRNA expression with a high level for the CT genotype, compared with the TT genotype. A significantly different expression level was found for the TT genotype between Chinese and Caucasian populations. However, the immunohistochemistry assayfor the protein expression did not confirm thisassociation. However, further in vitrofunctional experiments showed that the relative luciferase activity in the pGL3-promoterwas significantly different by the polymorphic allele rs2536A co-transfected withmiR-767-3p), compared with that in the pGL3promoter with rs2536G (Student’stest, P<0.05), indicating that the mTOR-rs2536SNP may have an impact on the binding site of special miRNA that regulates mTOR exprssion.Taken together, the mTOR-rs2536 SNP may function by affecting the affinity of miR-767-3pbinding to the 3’-UTR of mTOR and regulating the mRNA and protein expression of mTOR, thus contributing to prostate cancer susceptibility.Part Ⅲ Genetic variants in the mTORC1-related genes predict clinical outcomes in prostate cancerTo investigate effects of SNPs in the mTORCl-related genes on prognosis of prostate cancer, we recruited 423prostate cancer patients from the Part Ⅰ case set, whohadadequate follow-up information. We mainly analyzedfour potential functional SNPs, mTOR-rs2536,-rs103452,-rs2295080, and RPTOR-rs 1062935 and found that significant associations between SNPs and biorecurrence were observed under significancelevels of 0.1; for example, patients with mTOR-rs2536 GG/AG genotypes showeda higher biorecurrence rate inthe short-term follow-up, compared with patients with the AA genotype (P=0.056); patients with mTOR-rs 1062935 CT/CC genotypesalso showeda higher biorecurrence rate inthe long-term follow-up,compared with patients with the TT genotype (P=0.067).Additionally, the higher expression of mTOR,4EBP1, and p70S6K in prostate cancer samples indicated the possible roles for PI3K/AKT/mTOR signaling pathway in prostate cancer.These findings suggest thatvariations in the mTORC1-related genes, especially those in mTOR, play important roles in the development of prostate cancer and may be predictive biomarkers for prognosis of prostate cancer.