Genetic Variations Within Alternative Splicing Associated Genes Are Associated With Breast Cancer Susceptibility In Chinese Women

Breast cancer is a common cancer and the main cause of cancer death among women worldwide,with the proportion of 25%in all women tumors events and 15%of cancer deaths in 2012.Although incidence of breast cancer is lower in China than that in western countries relatively,it has mushroomed rapidly in last twenty years.It was estimated that,in 2015,there were 268.6 thousands breast cancer new cases diagnosed in China,accounting for 15%of all new cancer cases.Early identification of high-risk individuals will be able to effectively reduce the morbidity and mortality of breast cancer,which is also a basic strategy and a vital challenge that we faces.The progression of breast cancer is a complicated process involving multiple factors,such as age,increased hormone exposure,early menarche,late menopause,alcohol consumption,postmenopausal obesity,endocrine therapy and family history of breast cancer.Additionally,genetic factors have been widely proved to be a critical element in individual susceptibility to breast cancer.Previous studies have discovered several high penetration of susceptibility genes related with breast carcinoma;for instance,BRCA1 and BRCA2,by using linkage analysis and positional cloning in families with multiple affected individuals.More recently,over 80 common,low penetrance risk loci which were related to breast cancer have be found though genome-wide association studies(GWASs);however,the heritability analysis revealed that the mutation sites just illustrated a fringe of breast cancer risk only.Thus,the further efforts based on potential candidate genes still can give us a glimpse into finding out the missing heritability of breast cancer in the post-GWAS era.Alternative splicing(AS)regulate the process of primary RNA transcripts,which may produce diverse isoforms from a single pre-mRNA molecule.The modification of AS can be easily affected by relatively small changes in the levels of splicing factors,such as mutations or genetic variants.Recently,genome-wide scale research has found most part of genes experience alternative splicing,and abnormal splicing isoforms play a crucial role in motility,transformation and metastasis of carcinoma tissues.Lots of cancer genes are mediated by alternative splicing.For example,numerous p53 splice site mutations have been identified in more than 12 disparate types of cancer.The serine/arginine(SR)-rich family is phylogenetically conserved and plays an important roles in AS.Studies have shown that SRs usually favor definite introns and exons through binding enhancer sequences and enrolling the spliceosome to the pre-mRNA,thus stimulating splicing.Serine/arginine-rich splicing factor 3(SFRS3,formerly named SRp20)is the smallest member of SR-proteins,which regulates splicing of numerous cellular transcripts and has been claimed to be the proto-oncogene.Previous studies have showed that SFRS3 is highly expressed in several cancers,such as ovarian cancer,clear cell renal cell carcinoma,hepatocellular carcinoma and colon cancer.Furthermore,epithelial splicing regulatory proteins 1 and 2(ESRP1 and ESRP2)also regulate diverse types of AS events.The recent research implicated that these two factors can make a contribution to the process of epithelial-to-mesenchymal transition(EMT)in many cancers through targeting several genes,such as FGFR2,ENAH CD44 and CTNND1.Meanwhile,studies have suggested that ESRP1 might functionally collaborate with SFRS3 in the alternative splicing of a member of RAS superfamily-Racl-in human cancer.Taken together,alternative splicing events have appeared as an significant focus in cancer research field;however,the contribution of alternative splicing to the occurrence of breast cancer is poorly understood.In this study,we hypothesized that genetic variants in three critical genes(SFRS3,ESRP1 and ESRP2)might change the alternative splicing of numerous genes,thereby substantially affecting the levels of various protein isoforms expression and breast cancer development.Therefore,1,064 BC cases and 1,073 healthy controls were enrolled in the case-control study to estimate the effect of common polymorphisms in three genes(SFRS3,ESRPI and ESRP2)on the breast cancer risk.Briefly,cases were enrolled from the the Cancer Hospital of Jiangsu Province,First Affiliated Hospital of Nanjing Medical University and the Gulou Hospital,Nanjing,China,from January 2004 to April 2010.All breast cancer patients were diagnosed on the histopathological.We selected controls from a group of participants in a community-based non-infectious diseases screening program in Jiangsu Province,China.In the discovery phase,the 1,064 cases and 1,073controls were genotyped with Illumina Infinium(?)HumanExome Beadchip.247,870 variants in the chip were flow into quality control.We calculated the P values,odds ratio(OR)and 95%confidence intervals(CI)in the additive model by logistic regression.SNPs were further screened based on the following criteria:(ⅰ)P value of Hardy-Weinberg equilibrium(HWE)≥0.05,(ⅱ)genotyping rate≥90%,(ⅲ)minor allele frequency(MAF)≥0.05,and(ⅳ)retaining one SNP when multiple SNPs were in strong linkage disequilibrium(r2>0.8).We found only A allele of rs2145048(near SFRS3)was significantly associated with breast cancer risk with adjustment of age,age at menarche and menopausal status after multiple corrections.The variants A allele of rs2145048 near SFRS3 at 6p15 conferred to a decreased risk of breast cancer(rs2145048,C>A,OR=0.81,95%CI=0.71-0.92,P=0.016).In the stratification analysis,the effect of rs2145048 A allele on breast cancer remained significant among women with earlier menarche,younger first live birth,premenopausal status and HR negative status.This study provided the evidence that genetic variations in the splicing-associated gene SFRS3 might contribute to individuals’ susceptibility to breast cancer among Chinese women.Further large and functional studies are warranted to confirm our findings.