Rs12516 A allele elevates the risk of colorectal cancer via functional CeRNA network of BDNF-AS, miR-4704-5p and BRCA1.

[BACKGROUND] DNA double-strand break repair has emerged as a vital pathway to repair DNA damage seriously related to the risk of colorectal cancer (CRC).

[METHODS] To explore valid susceptible biomarkers of CRC via investigating the association of single nucleotide polymorphisms in DSBR genes with CRC risk, seven polymorphisms located in 3'-untranslated regions of DSBR genes including RAD51 rs11852786, RAD51B rs963917, BRCA1 rs12516 and rs8176318, BRCA2 rs15869, XRCC4 rs2035990 and XRCC5 rs2440 were detected and analyzed in a CRC case-control study (cases (202) and also controls (202)). The PolymiRTs and miRSNP database were used to predict the microRNAs that can bind to 3'UTR SNPs. Since long non-coding RNA as a miRNA "sponge" played the role of competing endogenous RNA, DAVID database was used to find the lncRNAs that can bind to the candidate miRNA seed sequences.

[RESULTS] BRCA1 rs12516 minor A allele was found to be linked with a higher risk of CRC than its major G allele (OR = 2.716, 95%CI: 1.394-5.292, P = 0.003). The stratified analyses demonstrated rs12516 AA genotype with a more elevated risk of CRC in male (OR = 3.089, 95% CI:1.315 ~ 7.255) or age > 50 population (OR = 3.318, 95%CI:1.571 ~ 7.006) than its GG genotype. BRCA1 rs12516 A allele created a novel miR-4704-5p binding target, and there was a negative correlation between miR-4704-5p and BRCA1 expression (r =-0.7199, P = 0.0440). Based on the theory of ceRNA network, it was predicted that lncRNA BDNF-AS can competitively bind to miR-4704-5p, whose expression was exhibited to be negatively correlated with BDNF-AS (r=-0.3481, P = 0.0375). On the contrary, BDNF-AS expression showed a positive correlation with BRCA1 mRNA level in colorectal tissue carrying rs12516 of A allele (adjacent tissue: r = 0.7269, P = 0.0411; cancer tissue: r = 0.7134, P = 0.0469). ROC curve showed both BDNF-AS (AUC = 0.651, P = 0.0277) and miR-4704-5p (AUC = 0.7215, P = 0.0012) can distinguish CRC tissues from their adjacent tissues.

[CONCLUSION] BRCA1 rs12516 is characterized as a potential biomarker associated with CRC risk, via a possible functional ceRNA network of BDNF-AS, miR-4704-5p and BRCA1. The interaction of a lower expression of BDNF-AS, a higher expression of miR-4704-5p and rs12516 A allele could together increase the risk of colorectal cancer.