Functional role of BTB and CNC Homology 1 gene in pancreatic cancer and its association with survival in patients treated with gemcitabine

Genetic variation (rs372883C/T) in the 3'-untranslated region of BTB and CNC homology 1 (BACH1) has been associated with pancreatic ductal adenocarcinoma (PDAC) risk in our previous genome-wide association study; however, the action roles of this genetic variation in PDAC remains unknown. Methods: BACH1 expression was measured by quantitative real-time PCR, Western blot and immunohistochemistry. The effects of BACH1 on cell proliferation and sensitivity to gemcitabine were examined by alteration of BACH1 expression in PDAC cells. Angiogenesis was determined in vitro using a human umbilical vein endothelial cell model. Reporter gene assays were conducted to compare the effects of microRNA-1257 on rs372883 variation. The associations between rs372883 variants and survival time in patients treated with gemcitabine were estimated by logistic regression. Results: We found substantially lower BACH1 expression in PDAC compared with normal pancreatic tissues and the rs372883T allele had significantly lower BACH1 levels than the rs372883C allele in both tumor and normal tissues. Knockdown of BACH1 expression provoked proliferation of PDAC cells and angiogenesis, which might result from upregulation of hemeoxygenase-1 that evokes oncogenic AKT and ERK signaling. The rs372883T>C change inhibits interaction of BACH1 with microRNA-1257, resulting in increased BACH1 expression. PDAC patients with the rs372883T allele were more resistant to gemcitabine and had shorter survival time compared with those with the rs372883C allele. Conclusion: These results shed light on the mechanism underlying the associations of BACH1 rs372883 variation with risk of developing PDAC and differential gemcitabine sensitivity in patients.