BACH1 promotes pancreatic cancer metastasis by repressing epithelial genes and enhancing epithelial-mesenchymal transition.

Pancreatic ductal adenocarcinoma (PDAC) is among the cancers with the poorest prognoses due to its highly malignant features. BTB and CNC homology 1 (BACH1) has been implicated in RAS-driven tumor formation. We focused on the role of BACH1 in PDAC, more than 90% of which have KRAS mutation. Knockdown of BACH1 in PDAC cell lines reduced cell migration and invasion in part by increasing E-cadherin expression, whereas its overexpression showed opposite effects. BACH1 directly repressed the expression of FOXA1 which is known to activate the expression of CDH1 encoding E-cadherin and to inhibit epithelial-mesenchymal transition. BACH1 also directly repressed the expression of genes important for epithelial cell adhesion including CLDN3 and CLDN4. In a mouse orthotopic implantation model, BACH1 was required for the high metastatic ability of AsPC-1 cells. Immunohistochemistry analysis of clinical specimens with a newly developed anti-BACH1 monoclonal antibody revealed that high expression of BACH1 is a poor prognostic factor. These results suggest that the gene regulatory network of BACH1 and downstream genes including CDH1 contribute to the malignant features of PDAC by regulating epithelial-mesenchymal transition.