BMI1 and pancreatic intraductal papillary-mucinous neoplasm: Additionally, we examined the expression of BMI-1 (B lymphoma Moloney murine leukemia virus insertion region 1 homolog), another polycomb protein, during pancreatic IPMN progression, since BMI-1 plays an important role in cancer cell proliferation via transcriptional repression [25], [26].