Loss of histone demethylase KDM6B enhances aggressiveness of pancreatic cancer through downregulation of C/EBPα.

Genetic mutations in pancreatic ductal adenocarcinoma (PDAC) with critical roles have been well examined. The recent discovery of alterations in genes encoding histone modifiers suggests their possible roles in the complexity of cancer development. We previously reported loss of heterozygosity of the KDM6B gene, which encodes a histone demethylase for trimethylated histone H3 lysine 27, a repressive chromatin mark, in PDAC cells. In this study, we demonstrated that loss of KDM6B enhanced aggressiveness of PDAC cells. KDM6B has been regarded as a tumor suppressor that mediates oncogenic KRAS-induced senescence. Consistently, KDM6B was highly expressed in pancreatic precancerous lesions (pancreatic intraepithelial neoplasms); then, the expression decreased as the malignant grade progressed. We found that knockdown of KDM6B in PDAC cells promoted tumor sphere formation and increased peritoneal dissemination and liver metastasis in vivo. Microarray and chromatin immunoprecipitation analysis implicated CEBPA for aggressiveness induced by KDM6B knockdown. CEBPA knockdown recapitulated the phenotypic change of PDAC cells after KDM6B knockdown, which was reversed by forced expression of C/EBPα. Moreover, similar protein expression patterns of KDM6B and C/EBPα in human PDAC emphasized their functional correlation. Notably, pharmacological inhibition of the H3K27 methylase EZH2 in PDAC cells inhibited tumor sphere formation along with the upregulation of CEBPA expression, and this effect was impaired in KDM6B knockdown cells, highlighting the role for KDM6B in the activation of CEBPA. Together, our results propose a significant role for the KDM6B-C/EBPα axis in the PDAC phenotype.