Histone methyltransferases and demethylases are known to regulate transcription by altering the epigenetic marks on
histones, but the pathologic roles of their dysfunction in human diseases, such as
cancer, still remain to be elucidated. Herein, we show that the
histone demethylase JMJD2B is involved in human
carcinogenesis. Quantitative real-time PCR showed notably elevated levels of JMJD2B expression in
bladder cancers, compared with corresponding nonneoplastic tissues (P < 0.0001), and elevated
protein expression was confirmed by immunohistochemistry. In addition,
cDNA microarray analysis revealed transactivation of JMJD2B in
lung cancer, and immunohistochemical analysis showed
protein overexpression in
lung cancer.
siRNA-mediated reduction of expression of JMJD2B in bladder and
lung cancer cell lines significantly suppressed the proliferation of
cancer cells, and suppressing JMJD2B expression lead to a decreased population of
cancer cells in S phase, with a concomitant increase of cells in G(1) phase. Furthermore, a clonogenicity assay showed that the demethylase activity of JMJD2B possesses an oncogenic activity. Microarray analysis after knockdown of JMJD2B revealed that JMJD2B could regulate multiple pathways which contribute to
carcinogenesis, including the cell-cycle pathway. Of the downstream genes,
chromatin immunoprecipitation showed that CDK6 (
cyclin-dependent kinase 6), essential in G(1)-S transition, was directly regulated by JMJD2B, via demethylation of
histone H3-K9 in its promoter region. Expression levels of JMJD2B and CDK6 were significantly correlated in various types of cell lines. Deregulation of
histone demethylation resulting in perturbation of the cell cycle, represents a novel mechanism for human
carcinogenesis and JMJD2B is a feasible molecular target for anticancer
therapy.