Abstract

Elevated expression of lysine demethylase 6A (KDM6A) and 6B (KDM6B) has been reported in prostate cancer (PCa). However, the mechanism underlying the specific role of KDM6A/B in PCa is still fragmentary. Here, we report novel KDM6A/B downstream targets involved in controlling PCa cell proliferation. KDM6A and KDM6B mRNAs were higher in LNCaP but not in PC3 and DU145 cells. Higher KDM6A mRNA was confirmed at the protein level. A metastasis associated gene focussed oligonucleotide array was performed to identify KDM6A/B dependent genes in LNCaP cells treated with a KDM6 family selective inhibitor, GSK-J4. This identified 5 genes (c-MYC, NF2, CTBP1, EPHB2, PLAUR) that were decreased more than 50 % by GSK-J4 and c-MYC was the most downregulated gene. Array data was validated by quantitative RT-PCR, which detected a reduction in c-MYC steady state mRNA and pre-spliced mRNA, indicative of transcriptional repression of c-MYC gene expression. Furthermore, c-MYC protein was also decreased by GSK-J4. Importantly, GSK-J4 reduced mRNA and protein levels of c-MYC target gene, CyclinD1 (CCND1). Silencing of KDM6A/B with siRNA confirmed that expression of both c-MYC and CCND1 are dependent on KDM6B. Phosphorylated Retinoblastoma (pRb), a marker of G1 to S-phase transition, was decreased by GSK-J4 and KDM6B silencing. GSK-J4 treatment resulted decrease in cell proliferation and cell number, detected by MTS assay and conventional cell counting, respectively. Consequently, we conclude that KDM6B controlling c-MYC, CCND1 and pRb contribute regulation of PCa cell proliferation, which represents KDM6B as a promising epigenetic target for the treatment of advanced PCa.

Significance Statement Lysine demethylase 6A (KDM6A) and 6B (KDM6B) were upregulated in prostate cancer (PCa). Here, we reported novel KDM6A/B downstream targets involved in controlling PCa cell proliferation. Amongst 84 metastasis associated genes, c-MYC was the most inhibited gene by KDM6 family inhibitor, GSK-J4. This was accompanied by decreased c-MYC target gene, CCND1 and pRb, which were selectively dependent on KDM6B. GSK-J4 decreased proliferation and cell counting. Consequently, we conclude that KDM6B controlling c-MYC, CCND1 and pRb contribute regulation of PCa proliferation.