Rabbit Anti-Human CCNE1 (Phospho-Thr395) polyclonal antibody

MicroRNAs (miRNAs) play important roles in the progression of human cancer including esophageal squamous cell carcinoma (ESCC). Although previous reports showed that miR-125b-5p was down-regulated in ESCC, the roles and mechanisms of loss of function of miR-125b-5p in ESCC were still unknown. Using microRNA microarray and GEO datasets, we found and confirmed that miR-125b-5p was down-regulated in ESCC tissues. In-vitro assays showed that ectopic miR-125b-5p expression repressed cell proliferation, migration and invasion, and induced cell senescence. We also found that miR-125b-5p reduced the expressions of cell cycle regulatory genes including CCNA2, CCND1 and CCNE1, and regulated the markers of epithelial to mesenchymal transition (EMT) including E-cadherin, N-cadherin and EMT associated transcription factor Slug, and also decreased the MMPs including MMP2, MMP7 and MMP13. Furthermore, the candidate target gene HMGA2 was negatively regulated by miR-125b-5p both in mRNA and protein levels. Importantly, knockdown of HMGA2 partially phenocopied the effects of miR-125b-5p overexpression on cell cycle regulators and EMT markers. In conclusion, our results suggested that overexpression of miR-125b-5p inhibited cell proliferation, migration and invasion partially by down-regulating HMGA2 in ESCC.

The cyclin-dependent kinase 2 (CDK2) inhibitor dinaciclib, a potential anti-cancer drug, has been tested in clinical trials and reported to suppress tumor initiating cells. Our recent study demonstrated that pharmacological inhibition of CDK2 or enhancer of zeste homolog 2 (EZH2) allows re-expression of ER alpha and converts triple-negative breast cancers (TNBC) to luminal ER alpha-positive, rendering TNBC cells targetable by tamoxifen. Like TNBC, EZH2 is also commonly overexpressed in ovarian cancers, and overexpression of cyclin El gene (CCNE1) and/or amplification of its associated kinase CDK2 gene is present in ovarian tumor specimens, both of which are associated with primary treatment resistance and poor outcome in high-grade serous ovarian cancer (HGSC). We determined whether inhibition of CDK2-mediated phosphorylation of EZH2 activates ER alpha expression in ER alpha-negative HGSOC cells, rendering them targetable by hormonal therapy. The specific CDK2 inhibitor repressed phosphorylation of EZH2 at T416, and in turn activated the expression of its downstream target ER alpha gene (ESR1). We tested the efficacy of the combination of CDK2 inhibitor and tamoxifen and found significant synergistic inhibition. We further demonstrated that CDK2 inhibitor is a more promising agent than EZH2 inhibitor in repressing TNBC and HGSOC due to a feedback increase in CDK2 activity by EZH2 inhibitor. Our results indicated that the combination treatment of CDK2 inhibitor and tamoxifen has the potential to benefit patients with ER alpha-negative HGSOC.