ABSTRACT
Despite impressive advances in the treatment of prostate cancer with various efficacious inhibitors along the androgen/androgen receptor axis, eventual development of incurable metastatic Castration-Resistant Prostate Cancer (mCRPC) is inevitable and remains a major clinical challenge. Constitutively active androgen receptor (AR) spliced variants have emerged as primary means of resistance to anti-androgens and androgen synthesis inhibitors. The alternatively spliced AR variant, ARv7, has attracted significant interest due to its constitutively active status in CRPC that drives androgen-independence. Factors that are involved in regulating ARv7 levels in CRPC are not clearly known. We recently demonstrated that a protein kinase, T-LAK cell-originated protein kinase (TOPK) level correlates with the aggressiveness of prostate cancer and its invasive behavior. In this study, we investigated whether TOPK plays a role in driving androgen-independence in prostate cancer cells. Our data demonstrate that TOPK overexpression in androgen-dependent LNCaP and VCaP induces ARv7 and drives androgen-independent growth. On the other hand, pharmacological inhibition of TOPK in androgen-independent LNCaP95 and 22Rv1 represses AR transactivation, and AR stability. In summary, this study illustrates a direct role of TOPK in regulating ARv7 and driving androgen-independence in prostate cancer cells.
Subject(s)
Antineoplastic Combined Chemotherapy Protocols/pharmacology , Mitogen-Activated Protein Kinase Kinases/metabolism , Neoplasm Recurrence, Local/genetics , Prostatic Neoplasms, Castration-Resistant/genetics , Receptors, Androgen/genetics , Alternative Splicing , Androgen Antagonists/pharmacology , Androgen Antagonists/therapeutic use , Androgens/metabolism , Antineoplastic Agents, Hormonal/pharmacology , Antineoplastic Agents, Hormonal/therapeutic use , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Biomarkers, Tumor/analysis , Biomarkers, Tumor/antagonists & inhibitors , Biomarkers, Tumor/metabolism , Cell Line, Tumor , Disease-Free Survival , Drug Resistance, Neoplasm/drug effects , Drug Resistance, Neoplasm/genetics , Humans , Inhibitory Concentration 50 , Male , Mitogen-Activated Protein Kinase Kinases/analysis , Mitogen-Activated Protein Kinase Kinases/antagonists & inhibitors , Neoplasm Recurrence, Local/epidemiology , Neoplasm Recurrence, Local/prevention & control , Prognosis , Prostate/pathology , Prostatic Neoplasms, Castration-Resistant/drug therapy , Prostatic Neoplasms, Castration-Resistant/mortality , Prostatic Neoplasms, Castration-Resistant/pathology , Protein Kinase Inhibitors/pharmacology , Protein Kinase Inhibitors/therapeutic use , Quinolones/pharmacology , Quinolones/therapeutic use , Receptors, Androgen/metabolism , Signal Transduction/drug effects , Signal Transduction/genetics , Thiophenes/pharmacology , Thiophenes/therapeutic use , Transcriptional Activation/drug effectsABSTRACT
The roles of protection of telomeres 1 (POT1) in human ovarian cancer have not been fully elucidated. Here, we investigated the impact of POT1 knockdown (POT1-KD) on in vitro cell proliferation, tumorigenesis, and histone deacetylase inhibitor (HDACi) response in human ovarian cancer-derived SK-OV3 cells. The POT1 gene was knocked down by infection with POT1 lenti-shRNA. POT1, c-Myc, and hTERT mRNA levels and relative telomere length were determined by qRT-PCR; POT1 protein levels were determined by western blot. The relative telomerase activity levels were detected using qTRAP; cell proliferation was assessed using cumulative population doubling (cPD) experiments. Cell tumorigenicity was evaluated by anchorage-independent cell growth assays, and cell response to HDACi was determined by luminescence cell viability assays. Results indicate that lenti-shRNA-mediated POT1-KD significantly reduced POT1 mRNA and protein expression. POT1-KD immediately downregulated c-Myc expression, which led to the inhibition of cell proliferation, tumorigenesis, and HDACi response. However, after brief suppression, c-Myc expression increased in the medium term, which resulted in enhanced cell proliferation, tumorigenesis, and HDACi response in the POT1-KD cells. Furthermore, we discovered that c-Myc regulated cell proliferation and tumorigenesis via hTERT/telomerase/telomere pathway.
