Construction of enzalutamide-resistant cell model of prostate cancer and preliminary screening of potential drug-resistant genes

Enzalutamide combination with Arsenic trioxide suppresses the progression of castration-resistant prostate cancer

The study aimed to investigate the anti-tumor effects and underlying mechanisms of Enzalutamide (ENZ) and Arsenic trioxide (ATO) co-treatment on castration-resistant prostate cancer (CRPC). The effects on C4-2B cells were initially evaluated by colony formation assay, FACS analysis, and DNA fragmentation detection. Bioinformatics methods including mRNA-sequencing and gene enrichment analysis were used to screen the underlying target genes and pathways related to their actions. Western blot was employed to assess the expression levels of protein-related angiogenesis, apoptosis, DNA repair, and the screened genes. Finally, the effects were further verified in subcutaneous tumor models and tissue sections from the xenografts. It was found that not only could ENZ combination with ATO significantly inhibit cell proliferation and angiogenesis, but also induce cell arrest and apoptosis in C4-2B cells. In addition, interruption of the DNA damage repair-related pathways also occurred as a result of their combined effects. Western blot analysis further suggested that proteins involved in these pathways, especially P-ATR and P-CHEK1 were significantly reduced. In addition, their combination also inhibited the tumor growth of xenografts. Altogether, ENZ combination with ATO synergistically improved the therapeutic effects and suppressed CRPC progression through regulation of the ATR-CHEK1-CDC25C pathway.

Antiandrogen-Equipped Histone Deacetylase Inhibitors Selectively Inhibit Androgen Receptor (AR) and AR-Splice Variant (AR-SV) in Castration-Resistant Prostate Cancer (CRPC)

Background: Epigenetic modification influences androgen receptor (AR) activation, often resulting in prostate cancer (PCa) development and progression. Silencing histone-modifying enzymes (histone deacetylases-HDACs) either genetically or pharmacologically suppresses PCa proliferation in preclinical models of PCa; however, results from clinical studies were not encouraging. Similarly, PCa patients eventually become resistant to androgen ablation therapy (ADT). Our goal is to develop dual-acting small molecules comprising antiandrogen and HDAC-inhibiting moieties that may overcome the resistance of ADT and effectively suppress the growth of castration-resistant prostate cancer (CRPC). Methods: Several rationally designed antiandrogen-equipped HDAC inhibitors (HDACi) were synthesized, and their efficacy on CRPC growth was examined both in vitro and in vivo. Results: While screening our newly developed small molecules, we observed that SBI-46 significantly inhibited the proliferation of AR+ CRPC cells but not AR- CRPC and normal immortalized prostate epithelial cells (RWPE1) or normal kidney cells (HEK-293 and VERO). Molecular analysis confirmed that SBI-46 downregulated the expressions of both AR+ and AR-splice variants (AR-SVs) in CRPC cells. Further studies revealed the downregulation of AR downstream (PSA) events in CRPC cells. The oral administration of SBI-46 abrogated the growth of C4-2B and 22Rv1 CRPC xenograft tumors that express AR or both AR and AR-SV in xenotransplanted nude mice models. Further, immunohistochemical analysis confirmed that SBI-46 inhibits AR signaling in xenografted tumor tissues. Conclusion: These results demonstrate that SBI-46 is a potent agent that inhibits preclinical models of CRPC by downregulating the expressions of both AR and AR-SV. Furthermore, these results suggest that SBI-46 may be a potent compound for treating CRPC.

VIM‑AS1 promotes proliferation and drives enzalutamide resistance in prostate cancer via IGF2BP2‑mediated HMGCS1 mRNA stabilization

VIM‑AS1, a cancer‑specific long non‑coding RNA, has been recognized as a pivotal regulator in multiple types of cancer. However, the role of VIM‑AS1 in the proliferation and resistance to anti‑androgen therapy of LNCaP and C4‑2 prostate cancer cells remains to be determined. In the current study, gain‑and‑loss experiments were used to investigate the effects of VIM‑AS on the proliferation and anti‑androgen therapy of LNCaP and C4‑2 cells. RNA sequencing, RNA pulldown and RNA immunoprecipitation were used to elucidate the underlying mechanism of VIM‑AS1 driving prostate progression. It was demonstrated that VIM‑AS1 was upregulated in C4‑2 cells, an established castration‑resistant prostate cancer (CRPC) cell line, compared with in LNCaP cells, an established hormone‑sensitive prostate cancer cell line. The present study further demonstrated that VIM‑AS1 was positively associated with the clinical stage of prostate cancer. Functionally, overexpression of VIM‑AS1 decreased the sensitivity to enzalutamide treatment and enhanced the proliferation of LNCaP cells in vitro, whereas knockdown of VIM‑AS1 increased the sensitivity to enzalutamide treatment and reduced the proliferation of C4‑2 cells in vitro and in vivo. Mechanistically, 3‑hydroxy‑3‑methylglutaryl‑CoA synthase 1 (HMGCS1) was identified as one of the direct downstream targets of VIM‑AS1, and VIM‑AS1 promoted HMGCS1 expression by enhancing HMGCS1 mRNA stability through a VIM‑AS1/insulin like growth factor 2 mRNA binding protein 2 (IGF2BP2)/HMGCS1 RNA‑protein complex. Rescue assays indicated that knockdown of HMGCS1 expression ameliorated the increase in proliferation and enzalutamide resistance of prostate cancer cells induced by VIM‑AS1 overexpression. Overall, the present study determined the roles and mechanism of the VIM‑AS1/IGF2BP2/HMGCS1 axis in regulating proliferation and enzalutamide sensitivity of prostate cancer cells and suggested that VIM‑AS1 may serve as a novel therapeutic target for the treatment of patients with CRPC.

Enzalutamide-Resistant Progression of Castration-Resistant Prostate Cancer Is Driven via the JAK2/STAT1-Dependent Pathway

Previous studies showed that CXCR7 expression was upregulated after enzalutamide (ENZ) treatment, and an increased level of CXCR7 could increase the invasion, migration, and angiogenesis of castration-resistant prostate cancer (CRPC) cells. This study demonstrated that the levels of p-JAK2, p-STAT1, C-Myc, and VEGFR2 were significantly reduced after CCX771, a specific CXCR7 inhibitor, treatment. This effect further increased after the combination treatment of ENZ and CCX771. Then, we verified that targeting the inhibition of JAK2 or STAT1 could remarkably increase apoptosis and DNA damage and decrease the migration of CRPC cells. More importantly, the combination treatment of ENZ + JAK2/STAT1 led to much greater suppression than the single-agent treatment of JAK2 or STAT1. Subcutaneous CRPC xenograft tumor growth was also reduced by single-agent ENZ treatment and single-agent FLUD, a specific STAT1 antagonist, treatment; but much superior effect was elicited by the combination treatment of ENZ + FLUD. The proliferative indices significantly decreased following combination treatment in tumor tissues compared with control-treatment tissues and single-agent-treatment tissues. Our results demonstrated that CXCR7, which signifies an androgen receptor (AR)-independent signaling pathway, caused CRPC progression via the downstream JAK2/STAT1 signal transduction cascade. Combined inhibition targeting both the AR and JAK2/STAT1 resulted in substantial tumor suppression due to the reduction in DNA damage repair ability and increment in apoptosis.