Docetaxel is used as a standard treatment in patients with metastatic castration-resistant prostate cancer. However, a large subset of patients develops resistance. Understanding resistance mechanisms, which are largely unknown, will allow identification of predictive biomarkers and therapeutic targets. We established resistant IGR-CaP1 prostate cancer cell lines for different doses of Docetaxel. We investigated gene expression profiles by microarray analyses in these cell lines and generated a signature of 99 highly differentially expressed genes potentially implicated in chemoresistance. We focused on the role of the cell cycle regulator LZTS1, which was under-expressed in the Docetaxel-resistant cell lines, its inhibition resulting from the promoter methylation. Knockdown of LZTS1 in parental cells with siRNA showed that LZTS1 plays a role in the acquisition of the resistant phenotype. Furthermore, we observed that targeting CDC25C, a partner of LZTS1, with the NSC663284 inhibitor specifically killed the Docetaxel-resistant cells. To further investigate the role of CDC25C, we used inhibitors of the mitotic kinases that regulate CDC25C. Inhibition of CHEK1 and PLK1 induced growth arrest and cell death in the resistant cells. Our findings identify an important role of LZTS1 through its regulation of CDC25C in Docetaxel resistance in prostate cancer and suggest that CDC25C, or the mitotic kinases CHEK1 and PLK1, could be efficient therapeutic targets to overcome Docetaxel resistance

Background: In patients with bone metastases from castration-resistant prostate cancer (CRPC) not pretreated with a bisphosphonate elevated N-telopeptide of type I collagen (uNTx), a marker of bone resorption, predicts skeletalrelated events (SRE). The aim of this study was to assess the prognostic value of uNTx for overall survival (OS) and the incidence of SRE in patients with bone metastases from CRPC receiving zoledronic acid.Methods: From 2004 to 2007, 94 patients with bone metastases from CRPC receiving zoledronic acid for at least 2 months were screened for uNTx.Results: Median age was 66 years (range 46-88). Median serum prostate-specific antigen (PSA) was 66 ng/ml (0-3984) and median uNTx was 19 nmol/mM creatinine (3-489). During follow-up, 38 patients (40%) experienced an SRE. Median OS was 20 months [95% (CI) confidence interval 15-24). In the multivariate analysis, elevated uNTx [hazard ratio (HR) 2.2 (95% CI 1.2-4.0)], serum PSA [HR 2.8 (95% CI 1.6-5.1)], and ECOG performance status were the only independent prognostic factors for OS. Median OS was 12 months (10-16) and 25 months (21-34) in patients with uNTx ‡20 nmol/mM creatinine and in those with uNTx <20 nmol/mM creatinine, respectively. Conclusion:An elevated uNTx level is an independent prognostic factor for OS in patients with bone metastases from CRPC receiving a bisphosphonate.

Prostate cancer is the most common male cancer. About 90% of metastatic patients will develop bone metastases. Bone disease is responsible of pain, deterioration of quality of life and serious bone complications. Proliferation of prostate cancer cells in the bone marrow induces osteoclast activation and osteolysis. Targeting the bone microenvironment reduces morbidity. Relevant preclinical and clinical studies of bone-targeted therapies in castration-resistant prostate cancer were identified in PubMed and clinical trial databases. Different drugs are available or in development that target bone resorption (bisphosphonates, RANK ligand inhibitors), bone formation (endothelin 1 inhibitors), cancer cell migration (SRC-family kinase inhibitors, vascular endothelial growth factor-MET inhibitors), and survival (radiopharmaceuticals). In phase III trials, zoledronic acid, denosumab, and radium-223 were shown to significantly delay skeletal-related events. Radium-223 was also shown to improve overall survival. Biomarkers of bone resorption (urinary N-telopeptide) and bone making (alkaline phosphatase) have an independent prognostic impact. Targeting the bone microenvironment is an important component of castration-resistant prostate cancer management to reduce bone complications and improve overall survival. Biomarkers of bone turnover have an independent prognostic impact.