Circulating microRNAs associated with docetaxel-resistant castration resistant prostate cancer.

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44 Background: Despite a range of new treatments, docetaxel (DTX) remains the first-line chemotherapy for castration-resistant prostate cancer (CRPC). However, only 50% of patients respond to docetaxel at the cost of potentially significant toxicity. Therefore, there is a need for new biomarkers to identify early response to therapy. This study aims to determine if circulating microRNAs are associated with DTX chemotherapy outcome in CRPC. Methods: Global microRNA profiling was performed on DTX-resistant and sensitive cell lines to identify candidate circulating microRNA biomarkers. Custom Taqman Array MicroRNA cards measured the levels of 46 candidate microRNAs in plasma/serum from 97 CRPC patients, collected pre- and three weeks post-cycle one of DTX. Responses were defined by the PCWG1 serum prostate-specific antigen (PSA) response criteria; partial response (PR), stable disease (SD), progressive disease (PD). Multiple T-test, Mann-Whitney U, Kaplan-Meier, Receiver Operating Characteristic (ROC), and Cox regression analyses were used to assess the associations between microRNA levels and clinical outcomes. Results: Eighteen microRNAs were associated with PSA response or overall survival (p<0.05). DTX non-responders (PD+SD) and patients with shorter survival had high pre-DTX levels of miR-200 family members (miR-200a, miR-200b, miR-200c, miR-429; p<0.05), or decreased/unchanged post-DTX levels of miR-17 family members (miR-19b, miR-20a, miR-20b; p<0.05). The combined levels of miR-20a, miR-146a, miR-200b, miR-200c, miR-222, and miR-301b predicted PSA response (ROC AUC 0.74, 95% CI 0.64-0.84). Pre-DTX miR-200a levels (HR 3.0, 95%CI 1.6-5.8; p=0.001) and post-DTX change in miR-20a (HR 3.4, 95%CI 1.8-6.3; p=0.0002) were independent predictors of overall survival when modeled with hemoglobin levels (HR 2.6, 95%CI 1.4-5.1; p=0.02), PSA response (HR 2.1, 95%CI 1.1-3.9; p=0.03), and visceral metastases (HR 2.0, 95%CI 1.1-3.5; p=0.03). Conclusions: Circulating microRNAs are potential early predictors of DTX chemotherapy outcome and may be useful in stratifying patients in future clinical trials. These microRNAs may also be involved in DTX resistance and represent potential therapeutic targets.