Exosomal TUBB3 mRNA expression of metastatic castration-resistant prostate cancer patients: Association with patient outcome under abiraterone

Background To use ddPCR to quantify plasma exosomal class III beta-tubulin (beta III-tubulin, TUBB3, encoded by the TUBB3 gene) mRNA expression in metastatic castration-resistant prostate cancer (mCRPC) patients, and study the association of this expression with abiraterone efficacy. Methods Blood samples were prospectively collected from 52 mCRPC patients using abiraterone as first-line therapy to measure plasma exosomal TUBB3 mRNA expression value before the initiation of abiraterone. Study endpoints were PSA response rate, PSA-progression-free survival (PSA-PFS), and overall survival (OS, from CRPC to death). Results Patients with positive exosomal TUBB3 expression showed shorter PSA-PFS (negative TUBB3 vs. positive TUBB3: 11.0 vs. 7.9 months; p = 0.014). Further analysis demonstrated that patients with strongly positive exosomal TUBB3 (>20 copies/20 mu l) was associated with even shorter PSA-PFS (negative TUBB3 vs. positive TUBB3 [TUBB3 [>20 copies/20 mu l]: 11.0 vs. 8.3 vs. 3.6 months, p = 0.005). In multivariate analyzes, TUBB3 (+) (HR: 2.114, p = 0.033) and ECOG score >2 (HR: 3.039, p = 0.006) were independent prognosticators of poor PSA-PFS. PSA response and OS did not present significant differences. Conclusion The exosomal TUBB3 mRNA expression level is associated with poor PSA-PFS of abiraterone in mCRPC patients. The detection of exosomal TUBB3 can be valuable in their management.

Automated summary

The expression level of exosomal TUBB3 mRNA is associated with poor PSA-PFS in mCRPC patients treated with abiraterone, with TUBB3 (+) and ECOG score >2 being independent predictors of unfavorable PSA-PFS.