High-exosomal AKR1C3 mRNA expression as a marker of poor efficacy of abiraterone in metastatic PCa patients.

Abstract

196 Background: Aldo-keto reductase family 1 member C3 (AKR1C3) has been proved to be an important part in the androgen biosynthesis process. Previous researches have showed that immunohistochemical (IHC) AKR1C3 expression is a prognosticator in prostate cancer (PCa) patients treated with abiraterone. This study is to find out the relationship between exosomal AKR1C3 mRNA expression and the efficacy of abiraterone in metastatic PCa patients. Methods: Blood samples of metastatic prostate cancer patients during different disease stages were collected. We isolated the exosomes and extracted the RNA for analysis of AKR1C3 by ddPCR. Absolute target mRNA concentration was measured by ddPCR as copies per milliliter (copies/20ul). Clinical data were collected for all patients. Primary study endpoint was progression-free survival (PFS). Statistical analyses were performed with SPSS 25.0. Results: Exosomal AKR1C3 mRNA expression was positive in 71.9% (41/57) patients, and high expression (defined as ≥ 20 copies/20μl) was found in 12.3% (7/57) patients. High exosomal AKR1C3 mRNA expression was not related to positive IHC AKR1C3 expression ( P=0.723). Patients with high exosomal AKR1C3 expression and negative IHC AKR1C3 expression harbored only 4.866 months’ median progression-free survival (PFS) compared with the whole cohort (9.37 months). High exosomal AKR1C3 expression is significantly associated with shorter PFS (median PFS 8.036 months, p<0.001). Multivariate Cox regression analysis revealed that high exosomal AKR1C3 expression was an independent prognosticator of abiraterone treatment efficacy (OR: 8.891, 95%CI: 1.309-61.631, P=0.026). In subsequently subgroup analyses, high exosomal AKR1C3 expression demonstrates particularly high hazard ratio in multiple subgroups (patients with baseline PSA >100 ng/mL, ALP >71 IU/L, HGB >120 g/L, and patients receiving abiraterone as first-line therapy in castration resistant prostate cancer). Conclusions: Exosomal AKR1C3 level is an independent adverse prognosticator in metastatic PCa patients receiving abiraterone treatment, especially when abiraterone was used as first-line therapy in castration resistant prostate cancer.