Evaluation of ability of low-molecular-weight protein tyrosine phosphatase expression to predict primary hormone therapy efficacy among men with metastatic hormone-naïve prostate cancer.

Abstract

316 Background: Protein tyrosine phosphorylation is an important event associated with the processes of cellular metabolism and is regulated by protein tyrosine kinases and protein tyrosine phosphatases (PTPs). Recent studies showed that low-molecular-weight protein tyrosine phosphatase (LMW-PTP) could be a biomarker for predicting overall survival among men with metastatic hormone-naïve prostate cancer (mHNPC). In this study, we evaluated the value of LMW-PTP expression for predicting primary hormone therapy efficacy among men with mHNPC. Methods: A total of 45 men with mHNPC diagnosed from 2003 to 2009 were enrolled in this retrospective study. All patients had received androgen ablation therapy as first-line treatment. Prostate cancer tissues obtained by needle biopsies before treatment were immunohistochemically stained for LMW-PTP. Correlations between the baseline clinical factors of age, PSA, Gleason scores, T stage, N stage, extent of disease on bone scan (EOD), LMW-PTP expression and primary hormone therapy efficacy (time to castration-resistant prostate cancer [CRPC]) were investigated by multivariate analysis using the Cox proportional hazard model. Continuous variables were classified as dichotomous. Results: Median age and PSA were 70.0 years and 87.8 ng/mL, respectively. Distribution number of Gleason score 8-10/6-7, T4/≤3, N1/0, and EOD 3-4/0-2 were 30 (66.7%)/15 (33.3%), 13 (28.9%)/32 (71.1%), 25 (55.6%)/20 (44.4%), and 7 (15.5%)/38 (84.5%). Median time to CRPC was 40.2 months. Patients with high LMW-PTP expression had significantly shorter time to CRPC than those with low expression (p = 0.005). Multivariate analysis showed that age (≥70 vs < 70, HR 2.5, 95%CI 0.96-6.32, p = 0.060) and LMW-PTP expression (high vs low; HR 3.3, 95%CI 1.2-8.6, p = 0.02) were significant prognostic biomarkers for predicting time to CRPC. Conclusions: LMW-PTP expression could be a potential biomarker for predicting primary hormone therapy efficacy among men with mHNPC.