Nuclear expression of pSTAT3Tyr705 and pSTAT3Ser727 in the stromal compartment of localized hormone-naïve prostate cancer.

BACKGROUND:The signal transducer and activator of transcription 3 (STAT3) is involved in the progression of different tumors including prostate cancer (PCa). The expression of STAT3 in benign and malignant epithelium has been described previously but it has not been described in the stromal compartment. The aim of the present study was to evaluate the nuclear expression and prognostic value of different forms of phosphorylated STAT3 in the stromal compartment of non-cancer and cancer areas of prostatic tissue. MATERIAL AND METHODS:Tissue microarray cores from radical prostatectomy of 225 patients with hormone-naïve localized PCa were immunostained for two phosphorylated forms of STAT3, pSTAT3Tyr705 and pSTAT3Ser727. The prognostic value of the expression levels was studied by Cox regression analysis and biochemical recurrence (BCR)-free survival illustrated by Kaplan-Meier curves. RESULTS:Expression of pSTAT3Tyr705 and pSTAT3Ser727 in the stromal compartment of cancer tissue was lower compared with non-cancer areas. In univariable and multivariable Cox regression analysis, expression levels of pSTAT3Tyr705 and STAT3Ser727 showed similar prognostic value as pathological T-stage, Gleason score and surgical margin status. Kaplan-Meier survival analysis showed that low nuclear expression levels of pSTAT3Tyr705 and pSTAT3Ser727 in stromal cells in cancer compartment and in non-cancer areas were related to BCR-free survival. CONCLUSIONS:Nuclear expression of pSTAT3Tyr705 and pSTAT3Ser727 in the stromal cells mirrors previous findings in the epithelial component in that it displays prognostic value in men undergoing radical prostatectomy for localized hormone-naïve PCa.