Purpose: We evaluated expression levels of major heat shock proteins in radical prostatectomy specimens to clarify the significance of heat shock protein expression in prostate cancer.
Materials and methods: Expression levels of heat shock proteins 27, 70 and 90 in radical prostatectomy specimens from 172 patients with clinically organ confined prostate cancer who had not received neoadjuvant hormonal therapy were measured by immunohistochemical staining. Cell proliferative activities and apoptotic features in these specimens were investigated using Ki-67 immunostaining and TUNEL assay, respectively. These findings were analyzed with respect to several clinicopathological factors.
Results: Various levels of heat shock protein 27 expression were noted in all prostate cancer specimens. Expression levels of heat shock protein 27 in prostate cancer tissues was significantly associated with pathological stage, Gleason score, surgical margin status, lymph node metastasis and tumor volume but not with other parameters, including patient age, serum prostate specific antigen and perineural invasion. Similarly most prostate cancer tissues showed heat shock protein 70 and 90 expression. However, there was no significant correlation between expression levels of these 2 heat shock proteins and several clinicopathological factors examined. Cell proliferative activity in prostate cancer specimens was significantly associated with heat shock protein 27 expression but not with that of heat shock proteins 70 and 90, while there was no significant correlation between the apoptotic index and the expression of these 3 heat shock proteins. Furthermore, despite the lack of prognostic significance in heat shock proteins 70 and 90 expression, biochemical recurrence-free survival in patients with strong heat shock protein 27 expression in radical prostatectomy specimens was significantly lower than that in those with weak heat shock protein 27 expression. However, multivariate analysis showed that strong heat shock protein 27 expression could not be an independent predictor of biochemical recurrence after radical prostatectomy.
Conclusions: These findings suggest that, despite the limited significance of heat shock proteins 70 and 90 expression, heat shock protein 27 may be involved in the progression of prostate cancer. The expression level of heat shock protein 27 in prostate cancer tissue could be used as a useful predictor of biochemical recurrence in patients undergoing radical prostatectomy.