GRP78 as potential predictor for breast cancer response to adjuvant taxane therapy

Few predictive markers exist for response to adjuvant chemotherapy in breast cancer. The 78-kDa glucose-regulated protein (GRP78) is a potent antiapoptotic factor, conferring drug resistance. Recently, we reported that high GRP78 expression in breast cancer specimens predicts a shorter recurrence-free survival in patients who received doxorubicin-based adjuvant chemotherapy. Interestingly, the opposite effect was observed in 25 patients who additionally received a taxane. To confirm this potentially paradigm shifting finding, we investigated whether GRP78 is associated with recurrence-free survival in an independent cohort of taxane-treated breast cancer patients. Immunohistochemical staining of GRP78 was performed on archival paraffin-embedded formalin-fixed tumor specimens obtained from 48 female breast cancer patients before chemotherapy treatment. These patients received doxorubicin and cyclophosphamide, followed by paclitaxel or docetaxel on a clinical trial. GRP78 expression level was evaluated by a pathologist, masked to all clinical and outcome data. Association between GRP78 expression and recurrence-free survival was evaluated. GRP78 positivity predicts a better recurrence-free survival, independent of other prognostic factors [hazard ratio (HR) for moderate positivity: 0.40 (95% confidence interval (CI): 0.087-1.83); HR for strong positivity: 0.16 (95% CI: 0.018-1.50); p(trend) = 0.053]. In a pooled analysis with the previous 25 patients, almost identical HRs were obtained with p(trend) = 0.024. This provides further evidence that GRP78 is a potential independent predictor for response to taxane-based adjuvant chemotherapy in breast cancer.