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.