Purpose: The purpose of this study was to investigate the relationship between the level of expression of ATP-binding cassette (ABC) transporter proteins, and response to chemotherapy and prognosis in advanced non-small cell lung cancer (NSCLC).
Experimental design: Expression of ABC transporter proteins, including P-glycoprotein, multidrug resistance protein (MRP) 1, MRP2, MRP3, and breast cancer resistance protein (BCRP), was examined immunohistochemically in 72 formalin-fixed tumor samples from untreated stage IIIB or IV NSCLC patients. All of the patients received platinum-based chemotherapy. Response to chemotherapy, progression-free survival (PFS), and overall survival were compared in relation to expression of each of the ABC transporter proteins and clinicopathological factors.
Results: Expression of P-glycoprotein, MRP1, and MRP3 was not significantly associated with response to chemotherapy or survival. MRP2 expression was associated with overall survival (P = 0.002) but not with response to chemotherapy and PFS. By contrast, the response rate to chemotherapy of patients with BCRP-negative tumors was 44%, as opposed to 24% in patients with BCRP-positive tumors. Response rate was lower in BCRP-positive tumors, although this difference was not statistically significant (P = 0.08). BCRP-positive patients had also shorter PFS (P = 0.0003) and overall survival (P = 0.004) than BCRP-negative patients. Multivariate analysis confirmed BCRP status as an independent variable related to PFS (P = 0.001).
Conclusions: Positive immunostaining for BCRP appears to be a predictor of survival in patients with advanced NSCLC. These findings indicate that BCRP may serve as a molecular target for reducing drug resistance to chemotherapy in advanced NSCLC patients.