Expression of multidrug resistance-associated protein (MRP) in head and neck squamous cell carcinoma

We investigated the expression of multidrug resistance-associated protein (MRP) in 115 cases of head and neck squamous cell carcinoma (H&NSCC) by immunohistochemistry and examined the relationship between MRP expression and clinical factors. Thirty-four (30%) of 115 cases of H&NSCC had expression of MRP. The clinical stage was inversely associated with the expression of MRP (P=0.0090), but not with age, sex, tumor size, metastasis, recurrence, death from disease or overall survival rate for 5 years. In vitro chemosensitivity to five chemotherapeutic agents (cis-diamminedichloroplatinum, 5-fluorouracil, peplomycin, mitomycin C and Adriamycin) was tested by ATP assay and no correlation between the sensitivity of tumor cells to the cytotoxicity of any drug and MRP expression was found. These results suggest that the resistance to anticancer drugs is not dependent only on the expression of MRP in H&NSCC.