Expression of multidrug resistance protein in metastatic colorectal carcinomas

To clarify the relationship between multidrug resistance protein (MRP) and clinicopathologic features, the influence of adjuvant chemotherapy, and pro gnosis of patients who underwent resection of metastatic liver carcinomas o riginating from colorectal carcinomas, we examined the expression of MRP in tumor tissues by immunostaining. Specimens of 38 primary colorectal tumors and 44 metastatic liver tumors of colorectal origin were examined (metasta tic group). We also examined 28 nonmetastatic colorectal carcinomas. The pe rcentages of nonmetastatic tumors and of primary and metastatic tumors of t he metastasis group that expressed MRP were similar. MRP expression in prim ary and metastatic tumors did not correlate with any clinicopathologic feat ures. The use of adjuvant chemotherapy after operation for primary colorect al carcinomas was associated with increased MRP expression among metastatic liver tumors. Expression of MRP in the tumor did not influence the prognos is or survival rate after resection of primary or metastatic tumors. Our da ta suggest that MRP expression in metachronous liver metastases from colore ctal carcinomas may be induced by administration of anticancer drugs but is not associated with clinicopathologic features of the tumor, liver metasta sis, or prognosis.