A study on the correlations of MRP-1 expression with the pathogenesis and prognosis of colorectal cancer.

PURPOSE: To investigate the expression level of multidrug resistance-associated protein 1 (MRP-1) and its correlation with prognosis in the pathogenetic process of colorectal cancer. METHODS: 116 patients with colorectal adenocarcinoma and 50 patients with colorectal adenomas were studied. Thirty cut-end normal tissue sections were subjected to immunohistochemical staining, real-time polymerase chain reaction (RT-PCR) and Western blotting, to detect the expression levels of MRP-1 gene and protein in tissues. Besides, the correlations of the expression of MRP-1 in colorectal adenocarcinoma tissues with clinicopathological features and prognosis were analyzed. RESULTS: MRP-1 was mainly expressed in the cell membrane and cytoplasm in colorectal adenocarcinoma. The positive expression rates of MRP-1 in colorectal adenocarcinoma tissues, colorectal adenoma tissues and normal tissues were 73.28, 46.0 and 20.0%, respectively, showing statistically significant differences (p<0.05). In adenocarcinoma tissues, MRP-1 expression level was associated with the differentiation grade, TNM staging and whether there was lymph node metastasis (p<0.05 in all comparisons). The 5-year survival rates of patients with negatively expressed MRP-1 protein, no lymph node metastasis and high/moderate grade of differentiation as well as in stage I+II were remarkably higher (p<0.01 in all comparisons). CONCLUSION: In colorectal adenocarcinoma tissues, the expression of MRP-1 is elevated and patients with negatively expressed MRP-1 have a better prognosis. Therefore, MRP-1 can be a reference indicator for clinical diagnosis and prognosis.