Expression of monocarboxylate transporter (MCT)-4 in colorectal cancer and its role: MCT4 contributes to the growth of colorectal cancer with vascular endothelial growth factor.

Background: In tumor cells, monocarboxylate transporter (MCT)-4 regulates the excretion of lactate produced by glycolysis from the cell. MCT4 has also been reported to be involved in tumor growth and infiltration. Similarly, vascular endothelial growth factor (VEGF) is known to be involved in the growth, infiltration, and metastasis of tumors. In this study, we clinically evaluated the relationship between MCT4 and VEGF in colorectal cancer. Materials and Methods: A prospective study was conducted in 210 patients with colorectal cancer who underwent surgical treatment. The clinicopathological data were correlated with the expression of MCT4 and VEGF obtained from immunohistochemical analysis. Results: MCT4 and VEGF were expressed in tumors of 102 (49%) and 129 (61%) patients, respectively. A maximum tumor diameter of 45 mm or more (p<0.0001) and a tumor invasion depth of T1 or less (p<0.0119) were factors independently correlated with the expression of MCT4 and VEGF, respectively. The tumor size was significantly smaller (p=0.0031), and the disease was significantly less advanced (p=0.0017), in MCT4-negative/VEGF-positive than MCT4-positive/VEGF-negative cases. Conclusion: We suspect that in colorectal cancer, VEGF is involved in the early stages of tumor growth and MCT4 expression appears as the tumor enlarges and contributes to its further infiltration and growth.