AIM: To investigate the expressions of omithine decarboxylase (ODC), MMP-2, and Erk, and their relationship in human colon tumors. METHODS: ODC activity, MMP-2 expression, and mitogen-activated protein (MAP) kinase activity (Erk phosphorylation) were determined in 58 surgically removed human colon tumors and their adjacent normal tissues, using [1-14C]-ornithine as a substrate, ELISA assay, and Western blotting, respectively. RESULTS: ODC activity, MMP-2 expression, and Erk phosphorylation were significantly elevated in colon tumors, compared to those in adjacent normal tissues. A significant correlation was observed between ODC activities and MMP-2 levels. CONCLUSION: This is the first report showing a significant correlation between ODC activities and MMP-2 levels in human colon tumors. As MMP-2 is involved in cancer invasion and metastasis, and colon cancer overexpresses ODC, suppression of ODC expression may be a rational approach to treat colon cancer which overexpresses ODC. METHODS: ODC activity, MMP-2 expression, and mitogen-activated protein (MAP) kinase activity (Erk phosphorylation) were surgically removed human colon tumors and their adjacent normal tissues, using [1-14C] -ornithine as a substrate, ELISA assay, and Western blotting respectively. RESULTS: ODC activity, MMP-2 expression, and Erk A significant correlation was observed between ODC activities and MMP-2 levels. CONCLUSION: This is the first report shows a significant correlation between ODC activities and MMP-2 levels in human colon tumors. As MMP-2 is involved in cancer invasion and metastasis, and colon cancer overexpresses ODC, suppression of ODC expression may be a rational approach to treat colon cancer which overexpresses ODC.