We determined whether the upregulation of several metastasis-related genes in human colon carcinoma (HCC) cells implanted into the cecal wall of nude mice precedes HCC invasion of the muscle layer and subserosa and, ultimately, distant metastasis. HCC KM12SM cells were implanted into the subcutis (ectopic) or cecal wall (orthotopic). At weekly intervals for up to 6 weeks, cecectomy and resection of SC tumors were performed on different groups of mice. Survival and metastasis were assessed at 13 weeks. During the first 2 weeks after orthotopic implantation, the HCC cells grew progressively in the mucosa and submucosal layers of the cecum. By the third week, the cells invaded the muscularis propria and then the serosa. All mice undergoing cecectomy at weeks 1 and 2 were cured, whereas those undergoing cecectomy at later weeks were not. In situ hybridization analysis for expression of several metastasis-related genes-epidermal growth factor receptor (EGF-R), basic fibroblast growth factor (bFGF), collagenase type IV, and E-cadherin-revealed that the expression level of EGF-R, bFGF, and collagenase type IV in the early cecal tumors was low but increased just before invasion of the muscularis propria. At all times, the level of gene expression in the cecal tumors was higher than in the SC tumors. In contrast, the expression level of E-cadherin remained constant and did not differ between tumors in ectopic or orthotopic organs. The data suggest that the upregulation of some metastasis-related genes precedes tumor cell invasion and production of metastasis.