Colony-forming ability in vitro and clonology of colorectal cancer.

One hundred and twenty-three specimens (83 primary and 40 metastatic) of colorectal cancers from 102 patients were subjected to the human tumor clonogenic assay (HTCA) to determine the clonogenicities of tumor specimens stratified by the degree of histological differentiation and of tumor progression. No statistically significant differences in the clonogenicity were observed among the tumors with different histological differentiation. Viable malignant cells were abundant in the primary tumor specimens with submucosal (sm) and muscular layer (pm) invasion, and decreased significantly in number per gram of wet specimen as the tumors progressed (P less than 0.05). Clonogenicity was also higher in "sm" and "pm" primary tumor specimens, and decreased as the tumors advanced (P less than 0.05). These findings suggest that, at the onset or in the relatively early phase of the tumor progression, tumors are medullary and have a large fraction of clonogenic cells, and that they then develop more stroma while losing the clonogenic cell fraction by tumor progression. HTCA appears to be still valuable for analysis of the changes in biological properties over time in large bowel tumors.