Heterogeneity of Malignant Cells from a Human Colonie Carcinoma1

Three subpopulations of malignant cells were isolated from a primary cell culture of a single human colonie carcinoma. The variant cells were established as cell lines designated HCT 116, HCT 116a, and HCT 116b, respectively. In vitro charac terizations of the variant lines included growth in 0.5% agarose and growth on confluent layers of mouse fibroblasts. HCT 116a showed the highest colony formation in agarose and on con fluent fibroblasts, while colony formation by HCT 116 was higher than that of HCT 116b in both of these systems. All of the variant lines were tumorigenic in athymic nude mice given injections of 10 x 106 cells, but the time between inoculation and tumor development (latency period) was approximately 10 times longer for HCT 116b as for HCT 116a and 8 times longer than for HCT 116. HCT 116b was not tumorigenic at an inoculum of 5 X 106 cells, while both HCT 116 and 116a were tumorigenic at this level. However, HCT 116a was clearly more tumorigenic than was HCT 116 on the basis of the number of animals developing tumors at inocula of both 10 x 106 and 5 x 106 cells and on the basis of their differences in latency periods. While all the cell lines had near diploid numbers of chromosomes, each line showed a distinct histological pattern when grown as xenografts in athymic nude mice.