[Tumor stem cell cultures on agar: 1st results].

Hamburger and Salmon have recently developed an in vitro assay for human tumor stem cells which permits formation of colonies of human solid tumors and lymphomas in soft agar. In 50 patients with solid tumors or lymphomas studied by us, tumor colonies grew from effusions and biopsies in 75% of patients (17 of 21) with histologically or cytologically involved specimens. Lymphoid colony growth was obtained in about 25% of specimens (5 of 19) including malignant lymphomas. Conversely, no colony growth was observed in 10 cases where the biopsies or effusions were histologically or cytologically negative. The effect of various conditioned media on tumor growth in agar was investigated. Colony formation of solid tumors was promoted to an especially marked extent by cell-free malignant effusions. This assay yields satisfactory results in solid tumors and appears useful for investigation of different cytotoxic effects of anticancer drugs on the survival of human tumor colony-forming cells.