The Effects of Vincristine and Doxorubicin on the Clonogenic Cells of a Human Lung Cancer Cell Line in Methylcellulose and Suspension Culture

The effects of vincristine (VCR) and doxorubicin (DOX) on the growth of an established line of human lung cancer cells, PC9, were studied in methylcellulose and suspension cultures. The secondary colony formation in methylcellulose and recovery of clonogenic cells in suspension were considered to reflect well the self‐renewal of the clonogenic cells. When dose‐response curves were obtained for VCR and DOX, the primary clonogenic cells (PE1) were more sensitive than secondary clonogenic cells (PE2) or clonogenic cells in suspension. Repeated exposure to VCR in suspension did not inhibit the exponential growth of the clonogenic cells. These data indicated that both drugs were relatively ineffective in specifically suppressing the self‐renewal of the clonogenic cells.