In vitro cytotoxic drug sensitivity of human normal and malignant lymphocyte-clone-forming cells

Cytotoxic drug sensitivity of normal human lymphocytes and malignant lymphocytes was estimated by a clonogenic method. Malignant T and B lymphocytes were relatively more sensitive than normal T lymphocytes to vincristine and Adriamycin. Since no plateau was observed in the clone survival with associated increasing drug concentration, spontaneous mutants could not be detected. It is suggested that the resistance to "natural product" drugs such as vincristine arises from induced mutations and not from the selection of already existing spontaneous mutants.