Vitamin A Does Not Enhance the Antileukemic Effect of Vincristine, Daunorubicin, and 6-Thioguanine in Acute Lymphoblastic Leukemia Cells

Abstract

Retinoids, analogs of vitamin A, have been shown to inhibit growth and induce maturation in a large variety of tumor types. The results of many studies on this subject have been reviewed extensively by Lippman et al. [1,2]. In these reviews it was suggested that retinoids have synergistic activity in combination with cytostatic drugs. The data to support this suggestion are however scarce and all reports on these studies dealt with cell lines or animal models [3–7]. No studies using cells derived directly from patients have been reported as far as we know. We recently adapted the MTT assay to assess in vitro cytotoxic effects of chemotherapeutic drugs upon cells derived from leukemic patients [8,9]. With this assay combinations of resistance modifying agents with anticancer drugs were tested using cells from leukemic patients [10]. In the present study we evaluated whether vitamin A was capable of potentiating the cytotoxic effect of anticancer drugs against tumor cells obtained from patients with acute lymphoblastic leukemia (ALL).