Evaluation of immunomodulatory and antitumor activity of all trans retinoic acid (ATRA) in solid tumor bearing mice.

Natural or synthetic agents can modify the immune system and, in some cases, impart a therapeutic benefit. Cancer, a disease of uncontrolled growth and spread of abnormal cells, is a major cause of death. The Vitamin A metabolite all-trans retinoic acid (ATRA) and its other active derivatives are potent modulators of cell growth and differentiation, and because it has an influence on cancer, it can be used as a chemotherapeutic and -preventive agent. To evaluate the immunomodulatory activity of ATRA, the impact of treatment on various parameters, e.g. delayed-type hypersensitivity (DTH), bone marrow cellularity, hematology, and levels of esterase-positive cells, was assessed in Balb/c mice. To evaluate antitumor effects of ATRA, tumor volume and host survival rate were monitored in B16F10 melanoma cell-injected mice. The results showed that administration of ATRA (0.60 mg/kg/dose, IP) caused a decrease in DTH (footpad thickness) in response to challenge with sheep red blood cells (SRBC) in SRBC-sensitized hosts. ATRA also caused increases in WBC counts and bone marrow cell numbers. In tumor-inoculated mice, ATRA caused tumor growth suppression and gave rise to a heightened survival rate. It was also found that ATRA had differential effects on serum levels of reduced glutathione (GSH) and nitric oxide (NO) was reduced in serum. Based on these results, we conclude that ATRA has a potent immunomodulatory potential but also could significantly impact upon solid tumor growth and prolong host survival.