Reduction in Carboplatin Hematopoietic Toxicity in Tumor Bearing Mice: Comparative Mechanisms and Effects of Interleukin-1β and Corticosteroids

Abstract

Increasing clinical evidence suggests that treatment of certain cancers is more effective with high dose chemotherapy compared to standard dose chemotherapy. Efforts at reduction of high dose chemotherapy hematotoxicity have focused on post-chemotherapy administration of hematopoietic growth factors or stem cells. A pretreatment strategy to induce hematopoietic resistance has not been extensively examined experimentally or clinically. Pretreatment with agents can provide an alternative or additional method to reduce high-dose chemotherapy hematotoxicity. We have previously described a murine model in which normal mice were injected with high dose carboplatin (CB, 600 mg/m², intravenously). Within 7-12 days posttherapy, severe granulocytopenia and thrombocytopenia were induced and resulted in a granulocytopenic mortality of 70-80%. Utilizing this model, we observed that pretreatment of mice with interleukin (IL)-lβ and/or a corticosteroid effectively reduced CB hematotoxicity. In the current studies, we demonstrated that C3H/HeJ mice bearing 0.25-0.5 cm RIF-1 tumors, exhibited a tumor associated decrease in hematopoietic tolerance to CB compared to normal mice. However, IL-lβ(l ug/mouse/day for 7 days), cortisone acetate (CA 0.5 mg/mouse/day for 7 days) or both CA and IL-lβ, decreased CB induced mortality rates (control =73%, IL-lβ=46%, CA=30%, IL-lβ+CA=5%). Pretreatment with IL-lβ, CA, or both ameliorated CB—induced absolute granulocyte, lymphocyte and platelet count nadirs. Bone marrow granulocytemacrophage colony forming units (CFU-GM) from mice treated with IL-1 β demonstrated increased ex-vivo resistance to cisplatin, without altering its sensitivity to high specific activity ³H—thymidine (a measure of cell fraction in S-phase). Bone marrow CFU-GM from mice treated with CA exhibited increased resistance to both cisplatin and to high specific activity ³H-thymidine. Pretreatment with IL-lβ, CA or both did not alter tumor sensitivity to CB in vivo. These data suggest that IL-lβ, CA or the combination may be clinically useful in reducing the hematotoxicity of CB.