A novel in vivo model for predicting myelotoxicity of chemotherapeutic agents using IL-3/GM-CSF transgenic humanized mice.

Evaluating myelotoxicity is essential for ensuring the safety of novel drugs before they are approved for clinical applications. Although in vivo prediction of the maximum tolerated doses (MTDs) of anticancer drugs is usually performed in rodents, the results are not always applicable to clinical treatment because drugs may have different effects in human and rodent cells. Previously, we generated a human IL-3 and GM-CSF transgenic humanized mouse (hu-IL-3/GM Tg), in which human granulocytes effectively differentiated after hematopoietic stem cell transplantation. In this study, we established a novel in vivo preclinical evaluation model for predicting human myelotoxicity of anticancer drugs using these hu-IL-3/GM Tg mice. The myelotoxicity was investigated by kinetic flow cytometry of human or murine granulocytes and by colony-forming unit granulocyte/macrophage (CFU-GM) assays. In both in vivo and in vitro analyses, topotecan was more myelotoxic to human than murine granulocytes. In contrast, oxaliplatin was more myelotoxic to murine granulocytes. The level of myelotoxicity of paclitaxel treatment was comparable between human and mouse cells. These results demonstrate that our humanized mouse model can simultaneously evaluate myelotoxicity against human and mouse cells in vivo, and provides an effective preclinical tool for predicting appropriate doses of anticancer agents for clinical treatment.