Evaluation of potential ionizing irradiation protectors and mitigators using clonogenic survival of human umbilical cord blood hematopoietic progenitor cells

We evaluated the use of colony formation ( colony-forming unit-granulocyte macrophage [ CFU-GM], burst-forming unit erythroid [BFU-E], and colony-forming unit-granulocyte-erythroid- megakaryocyte-monocytes [ CFU-GEMM]) by human umbilical cord blood (CB) hematopoietic progenitor cells for testing novel small molecule ionizing irradiation protectorsand mitigators. The following compounds were added before (protection) or after (mitigation) ionizing irradiation: GS-nitroxides (JP4-039 and XJB-5-131), the bifunctional sulfoxide MMS-350, the phosphoinositol-3-kinase inhibitor LY29400, triphenylphosphonium–imidazole fatty acid, the nitric oxide synthase inhibitor (MCF-201-89), the p53/ mdm2/mdm4 inhibitor (BEB55), methoxamine, isoproterenol, propranolol, and the adenosine triphosphate–sensitive potassium channel blocker(glyburide). The drugs XJB-5-131, JP4-039, and MMS-350 were radiation protectorsfor CFU-GM. JP4-039 was also a radiation protectorfor CFU-GEMM. The drugs XJB-5-131, JP4-039, and MMS-350 were radiation mitigators for BFU-E, MMS-350 and JP4-039 were mitigators for CFU-GM, and MMS350 was a mitigator for CFU-GEMM. In contrast, other drugs were effective in murine assays; TTP-IOA, LY294002, MCF201-89, BEB55, propranolol, isoproterenol, methoxamine, and glyburide but showed no significant protection or mitigation in human CB assays. These data support the testing of new candidate clinical radiation protectorsand mitigators using human CB clonogenic assaysearly in the drug discovery process, thus reducing the need for animal experiments.