First, we evaluated the potential effect of these anaphylatoxins on proliferation of leukemic cells by adding C3a or C5a to liquid cultures of leukemic cells or by adding both ComC cleavage fragments to clonogenic colony-forming units of granulocyte-monocyte (CFU-GM) assays of CD33+ blasts isolated from patient AML or CML cells. This evidence concerns the gene C5 and chronic myelogenous leukemia, BCR-ABL1 positive.