Since it was shown that CD45 expression is higher in immature pro-B-ALL than in pre-B-ALL we could speculate that vincristine causes modulation of antigen expression towards the immunophenotype of pro-B-ALL.16 Additionally, it has been show that increased CD45 expression in blast cells is associated with decreased cell proliferation and treatment resistance but to determine the importance of changes in CD45 expression after exposure to daunorubicin and vincristine, further test would be needed.16 This evidence concerns the gene PTPRC and acute lymphoblastic leukemia.