THE ROLE OF C-MYC PROTOONCOGENE IN CHRONIC MYELOGENOUS LEUKEMIA

c-Myc transcriptional factor encoded by c-myc protooncogene plays an i mportant role in the regulation of cell cycle. It was also established that c-Myc is important for the transformation of fibroblasts and mur ine bone marrow cells induced by BCR/ABL tyrosine kinase encoded by bc r/abl oncogene localized on Philadelphia-chromosome (Phl). The role of c-Myc in the proliferation of the leukemic cells was not known. There fore, we examined the effect of c-Myc protein downregulation, using an tisense oligodeoxynucleotides, on the growth of the BCR/ABL- dependent cell line and chronic myelogenous leukemia (CML) patients cells. Down regulation of c-Myc expression caused complete inhibition of the proli feration of BCR/ABL-dependent BV173 cell line and 50-70% inhibition of the colony formation of CML cells. These results suggests that c-Myc cooperates with BCR/ABL and is neccessary for the growth of Ph(1)-posi tive leukemias.