The CD4 molecule belongs to the phenotypic repertoire of most cases of acute myeloid leukemia.
In the present study fresh leukemic cells obtained from 23 patients with acute myeloid leukemia (AML; FAB subtypes: three M1, five M2, two M3, five M4, eight M5) were investigated for the membrane expression of the CD4 molecule by cytofluorimetric analysis with an anti-CD4 monoclonal antibody (mAb). In 15 cases the presence of the CD4 mRNA was also investigated using Northern blot analysis. Membrane expression of the CD4 molecule was demonstrated in 19 out of 23 cases, and it was found to be weaker than in CD4+ lymphocytes and monocytes obtained from normal controls. Full-length CD4 mRNA was detected in 12 out of 15 (80%) cases, and AML cells positive for CD4 mRNA expression also expressed the CD4 antigen. Since the CD4 molecule expressed by T cells is associated with p56lck, a member of the src family of intracellular tyrosine kinases, we investigated whether the CD4 molecule expressed by myeloid blasts is also associated with a tyrosine kinase activity. In vitro kinase assays performed on anti-CD4 immunoprecipitates from lysates of myeloid leukemia cells from four CD4+ cases were negative for the presence of a tyrosine kinase activity. This finding was not due to the lack of expression of members of the src family since we were able to detect at least p60src and p59fyn in myeloid leukemia cells. According to our results, the CD4 molecule seems to belong to the phenotypic repertoire of most AML, irrespective of their FAB subtypes. However, in myeloid blasts this molecule is not associated with a tyrosine kinase activity as it occurs in T lymphocytes.
Vinante
F
F
Department of Hematology, Verona University School of Medicine, Italy.
Pizzolo
G
G
Rigo
A
A
Vincenzi
C
C
Sorio
C
C
Cassatella
M
M
Berton
G
G
D015152:Blotting, Northern; D015704:CD4 Antigens / Q000032:analysis*; D006801:Humans; D016130:Immunophenotyping; D007951:Leukemia, Myeloid / Q000145:classification / Q000201:enzymology / Q000276:immunology*; D011505:Protein-Tyrosine Kinases / Q000032:analysis*; D012333:RNA, Messenger / Q000032:analysis*; D012334:RNA, Neoplasm / Q000032:analysis*
D015704:CD4 Antigens; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D011505:Protein-Tyrosine Kinases