Unfavorable clinical implications for HLA-G expression in acute myeloid leukemia.
ABSTRACT Human leukocyte antigen-G (HLA-G) molecule exerts multiple immunoregulatory functions which have been suggested to contribute to the immune evasion of tumor cells. Studies on HLA-G expression in malignant hematopoietic diseases are controversial and the functions of HLA-G on this context are limited. In the current study, HLA-G expression was analyzed in different types of patients: de novo acute myeloid leukemia (AML, n=54), B cell acute lymphoblastic leukemia (B-ALL, n=13), chronic myeloid leukemia (CML, n=9) and myelodysplastic syndrome (MDS, n=11). HLA-G expression was observed in 18.5% cases of AML, 22.2% in CML and 18.2% in MDS, but not in B-ALL patients. In AML, HLA-G-positive patients had a significant higher bone marrow leukemic blast cell percentage when compared with that of HLA-G negative patients (p<0.01). Total T cell percentage was dramatically decreased in HLA-G positive patients (p<0.05). Cytogenetic karyotyping results showed that all HLA-G positive AML patients (n=5) were cytogenetically abnormal which was markedly different from that of HLA-G negative patients (p<0.01). ex vivo cytotoxicity analysis revealed that HLA-G expression in AML leukemic cells could directly inhibit NK cell cytolysis (p<0.01). These findings indicated that HLA-G expression in AML is of unfavorable clinical implications, and that HLA-G could be a potential target for therapy.