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Unfavourable clinical implications for HLA-G expression in acute myeloid leukaemia.

Yan WH, Lin A, Chen BG, Luo WD, Dai MZ, Chen XJ, Xu HH, Li BL - J. Cell. Mol. Med. (2008)

Bottom Line: In AML, HLA-G-positive patients had a significant higher bone marrow leukaemic 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).

View Article: PubMed Central - PubMed

Affiliation: Medical Research Center, Taizhou Hospital of Zhejiang province, Wenzhou Medical College, Linhai, Zhejiang, People's Republic of China. yanwhcom@yahoo.com

ABSTRACT
Human leukocyte antigen-G (HLA-G) molecule exerts multiple immunoregulatory functions that have been suggested to contribute to the immune evasion of tumour cells. Studies on HLA-G expression in malignant haematopoietic diseases are controversial, and the functions of HLA-G on this context are limited. In the current study, HLA-G expression was analysed in different types of patients: de novo acute myeloid leukaemia (AML, n = 54), B cell acute lymphoblastic leukaemia (B-ALL, n= 13), chronic myeloid leukaemia (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 leukaemic 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 leukaemic cells could directly inhibit NK cell cytolysis (P < 0.01). These findings indicated that HLA-G expression in AML is of unfavourable clinical implications, and that HLA-G could be a potential target for therapy.

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Cytotoxicity of NK cell against leukaemic cells isolated from AML patients and restored with an HLA-G-specific mAb 87G. Results were shown for 5-hr cytotoxicity assay using CD34-enriched leukaemic blasts isolated from different AML patients as the targets with an E:T ratio at 20:1. Experiments were performed in quadruplicate and the results were expressed as percentage of specific lysis ± S.D. (A) A PerCP-labelled anti-CD45 antibody was used to gate blasts that were characterized by CD45 dim/low side scatter (SSC) (upper panel). HLA-G-specific mAb FITC-labelled MEM-G/09 was used to measure HLA-G expression on the gated CD45 dim/low cells (low panel).(B) Cytotoxicity of NK cell against leukaemic cells isolated from AML patients and restored with an HLA-G-specific mAb 87G. For the blockade experiments, target cells were pre-incubated with 5 and 10 μg/ml 87G or an isotype-matched IgG as an internal control, respectively. For HLA-G-negative patients no.1 (n= 11).*P < 0.05, **P < 0.01.
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fig03: Cytotoxicity of NK cell against leukaemic cells isolated from AML patients and restored with an HLA-G-specific mAb 87G. Results were shown for 5-hr cytotoxicity assay using CD34-enriched leukaemic blasts isolated from different AML patients as the targets with an E:T ratio at 20:1. Experiments were performed in quadruplicate and the results were expressed as percentage of specific lysis ± S.D. (A) A PerCP-labelled anti-CD45 antibody was used to gate blasts that were characterized by CD45 dim/low side scatter (SSC) (upper panel). HLA-G-specific mAb FITC-labelled MEM-G/09 was used to measure HLA-G expression on the gated CD45 dim/low cells (low panel).(B) Cytotoxicity of NK cell against leukaemic cells isolated from AML patients and restored with an HLA-G-specific mAb 87G. For the blockade experiments, target cells were pre-incubated with 5 and 10 μg/ml 87G or an isotype-matched IgG as an internal control, respectively. For HLA-G-negative patients no.1 (n= 11).*P < 0.05, **P < 0.01.

Mentions: HLA-G expression on tumour cells has been supposed to be an important way for malignant cells escaping from host immunosurveillance. We then investigated whether HLA-G protein expression in AML leukaemic cells could be associated with a decreased susceptibility to NK cytolysis. For this purpose, the IL-2-dependent leukaemic cell line NK-92 was used as a model of the NK effector cells. The cell line NK-92 was proved to be an excellent model system to study NK cell biology and KIR functions for its strong target cell cytolysis and well-defined cell surface markers, such as receptors ILT2 and KIR2DL4, which were involved in HLA-G-specific recognition [23, 24]. To test whether HLA-G expression on leukaemic cells from AML could directly exert an inhibition effect on NK cell cytolysis, blockade experiments with the HLA-G-specific mAb 87G were performed, which could exclude the involvement of other HLA molecules present on cells in the inhibition of NK-92 cytolysis. In this ex vivo study, no markedly different cytolysis was observed for the HLA-G-negative leukaemic cells when HLA-G was blocked. However, for the HLA-G-positive leukaemic cells, data showed that the NK cell lysis could be dramatically enhanced in a antibody dose-dependent manner when the cell surface HLA-G was blocked (Fig. 3), suggesting that HLA-G expression could directly protect AML leukaemic cells from NK-92 cell cytolysis.


Unfavourable clinical implications for HLA-G expression in acute myeloid leukaemia.

Yan WH, Lin A, Chen BG, Luo WD, Dai MZ, Chen XJ, Xu HH, Li BL - J. Cell. Mol. Med. (2008)

Cytotoxicity of NK cell against leukaemic cells isolated from AML patients and restored with an HLA-G-specific mAb 87G. Results were shown for 5-hr cytotoxicity assay using CD34-enriched leukaemic blasts isolated from different AML patients as the targets with an E:T ratio at 20:1. Experiments were performed in quadruplicate and the results were expressed as percentage of specific lysis ± S.D. (A) A PerCP-labelled anti-CD45 antibody was used to gate blasts that were characterized by CD45 dim/low side scatter (SSC) (upper panel). HLA-G-specific mAb FITC-labelled MEM-G/09 was used to measure HLA-G expression on the gated CD45 dim/low cells (low panel).(B) Cytotoxicity of NK cell against leukaemic cells isolated from AML patients and restored with an HLA-G-specific mAb 87G. For the blockade experiments, target cells were pre-incubated with 5 and 10 μg/ml 87G or an isotype-matched IgG as an internal control, respectively. For HLA-G-negative patients no.1 (n= 11).*P < 0.05, **P < 0.01.
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Related In: Results  -  Collection

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fig03: Cytotoxicity of NK cell against leukaemic cells isolated from AML patients and restored with an HLA-G-specific mAb 87G. Results were shown for 5-hr cytotoxicity assay using CD34-enriched leukaemic blasts isolated from different AML patients as the targets with an E:T ratio at 20:1. Experiments were performed in quadruplicate and the results were expressed as percentage of specific lysis ± S.D. (A) A PerCP-labelled anti-CD45 antibody was used to gate blasts that were characterized by CD45 dim/low side scatter (SSC) (upper panel). HLA-G-specific mAb FITC-labelled MEM-G/09 was used to measure HLA-G expression on the gated CD45 dim/low cells (low panel).(B) Cytotoxicity of NK cell against leukaemic cells isolated from AML patients and restored with an HLA-G-specific mAb 87G. For the blockade experiments, target cells were pre-incubated with 5 and 10 μg/ml 87G or an isotype-matched IgG as an internal control, respectively. For HLA-G-negative patients no.1 (n= 11).*P < 0.05, **P < 0.01.
Mentions: HLA-G expression on tumour cells has been supposed to be an important way for malignant cells escaping from host immunosurveillance. We then investigated whether HLA-G protein expression in AML leukaemic cells could be associated with a decreased susceptibility to NK cytolysis. For this purpose, the IL-2-dependent leukaemic cell line NK-92 was used as a model of the NK effector cells. The cell line NK-92 was proved to be an excellent model system to study NK cell biology and KIR functions for its strong target cell cytolysis and well-defined cell surface markers, such as receptors ILT2 and KIR2DL4, which were involved in HLA-G-specific recognition [23, 24]. To test whether HLA-G expression on leukaemic cells from AML could directly exert an inhibition effect on NK cell cytolysis, blockade experiments with the HLA-G-specific mAb 87G were performed, which could exclude the involvement of other HLA molecules present on cells in the inhibition of NK-92 cytolysis. In this ex vivo study, no markedly different cytolysis was observed for the HLA-G-negative leukaemic cells when HLA-G was blocked. However, for the HLA-G-positive leukaemic cells, data showed that the NK cell lysis could be dramatically enhanced in a antibody dose-dependent manner when the cell surface HLA-G was blocked (Fig. 3), suggesting that HLA-G expression could directly protect AML leukaemic cells from NK-92 cell cytolysis.

Bottom Line: In AML, HLA-G-positive patients had a significant higher bone marrow leukaemic 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).

View Article: PubMed Central - PubMed

Affiliation: Medical Research Center, Taizhou Hospital of Zhejiang province, Wenzhou Medical College, Linhai, Zhejiang, People's Republic of China. yanwhcom@yahoo.com

ABSTRACT
Human leukocyte antigen-G (HLA-G) molecule exerts multiple immunoregulatory functions that have been suggested to contribute to the immune evasion of tumour cells. Studies on HLA-G expression in malignant haematopoietic diseases are controversial, and the functions of HLA-G on this context are limited. In the current study, HLA-G expression was analysed in different types of patients: de novo acute myeloid leukaemia (AML, n = 54), B cell acute lymphoblastic leukaemia (B-ALL, n= 13), chronic myeloid leukaemia (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 leukaemic 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 leukaemic cells could directly inhibit NK cell cytolysis (P < 0.01). These findings indicated that HLA-G expression in AML is of unfavourable clinical implications, and that HLA-G could be a potential target for therapy.

Show MeSH
Related in: MedlinePlus