Background:The interaction between activating receptor NKp30 and its major tumor ligand B7-H6 is important for NK cell-mediated tumor rejection.However,the regulation of B7-H6 by tumor therapeutics remains largely unk...Background:The interaction between activating receptor NKp30 and its major tumor ligand B7-H6 is important for NK cell-mediated tumor rejection.However,the regulation of B7-H6 by tumor therapeutics remains largely unknown.In this study,we investigated the regulation of B7-H6 by all-trans retinoic acid(atRA),a terminal differentiation inducer of tumor cells that is extensively used for clinical leukemia therapy.Methods:We investigated the role of NKp30:B7-H6 axis in NK cell-mediated tumor lysis against leukemia cells and the influence of atRA treatment on the cytotoxicity of NK cells using NK cell lines(NK92 and NKG)and leukemia cell lines(U-937 and THP-1).We evaluated the effect of atRA treatment on the expression of B7-H6 using real-time PCR,flow cytometry and western blotting.We used CRISPR/Cas9 to knockdown B7-H6 expression and siRNA to knockdown c-Myc in U-937 cells to evaluate the role of B7-H6 and c-Myc in atRA-induced tumor resistance against NK cells.Results:NK cell-mediated U-937 cell lysis was mainly dependent on NKp30/B7-H6 interaction.Blockade of B7-H6 by monoclonal antibody significantly impaired NK cytotoxicity.atRA treatment induced U-937 resistance to NK cell cytotoxicity by reducing B7-H6 expression,and showed no effect on NK cytotoxicity against B7-H6 knockdown U-937 cells.Epigenetic modifications,such as DNA methylation and histone deacetylase(HDAC),were not responsible for atRA-mediated B7-H6 down-regulation as inhibitors of these pathways could not restore B7-H6 mRNA expression.On the other hand,atRA treatment reduced c-Myc expression,which in turn inhibited the transcription of B7-H6 on leukemia cells.Conclusion:atRA treatment promotes tumor cell resistance against NK cellmediated lysis by down-regulating B7-H6 expression via the c-Myc signaling pathway,suggesting that more attention needs to be paid to the immunological adverse effects in the clinical use of atRA treatment.展开更多
基金This work was supported by the National Key R&D Program of China(2019YFA0508502)CAMS Innovation Fund for Medical Sciences(2019-I2M-5-073)the National Natural Science Foundation of China(31700754,81788101,and 81821001).
文摘Background:The interaction between activating receptor NKp30 and its major tumor ligand B7-H6 is important for NK cell-mediated tumor rejection.However,the regulation of B7-H6 by tumor therapeutics remains largely unknown.In this study,we investigated the regulation of B7-H6 by all-trans retinoic acid(atRA),a terminal differentiation inducer of tumor cells that is extensively used for clinical leukemia therapy.Methods:We investigated the role of NKp30:B7-H6 axis in NK cell-mediated tumor lysis against leukemia cells and the influence of atRA treatment on the cytotoxicity of NK cells using NK cell lines(NK92 and NKG)and leukemia cell lines(U-937 and THP-1).We evaluated the effect of atRA treatment on the expression of B7-H6 using real-time PCR,flow cytometry and western blotting.We used CRISPR/Cas9 to knockdown B7-H6 expression and siRNA to knockdown c-Myc in U-937 cells to evaluate the role of B7-H6 and c-Myc in atRA-induced tumor resistance against NK cells.Results:NK cell-mediated U-937 cell lysis was mainly dependent on NKp30/B7-H6 interaction.Blockade of B7-H6 by monoclonal antibody significantly impaired NK cytotoxicity.atRA treatment induced U-937 resistance to NK cell cytotoxicity by reducing B7-H6 expression,and showed no effect on NK cytotoxicity against B7-H6 knockdown U-937 cells.Epigenetic modifications,such as DNA methylation and histone deacetylase(HDAC),were not responsible for atRA-mediated B7-H6 down-regulation as inhibitors of these pathways could not restore B7-H6 mRNA expression.On the other hand,atRA treatment reduced c-Myc expression,which in turn inhibited the transcription of B7-H6 on leukemia cells.Conclusion:atRA treatment promotes tumor cell resistance against NK cellmediated lysis by down-regulating B7-H6 expression via the c-Myc signaling pathway,suggesting that more attention needs to be paid to the immunological adverse effects in the clinical use of atRA treatment.
