Epigenetic regulations in the IFNγ signalling pathway: IFNγ-mediated MHC class I upregulation on tumour cells is associated with DNA demethylation of antigen-presenting machinery genes

// Veronika Vlková 1, Ivan Štěpánek 1, Veronika Hrušková 1, Filip Šenigl 2, Veronika Mayerová 1, Martin Šrámek 1, Jana Šímová 1, Jana Bieblová 1, Marie Indrová 1, Tomáš Hejhal 1, Nicolas Dérian 3, 4, 5, 6, David Klatzmann 3, 4, 5, 6, Adrien Six 3, 4, 5, 6 and Milan Reiniš 1 1 Department of Tumour Immunology, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, v. v. i. , Prague 2 Department of Viral and Cellular Genetics, Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, v. v. i. , Prague 3 Sorbonne Universités, UPMC Univ Paris 06, UMR 7211, Immunology-Immunopathology-Immunotherapy (I3), Paris, France 4 CNRS, FRE 3632, Immunology-Immunopathology-Immunotherapy (I3), Paris, France 5 INSERM, UMRS 959, Immunology-Immunopathology-Immunotherapy (I3), Paris, France 6 AP-HP, Hôpital Pitié-Salpêtrière, CIC-BTi Biotherapy & Département Hospitalo-Universitaire (DHU) Inflammation-Immunopathology-Biotherapy (i2B), Paris, France Correspondence: Milan Reiniš, email: // Keywords: IFNγ signalling, DNA demethylation, 5-azacytidine, MHC class I downregulation, tumour immunology Received: July 4, 2014 Accepted: July 13, 2014 Published: July 15, 2014 Abstract Downregulation of MHC class I expression on tumour cells, a common mechanism by which tumour cells can escape from specific immune responses, can be associated with coordinated silencing of antigen-presenting machinery genes. The expression of these genes can be restored by IFNγ. In this study we documented association of DNA demethylation of selected antigen-presenting machinery genes located in the MHC genomic locus (TAP-1, TAP-2, LMP-2, LMP-7) upon IFNγ treatment with MHC class I upregulation on tumour cells in several MHC class I-deficient murine tumour cell lines (TC-1/A9, TRAMP-C2, MK16 and MC15). Our data also documented higher methylation levels in these genes in TC-1/A9 cells, as compared to their parental MHC class I-positive TC-1 cells. IFNγ-mediated DNA demethylation was relatively fast in comparison with demethylation induced by DNA methyltransferase inhibitor 5-azacytidine, and associated with increased histone H3 acetylation in the promoter regions of APM genes. Comparative transcriptome analysis in distinct MHC class I-deficient cell lines upon their treatment with either IFNγ or epigenetic agents revealed that a set of genes, significantly enriched for the antigen presentation pathway, was regulated in the same manner. Our data demonstrate that IFNγ acts as an epigenetic modifier when upregulating the expression of antigen-presenting machinery genes.