Histone Deacetylation, But Not Hypermethylation, Modifies Class II Transactivator and MHC Class II Gene Expression in Squamous Cell Carcinomas

Abstract

In this study, we first categorized nine squamous cell carcinoma (SCC) cell lines into two groups in terms of the expression of HLA-DR, -DP, and -DQ molecules. Subsequently, the expression of class II transactivator (CIITA) was studied in these cell lines, because it is widely accepted that the expression of MHC class II molecules is regulated by different types of CIITA transcripts that are initiated by distinct promoters. The majority of the SCC cell lines (six of nine) expressed HLA-DR molecules and CIITA promoter IV (pIV) transcripts in the presence of IFN-γ. In contrast, three of the nine SCC cell lines were completely negative for class II molecules and all types of CIITA, suggesting epigenetic changes in the promoter region in these cells. Previously, methylation of CIITA pIV was reported to silence CIITA gene expression. We extensively studied the methylation status of CIITA pIV using a panel of 22 SCC cell lines. Remarkably, none of the SCC cell lines demonstrated hypermethylation at the site. In contrast, treatment with a histone deacetylation inhibitor in combination with IFN-γ clearly restored the expression of the CIITA type IV gene in the HLA-DR-negative SCC cell lines, and the acetylation status of histone H3 examined by chromatin immunoprecipitation analysis was closely associated with the gene expression. Moreover, stable transfection of the CIITA gene into an HLA-DR-negative cell line restored constitutive expression of MHC class II molecules. Therefore, histone deacetylation, but not hypermethylation, modifies CIITA DNA and class II gene expression in SCC.

A Role for EZH2 in Silencing of IFN-γ Inducible MHC2TA Transcription in Uveal Melanoma

“…De-acetylation of histones at the promoter region has been demonstrated in tumor cells that show reduced CIITA expression (9,(12)(13)(14). In uninduced uveal melanoma cells, we could detect by ChIP varying levels of acetylated histone H3-lysines 9 and 14 and acetylated histone H4-lysines 5, 8, 12, and 16 in CIITA-PIV chromatin, which corresponded with transcript levels of CIITA in IFN-␥-uninduced cells (Fig.…”

“…It has been reported that the lack of IFN-␥-induced MHC2TA transcription is associated with CpG dinucleotide methylation of CIITA-PIV and CIITA-PIII DNA in several cancer cell types (3)(4)(5)(6)(7)(8)(9)(10)(11). Besides CpG dinucleotide methylation, it has been suggested that the lack of IFN-␥-induced transcription of MHC2TA in several cancer types is also associated with histone deacetylase activities (12)(13)(14).…”

Mini‐review: Specificity and expression of CIITA, the master regulator of MHC class II genes

“…The regulatory regions of the MHC2TA gene have been found to be hypermethylated at CpG dinucleotides in MHCII -T cell leukemias, B cell lymphomas and various tumor cells that are unable to express MHCII upon exposure to IFN-+ , including teratocarcinoma, choriocarcinoma, neuroblastoma, erythroleukemia and small cell lung cancer [95,97,[100][101][102]. Histone deacetylation rather than DNA hypermethylation has been implicated in silencing of MHC2TA expression in several squamous cell carcinoma cell lines [103].…”

HLA class II antigen-processing pathway in tumors: Molecular defects and clinical relevance

“…57 Furthermore, modification of histone deacetylation could be also associated with CIITA silencing in some tumor types, like squamous cell carcinoma and hematopoietic tumors. [58][59][60][61] The clinical relevance of the epigenetic control of HLA class II antigen expression was shown for esophageal squamous cell carcinoma and adrenocortical tumors promoting their recurrence and progression. 62,63 Impaired HLA class II-restricted TAA presentation due to abnormalities in the processing pathway could limit CD4 C Tcell help for the induction of CD8 C T-cell responses.…”