Nicotinic acetylcholine receptor CHRNA5 is overexpressed in head and neck squamous cell carcinoma patients with a recent tobacco smoking history

Tobacco smoking is a major driver of head and neck squamous cell carcinoma (HNSCC) occurrence, and previous studies have shed light on the precise molecular alterations in tobacco-related HNSCCs when compared to HNSCCs associated with other risk factors (ex: human papillomavirus/HPV status). In this study, we analyzed the gene expression differences in HNSCC cases with a recent smoking history and revealed that the nicotinic acetylcholine receptor CHRNA5 is differentially overexpressed in smoking-related HNSCCs. CHRNA5 overexpression in these HNSCCs corresponds with a worse prognosis and is inversely correlated with an immune expression signature commonly associated with better prognosis. From these results, our study highlights the potential role of the nicotine-activated CHRNA5 receptor in HNSCC progression and corresponds with other recent reports highlighting the potential role of nicotine induction in promoting cancer progression.

Abstract 3683: IL32 expression is epigenetically regulated in EpCAM-/Cd49f- basal-like breast cancers and can be suppressed by the bromodomain inhibitor JQ1

Metastatic basal-like breast cancers are believed to correspond with EpCAM-/Cd49f- cancer stem cell (CSC) enrichment. As well, basal-like breast cancers typically correspond with tumor inflammation and immunoediting phenotypes. However, the exact interplay between CSCs and the inflammatory signature of basal-like breast cancers is not well understood. To provide insight regarding the clinical overlap between breast cancer stem cells and tumor inflammation, we compared the 450K DNA methylation profile of EpCAM-/CD49f- CSCs from the isogenic MCF10A p53-/PTEN- breast cell line against the corresponding EpCAM+/CD49f+ and EpCAM-/CD49f+ subpopulations to determine whether differential DNA methylation occurred within the promoters of immune-related genes in CSCs. In addition, we also overlapped the 450K DNA methylation profile from 16 established breast cancer cell lines of varying EpCAM-/CD49f- concentrations to compare against the isolated CSCs. Based on our results, we identified 1432 differentially methylated promoter regions overall (ANOVA FDR p-value <0.001) and found IL32 to be differentially hypomethylated in the EpCAM-/CD49f- enriched cell lines. This hypomethylation of IL32 corresponded with increased expression of the beta isoform of IL32. Results from the cell lines were mirrored in The Cancer Genome Atlas (TCGA) breast cancer datasets, which revealed decreased promoter DNA methylation and increased gene expression of IL32 in basal-like patients. Further analysis of TCGA data using Gene Set Enrichment Analysis (GSEA) revealed that transcripts that tightly correlate with IL32 expression were preferentially involved in NF-kappaB mediated inflammation, with specific examples including REL, CCL5, PIK3CD, and IDO1. Furthermore, publicly available H3K27Ac and BRD4 ChIPseq data revealed that the IL32 promoter in the basal-like breast cancer cell line SUM159PT contains a high presence of H3K27 acetylation and BRD4 recruitment, with the latter event being disrupted by JQ1 treatment. These results complemented qRT-PCR results showing the IL32-beta isoform being quickly suppressed by 1uM JQ1 in SUM159PT as well as chick chorioallanotoic membrane (CAM) xenograft assays demonstrating suppressed metastasis and neovascularization of SUM159PT treated with JQ1. Collectively, these findings highlight the potential impact of IL32 promoter hypomethylation in basal-like breast cancer stem cells and how the overall epigenetic signature may predispose CSCs towards an immunomodulatory phenotype.

Citation Format: Emma V. Gray, Caroline E. Dyar, Maria Ouzounova, Max S. Wicha, Hasan Korkaya, Austin Y. Shull. IL32 expression is epigenetically regulated in EpCAM-/Cd49f- basal-like breast cancers and can be suppressed by the bromodomain inhibitor JQ1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3683.