Abstract 4911: HPV-independent methylation of specific TGF-B pathway-relevant genes in head and neck squamous cell carcinomas associated with prior radiation therapy and exposure to alcohol and tobacco

Abstract

Abstract Head and neck squamous cell carcinoma (HNSCC) is an aggressive malignancy with more than half a million people being diagnosed with the disease annually. Therefore, it is critical to identify early detection markers, such as DNA methylation, for more timely diagnosis. In a recent study, we identified five tumor suppressive genes (IRX1, EBF3, SLC5A8, SEPT9, and FUSSEL18) as frequently methylated in HNSCC biopsies using a global methylation analysis via restriction landmark genomic scanning (RLGS). Interestingly, we found these candidates are all potentially involved in the TGF-B signaling pathway, which is often disrupted in HNSCC. Therefore, we sought to determine coordinated epigenetic silencing of these candidate genes in HNSCC as potential key disruptors of TGF-B signaling, which could ultimately result in HNSCC progression. Through immunoprecipitation studies, all five of the investigated candidate genes were found to interact with components of the TGF-B pathway. Also, overexpression of SLC5A8, EBF3, and IRX1 resulted in decreased mitotic activity and increased apoptosis. These findings are significant because they reveal a set of genes that interact with components of the TGF-B pathway, and their silencing via methylation in HNSCC results in coordinated decrease in apoptosis, increased proliferation, and decreased differentiation. We went on to define the methylation of these genes in relationship to HPV16-positivity, radiation therapy, and alcohol and tobacco exposure. By utilizing the available clinical information linked to the patient specimens, we found a strong association between promoter methylation of FUSSEL18, IRX1, and EBF3 and prior radiation therapy (P < 0.0001) irrespective of HPV status. Also, promoter methylation of FUSSEL18 and SEPTIN9 were found to correlate significantly with exposure to alcohol and tobacco (P = 0.021). Importantly, in this study we preliminarily show a trend between HPV16 positivity and specific target gene hypermethylation of IRX1, EBF3, SLC5A8, and SEPT9. Equally notable and independent of HPV status, hypermethylation of the promoters of a subset of these genes in recurrences especially in the setting of prior radiation or in the setting of alcohol and tobacco use might help guide adjunctive inclusion or exclusion or epigenetic therapy. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4911.