Investigation of EZH2 pathways for novel epigenetic treatment strategies in oropharyngeal cancer

Abstract

BackgroundIn recent decades, the incidence of oropharyngeal squamous cell carcinoma (OPSCC) has been rising worldwide as a result of increasing oncogenic human papillomavirus (HPV) infections in the oropharynx. EZH2 is an epigenetic regulatory protein associated with tumor aggressiveness and negative survival outcomes in several human cancers. We aimed to determine the role of EZH2 as a potential therapeutic epigenetic target in HPV-positive and negative OPSCC.MethodsThe expression of EZH2 was measured by immunohistochemistry (IHC) and droplet digital PCR (ddPCR) in 2 HPV-positive and 2 HPV-negative cell lines. The cell lines were then cultured and treated with one of 3 EZH2 epigenetic inhibitors (3-deazaneplanocin A, GSK-343 and EPZ005687) or DMSO (control). Following 2, 4 and 7 days of treatment, cells were analyzed and compared by gene expression, cell survival and proliferation assays.ResultsEZH2 targeting resulted in greater inhibition of growth and survival in HPV-positive compared to HPV-negative cells lines. The expression profile of genes important in OPSCC also differed according to HPV-positivity for Ki67, CCND1, MET and PTEN/PIK3CA, but remained unchanged for EGFR, CDKN2A and p53.ConclusionInhibition of EZH2 has anti-tumorigenic effects on OPSCC cells in culture that is more pronounced in HPV-positive cell lines. EZH2 is a promising epigenetic target for the treatment of OPSCC.

Novel insights into epigenetic drivers of oropharyngeal squamous cell carcinoma: role of HPV and lifestyle factors

“…In vitro studies demonstrated that EZH2 promoter can be activated by HPV E7 oncoprotein via the release of E2F factors from growth-inhibitory pocket proteins [ 115 ]. HPV-positive OPSCC have genome-wide elevation in the repressive H3K27me3 histone modification [ 116 ], thus confirming HPV-driven carcinogenesis and EZH2 overexpression are closely related. Furthermore, double immunofluorescence quantification of histone lysine methylation revealed that p16-positive OPSCC had global elevation of H3K27me3 and H4K20me1 that are both involved in generating a repressive gene environment through the formation of facultative heterochromatin [ 117 ].…”

“…Unlike DNMTi and HDACi, only a few HMT inhibitors are currently known, and most of them were discovered through random screening approaches [ 37 ]. In this context, epigenetic inhibitors targeting the EZH2 pathway have recently shown effectiveness in suppressing OPSCC growth and survival, with a major effect in HPV-positive cell lines [ 116 ]. Despite these promising results, no significant decrease in EZH2 and its substrate H3K27 was observed [ 116 ], thus indicating the mechanisms of these HMTi need to be further elucidated in OPSCC.…”

Efficacy of EZH2 inhibitory drugs in human papillomavirus-positive and human papillomavirus-negative oropharyngeal squamous cell carcinomas

“…This study is a continuation of our previous work in 2016 [ 19 ], with the aim of further expanding our investigation of EZH2 inhibition as a potential chemotherapeutic target for use in OPSCC. With the incidence of HPV-positive OPSCC rising [ 5 , 6 ], the need for targeted therapies becomes increasingly urgent.…”

Morphoproteomics, E6/E7 in-situ hybridization, and biomedical analytics define the etiopathogenesis of HPV-associated oropharyngeal carcinoma and provide targeted therapeutic options

“…This could account, in part, for the non-keratinizing/poorly keratinizing component of HPV-associated squamous cell carcinomas. The recent manuscript by Idris et al [ 17 ] showed that inhibition of EZH2 has anti-tumorigenic effects on oropharyngeal squamous cell carcinoma (OPSCC) cells in culture that is more pronounced in HPV-positive cell lines. This preclinical evidence plus the results of our study support the applicability of our approach for human patients.…”