Head and neck squamous cell carcinoma is a heterogeneous group of tumors with each subtype having a distinct histopathological and molecular profile. Most tumors share, to some extent, the same multistep carcinogenic pathways, which include a wide variety of genetic and epigenetic changes. Epigenetic alterations represent all changes in gene expression patterns that do not alter the actual DNA sequence. Recently, it has become clear that silencing of cancer related genes is not exclusively a result of genetic changes such as mutations or deletions, but it can also be regulated on epigenetic level, mostly by means of gene promoter hypermethylation. Results from recent studies have demonstrated that DNA methylation patterns contain tumor-type-specific signatures, which could serve as biomarkers for clinical outcome in the near future. The topic of this review discusses gene promoter hypermethylation in oral and oropharyngeal squamous cell carcinoma (OSCC). The main objective is to analyse the available data on gene promoter hypermethylation of the cell cycle regulatory proteins p16INK4A and p14ARF and to investigate their clinical significance as novel biomarkers in OSCC. Hypermethylation of both genes seems to possess predictive properties for several clinicopathological outcomes. We conclude that the methylation status of p16INK4A is definitely a promising candidate biomarker for predicting clinical outcome of OSCC, especially for recurrence-free survival.

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Objective: The aim of this study was to investigate whether fibroblast growth factor receptor 4 (FGFR4) could serve as a potential therapeutic target, prognostic biomarker or biomarker predicting radiotherapy sensitivity in oral squamous cell carcinoma (OSCC) and oropharyngeal squamous cell carcinoma (OPSCC). Methods: FGFR4 immunohistochemistry and FGFR4/CEN5q FISH were performed on tissue microarrays from 212 OSCC and 238 OPSCC patients. FGFR4 genotypes were determined by PCR and DNA sequencing in 76 random OPSCC samples. The response to radiotherapy was evaluated 3 months after the last radiotherapy treatment session by a head and neck radiation oncologist and/or surgeon during clinic visits. The results were correlated to overall survival and response to radiotherapy. Results: The FGFR4 protein was overexpressed in 64% (153/238) of OPSCCs and 41% (87/212) of OSCCs. The FGFR4 gene was amplified in 0.47% (1/212) of OSCCs and 0.42% (1/238) of OPSCCs, and the FGFR4 Gly388Arg polymorphism was detected in 62% (47/76) of OPSCCs. FGFR4 protein expression, FGFR4 gene copy numbers and FGFR4 genotypes were not related to overall survival or response to radiotherapy in OSCC or OPSCC. Conclusion: FGFR4 is frequently overexpressed in OSCC and OPSCC in the absence of gene amplification, and may serve as a potential predictive marker for FGFR4-directed targeted therapy in OSCC and OPSCC.

Volume seems to be more important than T-stage in prediction of DFS or OS in laryngeal squamous cell carcinoma patients. Perhaps prediction of DFS, OS, and LC could be improved by including tumor volume into the staging process.