**2.7 Other modifications in cancer**

Progression of any cancer is accompanied by genetic alteration(s) which leads to altered protein structure and function. In the last several years, the association between human papilloma virus (HPV) and head and neck cancer has been solidified (Wansom et al. 2010, Albers et al. 2005, Sirianni et al. 2004, Sirianni, Wang and Ferris 2005, Kumar et al. 2007, Kumar et al. 2008, Sisk et al. 2002). Interestingly, HPV associated head and neck cancers exhibit better prognosis and appear to respond better to chemo-radiation. Saliva or serum of head and neck cancer patients can be analyzed for p53, EGFR, and HPV status and microsatellite alterations. In addition, a number of epigenetic modifications have been detected in critical genes involved in this particular cancer type that could potentially serve as specific clinical biological markers. These include promoter DNA hypomethylation in Hras and CAGE genes in thyroid and laryngeal cancers respectively and promoter DNA hypermethylation in p14ARF and RASSF1A genes in esophageal and nasopharyngeal cancers respectively (Ziech et al. 2010).
