[Basics of tumor development and importance of human papilloma virus (HPV) for head and neck cancer]

Abstract

Head and Neck Squamous Cell Carcinoma (HNSCC) are the 6th most common cancers worldwide. While the incidence of larynx-hypopharynx carcinoma decreases, actually an increase in oropharyngeal squamous cell carcinoma (OSCC) is observed. Classical risk factors for HNSCC are smoking and alcohol. Though, it was shown recently for 25 to 60% of OSCC, to be associated with an infection by oncogenic human papilloma virus (HPV). The development of "common" head-neck-tumors is substantially enhanced by an accumulation of genetic changes, which lead to an inactivation of tumor suppressor genes or to an activation of proto-oncogenes. A more or less uniform sequence of different DNA-damages leads to genetic instability. In this context, an early and frequent event is deletion on the short arm of chromosome 9, which results in inactivation of the p16-gene. On the contrary, for HPV-induced carcinogenesis, expression of the viral proteins E6 and E7 is most important, since E6 and E7 lead to inactivation of the cellular tumor-suppressor-proteins p53 and Rb. The process of natural transoral infection is not yet clear. However, as a matter of fact peroral HPV-infection is not seldom and in most cases such an infection heals completely and uneventfully. Smoking seems to increases the probability for developing an HPV-associated tumor. The association of HNSCC with HPV can be proven with established methods in clinical diagnostics. In addition to classical prognostic factors, diagnosis of an HPV-association may become important for future therapies. Prognostic relevance of HPV probably surmounts many known risk-factors, for instance regional metastasis. Until now, no other molecular markers are established in clinical routine. Future therapy concepts may vary for the two subgroups of patients, especially patients with HPV-associated OSCC may take advantage of a less aggressive postoperative treatment. Finally an outlook will be given on possible target-aimed therapies, of which so far only antibodies against EGF-receptors are established in clinical practice.