[Can virus cause oral cancers?]

Tumour viruses are thought to contribute to the development of one fifth of all human cancers, although the mechanisms involved are still obscure. Human papilloma virus (HPV) is a DNA virus associated with oral carcinomas. It has been shown that virus DNA has to become integrated into cellular DNA in order to transform normal to malignant cells. Cellular oncogenes and tumour suppressor genes are potential cancer genes. They are involved in the control of growth and differentiation of normal cells. It is known that structural or regulatory changes (activation) of these genes will lead to malignant transformation. Virus integration will sometimes take place in close relation to cellular oncogenes. Such incorporation may result in oncogene activation. Other cellular factors that may contribute to the development of oral squamous cell carcinoma are also discussed.