Oral cancer with special reference to virus detection and quantitative gene expression

Background. Head and neck cancers (HNC) are among the most common malignancies worldwide, and about 90–92% of oral neoplasias are oral squamous cell carcinomas (OSCC). Alcohol and tobacco consumption have been recognized as the main risk factors for OSCC development. Oncogenic viruses, such as human papillomavirus (HPV) or Epstein-Barr virus (EBV), as well as genetic alterations may also contribute to tumour formation. Aims. To study the prevalence of HPV, EBV, Herpes simplex type-1 (HSV-1), and HPV-16 and their integration status as well as the molecular mechanisms that can serve as a basis for the development of OSCC. Results. In Paper I we reported a statistically significant increase in the prevalence of HPV-16 in oral epithelial dysplasia (OED) and OSCC samples compared to controls. A statistically significant increase was also seen in integrated HPV-16 compared to episomal viral forms when comparing OED and OSCC samples. Paper II reported the detection of HSV-1 in 54% of healthy samples, in 36% of oral leukoplakia samples, and 52% of OSCC samples. However, these differences were not statistically significant. In Paper III we reported a statistically significant increase in the detection of HPV-positive samples when comparing nested polymerase chain reaction (PCR) with single-PCR results in OSCC and fresh oral mucosa. Paper IV reported that the highest prevalence of HPV (65%) was seen in Sudan, while an HSV-1 prevalence of 55% and an EBV prevalence of 80% were seen in the UK. Finally, Paper V reported that the mRNA levels of Bcl-2, keratin 1, keratin 13, and p53 were significantly lower and that the level of survivin was significantly higher in the OSCC samples of the toombak users than in their paired control samples. Significant downregulation in keratin 1 and keratin 13 expression levels was found in the OSCC samples of the non-toombak users relative to their normal control samples. Conclusion. HPV-16 integration was increased in oral epithelial dysplasia and OSCC compared to normal oral mucosa. Nested PCR is a more accurate method of establishing HPV prevalence in samples containing low copy numbers of HPV DNA. HPV and EBV may be a risk factor in OSCC development. Our findings confirmed the role of survivin in OSCC carcinogenesis and survivin might be interesting as a biomarker to be monitored. The results presented here provide both clinical and biological insights that will bring us closer to the goal of managing this disease and improving treatment and outcomes for future patients