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Background Oral leukoplakia (OL) is a potentially malignant oral mucosal disorder. A casual association between OL, oral squamous cell carcinoma (OSCC) and human papillomavirus (HPV) infection has been suggested, but no conclusive evidence has been presented. p16, a tumour-suppressor protein, is used as a surrogate marker for HPV infection. The aim of this study was to investigate how overexpression of p16 correlates with HPV infection in OL and in OSCC. Patients and methods Seventy-four patients with OL and 13 with OSCC with p16 overexpressed, were analyzed by immunohistochemistry visualizing p16 and a real-time polymerase chain reaction (PCR) assay targeting HPV types 6, 11, 16, 18, 31, 33, 35, 39, 45, 52, 56, 58 and 59. Results Overexpression of p16 was observed in 18% of patients with OL. None of the HPV subtypes were detected by PCR analysis in patients with OL. In the p16-positive OSCC specimens, 38% were also HPV16-positive. Conclusion Overexpression of p16 was not found to be a reliable biomarker for HPV infection in patients with OL and OSCC.

Cancer in the oral cavity is often preceded by precursor lesions. Nine oral mucosal disorders are known to have an increased risk of malignant transformation. The etiology varies from disorders caused by exogenous factors such as tobacco and autoimmune inflammation to idiopathic or inherited genetic aberrations. In this review, these potentially malignant disorders (PMDs) are described regarding clinical presentation and histopathological architecture. Special attention is paid to the underlying etiologies of PMDs and the potential pathways leading to cancer. The clinical perspective focuses on the importance of accurate and timely diagnosis.

Oral leukoplakia (LPL) is considered a potentially malignant disorder in the oral cavity and the gastric tract. High mobility group A (HMGA) proteins are important in the transformation of normal cells into cancer cells, but there is a lack of knowledge on their importance in oral cancer development. The aim of the current project was to investigate HMGA expression in LPLs with different levels of dysplasia.Biopsies were histologically processed to visualize the expression of HMGA1 and HMGA2 using immunohistochemistry.An increase of HMGA1-positive cells correlating to the degree of dysplasia was registered in the epithelium and in the connective tissue. HMGA2 expression was seen in the epithelium and in the connective tissue but with no obvious correlation to the level of dysplasia.This is, to our knowledge, the first study showing the expression of HMGA proteins in healthy and non-healthy oral mucosa.

Epigenetic modifications, such as DNA methylation, are considered important in the regulation of target genes in cancer development. 5-Hydroxymethylcytosine (5hmC) was recently discovered to be related to the process of malignant transformation. The influence of DNA methylation in oral squamous cell carcinomas (OSCC) is not fully-understood. Therefore, the aim of the present study was to investigate the DNA methylation pattern in OSCC compared to healthy oral epithelium.Oral mucosal samples from patients with OSCC (n=15) and healthy mucosa (n=12) were analyzed using immunohistochemistry with antibodies against 5hmC, 5mC and ten-eleven-translocation-2 (TET2).A significant decrease in 5hmC and TET2 expression was found in OSCC compared to healthy oral epithelium. In contrast, there was a significant increase in 5mC expression in OSCC compared to healthy epithelium.Our results indicate that loss of 5hmC is an epigenetic event of OSCC.