Pattern of p63 expression in squamous cell carcinoma of the oral cavity

P63 is a recently discovered gene harbouring different isoforms by alternate splicing. The two main isoforms, TAp63 and DeltaNp63, have opposite functions, being responsible for cell-cycle arrest and cell proliferation, respectively. In addition, new isoforms have been described with the same sequence as TAp63 and DeltaNp63, but lacking exon 4 (Delta4Tap63 and DeltaNp73L). P63 as detected using immunohistochemistry is present in squamous cell carcinomas. To better define the role of p63 in squamous cell carcinomas of the oral cavity (OSCC), 39 patients were investigated using immunohistochemical analysis with a monoclonal antibody recognising all p63 isoforms and an anti-Ki67 antibody. Reverse-transcription polymerase chain reaction (PCR) and nested PCR were also performed using isoform-specific primers to evaluate the p63 mRNA expression pattern. Using immunohistochemistry, p63 was always present in OSCC, and its distribution was similar to that of Ki67. The percentage of positive cells increased from normal to neoplastic mucosa, but there was no relationship between the number of p63 positive cells and prognosis. P63 mRNA was found in all patients. The truncated isoforms Delta4TAp63 and DeltaNp73L were more frequently expressed in patients presenting with metastases. DeltaNp73L was found in 66.6% of tumours with lymph-node metastases, but in only 33.3% of those devoid of lymph-node metastases at presentation. An impaired expression of the p63 isoforms might favour cell proliferation and indirectly enhance the metastasising capacity of OSCC.