P53 PROTEIN EXPRESSION IN MALIGNANT, PREMALIGNANT AND NONMALIGNANT LESIONS OF THE LIP

Aim-To elucidate the role of the p53 tumour suppressor gene in the pat hogenesis of lip cancer. Methods-Expression of p53 was evaluated immun ocytochemically in a retrospective study of formalin fixed, paraffin w ax embedded tissue, Five cases each of four types of lip lesions were studied; these comprised squamous cell carcinoma (SCC), solar keratosi s (SK), chronic hyperplastic candidosis (CHC), and lichen planus (LP). Five cases each of normal lip mucosa, SCC, and SK from sun exposed fa cial skill as well as LP, CHC, and SCC from buccal mucosa were also an alysed, Immunolocalisation of p53 was scored semiquantitatively, The d egree of apoptosis was also assessed in selected lesions by determinin g fell nuclear fragmentation. Results-All SCCs from lip lesions were i mmunopositive for p53. All cases of SK and two of five CHC lip lesions were also p53 positive, Normal lip mucosa samples were p53 negative, Sun exposed skin lesions of SCC and SIC were all positive for p53, but only three of five cases of SCC from the buccal mucosa had detectable levels of p53, p53 expression was not detected in CHC and LP lesions of the buccal mucosa. Conclusions-The aberrant expression of p53 is li kely to occur early in the pathogenesis of lip cancer and may be relat ed to exposure to the sun, The immunopositive p53 cells identified in the benign LP lesions do not necessarily correlate with commitment of cells within the lesion to programmed cell death, In light of the prio r reports which indicate that p53 positive cells may progress to form malignant tumours, it is suggested that patients with p53 positive but otherwise benign lesions should be followed more closely.