Aberrant tyrosine phosphorylation in head and neck tumours and potentially premalignant tissues.

Protein tyrosine kinases (PTK) and protein tyrosine phosphatases (PTPase) activity in tumor tissue, obtained from 107 patients with squamous cell carcinoma of the upper aerodigestive tract, was determined. In 79 patients samples were also taken from a histologically proven non-tumourous part of the mucosa. In this extensive study we confirmed our previous findings of increased enzyme activities (cytosol PTK, membranes PTK, cytosol PTPase) in non-tumour tissues compared with control tissues. These biochemical changes suggesting a premalignant mucosa could not be correlated to a higher probability of secondary tumours.