CLINICAL RELEVANCE OF PROTEIN-TYROSINE (DE-)PHOSPHORYLATION IN HEAD AND NECK-CANCER

Previous studies have shown that protein tyrosine (de)phosphorylation plays an important role in head and neck cancer. Protein-tyrosine kina ses (PTR) and protein-tyrosine phosphatases (PTPase) activities in the cytosol of tumor tissue were significantly increased compared 60 norm al tissue of cancer patients as well as controls. Additionally, the en zyme activities in normal tissue of tumor patients were significantly higher than enzyme activities in normal tissue of the control group. I n this paper, we have correlated the cytosolic and membranous PTK and PTPase activity of tumor and nontumor tissue with several clinical and histological parameters known to influence the clinical outcome. Furt hermore, we have analyzed the value of the enzyme activities as an ind ependent predictor of clinical behavior and occurrence of second prima ry tumors. We confirmed our earlier observations that cytosolic and me mbranous PTK activities and cytosolic PTPase activities in tumor tissu es are increased compared to activities in nontumor tissues and contro ls. Moreover, we also confirmed the findings of increased enzyme activ ities in nontumor tissues compared to findings in control tissues, Thi s finding in histologically proven healthy mucosa is highly interestin g because it indicates that these biochemical changes are obviously no t (yet) translated into morphological changes. Significant differences were found in membranous PTK activity when the patients were grouped by sex, tumor localization, lymph node metastasis, and previous radiot herapy. During the follow-up period, no relation could be found betwee n enzyme activities in tumor and/or nontumor tissues and disease-free interval or occurrence of second primary tumors.