GLUTATHIONE PEROXIDASES IN HUMAN HEAD AND NECK-CANCER

Glutathione peroxidases (GPX), enzymes that catalyze the reduction of reactive intermediates have been implicated in the action of several c ytostatic drugs. Two major types of GPX have been found: a selenium-de pendent form (SeGPX) which is active with both hydrogen peroxide and o rganic hydroperoxides, and a selenium-independent GPX which is only ac tive with organic hydroperoxides. SeGPX and total GPX (tGPX) activity were assayed in cytosolic fractions from malignant and adjacent normal tissue in 13 patients with oral/oropharyngeal, and 10 patients with l aryngeal squamous cell carcinoma. Neck lymph node metastases were avai lable from 2 and 5 of these patient respectively. Tumors from the oral /oropharyngeal region contained significantly less SeGPX and tGPX acti vity than laryngeal tumors. Primary oral/oropharyngeal and laryngeal t umors had lower SeGPX activities than the matched normal mucosa. tGPX activities were similar in normal and tumor tissue. Metastases contain ed slightly more SeGPX acid tGPX activity than the matched tumor tissu e. We conclude that the inherent anti-tumor drug resistance of human h ead and neck squamous cell carcinoma is not mediated by increased glut athione peroxidase enzyme activity in the tumor tissue.