GLUTATHIONE S-TRANSFERASES AND GLUTATHIONE IN HUMAN HEAD AND NECK-CANCER

Glutathione S-transferase (GST) enzyme activity, GST isoenzyme composi tion and glutathione (GSH) concentration were assessed in normal and s quamous cell carcinoma specimens of 14 patients with oral or oropharyn geal cancer and 11 patients with laryngeal cancer. Comparing malignant with normal oral/oropharyngeal tissues, no significant differences in GSH content, GST enzyme activity or isoenzyme composition were found. However, some tumours had up to 3-fold increased GST enzyme activitie s and 11 malignant samples over-expressed GST-pi. GST-pi was present i n all normal and malignant oral/oropharyngeal specimens investigated, whereas class alpha and class mu were detected in only a few samples, GST-mu was present in 28% of the patients with oral/oropharyngeal tumo urs as compared with similar to 60% in the normal population. GST-alph a, -mu and -pi were detected in 91, 64 and 100% of the normal laryngea l tissues respectively. In laryngeal tumours significantly higher leve ls of GST-pi and GSH but significantly lower amounts of GST-alpha were detected. Levels of class mu GST were generally lower in cancerous ti ssues, but differences were not significant. In comparison with normal oral/oropharyngeal tissues, normal laryngeal tissues contained almost twice the amount of GST enzyme activity due to higher class alpha enz yme levels. It is concluded that GST-pi is elevated in 11 out of 14 tu mours of the oral cavity and values are significantly increased in tum ours of the larynx, which may contribute to the inherent anti-cancer d rug resistance of these malignancies. In laryngeal tumours the increas ed GSH levels may confer additional resistance to radiation therapy.