Immunohistochemical detection of glutathione S-transferase (GST)-π in head and neck carcinoma and its change by radiotherapy

It is well known that the 'placental form of glutathione S-transferase' (GST-π) is present in high concentrations in most human carcinomas. However, its expression in head and neck carcinomas have not yet been reported. The author investigated the expression of GST-π in the tissue of pharyngeal and laryngeal carcinomas by the immunohistochemical procedure. GST-π was positive in 80% of laryngeal carcinomas (35 cases) and 52.8% of pharyngeal carcinomas (36 cases). As a result, well differentiated squamous cell carcinomas showed stronger expression of GST-π than poorly differentiated squamous cell carcinomas. Although normal epithelia of the pharynx and larynx showed negative GST-π, it should be noticed that 54.6% of precancerous epithelia (11 cases) showed positive GST-π. Most patients treated with radiotherapy showed the diminution of GST-π expression after irradiation. However, correlation between the strength of initial GST-π expression and the effectiveness of radiotherapy was not observed (p<0.01). (author)