EXPRESSION OF FACILITATIVE GLUCOSE-TRANSPORTER ISOFORMS IN LUNG CARCINOMAS - ITS RELATION TO HISTOLOGIC TYPE, DIFFERENTIATION GRADE, AND TUMOR STAGE

Expression of facilitative glucose transporter (Glut) isoforms was stu died immunohistochemically in lung carcinomas. Glut-1 was expressed in 45 (74%) of 61 lung carcinomas, including 19 (100%) of 19 squamous ce ll carcinomas. No Glut-1 staining was seen in normal lung epithelium s urrounding the tumors. In squamous cell carcinomas and small cell carc inomas, Glut-1 immunostaining was stronger in the central area of tumo r cell nests corresponding to the hypoperfused region. Focal staining was seen in 14 (58%) of 24 adenocarcinomas, and positive staining was correlated to lesser differentiation, larger tumor size, and positive lymph node metastasis. Glut-2 was detected in normal airway epithelium , but no positive staining was seen in lung carcinomas. Glut-3 and Glu t-4 were not positively stained in normal lung epithelia, but a few lu ng carcinoma samples showed positive reaction (9 of 61 in Glut-3; 4 of 61 in Glut-4), Glut-4 immunoexpression was seen in regenerating alveo lar and bronchiolar epithelia around and in cancer tissues. Glut-5 exp ression was not detected in normal and tumor tissues. Reverse transcri ptase-polymerase chain reaction for Glut-1, Glut-3, and Glut-4 confirm ed the expression revealed by immunohistochemical analysis. Overexpres sion of Glut could enhance uptake of glucose into lung carcinoma cells , and the increased glucose influx could be involved in cell biologic activities.