GLUT-1 is preferentially expressed in atypical endometrial hyperplasia and endometrial adenocarcinoma

The facilitative transport of monosaccharides in human cells is accomplished by a family of transmembrane proteins, GLUT-1 to GLUT-7, that differ in their tissue distribution, affinities for specific monosaccharides, and physiologic regulation. GLUT-1, a high-affinity glucose transporter, is normally expressed in erythrocytes, the perineurium of peripheral nerves, and capillary endothelial cells of the blood-brain barrier. Although the aberrant expression of GLUT-1 has been reported in a wide spectrum of epithelial malignancies, its possible correlation with the malignant transformation of endometrial epithelium has not been clearly established. The purpose of this study was to evaluate the extent to which benign, hyperplastic, atypical, and malignant endometrial epithelia express GLUT-1. The authors examined the IHC expression of GLUT-1 in cases of proliferative endometrium (n=12), secretory endometrium (n=10), endometrial polyps (n=10), adenomyosis (n=18), simple hyperplasia (n=14), complex hyperplasia without atypia (n=17), complex hyperplasia with atypia (n=17), and adenocarcinoma (n=31). Positive staining was defined as distinct, linear membrane staining, particularly at cell-cell borders. Cells that showed only cytoplasmic staining were considered negative. The percentages of positive cells and staining intensity were assessed in a semiquantitative fashion and scored (1+ to 3+). All cases from proliferative endometrium, secretory endometrium, adenomyosis, and simple hyperplasia and 90% (9/10 cases) of the endometrial polyps were negative for GLUT-1. GLUT-1 was expressed in 24% (4/17 cases) of complex hyperplasia without atypia, 71% (12/17 cases) of complex hyperplasia with atypia, and 90% (28/31 cases) of adenocarcinomas. The extent of staining ranged from occasional positive foci to extensive multifocal staining. GLUT-1 positivity increased in intensity as the distance of tumor cells to stroma increased. The authors conclude that GLUT-1 is preferentially expressed in complex hyperplasia with atypia and in adenocarcinoma and that GLUT-1 immunostaining is useful in distinguishing benign hyperplasia from hyperplasia strongly associated with malignancy. GLUT-1-mediated glucose transport may allow hypoxic tumor cells distant from stromal blood vessels to survive through glycolysis. These data suggest that the expression of GLUT-1 transporter may be closely related to the malignant transformation of epithelial endometrial tumors by supporting their increased need for glucose metabolism.