Glut-1 expression in dysplastic and regenerative lesions of the colon

Monosaccaride transporter proteins are responsible for transmembrane transport of monosaccarides into cells. Glucose transporter protein 1 (Glut-1) is most prevalent in the cell membranes of erythrocytes and facilitates transport of glucose in tissues with barrier functions, i.e. blood brain barrier. Expression of Glut-1 in malignant tumors is increased due to increased metabolic need of the proliferating cell populations. In colorectal adenomas and carcinomas, membranous expression of Glut-1 has been associated with higher grade of tumors and decreased survival time. We studied the expression of Glut-1 in dysplastic proliferations of the colon which included sporadic adenomas and dysplasia associated lesions (DALM) in patients with ulcerative colitis and reactive/regenerative proliferations of the colon, including non-dysplastic chronic colitis, acute colitis and ischemia. Two patterns of Glut-1 expression were detected. Most adenomas and DALMs showed at least focal membranous expression of Glut-1. In addition a second staining pattern was recognized which consisted of prominent supranuclear dots. This pattern of staining was not only seen in adenomas and DALM but also in non-dysplastic areas immediately surrounding sporadic adenomas, in regenerative chronic colitis and in areas surrounding acute inflammation. Areas away from dysplasia did not show any positive staining for Glut-1. We conclude that two distinct patterns of Glut-1 expression may be found in colonic epithelial proliferation: membranous staining, associated with dysplasia, and, heretofore not described, supranuclear staining which may be related to Glut-1 expression secondary to expression of specific growth factors and not necessarily related to dysplasia.