It has been known for many years that changes in glucose metabolism are associated with neoplasia and research on this phenomenon has focused on the enhancement of glucose transport by malignant transformation. Viral transformation of fibroblastic cells provided the first system in which this enhancement could be studied using non-metabolizable glucose analogs. Kinetic and immunological analyses demonstrated that this was due to an increase in the number of glucose carriers at the plasma membrane. In the last 10 years glucose transporter (GLUT) proteins have been characterized by molecular cloning allowing direct examination of the molecular mechanisms of induction of transporter expression. GLUT proteins are a family of at least six separate isoforms which are encoded by distinct genes and differ in tissue distribution and regulation. Two of these isoforms, GLUT1 and GLUT3, are responsible for the changes associated with malignant transformation. The processes involved in the disregulation of these isoforms in the transformation of cultured fibroblastic and hematopoietic cells are described. Analysis of clinical samples indicates that GLUT1 and GLUT3 are often overexpressed in malignant tissue where they may aid tumor growth.

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