Complementary DNA of a rat brain glucose transporter gene was used to examine the expression of glucose-transporter messenger RNA in paired human hepatocellular carcinomas and adjacent nontumorous liver tissues, as well as in human hepatoma cell lines and human fetal liver samples. High expression of a major 2.8-kilobase glucose-transporter transcript was seen in all hepatoma cell lines and fetal liver samples examined, whereas a much lower level of expression was observed in liver tissues. When pairs of liver tissues were examined, elevation of glucose-transporter RNA levels was observed in most of the hepatocellular carcinoma tissues examined. (HEPATOLOGY 1990;11:118-
122.)
All mammalian cell membranes contain protein involved in glucose transport (1). However, different transporting systems may be involved in different tissues. In the kidneys and intestines, a sodiumdependent active glucose transport is observed, whereas in nonepithelial cells such as erythrocytes a facilitated carrier has been reported (1). In muscle and fat cells the glucose uptake is stimulated by insulin (1).
By screening cDNA libraries with an antibody against purified human erythrocyte glucose transporter, Mueckler et al. (2) and Birnbaum, Haspel and Rosen (3) obtained facilitated glucose-transporter cDNAs from a human hepatoma cell line, HepG2, and from a rat brain. The sequence of cDNA predicts that human and rat glucose transporters share 97.6% identity in protein sequence (3). More recently, cDNAs from liver, skeletal muscle and adipocytes have been cloned and show some degree of sequence homology to the erythrocyte glucose transporter (4-6). By using HepG2 or rat brain glucose-transporter cDNA as probes, a single 2.8-kilobase (kb) transcript was observed in most human and rat tissues studied (3, 7).