Expression of facilitative glucose transporters in gastric tumors.

BACKGROUND/AIMS: Although cancer cells are known to have an increased rate of glucose metabolism, the complete mechanism for increased glucose uptake in tumor cells is unknown.

METHODOLOGY

The presence of mRNA for 5 facilitative glucose transporter (GLUT) isoforms was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) in paired samples of normal gastric mucosa and gastric tumor from 20 individuals. Expression of GLUT proteins was immunohistochemically determined in 70 resected gastric cancer specimens.

RESULTS

By using RT-PCR, GLUT2 mRNA was detected in 80% of normal gastric mucosal samples, while GLUT4 mRNA was seen in only 40%, GLUT1 mRNA was not detected in normal gastric mucosa. In gastric carcinoma samples, GLUT1 mRNA was detected in 19 out of 20 cases (95%) and GLUT2, GLUT3, and GLUT4 mRNAs in all samples. By immunohistochemistry, GLUT1 protein was detected in 19% of the tumors. A majority of tumors (61%) expressed 1 or more transporter protein. The presence of GLUT1 protein in a tumor was positively correlated with the tumor's invasion into the gastric wall, lymphatics or blood vessels and with lymph node metastases. The post-operative survival of patients with tumor expressing GLUT1 protein was significantly worse than those with tumor without GLUT1 protein.

CONCLUSIONS

Gastric cancer cells may acquire the ability to produce GLUT1 mRNA by malignant transformation. Increased expression of the high-affinity glucose transporters, GLUT1 and/or GLUT4, in tumor cells may drain glucose preferentially to the tumor at the expense of the tumor-bearing host.