High expression of L-type amino acid transporter 1 in infiltrating glioma cells.

L-type amino acid transporter 1 (LAT1), a neutral amino acid transport agent, is essential for the transport of large neutral amino acids. LAT1 also corresponds to tumor-associated gene-1 (TA1), an oncofetal antigen that is expressed primarily in fetal tissues and cancer cells such as glioma cells. We have investigated the expression of the transporter in the human primary glioma tissue from 68 patients. Among these patients, we could see the border zone between tumors and normal bain tissues in 10 patients. By WHO criteria, two of the specimens were diagnosed as grade 2, three as grade 3, and five as grade 4 [glioblastoma multiforme (GBM)]. In 9 of 10 cases, we could identify the infiltrating glioma cells associated with stronger immunoreactivity for LAT1. These tumor cells aggregated around the neurons in the border zone and were often found in the perivascular space. In one GBM case, the tumors seemed to develop expansively and separated from the normal brain with a border of arachnoid membrane. The expression of LAT1 was always higher in infiltrating glioma cells than in cells located in the center of the tumor. These findings suggest that LAT1 is one of the molecular targets for glioma therapy.