Expression of the neutral amino acids transporter ASCT1 in esophageal carcinomas

Document Type

Journal Article

Publication Date

12-1-2000

Journal

Anticancer Research

Volume

20

Issue

5 C

Keywords

Adenocarcinoma; Amino acid transporter; ASCT1; Cancer; Esophagus; Glucose transporter; Glut-1; Glut1; Immunohistochemistry; Squamous cell carcinoma

Abstract

Cancers cells utilize more glucose and amino acids than their benign counterparts. Overexpression of the facilitative glucose transporter Glut1 in human cancers was found to correlate with aggressive biologic behavior. The aim of this work was to determine whether the neutral amino acid transporter ASCT1 is expressed in human esophageal carcinomas, and to correlate the findings with Glut1 expression. Sections of formalin-fixed and paraffin-embedded tissue from 42 cases of esophageal carcinomas were entered in the study. Immunohistochemical staining was performed using a rabbit anti-ASCT1 IgG developed in our laboratory, and anti-Glut1 antibody, using standard avidin-streptavidine immunoperoxidase method. Sections of formalin-fixed and paraffin-embedded HepG2 cells were used as positive controls. The percent of ASCT1-positive cells was scored. Statistical analysis was performed using Fisher's exact test. ASCT1 immunoreactivity was cytoplasmic, whereas Glut1 was membranous. Significantly more adenocarcinomas expressed ASCT1 than squamous cell carcinomas (p<0.0001), wherea's Glut1 expression was similar in both minor types. There was no association between the exppression of either transporter and lymph node metastasis. Glut1 was expressed more often in the better differentiated than the poorly differentiated squamous carcinomas (p=0.003). These results sugget that unlike in squamous cell carcinoma, ASCT1 plays a significant role in the recruitment of amino acids in adebnocarcinoma of the esophagus, and suggest that the metabolic needs, and uptake of neutrients, are regulated differently in these two tumor types. Additional studies with larger number of patients are needed to determine the biological significance of ASCT1 expression in esophageal carcinomas.

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