L-type amino acid transporter 1 (LAT1), a neutral amino acid transporter, requires covalent association with the heavy chain of 4F2 cell surface antigen (4F2hc) for its functional form. We investigated the importance of LAT1 and 4F2hc expressions to progression in upper urinary tract cancer. We examined their expressions and their relationships to clinicopathologic parameters and clinical outcome in 124 cases. Positive expressions of LAT1 (protein and messenger ribonucleic acid) and 4F2hc (protein) were recognized in 79.8, 89.5, and 87.9% of tumor samples, respectively. In tumor cells, LAT1 protein was detected either as nodular granules within the cytoplasm or diffusely within the cytoplasm and/or on plasma membrane. In the normal urothelium, its expression was detected as nodular granules within the cytoplasm. A correlation with stage was shown for LAT1 protein expression and for a cooperative expression of LAT1 protein with 4F2hc protein (active form of LAT1 protein). Further, in all tumors, a cooperative expression of LAT1 protein and 4F2hc protein was significantly correlated with both overall and disease-free survival rates in the univariate analysis but not in the multivariate analysis. In conclusion, the detection of the active form of LAT1 protein would appear to be of value in informing the risk of progression in transitional cell carcinoma of the upper urinary tract.

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No previous study has investigated neutral large amino acid transporter type 1 (LAT1) in normal lung cells, or in atypical adenomatous hyperplasia(s) (AAH) and nonmucinous bronchioloalveolar carcinoma(s) (NMBAC) of the lung. The authors examined: (1) the levels of LAT1 mRNA/glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA in 41 normal lung tissues and 34 NMBAC using semiquantitative reverse transcription-polymerase chain reaction; (2) LAT1 mRNA and protein expressions in 35 normal lung tissues, 34 AAH (11 lesions were interpreted as low-grade AAH and 23 as high-grade AAH), and 43 NMBAC using in situ hybridization and immunohistochemistry; and (2) the association of the incidences of LAT1 mRNA and protein expressions with cell proliferation in these lesions. The level of LAT1 mRNA/GAPDH mRNA (1) tended to be higher in NMBAC (12.0+/-8.1) than in normal lung tissues (1.0+/-0.2), and (2) covered a much wider range (from 0 to 276) in NMBAC than in normal lung tissues (from 0 to 5.8), with six NMBAC having values higher than 7.0, while 5.8 was the highest value detected in normal lung tissues. In peripheral normal lung tissues, LAT1 mRNA and protein were detected in bronchial surface epithelial cells and alveolar macrophages (but not in nonciliated bronchiolar epithelial cells, or in alveolar type I or type II cells). In bronchial surface epithelial cells, LAT1 protein appeared to be of a nodular type, which was considered to be a nonfunctional protein pattern. The incidences of positive expressions for LAT1 mRNA and protein were 54.5 and 27.3% in low-grade AAH, 65.2 and 52.2% in high-grade AAH, and 65.1 and 79.1% in NMBAC, respectively. In the case of LAT1 protein expression, significant differences could be shown between total (low-grade plus high-grade) AAH and NMBAC, and between low-grade AAH and NMBAC. Thus, in terms of the incidence of LAT1 protein expression, high-grade AAH appeared intermediate between low-grade AAH and NMBAC. The Ki-67 labeling index (a cell proliferation score) was significantly higher in those AAH and NMBAC that were LTA1-protein-positive than in their LAT1-protein-negative counterparts. In conclusion, LAT1 expression may increase with the upregulation of metabolic activity and cell proliferation in high-grade AAH and NMBAC.