Derangements of Cationic Amino Acid Transport in Fibroblasts from Human Desmoid Tumor
An increased rate of amino acid uptake by System A has been considered a consistent feature of tumor cells1. This inference is based on the following facts: (a) enhancements in the transport rates of site A-reactive amino acids are among the early events associated with cell transformation in vitro 2; (b) increased uptake of some amino acid substrates of System A has been reported for virus- and chemically-transformed cell lines3,4 and (c) rat fibroblasts made tumorigenic by ras transfection exhibit a somewhat faster uptake of 2-(methyl)aminoisobutyric acid (a transport-specific substrate of System A) than non-transfected cells5. However, tumor cell lines have been described that do not exhibit this metabolic feature6,7 and little is known on amino acid transport changes in cells from spontaneously occurring tumors8. We therefore devised experiments to investigate the amino acid transport in cells from a spontaneous human tumor (desmoid tumor fibroblasts) as compared with their normal counterpart (skin-derived fibroblasts). To avoid variability among individuals for transport, the comparison was made between cell cultures obtained from the same donor. The present study concerns the six transport systems for amino acids so far characterized in human fibroblasts9–13.
KeywordsAmino Acid Transport Desmoid Tumor Null Point Amino Acid Uptake Cationic Amino Acid Transport
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