Indoleamine 2,3-dioxygenase activity and L-tryptophan transport in human breast cancer cells

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Travers, M. and Gow, Iain F. and Barber, M.C. and Thomson, Jean and Shennan, David B. (2004) Indoleamine 2,3-dioxygenase activity and L-tryptophan transport in human breast cancer cells. BBA - Biomembranes, 1661 (1). pp. 106-112. ISSN 0005-2736 (http://dx.doi.org/10.1016/j.bbamem.2003.12.004)

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Abstract

The activity and expression of indoleamine 2,3-dioxygenase together with -tryptophan transport has been examined in cultured human breast cancer cells. MDA-MB-231 but not MCF-7 cells expressed mRNA for indoleamine 2,3-dioxygenase. Kynurenine production by MDA-MB-231 cells, which was taken as a measure of enzyme activity, was markedly stimulated by interferon-γ (1000 units/ml). Accordingly, -tryptophan utilization by MDA-MB-231 cells was enhanced by interferon-γ. 1-Methyl- -tryptophan (1 mM) inhibited interferon-γ induced kynurenine production by MBA-MB-231 cells. Kynurenine production by MCF-7 cells remained at basal levels when cultured in the presence of interferon-γ. -Tryptophan transport into MDA-MB-231 cells was via a Na+-independent, BCH-sensitive pathway. It appears that system L (LAT1/CD98) may be the only pathway for -tryptophan transport into these cells. 1-Methyl- , -tryptophan trans-stimulated -tryptophan efflux from MDA-MB-231 cells and thus appears to be a transported substrate of system L. The results suggest that system L plays an important role in providing indoleamine-2,3-dioxygenase with its main substrate, -tryptophan, and suggest a mechanism by which estrogen receptor-negative breast cancer cells may evade the attention of the immune system.

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