Targeting glutamine transport to suppress melanoma cell growth

Abstract

Amino acids, especially leucine and glutamine, are important for tumor cell growth, survival and metabolism. A range of different transporters deliver each specific amino acid into cells, some of which are increased in cancer. These amino acids consequently activate the mTORC1 pathway and drive cell cycle progression. The leucine transporter LAT1/4F2hc heterodimer assembles as part of a large complex with the glutamine transporter ASCT2 to transport amino acids. In this study, we show that the expression of LAT1 and ASCT2 is significantly increased in human melanoma samples and is present in both BRAF WT (C8161 and WM852) and BRAF V600E mutant (1205Lu and 451Lu) melanoma cell lines. While inhibition of LAT1 by BCH did not suppress melanoma cell growth, the ASCT2 inhibitor BenSer significantly reduced both leucine and glutamine transport in melanoma cells, leading to inhibition of mTORC1 signaling. Cell proliferation and cell cycle progression were significantly reduced in the presence of BenSer in melanoma cells in 2D and 3D cell culture. This included reduced expression of the cell cycle regulators CDK1 and UBE2C. The importance of ASCT2 expression in melanoma was confirmed by shRNA knockdown, which inhibited glutamine uptake, mTORC1 signaling and cell proliferation. Taken together, our study demonstrates that ASCT2-mediated glutamine transport is a potential therapeutic target for both BRAF WT and BRAF V600E melanoma.

Amino Acid Transporters in Cancer and Their Relevance to “Glutamine Addiction”: Novel Targets for the Design of a New Class of Anticancer Drugs

“…Leucine is a well-known activator of mTOR signaling (12), and pharmacologic inhibition of SLC7A5 transport function suppresses mTOR signaling and tumor growth in a number of model systems (13)(14)(15)(16). But how does SLC7A5, an obligatory exchanger, mediate the entry of leucine into cancer cells to impact on mTOR?…”

Relationship between [ 14 C]MeAIB uptake and amino acid transporter family gene expression levels or proliferative activity in a pilot study in human carcinoma cells: Comparison with [ 3 H]methionine uptake

“…There are approximately fifty different types of amino acid transporters, but only LAT1 [50], LAT3 [51], ASCT2 [52], ATB 0, + [53] and xCT [54] have been reported to be expressed at high levels on the surface of cancer cells. Recently, there have been numerous reports in cancer cells related to glutamine transport via ASCT2 and LAT1 [55][56][57].…”

N‑Myc downstream‑regulated gene 2 restrains glycolysis and glutaminolysis in clear cell renal cell carcinoma

“…ASC amino-acid transporter 2 (ASCT2) is the primary glutamine transporter in cancer cells (14). support their proliferation (15); on the basis of this mechanism, inhibiting glutamine transportation by ASCT2 has the potential to be a cancer therapy (16). In glutaminolysis, glutaminase 1 (GLS1) is the first rate-limiting enzyme, and is regulated by v-myc avian myelocytomatosis viral oncogene (c-Myc) (17)(18)(19).…”