ASCT2 is the major glutamine transporter in MM cells. (A) SLC38A1, SLC1A5, and SLC7A5 gene expression in MM cells, incubated in standard growth medium ([Gln] = 4 mM), were analyzed through real-time PCR. Transporter expression in the human hepatocellular carcinoma cell line HepG2 was used as a positive control. Gene expression was normalized to the expression of RPL-15. Means ± SD of 3 experiments, with 2 determinations each, are shown. (B) SNAT1, ASCT2, and LAT1 expression in HMCLs, incubated in standard growth medium, was analyzed by western blot. HepG2 cells were used as a positive control. β-Tubulin was used for loading control. (C) 1-Min uptake of l-[3,4-³H(N)] Gln (0.6 mM, 20 μCi/mL; Amersham) by RPMI 8226 was performed in serum-free culture medium in the absence (−) or in the presence of the transport inhibitors α-(methylamino)isobutyric acid (MeAIB, 20 mM), l-γ-glutamyl-p-nitroanilide (GPNA, 3 mM), or 2-amino-2-norbornanecarboxylic acid (BCH, 20 mM). Means ± SD of 3 experiments, with 5 independent determinations each, are shown. ***P<.001 vs control. (D) ASCT2 expression was investigated in lysates of the CD138⁺ population isolated from monoclonal gammopathies patients. The same membrane shown in Figure 2E was blotted with anti-ASCT2 antibody.