Characterization of the system L amino acid transporter in T24 human bladder carcinoma cells

Abstract

System L is a major nutrient transport system responsible for the Na(+)-independent transport of large neutral amino acids including several essential amino acids. In malignant tumors, a system L transporter L-type amino acid transporter 1 (LAT1) is up-regulated to support tumor cell growth. LAT1 is also essential for the permeation of amino acids and amino acid-related drugs through the blood-brain barrier. To search for in vitro assay systems to examine the interaction of chemical compounds with LAT1, we have investigated the expression of system L transporters and the properties of [14C]L-leucine transport in T24 human bladder carcinoma cells. Northern blot, real-time quantitative PCR and immunofluorescence analyses have reveled that T24 cells express LAT1 in the plasma membrane together with its associating protein 4F2hc, whereas T24 cells do not express the other system L isoform LAT2. The uptake of [14C]L-leucine by T24 cells is Na(+)-independent and almost completely inhibited by system L selective inhibitor BCH. The profiles of the inhibition of [14C]L-leucine uptake by amino acids and amino acid-related compounds in T24 cells are comparable with those for the LAT1 expressed in Xenopus oocytes. The majority of [14C]L-leucine uptake is, therefore, mediated by LAT1 in T24 cells. Consistent with LAT1 in Xenopus oocytes, the efflux of preloaded [14C]L-leucine is induced by extracellularly applied substrates of LAT1 in T24 cells. This efflux measurement has been proven to be more sensitive than that in Xenopus oocytes, because triiodothyronine, thyroxine and melphalan were able to induce the efflux of preloaded [14C]L-leucine in T24 cells, which was not detected for Xenopus oocyte expression system. T24 cell is, therefore, proposed to be an excellent tool to examine the interaction of chemical compounds with LAT1.

18F-FMT Uptake Seen Within Primary Cancer on PET Helps Predict Outcome of Non–Small Cell Lung Cancer

“…In the present study, the mean SUV max of 18 F-FMT differed significantly between adenocarcinoma (mean, 1.6 6 0.8) and nonadenocarcinomatous disease (mean, 2.1 6 1.1; P 5 0.0031). LAT1 is widely expressed in primary human cancers and several cancer cell lines, where it has been shown to play essential roles in growth and survival (21)(22)(23)(24)(25). LAT1 is overexpressed in malignant tumors and is associated with tumor proliferation, angiogenesis, and poor survival.…”

Potential Biomarker of L-type Amino Acid Transporter 1 in Breast Cancer Progression

“…It has been shown that LAT1 is overexpressed in some tumor tissues [34,35] and is actively involved in the proliferation of vascular smooth muscle cells [36]. In order to investigate whether or not LAT1 is involved in the proliferation of breast cancer cells, we employed BCH, a selective inhibitor of LAT1 [37,38], to inhibit the proliferation of malignant MDA-MB-231 cells. In the presence of 10 mM BCH, the proliferation of MDA-MB-231 cells was significantly reduced in comparison with control cells grown in the absence of BCH at either 24 h or 48 h post-cell treatment (Fig.…”

Activation of a system A amino acid transporter, ATA1/SLC38A1, in human hepatocellular carcinoma and preneoplastic liver tissues

“…Indeed, most cells activate various different systems that are required for amino acid transport (1). Among these systems, the system L-type amino acid transporter-1 (LAT-1) is up-regulated in human bladder carcinoma cells (2), esophageal adenocarcinoma (3), epidermoid carcinoma (4), oral squamous cell carcinoma (5) and liver cancer (6). On the other hand, another of the major amino acid transport systems, system A, catalyses the transport of most of the small aliphatic amino acids including alanine, serine and glutamine (1).…”