l-Leucine transport in human breast cancer cells (MCF-7 and MDA-MB-231): kinetics, regulation by estrogen and molecular identity of the transporter

Abstract

The transport of L-leucine by two human breast cancer cell lines has been examined. L-leucine uptake by MDA-MB-231 and MCF-7 cells was via a BCH-sensitive, Na+ -independent pathway. L-leucine uptake by both cell lines was inhibited by L-alanine, D-leucine and to a lesser extent by L-lysine but not by L-proline. Estrogen (17beta-estradiol) stimulated L-leucine uptake by MCF-7 but not by MDA-MB-231 cells. L-leucine efflux from MDA-MB-231 and MCF-7 cells was trans-stimulated by BCH in a dose-dependent fashion. The effect of external BCH on L-leucine efflux from both cell types was almost abolished by reducing the temperature from 37 to 4 degrees C. There was, however, a significant efflux of L-leucine under zero-trans conditions which was also temperature-sensitive. L-glutamine, L-leucine, D-leucine, L-alanine, AIB and L-lysine all trans-stimulated L-leucine release from MDA-MB-231 and MCF-7 cells. In contrast, D-alanine and L-proline had little or no effect. The anti-cancer agent melphalan inhibited L-leucine uptake by MDA-MB-231 cells but had no effect on L-leucine efflux. Quantitative real-time PCR revealed that LAT1 mRNA was approximately 200 times more abundant than LAT2 mRNA in MCF-7 cells and confirmed that MDA-MB-231 cells express LAT1 but not LAT2 mRNA. LAT1 mRNA levels were higher in MCF-7 cells than in MDA-MB-231 cells. Furthermore, LAT1 mRNA was more abundant than CD98hc mRNA in both MDA-MB-231 and MCF-7 cells. The results suggest that system L is the major transporter for L-leucine in both MDA-MB-231 and MCF-7 cells. It is possible that LAT1 may be the major molecular correlate of system L in both cell types. However, not all of the properties of system L reflected those of LAT1/LAT2/CD98hc.

The Farnesoid X Receptor Is Expressed in Breast Cancer and Regulates Apoptosis and Aromatase Expression

“…This differential regulation between liver and breast may be due to numerous tissue-specific differences, including coactivator/corepressor balance or availability. Given the key role of FXR in regulating the expression of transporters in the liver and the restricted high-level expression of FXR in normal ductal epithelial cells, the effects of FXR ligand on the expression of other transporters, known to be expressed in breast, were examined (37,47). Both MRP1 and SLC7A5 were down-regulated by FXR ligand in MCF-7 cells.…”

L-Type Amino Acid Transporter-1 Expressed in Human Astrocytomas, U343MGa

“…They also studied the protein expression of LAT1 and 4F2hc in T24 cells. 18,19) Shennan et al 27) reported the Na ϩ -independent BCH-sensitive L-leucine transport activity and expression of LAT1 mRNA in human breast cancer cells, MCF-7 and MDA-MB-231. Here, we studied to compare the expression levels of LAT1 and 4F2hc mRNAs and the proteins in several human tumor cell lines including gastrointestinal epithelial cell lines, with those in HeLa and T24 cells by real-time quantitative PCR and Western blotting, respectively.…”

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

“…Actively proliferating cancer cells require more nutrients, such as amino acids and glucose, than quiescent cells. With regard to the relationship between LAT1 and breast cancer, there have been only four publications so far reporting the role of LAT1 in two cultured breast cancer cell lines, from Shennan and his colleagues [17][18][19][20].…”