Glutamine, the most abundant amino acid in bloodstream, is the preferred fuel source for enterocytes. Glutamine exerts its functions through the activity of its transporters, which are located in cytomembrane, to transport it into or out of intestinal epithelial cells. Intestine is the primary center for glutamine metabolism in the body. As ASCT2 and B(0)AT1 are the most important glutamine transporters in the intestine, it wound be helpful to gain the knowledge of the structure, function, and pathologic changes and control strategy of the two transporters in order to have a better understanding of the metabolism and function of glutamine.
Amino Acid Transport System ASC ; Biological Transport ; Enterocytes ; Epithelial Cells ; metabolism ; pathology ; Glutamine ; metabolism ; Humans ; Intestine, Small ; metabolism

OBJECTIVETo investigate the effect of ASCT2 gene (glutamine transporter) knock-down by shRNA on biological behaviors of colorectal cancer cells.

METHODSshRNA was transfected into colorectal cancer cells Lovo and SW480 to knockdown ASCT2 mediated by Lipofectamine 2000. Reverse transcription-PCR and Western blot were used to examine the mRNA and protein expression of ASCT2. MTT and transwell assay were used to determine the proliferation and invasiveness of Lovo and SW480 cells. Radioactive-tracer was used to detect the uptake of glutamine.

RESULTSASCT2 mRNA and protein levels were significantly down-regulated by shRNA in Lovo and SW480 cells(P<0.01). MTT and transwell assays showed that ASCT2 knock-down could significantly inhibit the proliferation of Lovo and SW480 cells (A490) and decrease the number of invasive Lovo and SW480 cells from the membrane (both P<0.01). The number of membrane Lovo cells in shASCT group and control group was 46.3±5.9 and 197.7±9.1, respectively while the number of membrane SW480 cells in shASCT group and control group was 29.7±3.8 and 139.0±9.5, respectively. Radioactive-tracer showed that shASCT2 transfection could significantly reduce the uptake of glutamine, with an inhibition rate of 79.15% in Lovo and 67.22% in SW480 cells (both P<0.01).

CONCLUSIONSASCT2 plays an oncogenic role in colonic cancer, and its promotion mechanism may be associated with glutamine metabolism. ASCT2 may be a novel therapeutic target of colonic cancer.

Amino Acid Transport System ASC ; drug effects ; genetics ; physiology ; Cell Line, Tumor ; physiology ; Cell Proliferation ; genetics ; Colorectal Neoplasms ; genetics ; physiopathology ; Down-Regulation ; drug effects ; Gene Knockdown Techniques ; methods ; Glutamine ; drug effects ; genetics ; physiology ; Humans ; Minor Histocompatibility Antigens ; drug effects ; genetics ; physiology ; Neoplasm Invasiveness ; genetics ; physiopathology ; Oncogenes ; drug effects ; genetics ; RNA, Messenger ; physiology ; RNA, Small Interfering ; pharmacology ; Transfection