ABSTRACT
Most normal cells express L-type amino acid transporter 2 (LAT2). However, L-type amino acid transporter 1 (LAT1) is highly expressed in many tumor cells and presumed to support their increased growth and proliferation. This study examined the effects of JPH203, a selective LAT1 inhibitor, on cell growth and its mechanism for cell death in Saos2 human osteosarcoma cells. FOB human osteoblastic cells and Saos2 cells expressed LAT1 and LAT2 together with their associating protein 4F2 heavy chain, but the expression of LAT2 in the Saos2 cells was especially weak. JPH203 and BCH, a non-selective L-type amino acid transporter inhibitor, potently inhibited L-leucine uptake in Saos2 cells. As expected, the intrinsic ability of JPH203 to inhibit L-leucine uptake was far more efficient than that of BCH in Saos2 cells. Likewise, JPH203 and BCH inhibited Saos2 cell growth with JPH203 being superior to BCH in this regard. Furthermore, JPH203 increased apoptosis rates and formed DNA ladder in Saos2 cells. Moreover, JPH203 activated the mitochondria-dependent apoptotic signaling pathway by upregulating pro-apoptotic factors, such as Bad, Bax, and Bak, and the active form of caspase-9, and downregulating anti-apoptotic factors, such as Bcl-2 and Bcl-xL. These results suggest that the inhibition of LAT1 activity via JPH203, which may act as a potential novel anti-cancer agent, leads to apoptosis mediated by the mitochondria-dependent intrinsic apoptotic signaling pathway by inducing the intracellular depletion of neutral amino acids essential for cell growth in Saos2 human osteosarcoma cells.
Subject(s)
Humans , Amino Acid Transport Systems , Amino Acids, Neutral , Fusion Regulatory Protein 1, Heavy Chain , Apoptosis , Caspase 9 , Cell Death , DNA , Leucine , Osteoblasts , OsteosarcomaABSTRACT
Objective To explore the expression and role of LAT 1 in mouse uterus on early placenta formation on day 8 of pregnancy (D8).Methods One hundred and twenty 6-8-week old SPF female Kunming mice were used in this study.Immunohistochemistry was applied to determine the localization of LAT 1 protein in the mouse uterus on D8 of preg-nancy.The ectoplacental cones (EPCs) were dissected out from D8.5 uterus, and then cultured in vitro with different con-centrations of BCH (2-aminobicyclo-(2,2,1)-heptane-2-carboxylic acid, specific antagonist of LAT1) and L-leucine ( substrate of LAT1) to determine the role of LAT1 during the EPC attachment and outgrowth .Results LAT1 protein was highly expressed in secondary decidual zone and also positively expressed in the mouse uterus on D 8.As a specific antago-nist of LAT1, BCH significantly suppressed the ectoplacental cone outgrowth , whereas L-leucine showed no significant effect on it.Conclusions LAT1 is expressed in the mouse uterus during early placenta formation and promotes ectoplacen -tal cone outgrowth , suggesting that LAT1 may promote the trophoblast invasion into maternal decidual tissue , and partici-pates in the early formation of placenta .
ABSTRACT
L-amino acid transporter 1 ( LAT1) is a member of L-amino transporter family and an important heterodi?meric amino acid transporter that belongs to subfamily of SLC7. LAT1 mainly mediates trans-membrane transportation of those neutral amino acids that had cyclobenzene or long side chains with high molecular mass such as L-Leu, L-Met and L-Phe as well as some amino acid analogues such as melphalan, L-DOPA and thyroxine in a Na+and ATP-independent diffu?sion. As LAT1 was abnormally overexpressed in various transformed cell lines, it might be related with tumor stage and prog?nosis. It is not only a biomarker that specifically expressed in some tumor cells but also plays an important role in tumor diag?nosis and therapy. Here we demonstrate the structure of LAT1 and its mechanism in transport peculiarity. We also reviewed the development of LAT1 in tumor diagnosis and treatment.