Hemocompatible LAT1-inhibitor can induce apoptosis in cancer cells without affecting brain amino acid homeostasis

Abstract

Increased amounts of amino acids are essential for cancer cells to support their sustained growth and survival. Therefore, inhibitors of amino acid transporters, such as l-type amino acid transporter 1 (LAT1) have been developed. In this study, a previously reported LAT1-inhibitor (KMH-233) was studied for its hemocompatibility and toxicity towards human umbilical vein endothelial cells (HUVEC) and human aortic smooth muscle cells (AoSMCs). Furthermore, the cytotoxic effects against human breast adenocarcinoma cells (MCF-7) and its ability to affect mammalian (or mechanistic) target of rapamycin (mTOR) and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling were evaluated. Moreover, the effects of this inhibitor to modulate LAT1 function on the cell surface and the brain amino acid homeostasis were evaluated after intraperitoneal (i.p.) administration of LAT1-inhibitor (23 µmol/kg) in mice. The results showed that LAT1-inhibitor (KMH-233) is hemocompatible at concentrations below 25 µM and it does not affect coagulation in plasma. However, it can reduce the total protein amount of mTOR and NF-κB, resulting in increased apoptosis in LAT1-expressing cancer cells. Most importantly, the inhibitor did not affect mouse brain levels of l-Leu, l-Tyr or l-Trp or modulate the function of LAT1 on the MCF-7 cell surface. Therefore, this inhibitor can be considered as a safe but effective anti-cancer agent. However, due to the compensative mechanism of cancer cells for their increased amino acid demand, this compound is most effective inducing apoptosis when used in combinations with other chemotherapeutics, such as protease inhibitor, bestatin, as demonstrated in this study.

L-Type Amino Acid Transporter 1 Enables the Efficient Brain Delivery of Small-Sized Prodrug across the Blood–Brain Barrier and into Human and Mouse Brain Parenchymal Cells

“…10,11 In addition, LAT1 is also expressed in mouse brain parenchymal cells such as astrocytes and microglia. 12 Moreover, LAT1 utilization does not interrupt the brain amino acid homeostasis, 8,13,14 inflammatory insult. 15 Therefore, LAT1 is believed to transport its substrates across the BBB and the cellular barriers of the brain parenchyma effectively and harmlessly.…”

“…Despite the low transport capacity of LAT1 compared to that of glucose transporter(s), LAT1 is highly and selectively expressed in both luminal and abluminal sides of the BBB. , In addition, LAT1 is also expressed in mouse brain parenchymal cells such as astrocytes and microglia . Moreover, LAT1 utilization does not interrupt the brain amino acid homeostasis, ,, and its expression and function are not altered by the inflammatory insult . Therefore, LAT1 is believed to transport its substrates across the BBB and the cellular barriers of the brain parenchyma effectively and harmlessly.…”

Functional Characterization of the Solute Carrier LAT-1 (SLC7A5/SLC3A2) in Human Brain Capillary Endothelial Cells with Rapid UPLC-MS/MS Quantification of Intracellular Isotopically Labelled L-Leucine

“…High LAT-1 HD expression at the BBB and in brain tumors can be used for the PET imaging of tumors with radiolabeled amino acid tracers [ 20 , 21 , 22 ] and as a potential target for cancer pharmacotherapy. Various LAT-1 HD targeting approaches for cancer treatment and brain delivery are currently under investigation [ 23 , 24 , 25 , 26 , 27 ]. A potential dual targeting of brain tumors, based on the high expression of LAT-1 HD in both the BBB and brain tumors, could contribute to the development of effective treatment options.…”

Amino Acid Transporter LAT1 (SLC7A5) Mediates MeHg-Induced Oxidative Stress Defense in the Human Placental Cell Line HTR-8/SVneo

“…The global importance of LAT1 is evident in LAT1 knockout mice that were embryonically lethal in the homozygous but not in the heterozygous state [ 36 ]. Furthermore, inhibition of LAT1 reduced cell viability in human umbilical vein endothelial cells, human primary aortic smooth muscle cells, and two human renal cancer cell lines [ 37 , 38 ]. While LAT1 deficiency is involved in many pathophysiological disorders, it may also be relevant for pregnancy conditions, such as fetal growth restriction (FGR) [ 39 , 40 ].…”