Tyrosine-Chlorambucil Conjugates Facilitate Cellular Uptake through L-Type Amino Acid Transporter 1 (LAT1) in Human Breast Cancer Cell Line MCF-7.

Piman Pocasap,Jukka Leppänen,Juulia Järvinen,Juri Timonen,Jussi Kärkkäinen,Jarkko Rautio,Natthida Weerapreeyakul

doi:10.3390/ijms21062132

Abstract

l-type amino acid transporter 1 (LAT1) is an amino acid transporter that is overexpressed in several types of cancer and, thus, it can be a potential target for chemotherapy. The objectives of this study were to (a) synthesize LAT1-targeted chlorambucil derivatives and (b) evaluate their LAT1-mediated cellular uptake as well as antiproliferative activity in vitro in the human breast cancer MCF-7 cell line. Chlorambucil was conjugated to l-tyrosine—an endogenous LAT1 substrate—via either ester or amide linkage (compounds 1 and 2, respectively). While chlorambucil itself did not bind to LAT1, its derivatives 1 and 2 bound to LAT1 with a similar affinity as with l-tyrosine and their respective cellular uptake was significantly higher than that of chlorambucil in MCF-7. The results of our cellular uptake study are indicative of antiproliferative activity, as a higher intracellular uptake of chlorambucil derivatives resulted in greater cytotoxicity than chlorambucil by itself. LAT1 thus contributes to intracellular uptake of chlorambucil derivatives and, therefore, increases antiproliferative activity. The understanding gained from our research can be used in the development of LAT1-targeted anticancer drugs and prodrugs for site-selective and enhanced chemotherapeutic activity.

Highlights

Division of Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, Khon Kaen University, Human High Performance and Health Promotion Research Institute, Khon Kaen University, Khon Kaen 40002, Thailand
Our results demonstrate that the increased intracellular uptake attributed to l-type amino acid transporter 1 (LAT1) transport of derivatives 1 and 2 is positively related to their higher antiproliferative activity
We suggest that thedrug design approach might be applied to other chemotherapeutic agents that contain available functional group(s) to conjugate to the LAT1 substrate, rectifying permeability and selectivity issues

Summary

Introduction

Division of Pharmaceutical Chemistry, Faculty of Pharmaceutical Sciences, Khon Kaen University, Human High Performance and Health Promotion Research Institute, Khon Kaen University, Khon Kaen 40002, Thailand. The objectives of this study were to (a) synthesize LAT1-targeted chlorambucil derivatives and (b) evaluate their. While chlorambucil itself did not bind to LAT1, its derivatives 1 and 2 bound to LAT1 with a similar affinity as with l-tyrosine and their respective cellular uptake was significantly higher than that of chlorambucil in MCF-7. LAT1 contributes to intracellular uptake of chlorambucil derivatives and, increases antiproliferative activity. The understanding gained from our research can be used in the development of LAT1-targeted anticancer drugs and prodrugs for site-selective and enhanced chemotherapeutic activity. LAT1 has been demonstrated to transport amino acid-containing prodrugs, in which amino acids as promoieties have been linked with non-substrate parent drugs. The prodrug strategy has been exploited, for example, to utilize LAT1 as a drug carrier to increase drug permeability through the blood–brain barrier by conjugating various drugs (e.g., dopamine, ketoprofen, and valproic acid) to various amino acids [2,3,4]

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