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Title: Regulation of L-Type Amino Acid Transporter 1 (LAT1) in breast cancer cells by Aryl
Hydrocarbon Receptor (AHR)
T. Salisbury1, J. Tomblin1, S. Arthur2, D. Primerano3, J. Fan3, R. and J. Denvir3
1 Department of Pharmacology, Physiology and Toxicology, 2 Clinical & Translational Science,
3 Department of Biochemistry and Microbiology, Joan C. Edwards School of Medicine, Marshall
University, Huntington, WV 25755, USA.
Background and Objective: Obesity increases breast cancer risk. LAT1 is an amino acid
transporter that is upregulated in cancer. AHR is a ligand-activated transcription factor. RNAseq and published ChIP-seq work indicate that LAT1 is a direct AHR gene target. Our objective
was establish the regulation of LAT1 by AHR in breast cancer cells (BCCs).
Methods: MCF-7 cells were treated with vehicle, adipocyte conditioned medium (adipo-CM), or
the AHR ligand TCDD (10 nM) and quantitative PCR (Q-PCR), chromatin immunoprecipitation
(ChIP), western blot, leucine uptake and proliferation experiments were performed. AHR
knockdown experiments were performed to confirm the role of AHR in the regulation of LAT1.
Results: Adipo-CM and TCDD stimulated increases in LAT1 mRNA and LAT1 protein.
Increases in LAT1 expression correlated with increased binding of AHR and associated
cofactors to an AHR binding site in the LAT1 gene. Upregulation of LAT1 promoted leucine
uptake. Proliferation and LAT1 activation was reduced by AHR knockdown.
Discussion and Conclusion: We have identified an active AHR binding site in the LAT1 gene.
We are investigating which adipocyte factor increases LAT1 transcription via AHR.
Acknowledgements: Supported by a grant from the Appalachian Clinical and Translational
Science Institute, Marshall University Joan C Edwards School of Medicine, and the WV-INBRE
grant (P20GM103434).