Genetic Disruption of the Multifunctional CD98/LAT1 Complex Demonstrates the Key Role of Essential Amino Acid Transport in the Control of mTORC1 and Tumor Growth.
The CD98/LAT1 complex is overexpressed in aggressive human cancers and is thereby described as a potential therapeutic target. This complex promotes tumorigenesis with CD98 (4F2hc) engaging β-integrin signaling while LAT1 (SLC7A5) imports essential amino acids (EAA) and promotes mTORC1 activity. However, it is unclear as to which member of the heterodimer carries the most prevalent protumoral action. To answer this question, we explored the tumoral potential of each member by gene disruption of CD98, LAT1, or both and by inhibition of LAT1 with the selective inhibitor (JPH203) in six human cancer cell lines from colon, lung, and kidney. Each knockout respectively ablated 90% (CD98 KO: ) and 100% (LAT1 KO: ) of Na(+)-independent leucine transport activity. LAT1 KO: or JPH203-treated cells presented an amino acid stress response with ATF4, GCN2 activation, mTORC1 inhibition, and severe in vitro and in vivo tumor growth arrest. We show that this severe growth phenotype is independent of the level of expression of CD98 in the six tumor cell lines. Surprisingly, CD98 KO: cells with only 10% EAA transport activity displayed a normal growth phenotype, with mTORC1 activity and tumor growth rate undistinguishable from wild-type cells. However, CD98 KO: cells became extremely sensitive to inhibition or genetic disruption of LAT1 (CD98 KO: /LAT1 KO: ). This finding demonstrates that the tumoral potential of CD98 KO: cells is due to residual LAT1 transport activity. Therefore, these findings clearly establish that LAT1 transport activity is the key growth-limiting step of the heterodimer and advocate the pharmacology development of LAT1 transporter inhibitors as a very promising anticancer target. Cancer Res; 76(15); 4481-92. ©2016 AACR.
Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco.
Yann
Y
Cormerais
Institute for Research on Cancer & Aging (IRCAN), CNRS, INSERM, Centre A. Lacassagne, University of Nice-Sophia Antipolis, Nice, France.
Sandy
S
Giuliano
Institute for Research on Cancer & Aging (IRCAN), CNRS, INSERM, Centre A. Lacassagne, University of Nice-Sophia Antipolis, Nice, France.
Renaud
R
LeFloch
Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco.
Benoît
B
Front
Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco.
Jerome
J
Durivault
Marine Biology Department, Centre Scientifique de Monaco (CSM), Monaco.
Eric
E
Tambutté
Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco.
Pierre-André
PA
Massard
Institute for Research in Biomedicine, University of Barcelona and CIBERER, Barcelona, Spain.
Laura Rodriguez
LR
de la Ballina
Research & Development, Fuji Biomedix Co. Ltd, Tokyo, Japan.
Hitoshi
H
Endou
School of Pharmacy, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado.
Michael F
MF
Wempe
Institute for Research in Biomedicine, University of Barcelona and CIBERER, Barcelona, Spain.
Manuel
M
Palacin
Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco.
Scott K
SK
Parks
Medical Biology Department, Centre Scientifique de Monaco (CSM), Monaco. Institute for Research on Cancer & Aging (IRCAN), CNRS, INSERM, Centre A. Lacassagne, University of Nice-Sophia Antipolis, Nice, France. jacques.pouyssegur@unice.fr.
Jacques
J
Pouyssegur
D000601:Amino Acids, Essential; D000818:Animals; D001692:Biological Transport; D045744:Cell Line, Tumor; D005260:Female; D027261:Fusion Regulatory Protein-1; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D008819:Mice, Nude; D046912:Multiprotein Complexes / Q000235:genetics*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics*; D014162:Transfection
D000601:Amino Acids, Essential; D027261:Fusion Regulatory Protein-1; D046912:Multiprotein Complexes; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases