Image-based RNA interference screening reveals an individual dependence of acute lymphoblastic leukemia on stromal cysteine support

// Jeannette Boutter 1, 8, * , Yun Huang 1, 8, * , Blerim Marovca 1, 8 , Andreas Vonderheit 2 , Michael A. Grotzer 1, 8 , Cornelia Eckert 3 , Gunnar Cario 4 , Bernd Wollscheid 5 , Peter Horvath 6, 7 , Beat C. Bornhauser 1, 8, * , Jean-Pierre Bourquin 1, 8, * 1 Department of Pediatric Oncology, University Children’s Hospital Zurich, Zurich, Switzerland 2 Institute of Molecular Biology, Mainz, Germany 3 Department of Pediatric Oncology/Hematology, Charité Universitätsmedizin Berlin, Germany 4 Department of Pediatrics, University Medical Centre Schleswig-Holstein, Kiel, Germany 5 Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, Zurich, Switzerland 6 Synthetic and Systems Biology Unit, Biological Research Center, Szeged, Hungary 7 Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland 8 Children's Research Center (CRC), University Children's Hospital Zurich, Zurich, Switzerland * These authors contributed equally to this work Correspondence to: Jean-Pierre Bourquin, email: Jean-Pierre.Bourquin@kispi.uzh.ch Keywords: acute lymphoblastic leukemia, bone marrow stroma, microenvironment, oxidative stress, RNAi screen Received: September 02, 2014      Accepted: October 03, 2014      Published: November 01, 2014 ABSTRACT Interactions with the bone marrow microenvironment are essential for leukemia survival and disease progression. We developed an imaging-based RNAi platform to identify protective cues from bone marrow derived mesenchymal stromal cells (MSC) that promote survival of primary acute lymphoblastic leukemia (ALL) cells. Using a candidate gene approach, we detected distinct responses of individual ALL cases to RNA interference with stromal targets. The strongest effects were observed when interfering with solute carrier family 3 member 2 (SLC3A2) expression, which forms the cystine transporter x c − when associated with SLC7A11. Import of cystine and metabolism to cysteine by stromal cells provides the limiting substrate to generate and maintain glutathione in ALL. This metabolic interaction reduces oxidative stress in ALL cells that depend on stromal x c − . Indeed, cysteine depletion using cysteine dioxygenase resulted in leukemia cell death. Thus, functional evaluation of intercellular interactions between leukemia cells and their microenvironment identifies a selective dependency of ALL cells on stromal metabolism for a relevant subgroup of cases, providing new opportunities to develop more personalized approaches to leukemia treatment.