FAM96A is a novel pro-apoptotic tumor suppressor in gastrointestinal stromal tumors Journal Article

Author(s): Schwamb, Bettina; Pick, Robert; Fernández, Sara B; Völp, Kirsten; Heering, Jan; Dötsch, Volker; Bösser, Susanne; Jung, Jennifer; Beinoravičiute-Kellner, Rasa; Wesely, Josephine; Zörnig, Inka; Hammerschmidt, Matthias; Nowak, Matthias; Penzel, Roland; Zatloukal, Kurt; Joos, Stefan; Rieker, Ralf J; Agaimy, Abbas; Söder, Stephan; Reid-Lombardo, Kmarie M; Kendrick, Michael L; Bardsley, Michael R; Hayashi, Yujiro; Asuzu, David T; Syed, Sabriya A; Ördög, Tamás; Zörnig, Martin
Article Title: FAM96A is a novel pro-apoptotic tumor suppressor in gastrointestinal stromal tumors
Affiliation IST Austria
Abstract: The ability to escape apoptosis is a hallmark of cancer-initiating cells and a key factor of resistance to oncolytic therapy. Here, we identify FAM96A as a ubiquitous, evolutionarily conserved apoptosome-activating protein and investigate its potential pro-apoptotic tumor suppressor function in gastrointestinal stromal tumors (GISTs). Interaction between FAM96A and apoptotic peptidase activating factor 1 (APAF1) was identified in yeast two-hybrid screen and further studied by deletion mutants, glutathione-S-transferase pull-down, co-immunoprecipitation and immunofluorescence. Effects of FAM96A overexpression and knock-down on apoptosis sensitivity were examined in cancer cells and zebrafish embryos. Expression of FAM96A in GISTs and histogenetically related cells including interstitial cells of Cajal (ICCs), “fibroblast-like cells” (FLCs) and ICC stem cells (ICC-SCs) was investigated by Northern blotting, reverse transcription—polymerase chain reaction, immunohistochemistry and Western immunoblotting. Tumorigenicity of GIST cells and transformed murine ICC-SCs stably transduced to re-express FAM96A was studied by xeno- and allografting into immunocompromised mice. FAM96A was found to bind APAF1 and to enhance the induction of mitochondrial apoptosis. FAM96A protein or mRNA was dramatically reduced or lost in 106 of 108 GIST samples representing three independent patient cohorts. Whereas ICCs, ICC-SCs and FLCs, the presumed normal counterparts of GIST, were found to robustly express FAM96A protein and mRNA, FAM96A expression was much reduced in tumorigenic ICC-SCs. Re-expression of FAM96A in GIST cells and transformed ICC-SCs increased apoptosis sensitivity and diminished tumorigenicity. Our data suggest FAM96A is a novel pro-apoptotic tumor suppressor that is lost during GIST tumorigenesis.
Keywords: Apoptosis; GIST; ICC; FAM96A; tumor suppressor
Journal Title: International Journal of Cancer
Volume: 137
Issue 6
ISSN: 1097-0215
Publisher: Wiley-Blackwell  
Date Published: 2015-09-01
Start Page: 1318
End Page: 1329
DOI: 10.1002/ijc.29498
Notes: The authors are thankful to Dr. Michael Baudis (Institute of Molecular Life Sciences, University of Zurich, Switzerland) for help with the Progenetix database. The authors also thank Dr. Jason T. Lewis (Department of Pathology and Laboratory Medicine, Mayo Clinic, Rochester, Minnesota, USA) for providing blind scores of FAM96A expression in GIST samples. FAM96A staining and genotyping of GIST samples were performed at the Mayo Clinic Pathology Research Core (Director: Dr. Thomas J. Flotte) and in the Cytopathology and Molecular Anatomic Pathology Laboratory (Director: Dr. Andre M. Oliveira), respectively. GIST48 and GIST882 cells were kindly provided by Jonathan A. Fletcher (Department of Pathology, Brigham and Women's Hospital, Boston, MA, USA) and Sebastian Bauer (Sarcoma Center, West German Cancer Center, University of Essen, Medical School, Essen, Germany). The excellent technical assistance of Bettina Strohmeier (Institute of Pathology, Medical University of Graz, Austria), Rudolf Jung (Institute for Pathology, University Hospital Erlangen, Germany) and Laurie A. Popp (Mayo Clinic) is gratefully acknowledged. We thank Florian Greten (Georg-Speyer-Haus, Frankfurt, Germany) for critical evaluation of the manuscript.
Open access: no