Transmembrane adaptor protein PAG1 is a novel tumor suppressor in neuroblastoma

// Saurabh Agarwal 1, * , Rajib Ghosh 2, * , Zaowen Chen 1 , Anna Lakoma 3 , Preethi H. Gunaratne 2 , Eugene S. Kim 3, 4 , Jason M. Shohet 1 1 Department of Pediatrics, Section of Hematology-Oncology, Texas Children’s Cancer Center, and Center for Cell and Gene Therapy, Baylor College of Medicine, Houston, Texas 77030, USA 2 Department of Biology & Biochemistry, University of Houston, Houston, Texas 77204, USA 3 Michael E. DeBakey, Department of Surgery, Division of Pediatric Surgery, Baylor College of Medicine, Houston, Texas 77030, USA 4 Department of Surgery, Division of Pediatric Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California 90027, USA * SA and RG are co-first authors Correspondence to: Jason M. Shohet, e-mail: jmshohet@txch.org Keywords: neuroblastoma, Src, PAG1, tumor suppressor Received: September 29, 2015     Accepted: March 01, 2016     Published: March 16, 2016 ABSTRACT Neuroblastoma (NB) is the most common extracranial pediatric solid tumor with high mortality rates. The tyrosine kinase c-Src has been known to play an important role in differentiation of NB cells, but the mechanism of c-Src regulation has not been defined. Here, we characterize PAG1 (Cbp, Csk binding protein), a central inhibitor of c-Src and other Src family kinases, as a novel tumor suppressor in NB. Clinical cohort analysis demonstrate that low expression of PAG1 is a significant prognostic factor for high stage disease, increased relapse, and worse overall survival for children with NB. PAG1 knockdown in NB cells promotes proliferation and anchorage-independent colony formation with increased activation of AKT and ERK downstream of c-Src, while PAG1 overexpression significantly rescues these effects. In vivo, PAG1 overexpression significantly inhibits NB tumorigenicity in an orthotopic xenograft model. Our results establish PAG1 as a potent tumor suppressor in NB by inhibiting c-Src and downstream effector pathways. Thus, reactivation of PAG1 and inhibition of c-Src kinase activity represents an important novel therapeutic approach for high-risk NB.