Neuroblastoma, a highly malignant tumor that arises in the peripheral sympathetic nervous system, accounts for ~10% of all cancer-related deaths in children. Recent genomic resequencing of high-risk neuroblastoma has uncovered three main classes of mutations: those activating the ALK tyrosine kinase (8- 10% of cases), those activating the SHP2 phosphatase (2-3%), and microdeletions involving the PTPRD locus (6-10%). I recently demonstrated that activated ALK synergizes with MYCN to induce neuroblastoma in zebrafish by inhibiting a developmentally-timed apoptotic response (Zhu et al, Cancer Cell). I have now discovered that activated SHP2 or Ptprd loss also accelerates MYCN-induced neuroblastoma, but in a different way than does activated ALK. On the advice of my close collaborator, Dr. Ben Neel, an internationally recognized expert on phosphatase biology, I have determined that multiple components of the SHP2 pathway are highly overexpressed in most human neuroblastomas, including GAB2, a known oncogene and SHP2 regulator, as well as ALK and NTRK1. The central hypothesis to be explored here is that SHP2 and PTPRD represent vital pathways to the development of neuroblastoma and warrant further intensive investigation. My key objective is to elucidate the underlying mechanisms by which these two pathways influence neuroblastoma initiation and maintenance.
My specific aims are (1) to define the mechanisms by which mutationally activated SHP2 contributes to neuroblastoma initiation and maintenance, and determine whether the SHP2 pathway is aberrantly activated in neuroblastoma cases that lack SHP2 mutations;and (2) to elucidate the mechanisms by which loss of the PTPRD tumor suppressor gene contributes to neuroblastoma initiation and maintenance. In these two Aims, I will use mosaic and stable transgenic as well as structure- function approaches to implicate key downstream pathways and a novel tissue-specific, conditional doxycycline-regulated system to establish whether activated SHP2 or loss of PTPRD is continuously required for tumor cell survival, thus qualifying as "drivers" of neuroblastoma pathogenesis. Dr. Shizhen (Jane) Zhu is an instructor in the Department of Pediatric Oncology at the Dana-Farber Cancer Institute (DFCI) working under the mentorship of Dr. A. Thomas Look, a pioneer in the field of zebrafish cancer biology. Building on Dr. Zhu's medical and scientific training in China and Singapore, she is now defining the roles of aberrant SHP2 and PTPRD tyrosine phosphatase pathways in the neuroblastoma pathogenesis. Dr. Look's proven mentorship coupled with the rigorous and nurturing scientific environment offered by the research community at DFCI and affiliated institutions offer the maximal opportunity for Dr. Zhu's success during her award period as an instructor and in her transition to become an independent investigator.
Improved understanding of the stepwise development of childhood neuroblastoma will require detailed investigations in living animals of the abnormal molecular pathways now emerging from the integration of laboratory findings at the DNA, RNA, protein and functional levels. By establishing the mechanisms that underlie aberrant signaling by two candidate phosphatases, SHP2 and PTPRD, my proposed studies will very likely lead to identification of novel molecular targets for improved treatment of this devastating childhood disease.