The objective of this mentored research career development proposal is to investigate the role of the anaplastic lymphoma kinase (ALK) receptor in central nervous system development (CNS), neural stem cell (NSC) biology, response to hypoxic injury and glioblastoma (GBM). The rationale for this study is based on the high expression levels of ALK and its ligands Pleiotrophin (PTN) and Midkine (MK) during murine CNS development. The PTN-ALK signaling axis also provides neuroprotective effects after ischemic injury in the adult CNS and is reactivated in adult GBMs;however, an opportunity remains to define the function and mechanisms of action for ALK during these normal and diseased states. To determine how ALK signaling contributes to or regulates NSC biology, previously generated human and murine fetal NSC lines will be utilized to test how gain- or loss-of ALK expression alters NSC proliferation, apoptosis or differentiation. Additionally the intracellular signaling cascades and transcriptional networks activated in the presence or absence of ALK ligands (pleiotrophin and midkine) will be mapped in normal NSCs. Preliminary data suggests that ALK expression in GBM defines a distinct patient population with sensitivity to the ALK inhibitor crizotinib;therefore, a research study was designed to test whether ALK is a prognostic biomarker for GBM patients and determine if novel ALK fusions or mutations are involved in the pathogenesis of GBM. The functional effects of ALK fusions or mutations will be determined using scientifically relevant primary GBM cell lines. The Dana- Farber Cancer Institute Brain Tumor Biorepository and Living Tissue Banks provide unique access to a large cohort of clinically annotated GBM tissues and primary cell lines that will be used to conduct the proposed experiments. These research studies encompass a wide array of disciplines including neurodevelopment, ischemic brain injury, glioma biology, next generation sequencing, and clinic pathologic analyses, which together will delineate the mechanisms of action for the PTN-ALK signaling axis during normal CNS development and gliomagenesis.
The specific aims are:
Aim One : To characterize ALK rearrangements and evaluate ALK as a prognostic biomarker for GBM.
Aim Two : To determine intracellular signaling pathways and transcriptional networks activated by wild-type or mutant ALK (p.P399S, p.H1030P, or p.K1612N) in primary GBM cell lines and normal neural stem cells.
Aim Three : To test whether disruption of the Pleiotrophin-ALK signaling axis through in vivo loss of ALK alters neural stem cell biology or response to hypoxic brain injury.
ALK is a receptor tyrosine kinase highly expressed in the developing brain with retained expression throughout adulthood and is aberrantly activated in 10% of glioblastomas;however the precise function and mechanisms of action for ALK in the central nervous system and gliomagenesis remain largely unexplored. This proposal will deliver a comprehensive analysis of ALK signaling in neural stem cell biology, determine the relevance of the Pleiotrophin-ALK axis in response to ischemic brain injury, and demonstrate the scientific and clinical relevance of ALK as a biomarker and therapeutic target for glioblastoma patients.