PROJECT 1: From Neurofibroma to MPNST: Models, Biology and Translation to Clinic

点击翻译按钮获取中文摘要

ABSTRACT (Project 1) Plexiform neurofibromas (PNF) are a hallmark manifestation of neurofibromatosis type 1 (NF1) that affect up to 50% of patients and causes lifelong morbidity. A subset of PNF progress to atypical neurofibroma (ANF) and/or malignant peripheral nerve sheath tumors (MPNST). These treatment refractory sarcomas represent the leading cause of death in NF1 patients. Clinical genomic studies and novel genetically engineered mouse (GEM) models, led and developed by Project 1 investigators, have provided strong evidence that loss of CDKN2A (INK4A) and/or its alternate reading frame (ARF) is a key driver event in the majority of NF1- associated ANF and MPNST. These models will serve as tractable platforms for characterizing key events in the evolution of PNF to MPNST, and for preclinical evaluation of novel experimental therapeutics. Our studies to date have identified the first two broadly clinically effective drugs for PNF, the MEK inhibitor, selumetinib, and the multi-RTK inhibitor, cabozantinib. Mechanistic insights from preclinical models and initial phase 2 trials showed that selumetinib and cabozantinib have distinct pharmacodynamic characteristics, in both the molecular targets within neoplastic Schwann cells as well as the tumor microenvironment. Collectively, these results suggest that combining these two drugs may enhance efficacy in PNF, and perhaps impede the progression to ANF and MPNST. The heterozygous NF1 mutant tumor microenvironment is essential in PNF development, and thus is a key consideration for implementing more effective combination therapies. Although collagen and other extracellular matrix (ECM) proteins are primary constituents of the PNF microenvironment, their respective roles in tumor initiation and maintenance remain unexplored. To inform ongoing translational efforts to develop novel therapies for NF1 patients affected by tumors across the PNF-ANF-MPNST continuum, we will accomplish the following: (1) Identify actionable therapeutic targets within NF1+/- fibroblasts and ECM proteins of the tumor microenvironment that interact with neoplastic Schwann cells to accelerate PNF formation and maintenance; (2) Extend preclinical studies in novel GEM and PDX models to investigate potential synergism of therapeutic combinations (including MEKi, BETi, SHP-2, and cabozantinib) in treating existing PNF, ANF and MPNST as well as in preventing malignant transformation of precursor lesions; (3) Conduct an early phase clinical trial of MEKi and cabozantinb combination therapy in PNF that may extend to more advanced nerve sheath tumors (ANF and MPNST) as informed by ongoing preclinical studies; (4) Leverage state-of-the-art technologies in Omics (Core B) and Biospecimen/Pathology (Core C) to define adaptive responses of PNF, ANF, and MPNST in GEM models as well as patient biopsy specimens by evaluation of the genome, transcriptome, and functionally enriched kinome before and after treatment.