Description of Research Expertise

Research Interests
Molecular biology and genetics of childhood cancer, especially neuroblastoma; Pediatric cancer predisposition and surveillance; Nanoparticle drug delivery

Key words: neuroblastoma, MYCN, 1p36 deletion, tumor suppressor gene, CHD5, chromatin remodeling, TrkA, TrkB, Trk inhibitor, Trk signaling, nanoparticle drug delivery, ALK, cancer predisposition, nanoparticles.

Description of Research
Prior Research Interests
Identification of MYCN Amplification as a Prognostic Marker for Neuroblastomas. We first demonstrated that MYCN amplification occurred in about 22% of primary neuroblastomas, and amplification is strongly associated with advanced stage, adverse prognostic factors and poor outcome. This was the first example of an oncogene shown to have prognostic significance in a human cancer, introducing the concept of molecular profiling to predict outcome and tailor the intensity of therapy. Assessment of neuroblastomas for MYCN amplification is currently done throughout the world on all newly diagnosed tumors, and it remains one of the most potent predictors of poor outcome in this disease.

Cloning and Characterization of the Tumor Suppressor Gene, CHD5, Deleted from 1p36. We were the first to identify and clone CHD5, the fifth member of the chromodomain-helicase-DNA binding family, as a candidate tumor suppressor gene deleted from 1p36 in neuroblastomas and possibly other tumors. We showed that high CHD5 expression was strongly associated with favorable prognostic features and outcome. We further demonstrated that CHD5 functioned as a tumor suppressor gene in vitro and in vivo in a mouse xenograft model of neuroblastoma. In addition, we showed that the CHD5 promoter was frequently methylated in tumors with 1p36 deletion, transcriptionally silencing the remaining allele in these tumors. CHD5 likely functions as part of a NuRD-type chromatin remodeling complex. Finally we showed the CHD5 expression was required for normal spermatogenesis and chromatin condensation, regulating the substitution of histone for protamine at stage 9, step 9 of spermiogenesis.

Demonstration of the roles of TrkA and TrkB in Neuroblastoma Behavior. We were the first to demonstrate that TrkA, the receptor for nerve growth factor (NGF), is expressed on most favorable tumors, and the NGF/TrkA pathway may be involved in the spontaneous regression or differentiation seen in favorable NBs, especially in infants. Conversely, TrkB and its primary ligand, brain-derived neurotrophic factor (BDNF), are expressed in many unfavorable NBs, and the autocrine activation of this pathway contributes to aggressive behavior, such as enhanced survival, invasion, metastasis, angiogenesis and drug resistance. Therefore, targeting this pathway with selective Trk receptor inhibitors, alone or in combination with other agents, should be an effective and relatively nontoxic approach to treat aggressive NBs.

Development and implementation of TRK-Targeted Therapy for Neuroblastomas. TrkB and its ligand, BDNF, are overexpressed in over half of high-risk neuroblastomas and contributes to its aggressive phenotype, including invasion, metastasis, angiogenesis and drug resistance. We have worked with several pharmaceutical companies to develop TRK-selective inhibitors as a form of targeted therapy for neuroblastomas. We first developed CEP-701 (Lestaurtinib) as a TRK-selective inhibitor, and our preclinical work (Evans AE et al, Cancer Res, 1999) led to a phase 1 clinical trial in neuroblastomas. Half of the patients receiving a pharmacologically adequate dose had durable responses lasting a mean of 10+ months (some lasting over 2 years) with essentially no clinical toxicity. We are now testing entrectinib and larotrectinib, second-generation TRK inhibitors that far more potent and selective than prior inhibitors we have tested.


Current Research Interests
Nanoparticle (NP) Drug Delivery. We are working closely with Drs. Michael Chorny and Ivan Alferiev at CHOP. Our goal is to develop more effective, less toxic therapy for pediatric cancers, especially solid tumors like neuroblastoma. Although agents targeting specific genes, proteins and pathways are needed, targeted drug delivery could dramatically improve efficacy and decrease toxicity. We are developing several novel approaches for nanoparticle design and formulation. Furthermore, we are using several robust animal models of neuroblastoma (flank, orthotopic, and PDX xenografts; transgenic TH-MYCN mice) for testing nanocarrier formulations. This work has led to two recent publications, demonstrating our successful collaboration to study nanocarrier delivery of a PLA-PEG NP carrying SN38 co-drug with tocopherol succinate. Indeed, we have improved on this formulation, as described in a third paper that has recently been accepted (see below). This proposal extends our efforts to optimize nanocarrier drug delivery by development of single-component, multivalent nanomedicines containing camptothecin derivatives SN38 or SN22 for enhanced delivery of cancer therapeutics to pediatric solid tumors like neuroblastoma and sarcomas.

Cancer Predisposition. I am currently the Director of the Cancer Predisposition Program at CHOP, which fulfills a longstanding interest in pediatric cancer predisposition. My interest began with my interest in neuroblastoma predisposition, which culminated in the identification of activated ALK as the gene responsible for most cases (Mosse, et al. Nature, 2008). As Chair of the AACR Pediatric Cancer Working Group, I organized an international workshop on Pediatric Cancer Predisposition and Surveillance with 65 participants from 11 countries to develop consensus protocols for cancer surveillance for the 60 most common predisposition syndromes. This resulted in 18 publications in Clinical Cancer Research (http://clincancerres.aacrjournals.org/pediatricseries). I am deeply committed to expanding our clinical and research efforts in pediatric cancer predisposition and surveillance, and to make our program at CHOP this space. I am also mentoring two junior faculty at CHOP who have each focused on specific subpopulations of patients with cancer predisposition (Jennifer Kalish and BWS/Overgrowth syndromes, Suzanne MacFarland and GI cancer predisposition syndromes). My lab is interested in the identification of novel cancer predisposition genes, determination of genotype-phenotype associations, development of enhanced surveillance techniques, and identification of epigenetic mechanisms leading to cancer predisposition.

Description of Itmat Expertise

My lab has been focused on identifying the genes, proteins and pathways responsible for malignant transformation and progression of human neuroblastoma. We are also interested in developing more effective, less toxic therapy for neuroblastoma and other pediatric solid tumors. We have identified several genes that play critical roles in this regard, including MYCN gene amplification, CHD5 deletion and epigenetic inactivation, and germline ALK activation in hereditary neuroblastoma. We also identified the importance of TrkA in favorable neuroblastoma and TrkB in unfavorable neuroblastoma. We provided the preclinical data to launch phase 1 clinical trials for two TRK inhibitors, Lestaurtinib and Entrectinib. Finally, we have collaborated with Dr. Michael Chorny and colleagues to formulate and test novel nanoparticle drug delivery vehicles that are highly effective in animal models.

Going forward, my lab will focus in two areas: 1) development and testing of novel nanomedicines o treat pediatric (and adult) solid tumors; and 2) genes responsible for pediatric cancer predisposition. We will formulate and test novel nanomedicines using both biocompatible polymeric nanoparticles (NPs) and single-component, multivalent nanomedicines. We will test prodrug and codrug constructs that enhance hydrophobicity and NP retention, as well as single component nano medicines that have greater tumor penetration. We will first test in animal models of neuroblastoma (flank xenograft, orthotropic, transgenic), as well as animal models of sarcomas and brain tumors. We will identify and characterize novel genes involved in pediatric cancer predisposition. We will also explore genotype-phenotype correlations, epigenetic modifications that affect penetrance and expressly, and optimize cancer surveillance protocols.