Development of animal models in pediatric cancer
Date
2014
Authors
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Publisher
University of Delaware
Abstract
The study was designed to develop xenograft mouse model in pediatric cancers with focus upon neuroblastoma - the most common form of solid tumors in childhood cancer and leukemia- the most prevalent form of pediatric cancer. The thesis consists of two sections- Section1 includes testing and validating the therapeutic efficacies of novel compounds in preclinical models of neuroblastoma and Section 2 details the development of an experimental animal model for childhood leukemia. The study on neuroblastoma was designed to test a panel of reversible and irreversible inhibitors of cathepsin B and L to induce death of neuroblastoma cells. Efficacy of the compounds depends on their ability to inhibit enzyme activity of cathepsins B and L. Five compounds that differ in mode and rate of inhibition of enzymes were tested to evaluate their ability to cause neuroblastoma cell death. Cysteine protease inhibitors that could not achieve at least 90% inhibition of enzyme activity in vitro failed to control neuroblastoma tumor growth in vivo. Treatment with inhibitors caused an increase in markers of cell stress and induced expression of autophagic markers LC3-II indicating that apoptosis was preceded by autophagy. The levels of LC3-II were highest for cells treated with irreversible inhibitors than reversible inhibitors. In contrast to irreversible inhibitors which markedly impaired tumor growth in vivo; reversible inhibitors failed to induce neuroblastoma cell death and did not control tumor growth .These results illustrated that irreversible inhibitors are better candidates for control of tumor growth and bring about death of neuroblastoma cells. It is concluded that development of drugs to target these two proteases may provide a novel approach in treating neuroblastoma. Section 2 includes the study designed to create human leukemia xenografts in immunodeficient mice. This would provide an important tool to understand various aspects of leukemia disease origin and subsequent progression while identifying and evaluating novel therapeutic strategies. The disease models developed in this study used both cell lines and primary human acute lymphoblastic leukemia cells to create xenografts that recapitulate clinical features of the disease. Similar to the human environment, the injected leukemia cells in the mouse are exposed to both favorable and unfavorable conditions for engraftment. Cells harvested from the spleens of engrafted mice readily initiated leukemia in secondary and tertiary recipients. High-level infiltration of bone marrow, spleen, and liver was observed. The immunophenotypes of xenografts were essentially unaltered compared with that of the patient sample. In this study we hypothesized that the biologic characteristics of childhood ALL xenografts accurately reflected the clinical disease. The animal disease models developed in this study provides powerful experimental tools to prioritize new therapeutic strategies for future clinical trials.