Abstract B132: A model of de novo acute myeloid leukemia with an autologous human immune system as a preclinical tool for testing immunotherapies

Abstract

Abstract Based on our understanding of the importance of the immune system in controlling tumor progression and the recent successes of immunotherapies for cancer treatment, there is a need to develop small animal models that faithfully recapitulate the human tumor-immune system interaction. These models would serve as preclinical platforms to test immunotherapies and to better understand immune editing of tumors in vivo. Acute Myeloid Leukemia (AML) is a cancer that primarily occurs in older adults who unfortunately, do not tolerate standard chemotherapy and often die of the disease. While new immunotherapies are being developed to treat AML, the lack of suitable preclinical model makes it difficult to accurately test the efficacy and toxicity of these therapies in vivo where the leukemia exists alongside a normal human immune system which includes T cells, Natural Killer cells and macrophages – immune cells that are required to elicit the cytotoxic effects of immunotherapies. Here, we demonstrate the development of a humanized mouse model of de novo Acute Myeloid Leukemia (AML) with an autologous human immune system. By lentiviral mediated expression of a patient-derived mutation of Nucleophosmin (NPM1) in human hematopoietic stem cells (HSCs), followed by engraftment of a mixed pool of transduced and untransduced HSCs in immune-compromised NOD-scid IL2rg-/- (NSG) mice, we have modeled AML which develops alongside an autologous immune system. NPM1 expression is monitored by GFP expression as both proteins are encoded for by the lentiviral construct and expressed in equal stoichiometry. We chose to model the disease with mutant NPM1 as this genetic lesion occurs in ~30% of adult AMLs and 60% of cases with a normal karyotype. The latency of disease is 14-26 weeks with complete penetrance. Tumorigenicity of the transduced leukemic cells was confirmed with secondary transplantation. In this model, the leukemia resembles the broad M2-M5 category of the human disease as per the French-American-British (FAB) classification system, mirroring the pattern demonstrated by patient AMLs with an NPM1 mutation. As is seen in AML patients and in AML xenograft mouse models, the disease in this model is characterized by the presence of blasts in the peripheral blood and bone marrow, anemia, weight loss, splenomegaly and hypocellularity of the bone marrow. Leukemic blasts are primarily CD13 and CD33 positive with low expression of CD14. In the bone marrow, which is the primary site of disease, we detect the presence of leukemic stem cells (LSC), which are hypothesized to seed the disease and are responsible for disease relapse upon conventional chemotherapy. Transcriptome analysis of the CD123+ LSCs demonstrates their stem cell-like expression profile akin to that seen with patient AML LSCs. Additionally, since NPM1 has been shown to be an early mutation in AML and the absence of other lesions results in a favorable prognosis, we sought to find co-operating hits that were driving disease. In summary, we have developed a model of human AML with an autologous human immune system, which recapitulates important features of the human disease. The co-existence of leukemic cells and normal immune cells in this model makes it a useful pre-clinical tool for testing immunotherapies that require functional normal immune cells. Citation Format: Mandeep Kaur, Amanda Hanson, Adam Drake, Ryan Phennicie, Jianzhu Chen. A model of de novo acute myeloid leukemia with an autologous human immune system as a preclinical tool for testing immunotherapies. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B132.