Bioengineered, patient-specific bonemarrow model for studying leukemic niche interactions

PROJECT SUMMARY / ABSTRACT Acute leukemias represent the most frequent group of cancer (~30%) in children and young adults. The advancement of experimental therapeutics for high risk leukemias has been limited by the inadequacy of immortalized cell lines and the cumbersome nature and limited throughput of in vivo xenograft models. In this context, the lack of robust systems for in vitro culture of primary leukemia samples is a significant barrier for the development of effective genetic and chemical screens in pediatric leukemia. In vitro systems, including engineered tissues and organ-on-a-chip systems, are gaining increased interest in the stem cell and cancer fields as human-specific platforms for the study of disease and therapeutic testing. In vitro models of the bone marrow (BM) have yet to gain momentum, largely due to their reduced throughput, technical barriers in biological research, and the heterogeneity of starting stromal cell populations. Further, there have been only few attempts to culture primary donor-derived malignant blood cells in engineered systems, which enable patient-specific studies of disease. In this proposed project, I will (Aim 1) engineer a human, induced pluripotent stem cell (iPSC)- derived bone marrow tissue model, comprised of osteoblasts, mesenchymal stromal cells, and endothelial cells within a bone scaffold, for maintenance of acute lymphoblastic leukemia (ALL) phenotype in vitro. I will then use this model to (Aim 2) study how the secretome of malignant ALL blasts, or the ALL blasts themselves, interact with both healthy hematopoietic stem and progenitor cells (HSPCs) and healthy stroma in the engineered model. I hypothesize that an engineered human BM microenvironment, capable of supporting HSPCs in vitro, will maintain the phenotype of ALL blasts closer to unmanipulated samples than monolayer cultures or patient derived xenograft models, further enabling studies of direct and indirect lymphoblast interactions with the healthy bone marrow. It has been well established that acute leukemias alter their microenvironmental niche, and in many cases, use the stroma to protect malignant clones during treatment; I hypothesize that this model system will be better able to predict therapeutic responses, identifying potential mechanisms of resistance in ALL. Our lab brings strong expertise in engineering human tissues, iPSC technologies, and therapeutic testing, and with support of experts in hematopoiesis, cancer, and sequencing, I believe that the proposed project will successfully establish a novel tool for studying the human bone marrow during malignant leukemic transformation and resistance to therapy.