Funded by the Dick Vitale Gala with a gift from Derek and Christin Thompson in memory of Bryan Lindstrom
Bone marrow failure syndromes are a collection of disorders characterized by inadequate production of blood cell lineages from a common progenitor, the hematopoietic stem cell. Dyskeratosis congenita is an inherited bone marrow failure syndrome that comes to clinical attention during early childhood, and is associated with high rates of malignancy in children and young adults, with cancer being a major cause of death in patients. DNA sequencing efforts have established that dyskeratosis congenita has a clear genetic determinant, with patients carrying mutations in their DNA that affect the function of telomerase, a dedicated protein complex that is primarily responsible for maintaining the structure of our chromosomes.
Research regarding dyskeratosis congenita has been hampered by a lack of adequate models. In this proposal we are using genetically engineered human pluripotent stem cells to precisely determine the role that TERC, one of the main components of the telomerase complex, plays in bone marrow failure and cancer in children afflicted with dyskeratosis congenita. Using our innovative model, we will understand the importance of TERC for stem cell regulation and blood development. Recently we developed the technology to differentiate these stem cells in a controlled, quantitative fashion, to become any particular blood cell type present in the circulatory system. This allows us to reproduce the clinical effect of this disease, in a tissue culture dish, and therefore precisely understand the disease progression in dyskeratosis congenita. Our goal is to help delineate novel treatment strategies against dyskeratosis congenita, a condition that currently has no cure.
Acute myeloid leukemia (AML) is a devastating disease with poor survival. The standard treatments of chemotherapy and/or stem cell transplantation are not specific, and are toxic to blood cells, resulting in severe treatment-related complications for patients. Leukemias are composed of rapidly dividing “blast” cells, and the more rare “leukemic stem cells” (LSCs). These LSCs can lead to resistance and relapse, because they can evade chemotherapy. To achieve long-term remissions in AML and prevent relapse, we need to find more specific ways to kill LSCs.
The enzyme PI3 kinase (PI3K), which can modify proteins inside the cell, is more active in leukemic cells than in normal cells. However, PI3K is also important in normal blood cells. We identified a strategy to specifically kill leukemic cells by blocking specific components of PI3K called “isoforms”, which can sometimes substitute for each other in normal blood cells. We will determine whether this therapeutic strategy can also be used to kill LSCs.
Leukemic cells can also evade chemotherapy by hiding in their bone marrow microenvironment, the “niche”. Niche cells and leukemic cells “talk” to each other by sending signals back and forth, which can protect leukemic cells from chemotherapy. Cells need PI3K to process such signals. Inhibition of PI3K in niche cells could potentially kill leukemic cells by short-circuiting this crosstalk with the niche. We have found that PI3K in the niche cells is important for blood development. We will now examine whether inhibition of PI3K in the niche can compromise leukemic growth and progression.
The CALM-AF10 chromosomal abnormality is seen in aggressive pediatric and adult acute leukemias that have a poor prognosis. Our lab has discovered that CALM-AF10 interacts with CRM1, a protein that helps transport other proteins from the nucleus to the cytoplasm. This interaction is required to activate HOXA genes, which play a critical role in both CALM-AF10 and other leukemias. This discovery suggests that CRM1 may be important in other leukemias as well, as is significant because a new class of drugs that inhibit interaction with CRM1 (SINEs-Selective Inhibitors of Nuclear Export) has recently been developed. These drugs are effective in a number of human tumor types, and are currently in clinical trials for adult leukemias. Our studies indicate that SINEs may block cancer cells through an unappreciated and novel mechanism-inhibiting CRM1 involvement in activating HOXA genes. In this proposal, we will examine the molecular mechanisms by which CRM1 activates HOXA genes. We will then identify additional CRM1 target genes that are involved in causing leukemias. Studying this previously unrecognized role for CRM1 will enhance our understanding of how SINEs work, and provide preclinical support for their use in pediatric leukemia clinical trials. Since HOXA genes are involved in many hematopoietic malignancies (including MLL-fusion leukemias that are seen in 80% of infant leukemias), these studies may have broad implications for leukemogenesis.
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