Acute myelogenous leukemia (AML) is a disease in which the accumulation of primitive non-functional precursor cells results in the death of >80% of patients due to bleeding and infection. Although allogeneic bone marrow transplantation is potentially curative, only 25% of AML patients are eligible for this therapy and only half of these survive long-term. Another 10-20% are cured by combination chemotherapy. In order to develop new directions for therapy of AML, we have developed novel approaches to bone marrow transplantation. We pioneered non-myeloablative regimen (""""""""mini-transplant"""""""") which had major impact on the practice of BMT by allowing this treatment modality to be used in older patients (the majority of patients with AML is >55 yrs of age). We are now proposing to implement our improved understanding of the apoptotic mechanisms responsible for resistance to therapy in AML, both to chemotherapy and transplantation. We have made significant progress in interrogating the mitochondrial/cytochrome c/ caspase 8 and TNF-receptor family/caspase 9 pathways, with particular focus on Bcl-2 family and Inhibitor of Apoptosis (IAP) proteins. Of note, several components of these pathways were analyzed first in AML by investigators of this Program Project. We studied their expression patterns, regulation and response to apoptotic triggers. These findings have already resulted in new therapeutic concepts targeting these molecules: antisense oligonucleotide (AS), directed against the anti-apoptotic Bcl-2, Bcl-XL, XIAP and survivin proteins and modulation of Bcl-2 by the PKC-alpha inhibitors Bryostatin and UCN01. The effects of UCNO1 on mechanisms of resistance to ara-C will be studied in vitro, and in a clinical trial. Furthermore, interference with AKT and MAPK signaling in AML by PI3 kinase and MEKK inhibition (which we expect to result in de-phosphorylation of Bad and re-establishment of its pro-apoptotic function) will be further investigated. Dolostatin, which we found to exert anti-leukemic effects by the modulation of XIAP and Bcl-2 family members is in clinical trial. These targeted in vitro and clinical studies will attempt to correlate molecular changes with the induction of apoptosis and clinical response. Apoptotic pathways in AML will further be elucidated by mapping expression patterns and interrogating mitochondrial, TNF receptor and granzyme B-mediated signaling at diagnosis and at relapse in longitudinal studies of individual patients, following chemotherapy and allogeneic transplantation. Functional genomics approaches will also be utilized. Early progenitor/stem cell compartments will be analyzed, utilizing state-of-the-art FACS and cell separation techniques and in vitro models of leukemic and normal hematopoiesis. The BMT program will optimize the non-ablative preparative regimen pioneered here. Dendritic cells will be generated from AML blasts that serve as antigen-presenting cells to elicit specific immune responses (""""""""graft-vs-leukemia""""""""). The studies are supported by well-established cores that conduct the clinical trials, process and bank leukemic cells, perform in vitro studies of clonogenic cells, isolate by FACS rare stem cell candidates for molecular and FISH analysis, and provide support for clinical trials and biostatistics. In this way, we hope to develop therapies targeted to molecular and biological defects in AML, which are less toxic to normal tissues and provide more durable remissions in all subsets of AML. Because the principles of therapy are also relevant to the treatment of epithelial neoplasms, we expect the information to be derived from this program to provide directions for improvement of solid tumor therapy as well.
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