Molecular understanding of leukemic bone marrow cytokine-Ras signals and metabolic dependence

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PROJECT SUMMARY/ABSTRACT Childhood Acute Lymphoblastic Leukemia (ALL) is a disease of the bone marrow with expansion of immature cells and treated with non-specific chemotherapy. ALL remains one of the leading causes of cancer death in persons <20 years old. The developmental origin of T cell ALL (T-ALL) is and profoundly impacts the clinic. Genetic mutations pointed aberrant Ras signals with causal role in 50% of T-ALL, but how such aberrant signals impact developmental trajectories in T-ALL is not known. Similarly, it is by and large unknown how to effectively inhibit aberrant Ras signals. During 1R01CA187318 we uncovered a new molecular paradigm in Ras signaling; Oncogenic Ras mutations (KRasG12D) and overexpression of the Ras activator RasGRP1 drive two very distinctive leukemic Ras signals. In the progress report with our new RoLoRiG/Mx1CRE mouse model, we show that these two aberrant Ras signals both induce abnormal hematopoiesis, but with opposing stem cell features. Capitalizing on our quantitative, multiplex flow cytometry platform we determined that Ras and RasGRP1 frequently connect to PI3K (phosphoinositide 3-kinase)-AKT/mTOR signaling in T-ALL. Next, we performed four extensive synthetic lethality screens with PI3K inhibitors to identify effective combination therapy in T-ALL. We confirmed ten predicted combination therapies with small molecule inhibitors and the PI3K inhibitor GDC0941 with tubulin inhibitor Vincristine yields broad synergy in five cancer types and in our preclinical mouse trials in vivo. The screens predict many metabolic targets, which remained unexplored. Our renewal focuses on understanding the connection between aberrant Ras-PI3K signals and cell metabolism with the goal of resolving the developmental origin of T-ALL and testing new combination therapies. We will determine the connections between Ras-PI3K signals and cell metabolism in our panel of 10 T-ALL cell lines by investigating six nutrient transporters (SLCs), identified in our screens (Aim 1). We will obtain mechanistic understanding of the signals, metabolic features, and hematopoietic composition and trajectories, as a function of leukemic Ras-PI3K signals with unprecedented resolution. We will continue efforts on RoLoRiG/Mx1CRE and KRasG12D/Mx1CRE mouse models that display completely opposite phenotypes in bone marrow stem cells (Aim 2). Lastly, we will obtain a comprehensive characterization of developmental-, biochemical- and metabolic- programs in pediatric T-ALL with single cell resolution. We will combine these efforts with preclinical trial to test the in vivo efficacy of PI3Kγ- and δ- inhibition, inhibition of SLC13A2 and SLC25A44, and combinations in our T-ALL/NGS platform (Aim 3). The synergistic aims, metabolic insights, new mouse models, patient sample-NSG pipeline, and innovative, single cell-resolution technology platforms (CyTOF, SCENITH, phospho-flow) will allow us to make significant contributions towards molecular understanding of T-ALL and precision medicine in cancer.