Emadi Lab Research Projects
Targeting Glutamine Metabolism with Asparaginase/Crisantaspase Combination Therapy
Acute myeloid leukemia
Metabolic reprogramming contributes to tumor development and introduces metabolic liabilities that can be exploited to treat cancer. All cells need the amino acids asparagine and glutamine for protein synthesis and growth, and while normal healthy cells can obtain most through its own synthesis, cancer cells cannot produce enough to meet cellular demands and must therefore rely on circulating levels.
Glutamine depletion has emerged as a therapeutic approach for cancers that are dependent on exogenous glutamine for survival and proliferation. L-asparaginaseis an enzyme which has dual asparaginase and glutaminase activity, meaning that it can deplete glutamine and asparagine. Clinically available asparaginase is derived from 2 bacterial sources: Escherichia coli and Erwinia chrysanthemi, with asparaginase from Erwinia demonstrating higher glutaminase activity.
L-asparaginase is a well-established treatment for pediatric and adult acute lymphoblastic leukemia. In addition, in a clinical study designed and conducted by Dr. Emadi, asparaginase led to complete plasma glutamine depletion in patients, which correlated to anti-leukemic activity in 40% of patients with relapsed or refractory acute myeloid leukemia (AML).
Pegcrisantaspase (PegC) is a PEGylated (polyethylene glycol attached), recombinant asparaginase from E. chrysanthemi. Depletion of plasma glutamine concentration has been shown to activate mitochondrial apoptotic pathway in pancreatic adenocarcinoma, suggesting that asparaginase therapy would synergize well with other inducers of mitochondrial regulated apoptosis. Venetoclax (Ven), a Bcl-2 specific BH3 mimetic has demonstrated anticancer efficacy, and is indicated in combination with azacitidine, decitabine or low-dose cytarabine to treat newly-diagnosed AML in adults age 75 years or older.
Recently, we have discovered that combination of Ven and PegC synergistically targets Gln metabolism and mTOR-eIF4E-driven ribosomal translational protein synthesis in AML cells. The Ven-PegC combination is synergistic against human AML cell lines and primary AML cells in vitro, and tolerable and highly active against AML in vivo.
Pancreatic adenocarcinoma is one of the most aggressive human cancer types and is predicted to be the second leading cause of cancer-related deaths in the United States by 2030(Rahib, Smith et al. 2014). It has one of the fastest growing incidence rates and because of the lack of early detection methods, the majority of patients are diagnosed at an advanced, disseminated stage when surgical cure is no longer attainable.
Standard chemotherapy regimens consist of gemcitabine plus nab-paclitaxel; or gemcitabine plus erlotinib however their anti-tumor effects are remarkably lower than for other solid tumors, and there is currently no chemotherapeutic regimen that provides meaningful clinical outcome beyond the first salvage therapy, underscoring the urgent need for novel therapeutic strategies.
Similar to AML cells, pancreatic cancer cells are also dependent on glutamine and rely on circulating levels to meet high cellular demands. Ongoing work in our lab us focused on investigating the potential of Ven-PegC as well as other PegC-based combination therapies in xenograft and syngeneic models of pancreatic cancer.
Overcoming Resistance to FLT3 Inhibitors in AML
Mutations in FMS-like tyrosine kinase 3 (FLT3), transmembrane ligand-activated receptor tyrosine kinase important for myeloid and lymphoid development, are one of the most common genetic alterations reported in AML are associated with a more aggressive disease and poor prognosis.
FLT3 mutations occur as either internal tandem repeats (ITDs) or point mutations in the tyrosine kinase domain (TKD), leading to constitutive receptor activation and cell proliferation through multiple signaling pathways including MAPK, STAT and PI3K/AKT. FLT3-ITD mutations are present in approximately 30% of de novo AML cases and are often associated with an aggressive phenotype, higher tumor bulk, and an increased risk of relapse. Due to its driving role in leukemia cell growth, significant effort has been made to develop FLT3 inhibitors (FLTi) with clinical benefit.
While the development of potent FLT3 inhibitors has improved outcome, responses are usually short-lived and acquired resistance to FLT3i therapy remains a challenge. One mechanism of resistance is the gain of secondary mutations within the FLT3 TKD that decrease the binding and inhibitory potential of many FLT3i.
An important strategy to overcome chemotherapy resistance in many tumor types has been the use of combination regimens. Given that glutaminolysis has been shown as a targetable vulnerability of AML undergoing FLT3i therapy, the Emadi lab is investigating the impact of targeting glutamine metabolism in FLT3i-resistant AML to develop novel combination therapies that can be translated to the clinic.
Exploring the impact of sialydase expression on leukemia engraftment
The modification of sialic acid residues on glycoproteins and glycolipids is among the most frequently recognized glycosylation aberrations used by cancer cells to assure proliferation, and is associated with invasiveness and metastatic potential.
Four mammalian sialidases, also known as neuraminidases, have been described in the human genome (NEU1, NEU2, NEU3, NEU4), differing in their sub-cellular location and enzymatic properties. While there are countless studies demonstrating the role of sialidases in solid tumors, there is a lack of research investigating their impact in leukemia.
It has been reported that in a chronic myeloid leukemia cell line, forced expression of expression of NEU2 induces apoptosis. Furthermore, primary lymphoblasts from acute lymphoblastic leukemia patients show a marked down regulation of NEU3, and NEU3 overexpression can induce apoptosis. The Emadi lab is investigating the potential impact of neuraminidase expression on leukemia engraftment.
Naphthoquinone chemotherapeutics for AML
Selective targeting of the oxidative state is an attractive strategy for developing novel anti-leukemic chemotherapeutics with potential applications in the treatment of acute myeloid leukemia (AML). Naphthoquinones (C10H6O2) are oxidized naphthalenes (C10H8), and similar to other quinones, such as benzoquinone and anthraquinone, they possess a conjugated electron system that can participate in chemical reactions transporting electrons to other molecules.
The quinone moiety is a well-known pharmacophore that elicits anti-cancer activity in clinically available compounds such as mitomycin C, mitoxantrone, daunorubicin and other anthracyclines. Monomeric naphthoquinones such as juglone, plumbagine, lapachol, and atovaquone have shown pre-clinical anti-neoplastic activity against hematologic and solid neoplasms.
Dimeric naphthoquinones (BiQs) are a novel class of compounds that have been shown to generate reactive oxygen species in cancer cells, making them excellent candidates for testing against AML. We have reported that synthetic halohydroxyl BiQ and aziridinyl BiQ have activity against AML cells. In order to improve the potency and aqueous solubility (i.e. bioavailability) of BiQ compounds, the Emadi lab is interested in the design and synthesis of the next generation of anti-cancer naphthoquinones, with the ultimate goal of identifying a BiQ that can proceed to a phase 1 clinical trial for the treatment of relapsed/refractory AML.