Maria Rain Jennings, PhD

Homo sapiens adenosine deaminase 1 (HsADA1; UniProt P00813) is an immunologically relevant enzyme with roles in T-cell activation and modulation of adenosine metabolism and signaling. Patients with genetic deficiency in HsADA1 suffer from severe combined immunodeficiency, and HsADA1 is a therapeutic target in hairy cell leukemias. Historically, insights into the catalytic mechanism and the structural attributes of HsADA1 have been derived from studies of its homologs from Bos taurus (BtADA) and… Show more

Homo sapiens adenosine deaminase 1 (HsADA1; UniProt P00813) is an immunologically relevant enzyme with roles in T-cell activation and modulation of adenosine metabolism and signaling. Patients with genetic deficiency in HsADA1 suffer from severe combined immunodeficiency, and HsADA1 is a therapeutic target in hairy cell leukemias. Historically, insights into the catalytic mechanism and the structural attributes of HsADA1 have been derived from studies of its homologs from Bos taurus (BtADA) and Mus musculus (MmADA). Here, the structure of holo HsADA1 is presented, as well as biochemical characterization that confirms its high activity and shows that it is active across a broad pH range. Structurally, holo HsADA1 adopts a closed conformation distinct from the open conformation of holo BtADA. Comparison of holo HsADA1 and MmADA reveals that MmADA also adopts a closed conformation. These findings challenge previous assumptions gleaned from BtADA regarding the conformation of HsADA1 that may be relevant to its immunological interactions, particularly its ability to bind adenosine receptors. From a broader perspective, the structural analysis of HsADA1 presents a cautionary tale for reliance on homologs to make structural inferences relevant to applications such as protein engineering or drug development. Show less

A small metabolite, adenosine, accumulates in tumors at concentrations up to 100-times normal levels. Under normal conditions, adenosine calms immune responses to allow the body to heal following trauma or infection. However, high concentrations within tumors suppress immune cells from responding properly. Further, adenosine signaling amongst the tumor cells potentiates a positive feedback loop which supports tumor growth and encourages production of more adenosine. Tumors produce adenosine by… Show more

A small metabolite, adenosine, accumulates in tumors at concentrations up to 100-times normal levels. Under normal conditions, adenosine calms immune responses to allow the body to heal following trauma or infection. However, high concentrations within tumors suppress immune cells from responding properly. Further, adenosine signaling amongst the tumor cells potentiates a positive feedback loop which supports tumor growth and encourages production of more adenosine. Tumors produce adenosine by multiple pathways and the metabolite acts on up to four receptors, thus, preventing either generation or signaling mediated by adenosine has proven challenging.

We report a novel approach to prevent adenosine-mediate immune suppression: the development of an enzyme to directly target adenosine itself. Adenosine deaminase (ADA), a naturally occurring enzyme, converts adenosine into nontoxic inosine so efficiently that the process is limited by substrate transport rather than the kinetic mechanism. We present here the optimization of an Escherichia coli production process and a single purification step to yield 15 milligrams of pure ADA per liter of culture. Prior to our work, this ADA variant had not yet been evaluated in pure form or produced at scale. In concert, we report the Michaelis-Menten kinetic parameters of the pure enzyme and will present its crystal structure. Most importantly, we will describe how tumor mouse models treated with ADA benefitted from a statistically significant survival advantage versus control mice. We will further discuss ongoing efforts to characterize the mechanistic in vivo impact of ADA on the murine immune system, including pharmacodynamic and pharmacokinetics studies, as well as phenotyping of immune cell subsets. From a 30,000-foot view, we intend to demonstrate the efficacy of adenosine depletion as therapeutic strategy for the treatment of solid cancers and to present ADA as an efficient means of doing so. Show less

Tumors accumulate metabolites that deactivate infiltrating immune cells and polarize them toward anti-inflammatory phenotypes. We provide a comprehensive review of the complex networks orchestrated by several of the most potent immunosuppressive metabolites, highlighting the impact of adenosine, kynurenines, prostaglandin E2, and norepinephrine and epinephrine, while discussing completed and ongoing clinical efforts to curtail their impact. Retrospective analyses of clinical data have… Show more

Tumors accumulate metabolites that deactivate infiltrating immune cells and polarize them toward anti-inflammatory phenotypes. We provide a comprehensive review of the complex networks orchestrated by several of the most potent immunosuppressive metabolites, highlighting the impact of adenosine, kynurenines, prostaglandin E2, and norepinephrine and epinephrine, while discussing completed and ongoing clinical efforts to curtail their impact. Retrospective analyses of clinical data have elucidated that their activity is negatively associated with prognosis in diverse cancer indications, though there is a current paucity of approved therapies that disrupt their synthesis or downstream signaling axes. We hypothesize that prior lukewarm results may be attributed to redundancies in each metabolites’ synthesis or signaling pathway and highlight routes for how therapeutic development and patient stratification might proceed in the future. Show less