Fully human anti-CD39 antibody potently inhibits ATPase activity in cancer cells via uncompetitive allosteric mechanism.

The extracellular ATP/adenosine axis in the tumor microenvironment (TME) has emerged as an important immune-regulatory pathway. Nucleoside triphosphate diphosphohydrolase-1 (NTPDase1), otherwise known as CD39, is highly expressed in the TME, both on infiltrating immune cells and tumor cells across a broad set of cancer indications. CD39 processes pro-inflammatory extracellular ATP to ADP and AMP, which is then processed by Ecto-5'-nucleotidase/CD73 to immunosuppressive adenosine. Directly inhibiting the enzymatic function of CD39 via an antibody has the potential to unleash an immune-mediated anti-tumor response via two mechanisms: 1) increasing the availability of immunostimulatory extracellular ATP released by damaged and/or dying cells, and 2) reducing the generation and accumulation of suppressive adenosine within the TME. Tizona Therapeutics has engineered a novel first-in-class fully human anti-CD39 antibody, TTX-030, that directly inhibits CD39 ATPase enzymatic function with sub-nanomolar potency. Further characterization of the mechanism of inhibition by TTX-030 using CD39+ human melanoma cell line SK-MEL-28 revealed an uncompetitive allosteric mechanism (α < 1). The uncompetitive mechanism of action enables TTX-030 to inhibit CD39 at the elevated ATP concentrations reported in the TME. Maximal inhibition of cellular CD39 ATPase velocity was 85%, which compares favorably to results reported for antibody inhibitors to other enzyme targets. The allosteric mechanism of TTX-030 was confirmed via mapping the epitope to a region of CD39 distant from its active site, which suggests possible models for how potent inhibition is achieved. In summary, TTX-030 is a potent allosteric inhibitor of CD39 ATPase activity that is currently being evaluated in clinical trials for cancer therapy.

Targeting CD39 in Cancer Reveals an Extracellular ATP- and Inflammasome-Driven Tumor Immunity.

We explored the mechanism of action of CD39 antibodies that inhibit ectoenzyme CD39 conversion of extracellular ATP (eATP) to AMP and thus potentially augment eATP-P2-mediated proinflammatory responses. Using syngeneic and humanized tumor models, we contrast the potency and mechanism of anti-CD39 mAbs with other agents targeting the adenosinergic pathway. We demonstrate the critical importance of an eATP-P2X7-ASC-NALP3-inflammasome-IL18 pathway in the antitumor activity mediated by CD39 enzyme blockade, rather than simply reducing adenosine as mechanism of action. Efficacy of anti-CD39 activity was underpinned by CD39 and P2X7 coexpression on intratumor myeloid subsets, an early signature of macrophage depletion, and active IL18 release that facilitated the significant expansion of intratumor effector T cells. More importantly, anti-CD39 facilitated infiltration into T cell-poor tumors and rescued anti-PD-1 resistance. Anti-human CD39 enhanced human T-cell proliferation and Th1 cytokine production and suppressed human B-cell lymphoma in the context of autologous Epstein-Barr virus-specific T-cell transfer. SIGNIFICANCE: Overall, these data describe a potent and novel mechanism of action of antibodies that block mouse or human CD39, triggering an eATP-P2X7-inflammasome-IL18 axis that reduces intratumor macrophage number, enhances intratumor T-cell effector function, overcomes anti-PD-1 resistance, and potentially enhances the efficacy of adoptive T-cell transfer.This article is highlighted in the In This Issue feature, p. 1631.

Paradoxical resistance of multiple myeloma to proteasome inhibitors by decreased levels of 19S proteasomal subunits.

Hallmarks of cancer, including rapid growth and aneuploidy, can result in non-oncogene addiction to the proteostasis network that can be exploited clinically. The defining example is the exquisite sensitivity of multiple myeloma (MM) to 20S proteasome inhibitors, such as carfilzomib. However, MM patients invariably acquire resistance to these drugs. Using a next-generation shRNA platform, we found that proteostasis factors, including chaperones and stress-response regulators, controlled the response to carfilzomib. Paradoxically, 19S proteasome regulator knockdown induced resistance to carfilzomib in MM and non-MM cells. 19S subunit knockdown did not affect the activity of the 20S subunits targeted by carfilzomib nor their inhibition by the drug, suggesting an alternative mechanism, such as the selective accumulation of protective factors. In MM patients, lower 19S levels predicted a diminished response to carfilzomib-based therapies. Together, our findings suggest that an understanding of network rewiring can inform development of new combination therapies to overcome drug resistance.

The "rule of halves" does not apply in Peru: awareness, treatment, and control of hypertension and diabetes in rural, urban, and rural-to-urban migrants.

OBJECTIVE: To determine the awareness, treatment, and control of hypertension and diabetes by migration status. DESIGN: Cross-sectional study, secondary analyses of the PERU MIGRANT study. PATIENTS: Rural, rural-to-urban migrants, and urban participants. MAIN OUTCOME MEASURES: Awareness, treatment, and control of hypertension and diabetes mellitus were calculated using weights to account for participant's group size. RESULTS: Of 205 of the 987 (weighted prevalence 24.1%, 95% confidence interval: 21.1%-27.1%) participants identified as hypertensive, 48.3% were aware of their diagnosis, 40% of them were receiving treatment, and 30.4% of those receiving treatment were controlled. Diabetes was present in 33 of the 987 (weighted prevalence 4.6%, 95% confidence interval: 3.1%-6%), and diabetes awareness, treatment, and control were 71.1%, 40.6%, and 7.7%, respectively. Suboptimal control rates, defined as those not meeting blood pressure or glycaemia targets among those with the condition, were 95.1% for hypertension and 97% for diabetes. Higher awareness, treatment, and control rates, for both hypertension and diabetes, were observed in rural-to-urban migrants and urban participants compared with rural participants. However, treatment rates were much lower among migrants compared with the urban group. CONCLUSIONS: These results identify major unmet needs in awareness, treatment, and control of hypertension and diabetes. Particular challenges are lack of awareness of both hypertension and diabetes in rural areas, and poor levels of treatment and control among people who have migrated from rural into urban areas.

IRE1α induces thioredoxin-interacting protein to activate the NLRP3 inflammasome and promote programmed cell death under irremediable ER stress.

When unfolded proteins accumulate to irremediably high levels within the endoplasmic reticulum (ER), intracellular signaling pathways called the unfolded protein response (UPR) become hyperactivated to cause programmed cell death. We discovered that thioredoxin-interacting protein (TXNIP) is a critical node in this "terminal UPR." TXNIP becomes rapidly induced by IRE1α, an ER bifunctional kinase/endoribonuclease (RNase). Hyperactivated IRE1α increases TXNIP mRNA stability by reducing levels of a TXNIP destabilizing microRNA, miR-17. In turn, elevated TXNIP protein activates the NLRP3 inflammasome, causing procaspase-1 cleavage and interleukin 1ß (IL-1ß) secretion. Txnip gene deletion reduces pancreatic ß cell death during ER stress and suppresses diabetes caused by proinsulin misfolding in the Akita mouse. Finally, small molecule IRE1α RNase inhibitors suppress TXNIP production to block IL-1ß secretion. In summary, the IRE1α-TXNIP pathway is used in the terminal UPR to promote sterile inflammation and programmed cell death and may be targeted to develop effective treatments for cell degenerative diseases.

IRE1alpha kinase activation modes control alternate endoribonuclease outputs to determine divergent cell fates.

During endoplasmic reticulum (ER) stress, homeostatic signaling through the unfolded protein response (UPR) augments ER protein-folding capacity. If homeostasis is not restored, the UPR triggers apoptosis. We found that the ER transmembrane kinase/endoribonuclease (RNase) IRE1alpha is a key component of this apoptotic switch. ER stress induces IRE1alpha kinase autophosphorylation, activating the RNase to splice XBP1 mRNA and produce the homeostatic transcription factor XBP1s. Under ER stress--or forced autophosphorylation--IRE1alpha's RNase also causes endonucleolytic decay of many ER-localized mRNAs, including those encoding chaperones, as early events culminating in apoptosis. Using chemical genetics, we show that kinase inhibitors bypass autophosphorylation to activate the RNase by an alternate mode that enforces XBP1 splicing and averts mRNA decay and apoptosis. Alternate RNase activation by kinase-inhibited IRE1alpha can be reconstituted in vitro. We propose that divergent cell fates during ER stress hinge on a balance between IRE1alpha RNase outputs that can be tilted with kinase inhibitors to favor survival.

Flagellar motility contributes to cytokinesis in Trypanosoma brucei and is modulated by an evolutionarily conserved dynein regulatory system.

The flagellum of Trypanosoma brucei is a multifunctional organelle with critical roles in motility and other aspects of the trypanosome life cycle. Trypanin is a flagellar protein required for directional cell motility, but its molecular function is unknown. Recently, a trypanin homologue in Chlamydomonas reinhardtii was reported to be part of a dynein regulatory complex (DRC) that transmits regulatory signals from central pair microtubules and radial spokes to axonemal dynein. DRC genes were identified as extragenic suppressors of central pair and/or radial spoke mutations. We used RNA interference to ablate expression of radial spoke (RSP3) and central pair (PF16) components individually or in combination with trypanin. Both rsp3 and pf16 single knockdown mutants are immotile, with severely defective flagellar beat. In the case of rsp3, this loss of motility is correlated with the loss of radial spokes, while in the case of pf16 the loss of motility correlates with an aberrant orientation of the central pair microtubules within the axoneme. Genetic interaction between trypanin and PF16 is demonstrated by the finding that loss of trypanin suppresses the pf16 beat defect, indicating that the DRC represents an evolutionarily conserved strategy for dynein regulation. Surprisingly, we discovered that four independent mutants with an impaired flagellar beat all fail in the final stage of cytokinesis, indicating that flagellar motility is necessary for normal cell division in T. brucei. These findings present the first evidence that flagellar beating is important for cell division and open the opportunity to exploit enzymatic activities that drive flagellar beat as drug targets for the treatment of African sleeping sickness.