mRNA vaccines induce durable immune memory to SARS-CoV-2 and variants of concern

The durability of immune memory after severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) messenger RNA (mRNA) vaccination remains unclear. In this study, we longitudinally profiled vaccine responses in SARS-CoV-2–naïve and –recovered individuals for 6 months after vaccination. Antibodies declined from peak levels but remained detectable in most subjects at 6 months. By contrast, mRNA vaccines generated functional memory B cells that increased from 3 to 6 months postvaccination, with the majority of these cells cross-binding the Alpha, Beta, and Delta variants. mRNA vaccination further induced antigen-specific CD4+ and CD8+ T cells, and early CD4+ T cell responses correlated with long-term humoral immunity. Recall responses to vaccination in individuals with preexisting immunity primarily increased antibody levels without substantially altering antibody decay rates. Together, these findings demonstrate robust cellular immune memory to SARS-CoV-2 and its variants for at least 6 months after mRNA vaccination.

LuNER: Multiplexed SARS-CoV-2 detection in clinical swab and wastewater samples

Clinical and surveillance testing for the SARS-CoV-2 virus relies overwhelmingly on RT-qPCR-based diagnostics, yet several popular assays require 2-3 separate reactions or rely on detection of a single viral target, which adds significant time, cost, and risk of false-negative results. Furthermore, multiplexed RT-qPCR tests that detect at least two SARS-CoV-2 genes in a single reaction are typically not affordable for large scale clinical surveillance or adaptable to multiple PCR machines and plate layouts. We developed a RT-qPCR assay using the Luna Probe Universal One-Step RT-qPCR master mix with publicly available primers and probes to detect SARS-CoV-2 N gene, E gene, and human RNase P (LuNER) to address these shortcomings and meet the testing demands of a university campus and the local community. This cost-effective test is compatible with BioRad or Applied Biosystems qPCR machines, in 96 and 384-well formats, with or without sample pooling, and has a detection sensitivity suitable for both clinical reporting and wastewater surveillance efforts.

Animal models of brain metastasis

Modeling of metastatic disease in animal models is a critical resource to study the complexity of this multi-step process in a relevant system. Available models of metastatic disease to the brain are still far from ideal but they allow to address specific aspects of the biology or mimic clinically relevant scenarios. We not only review experimental models and their potential improvements but also discuss specific answers that could be obtained from them on unsolved aspects of clinical management.

Phagocytic 'teeth' and myosin-II 'jaw' power target constriction during phagocytosis

Phagocytosis requires rapid actin reorganization and spatially controlled force generation to ingest targets ranging from pathogens to apoptotic cells. How actomyosin activity directs membrane extensions to engulf such diverse targets remains unclear. Here, we combine lattice light-sheet microscopy (LLSM) with microparticle traction force microscopy (MP-TFM) to quantify actin dynamics and subcellular forces during macrophage phagocytosis. We show that spatially localized forces leading to target constriction are prominent during phagocytosis of antibody-opsonized targets. This constriction is largely driven by Arp2/3-mediated assembly of discrete actin protrusions containing myosin 1e and 1f ('teeth') that appear to be interconnected in a ring-like organization. Contractile myosin-II activity contributes to late-stage phagocytic force generation and progression, supporting a specific role in phagocytic cup closure. Observations of partial target eating attempts and sudden target release via a popping mechanism suggest that constriction may be critical for resolving complex in vivo target encounters. Overall, our findings present a phagocytic cup shaping mechanism that is distinct from cytoskeletal remodeling in 2D cell motility and may contribute to mechanosensing and phagocytic plasticity.

MERTK on mononuclear phagocytes regulates T cell antigen recognition at autoimmune and tumor sites

Understanding mechanisms of immune regulation is key to developing immunotherapies for autoimmunity and cancer. We examined the role of mononuclear phagocytes during peripheral T cell regulation in type 1 diabetes and melanoma. MERTK expression and activity in mononuclear phagocytes in the pancreatic islets promoted islet T cell regulation, resulting in reduced sensitivity of T cell scanning for cognate antigen in prediabetic islets. MERTK-dependent regulation led to reduced T cell activation and effector function at the disease site in islets and prevented rapid progression of type 1 diabetes. In human islets, MERTK-expressing cells were increased in remaining insulin-containing islets of type 1 diabetic patients, suggesting that MERTK protects islets from autoimmune destruction. MERTK also regulated T cell arrest in melanoma tumors. These data indicate that MERTK signaling in mononuclear phagocytes drives T cell regulation at inflammatory disease sites in peripheral tissues through a mechanism that reduces the sensitivity of scanning for antigen leading to reduced responsiveness to antigen.

Robotic RNA extraction for SARS-CoV-2 surveillance using saliva samples

Saliva is an attractive specimen type for asymptomatic surveillance of COVID-19 in large populations due to its ease of collection and its demonstrated utility for detecting RNA from SARS-CoV-2. Multiple saliva-based viral detection protocols use a direct-to-RT-qPCR approach that eliminates nucleic acid extraction but can reduce viral RNA detection sensitivity. To improve test sensitivity while maintaining speed, we developed a robotic nucleic acid extraction method for detecting SARS-CoV-2 RNA in saliva samples with high throughput. Using this assay, the Free Asymptomatic Saliva Testing (IGI FAST) research study on the UC Berkeley campus conducted 11,971 tests on supervised self-collected saliva samples and identified rare positive specimens containing SARS-CoV-2 RNA during a time of low infection prevalence. In an attempt to increase testing capacity, we further adapted our robotic extraction assay to process pooled saliva samples. We also benchmarked our assay against nasopharyngeal swab specimens and found saliva methods require further optimization to match this gold standard. Finally, we designed and validated a RT-qPCR test suitable for saliva self-collection. These results establish a robotic extraction-based procedure for rapid PCR-based saliva testing that is suitable for samples from both symptomatic and asymptomatic individuals.

Endomembrane targeting of human OAS1 p46 augments antiviral activity

Many host RNA sensors are positioned in the cytosol to detect viral RNA during infection. However, most positive-strand RNA viruses replicate within a modified organelle co-opted from intracellular membranes of the endomembrane system, which shields viral products from cellular innate immune sensors. Targeting innate RNA sensors to the endomembrane system may enhance their ability to sense RNA generated by viruses that use these compartments for replication. Here, we reveal that an isoform of oligoadenylate synthetase 1, OAS1 p46, is prenylated and targeted to the endomembrane system. Membrane localization of OAS1 p46 confers enhanced access to viral replication sites and results in increased antiviral activity against a subset of RNA viruses including flaviviruses, picornaviruses, and SARS-CoV-2. Finally, our human genetic analysis shows that the OAS1 splice-site SNP responsible for production of the OAS1 p46 isoform correlates with protection from severe COVID-19. This study highlights the importance of endomembrane targeting for the antiviral specificity of OAS1 and suggests that early control of SARS-CoV-2 replication through OAS1 p46 is an important determinant of COVID-19 severity.

The WAVE complex associates with sites of saddle membrane curvature

How local interactions of actin regulators yield large-scale organization of cell shape and movement is not well understood. Here we investigate how the WAVE complex organizes sheet-like lamellipodia. Using super-resolution microscopy, we find that the WAVE complex forms actin-independent 230-nm-wide rings that localize to regions of saddle membrane curvature. This pattern of enrichment could explain several emergent cell behaviors, such as expanding and self-straightening lamellipodia and the ability of endothelial cells to recognize and seal transcellular holes. The WAVE complex recruits IRSp53 to sites of saddle curvature but does not depend on IRSp53 for its own localization. Although the WAVE complex stimulates actin nucleation via the Arp2/3 complex, sheet-like protrusions are still observed in ARP2-null, but not WAVE complex-null, cells. Therefore, the WAVE complex has additional roles in cell morphogenesis beyond Arp2/3 complex activation. Our work defines organizing principles of the WAVE complex lamellipodial template and suggests how feedback between cell shape and actin regulators instructs cell morphogenesis.

Bromodomain protein BRD4 directs and sustains CD8 T cell differentiation during infection

In response to infection, pathogen-specific CD8 T cells differentiate into functionally diverse effector and memory T cell populations critical for resolving disease and providing durable immunity. Through small-molecule inhibition, RNAi studies, and induced genetic deletion, we reveal an essential role for the chromatin modifier and BET family member BRD4 in supporting the differentiation and maintenance of terminally fated effector CD8 T cells during infection. BRD4 bound diverse regulatory regions critical to effector T cell differentiation and controlled transcriptional activity of terminal effector-specific super-enhancers in vivo. Consequentially, induced deletion of Brd4 or small molecule-mediated BET inhibition impaired maintenance of a terminal effector T cell phenotype. BRD4 was also required for terminal differentiation of CD8 T cells in the tumor microenvironment in murine models, which we show has implications for immunotherapies. Taken together, these data reveal an unappreciated requirement for BRD4 in coordinating activity of cis regulatory elements to control CD8 T cell fate and lineage stability.

SHP2 Targets ITK Downstream of PD-1 to Inhibit T Cell Function

PD-1 is a critical therapeutic target in cancer immunotherapy and antibodies blocking PD-1 are approved for multiple types of malignancies. The phosphatase SHP2 is the main effector mediating PD-1 downstream signaling and accordingly attempts have been made to target this enzyme as an alternative approach to treat immunogenic tumors. Unfortunately, small molecule inhibitors of SHP2 do not work as expected, suggesting that the role of SHP2 in T cells is more complex than initially hypothesized. To better understand the perplexing role of SHP2 in T cells, we performed interactome mapping of SAP, an adapter protein that is associated with SHP2 downstream signaling. Using genetic and pharmacological approaches, we discovered that SHP2 dephosphorylates ITK specifically downstream of PD-1 and that this event was associated with PD-1 inhibitory cellular functions. This study suggests that ITK is a unique target in this pathway, and since ITK is a SHP2-dependent specific mediator of PD-1 signaling, the combination of ITK inhibitors with PD-1 blockade may improve upon PD-1 monotherapy in the treatment of cancer.

Characterization and comparison of innate and adaptive immune responses at vaccine sites in melanoma vaccine clinical trials

The strength and durability of systemic anti-tumor immune responses induced by cancer vaccines depends on adjuvants to support an immunogenic vaccine site microenvironment (VSME). Adjuvants include water-in-oil emulsions with incomplete Freund's adjuvant (IFA) and combinations of toll-like receptor (TLR) agonists, including a preparation containing TLR4 and TLR9 agonists with QS-21 (AS15). IFA-containing vaccines can promote immune cell accumulation at the VSME, whereas effects of AS15 are largely unexplored. Therefore, we assessed innate and adaptive immune cell accumulation and gene expression at the VSME after vaccination with AS15 and compared to effects with IFA. We hypothesized that AS15 would promote less accumulation of innate and adaptive immune cells at the VSME than IFA vaccines. In two clinical trials, patients with resected high-risk melanoma received either a multipeptide vaccine with IFA or a recombinant MAGE-A3 protein vaccine with AS15. Vaccine site biopsies were obtained after one or multiple vaccines. T cells accumulated early after vaccines with AS15, but this was not durable or of the same magnitude as vaccination in IFA. Vaccines with AS15 increased durable expression of DC- and T cell-related genes, as well as PD-L1 and IDO1, suggesting complex activation and regulation of innate and adaptive immune function with AS15. These changes were generally greater with vaccines containing IFA, but IFA induced reduction in myeloid suppressor cells markers. Evidence of tertiary lymphoid structure (TLS) formation was observed with both adjuvants. Our findings highlight adjuvant-dependent changes in immune features at the VSME that may impact systemic immune responses.

Organ-on-a-chip technology for nanoparticle research

The last two decades have witnessed explosive growth in the field of nanoengineering and nanomedicine. In particular, engineered nanoparticles have garnered great attention due to their potential to enable new capabilities such as controlled and targeted drug delivery for treatment of various diseases. With rapid progress in nanoparticle research, increasing efforts are being made to develop new technologies for in vitro modeling and analysis of the efficacy and safety of nanotherapeutics in human physiological systems. Organ-on-a-chip technology represents the most recent advance in this effort that provides a promising approach to address the limitations of conventional preclinical models. In this paper, we present a concise review of recent studies demonstrating how this emerging technology can be applied to in vitro studies of nanoparticles. The specific focus of this review is to examine the use of organ-on-a-chip models for toxicity and efficacy assessment of nanoparticles used in therapeutic applications. We also discuss challenges and future opportunities for implementing organ-on-a-chip technology for nanoparticle research.

The Complexity of Targeting Chemokines to Promote a Tumor Immune Response

Immunotherapeutic treatment strategies greatly extend patient survival following malignant disease across a wide range of tumor types, including even those with metastatic disease. While diverse in approach, adoptive cell therapy, introduction of T cells that express chimeric antigen receptors, and checkpoint inhibitors all aim to re-invigorate the immune system to promote tumor cell identification and elimination. This review will focus on immune cell infiltration into tumors as well as a cellular organization within the tumor microenvironment as directed by the cell-specific expression patterns of chemokines and chemokine receptors. Through better understanding the chemokine network within tumors, we can uncover mechanisms to promote beneficial immune cell infiltration that can be combined with checkpoint inhibition. Conversely, chemokine expression is not limited to cells of the immune system, and it is understood that tumor cells also express chemokines and chemokine receptors. Tumor cells can hijack the chemokine networks to promote immune suppression and metastatic tumor cell trafficking. We will discuss the ways in which the chemokine network lies at the crossroad of immune evasion and tumor regression. Overall, this review will summarize key publications in the field of immune cell recruitment to tumors, highlight the dichotomous nature of chemokine interventions into cancer, and aims to identify therapeutic pathways forward.

CD8+ T cell immunity blocks the metastasis of carcinogen-exposed breast cancer

The link between carcinogen exposure and cancer immunogenicity is unclear. Single exposure to 12-dimethylbenz[a]anthracene (DMBA) at puberty accelerated spontaneous breast carcinogenesis in mouse mammary tumor virus-polyoma middle tumor-antigen transgenic (MMTV-PyMTtg or PyMT) and MMTV-Her2/neutg (Her2) mice. Paradoxically, DMBA-treated PyMT and Her2 animals were protected from metastasis. CD8+ T cells significantly infiltrated DMBA-exposed breast cancers. CD8+ T cell depletion resulted in severe lung and liver metastasis in DMBA-treated PyMT mice. Besides increasing tumor mutational burden, DMBA exposure up-regulated Chemokine (C-C motif) ligand 21 (CCL21) in cancer cells and heightened antigen presentation. CCL21 injection suppressed breast cancer growth, and CCL21 receptor deletion attenuated T cell immunity against cancer metastasis in DMBA-treated PyMT animals. CCL21 expression correlated with increased mutational burden and cytolytic activity across human cancers. Higher CCL21 levels correlated with increased CD8+ T cell infiltrates in human breast cancer and predicted lower breast cancer distant recurrence rate. Collectively, carcinogen exposure induces immune-activating factors within cancer cells that promote CD8+ T cell immunity against metastasis.

Distinct antibody and memory B cell responses in SARS-CoV-2 naïve and recovered individuals following mRNA vaccination

Novel mRNA vaccines for SARS-CoV-2 have been authorized for emergency use. Despite their efficacy in clinical trials, data on mRNA vaccine-induced immune responses are mostly limited to serological analyses. Here, we interrogated antibody and antigen-specific memory B cells over time in 33 SARS-CoV-2 naïve and 11 SARS-CoV-2 recovered subjects. SARS-CoV-2 naïve individuals required both vaccine doses for optimal increases in antibodies, particularly for neutralizing titers against the B.1.351 variant. Memory B cells specific for full-length spike protein and the spike receptor binding domain (RBD) were also efficiently primed by mRNA vaccination and detectable in all SARS-CoV-2 naive subjects after the second vaccine dose, though the memory B cell response declined slightly with age. In SARS-CoV-2 recovered individuals, antibody and memory B cell responses were significantly boosted after the first vaccine dose; however, there was no increase in circulating antibodies, neutralizing titers, or antigen-specific memory B cells after the second dose. This robust boosting after the first vaccine dose strongly correlated with levels of pre-existing memory B cells in recovered individuals, identifying a key role for memory B cells in mounting recall responses to SARS-CoV-2 antigens. Together, our data demonstrated robust serological and cellular priming by mRNA vaccines and revealed distinct responses based on prior SARS-CoV-2 exposure, whereby COVID-19 recovered subjects may only require a single vaccine dose to achieve peak antibody and memory B cell responses. These findings also highlight the utility of defining cellular responses in addition to serologies and may inform SARS-CoV-2 vaccine distribution in a resource-limited setting.

A Prospective Analysis of Plasma Phospholipid Fatty Acids and Breast Cancer Risk in 2 Provinces in Canada

BACKGROUND

Studies suggest that fatty acid status influences breast cancer etiology, yet the roles of individual fatty acids in breast cancer risk are unclear, specifically when central adiposity and menopausal status are considered.

OBJECTIVES

This study examined the associations of fatty acid status with breast cancer risk including location, menopausal status, and waist-to-hip ratio as key variables.

METHODS

Prediagnostic plasma phospholipid fatty acids were measured in women with breast cancer (n = 393) and age-matched controls (n = 786) from a nested case-control prospective study within Alberta's Tomorrow Project (ATP) and British Columbia Generations Project (BCGP) cohorts. Binary logistic regression models were used to evaluate associations of fatty acids and breast cancer risk with subgroup analysis for menopausal status and waist-to-hip ratio.

RESULTS

Women from BCGP had a higher n-3 (ɷ-3) fatty acid status compared with the ATP (6.4% ± 0.08% vs. 5.3% ± 0.06%; P < 0.001), so subsequent analysis was blocked by cohort. Overall, fatty acids had inconsistent associations with risk. In the ATP among premenopausal women, total long-chain n-3 fatty acids (ORQ4vsQ1 = 1.78; 95% CI: 0.58, 5.43; P-trend = 0.007, P-interaction = 0.07) were positively associated with breast cancer risk, whereas in BCGP, DHA (ORQ4vsQ1 = 0.66; 95% CI: 0.28, 1.53; P-trend = 0.03, P-interaction = 0.05) and total long-chain n-3 fatty acids (ORQ4vsQ1 = 0.66; 95% CI: 0.28, 1.54; P-trend = 0.03) were associated with decreased cancer risk when the waist-to-hip ratio was <0.85.

CONCLUSIONS

Our findings suggest that regional variations in fatty acid status influence breast cancer risk, resulting in positive associations of total long-chain n-3 fatty acids in premenopausal ATP women and negative associations of these fatty acids in BCGP women with a waist-to-hip ratio below guidelines. This study highlights the complexity and difficulty in using fatty acid status to predict breast cancer risk in diverse populations without the consideration of other risk factors.

Single-cell lineage mapping of a diverse virus-specific naive CD4 T cell repertoire

Tracking how individual naive T cells from a natural TCR repertoire clonally expand, differentiate, and make lineage choices in response to an infection has not previously been possible. Here, using single-cell sequencing technology to identify clones by their unique TCR sequences, we were able to trace the clonal expansion, differentiation trajectory, and lineage commitment of individual virus-specific CD4 T cells during an acute lymphocytic choriomeningitis virus (LCMV) infection. Notably, we found previously unappreciated clonal diversity and cellular heterogeneity among virus-specific helper T cells. Interestingly, although most naive CD4 T cells gave rise to multiple lineages at the clonal level, ∼28% of naive cells exhibited a preferred lineage choice toward either Th1 or TFH cells. Mechanistically, we found that TCR structure, in particular the CDR3 motif of the TCR α chain, skewed lineage decisions toward the TFH cell fate.

Optimising the value of immunomodulatory drugs during induction and maintenance in transplant ineligible patients with newly diagnosed multiple myeloma: results from Myeloma XI, a multicentre, open-label, randomised, Phase III trial

Second-generation immunomodulatory agents, such as lenalidomide, have a more favourable side-effect profile than the first-generation thalidomide, but their optimum combination and duration for patients with newly diagnosed transplant-ineligible myeloma (ND-TNE-MM) has not been defined. The most appropriate delivery and dosing regimens of these therapies for patients at advanced age and frailty status is also unclear. The Myeloma XI study compared cyclophosphamide, thalidomide and dexamethasone (CTDa) to cyclophosphamide, lenalidomide and dexamethasone (CRDa) as induction therapy, followed by a maintenance randomisation between ongoing therapy with lenalidomide or observation for patients with ND-TNE-MM. CRDa deepened response but did not improve progression-free (PFS) or overall survival (OS) compared to CTDa. However, analysis by age group highlighted significant differences in tolerability in older, frailer patients that may have limited treatment delivery and impacted outcome. Deeper responses and PFS and OS benefits with CRDa over CTDs were seen in patients aged ≤70 years, with an increase in toxicity and discontinuation observed in older patients. Our results highlight the importance of considering age and frailty in the approach to therapy for patients with ND-TNE-MM, highlighting the need for prospective validation of frailty adapted therapy approaches, which may improve outcomes by tailoring treatment to the individual.

A novel mouse model for checkpoint inhibitor-induced adverse events

Immune checkpoint inhibitors have demonstrated significant efficacy in the treatment of a variety of cancers, however their therapeutic potential is limited by abstruse immune related adverse events. Currently, no robust animal model exists of checkpoint inhibitor-induced adverse events. Establishing such a model will improve our mechanistic understanding of this process, which in turn will inform design of improved therapies. We developed a mouse model to determine inflammatory toxicities in response to dual checkpoint blockade in the presence of syngeneic tumors. Mice from susceptible genetic backgrounds received intraperitoneal injections of anti-mouse PD-1 and CTLA-4 antibodies. The mice were monitored for weight loss and histologic evidence of inflammation. Blood was collected for basic metabolic panels and titers of anti-nuclear antibodies. In parallel, mice were also treated with prednisolone, which is commonly used to treat immune related adverse events among cancer patients. Among all the genetic backgrounds, B6/lpr mice treated with anti-CTLA-4 and anti-PD-1 antibodies developed more substantial hepatitis, pancreatitis, colitis, and pneumonitis characterized by organ infiltration of immune cells. Mice that developed tissue infiltration demonstrated high serum levels of glucose and high titers of anti-nuclear antibodies. Finally, while administration of prednisolone prevented the development of the inflammatory adverse events, it also abrogated the protective anti-tumor effect of the checkout inhibitors. Genetic background and treatment modalities jointly modified the inflammatory adverse events in tumor bearing mice, suggesting a complex mechanism for checkpoint inhibitor-related inflammation. Future studies will assess additional genetic susceptibility factors and will examine possible contributions from the administration of other anti-inflammatory drugs.

Sustained Helicobacter pylori infection accelerates gastric dysplasia in a mouse model

More than 80% of gastric cancer is attributable to stomach infection with Helicobacter pylori (Hp). Gastric preneoplastic progression involves sequential tissue changes, including loss of parietal cells, metaplasia and dysplasia. In transgenic mice, active KRAS expression recapitulates these tissue changes in the absence of Hp infection. This model provides an experimental system to investigate additional roles of Hp in preneoplastic progression, beyond its known role in initiating inflammation. Tissue histology, gene expression, the immune cell repertoire, and metaplasia and dysplasia marker expression were assessed in KRAS+ mice +/-Hp infection. Hp+/KRAS+ mice had severe T-cell infiltration and altered macrophage polarization; a different trajectory of metaplasia; more dysplastic glands; and greater proliferation of metaplastic and dysplastic glands. Eradication of Hp with antibiotics, even after onset of metaplasia, prevented or reversed these tissue phenotypes. These results suggest that gastric preneoplastic progression differs between Hp+ and Hp- cases, and that sustained Hp infection can promote the later stages of gastric preneoplastic progression.

Dysregulated RASGRP1 expression through RUNX1 mediated transcription promotes autoimmunity

RasGRP1 is a Ras guanine nucleotide exchange factor, and an essential regulator of lymphocyte receptor signaling. In mice, Rasgrp1 deletion results in defective T lymphocyte development. RASGRP1-deficient patients suffer from immune deficiency, and the RASGRP1 gene has been linked to autoimmunity. However, how RasGRP1 levels are regulated, and if RasGRP1 dosage alterations contribute to autoimmunity remains unknown. We demonstrate that diminished Rasgrp1 expression caused defective T lymphocyte selection in C57BL/6 mice, and that the severity of inflammatory disease inversely correlates with Rasgrp1 expression levels. In patients with autoimmunity, active inflammation correlated with decreased RASGRP1 levels in CD4+ T cells. By analyzing H3K27 acetylation profiles in human T cells, we identified a RASGRP1 enhancer that harbors autoimmunity-associated SNPs. CRISPR-Cas9 disruption of this enhancer caused lower RasGRP1 expression, and decreased binding of RUNX1 and CBFB transcription factors. Analyzing patients with autoimmunity, we detected reduced RUNX1 expression in CD4+ T cells. Lastly, we mechanistically link RUNX1 to transcriptional regulation of RASGRP1 to reveal a key circuit regulating RasGRP1 expression, which is vital to prevent inflammatory disease.

Cancer Stemness Meets Immunity: From Mechanism to Therapy

Cancer stem cells (CSCs) are self-renewing cells that facilitate tumor initiation, promote metastasis, and enhance cancer therapy resistance. Transcriptomic analyses across many cancer types have revealed a prominent association between stemness and immune signatures, potentially implying a biological interaction between such hallmark features of cancer. Emerging experimental evidence has substantiated the influence of CSCs on immune cells, including tumor-associated macrophages, myeloid-derived suppressor cells, and T cells, in the tumor microenvironment and, reciprocally, the importance of such immune cells in sustaining CSC stemness and its survival niche. This review covers the cellular and molecular mechanisms underlying the symbiotic interactions between CSCs and immune cells and how such heterotypic signaling maintains a tumor-promoting ecosystem and informs therapeutic strategies intercepting this co-dependency.

Structures of diverse poxin cGAMP nucleases reveal a widespread role for cGAS-STING evasion in host-pathogen conflict

DNA viruses in the family Poxviridae encode poxin enzymes that degrade the immune second messenger 2'3'-cGAMP to inhibit cGAS-STING immunity in mammalian cells. The closest homologs of poxin exist in the genomes of insect viruses suggesting a key mechanism of cGAS-STING evasion may have evolved outside of mammalian biology. Here we use a biochemical and structural approach to discover a broad family of 369 poxins encoded in diverse viral and animal genomes and define a prominent role for 2'3'-cGAMP cleavage in metazoan host-pathogen conflict. Structures of insect poxins reveal unexpected homology to flavivirus proteases and enable identification of functional self-cleaving poxins in RNA-virus polyproteins. Our data suggest widespread 2'3'-cGAMP signaling in insect antiviral immunity and explain how a family of cGAS-STING evasion enzymes evolved from viral proteases through gain of secondary nuclease activity. Poxin acquisition by poxviruses demonstrates the importance of environmental connections in shaping evolution of mammalian pathogens.

Metabolic determinants of cellular fitness dependent on mitochondrial reactive oxygen species

Mitochondria-derived reactive oxygen species (mROS) are required for the survival, proliferation, and metastasis of cancer cells. The mechanism by which mitochondrial metabolism regulates mROS levels to support cancer cells is not fully understood. To address this, we conducted a metabolism-focused CRISPR-Cas9 genetic screen and uncovered that loss of genes encoding subunits of mitochondrial complex I was deleterious in the presence of the mitochondria-targeted antioxidant mito-vitamin E (MVE). Genetic or pharmacologic inhibition of mitochondrial complex I in combination with the mitochondria-targeted antioxidants, MVE or MitoTEMPO, induced a robust integrated stress response (ISR) and markedly diminished cell survival and proliferation in vitro. This was not observed following inhibition of mitochondrial complex III. Administration of MitoTEMPO in combination with the mitochondrial complex I inhibitor phenformin decreased the leukemic burden in a mouse model of T cell acute lymphoblastic leukemia. Thus, mitochondrial complex I is a dominant metabolic determinant of mROS-dependent cellular fitness.

Granzyme B nanoreporter for early monitoring of tumor response to immunotherapy

Despite recent advancements in cancer immunotherapy, accurate monitoring of its efficacy is challenging due to heterogeneous immune responses. Conventional imaging techniques lack the sensitivity and specificity for early response assessment. In this study, we designed a granzyme B (GrB) nanoreporter (GNR) that can deliver an immune checkpoint inhibitor to the tumor and track time-sensitive GrB activity as a direct way to monitor initiation of effective immune responses. Anti-programmed death-ligand 1 (PD-L1) antibody-conjugated GNRs inhibited PD-1/PD-L1 interactions efficiently and induced T cell-mediated GrB release that can be imaged using activatable imaging probe. GNRs enabled real-time immunotherapy response monitoring in a tumor-bearing mice model and distinguished between highly responsive and poorly responsive tumors. Furthermore, increasing doses resulted in a better response and enhanced sensitivity in poorly responsive tumors. These findings indicate that GNR has the potential to serve as a tool for sensitive and noninvasive evaluation of immunotherapy efficacy.