T Cell Responses to Individualized Neoantigen Therapy mRNA-4157 (V940) Alone or in Combination With Pembrolizumab in the Phase 1 KEYNOTE-603 Study.

mRNA-4157 (V940) is an individualized neoantigen therapy (INT) targeting up to 34 patient-specific tumor neoantigens to induce T cell responses and potentiate anti-tumor activity. We report mechanistic insights into the immunogenicity of mRNA-4157 via characterization of T cell responses to neoantigens from the first-in-human phase 1, KEYNOTE-603 study (NCT03313778) in patients with resected non-small cell lung cancer (Part A: 1mg mRNA-4157, n = 4) or resected cutaneous melanoma (Part D: 1mg mRNA-4157 + 200mg pembrolizumab, n = 12). Safety, tolerability, and immunogenicity were assessed. All patients experienced ≥1 treatment-emergent adverse event (AE); there were no grade 4/5 AEs or dose-limiting toxicities. mRNA-4157 alone induced consistent de novo, and strengthened pre-existing, T cell responses to targeted neoantigens. Following combination therapy, sustained mRNA-4157-induced neoantigen-specific T cell responses and expansion of cytotoxic CD8 and CD4 T cells were observed. These findings show the potential of a novel mRNA INT approach in oncology.

Spatial Mapping and Immunomodulatory Role of the OX40/OX40L Pathway in Human Non-Small Cell Lung Cancer.

PURPOSE: To evaluate the tissue distribution and clinical significance of OX40 and OX40L in human non-small cell lung cancer (NSCLC). EXPERIMENTAL DESIGN: Using multiplexed quantitative immunofluorescence, we conducted simultaneous and localized measurements of OX40 and OX40L proteins, major T-cell subsets, and conventional type 1 dendritic cells (cDC1) in 614 primary NSCLCs from three independent cohorts represented in tissue microarrays. We also measured OX40L protein in samples from a phase I clinical trial of intratumor administration of a lipid nanoparticle encapsulated mRNA encoding OX40L (mRNA-2416) in human solid tumors. Finally, we studied the OX40 pathway in 212 uterine/ovarian serous carcinomas. RESULTS: OX40 protein was expressed in approximately 90% of NSCLCs, and OX40L was detected in approximately 10% of cases. Increased expression of OX40 was associated with higher CD4+ and CD8+ T lymphocytes, as well as cDC1s. Elevated expression of OX40L was consistently associated with increased CD4+ tumor-infiltrating lymphocytes and longer overall survival. No association was found between OX40 or OX40L levels and oncogenic driver mutations in EGFR and KRAS in lung adenocarcinomas. Delivering OX40L mRNA using intratumor mRNA-2416 injection mediated increased local OX40L protein levels that was most prominent in a patient with ovarian serous carcinoma. Detectable OX40L protein levels were observed in 15% of primary uterine/ovarian serous malignancies and associated with longer survival. CONCLUSIONS: The OX40 pathway is expressed in a fraction of NSCLCs and is associated with a favorable immune contexture. Although OX40L is uncommonly expressed in NSCLC and serous malignancies, it is associated with better prognosis and can be introduced using exogenous mRNA.

Intratumoral IL12 mRNA Therapy Promotes TH1 Transformation of the Tumor Microenvironment.

PURPOSE: While immune checkpoint inhibitors such as anti-PD-L1 are rapidly becoming the standard of care in the treatment of many cancers, only a subset of treated patients have long-term responses. IL12 promotes antitumor immunity in mouse models; however, systemic recombinant IL12 had significant toxicity and limited efficacy in early clinical trials. EXPERIMENTAL DESIGN: We therefore designed a novel intratumoral IL12 mRNA therapy to promote local IL12 tumor production while mitigating systemic effects. RESULTS: A single intratumoral dose of mouse (m)IL12 mRNA induced IFNγ and CD8+ T-cell-dependent tumor regression in multiple syngeneic mouse models, and animals with a complete response demonstrated immunity to rechallenge. Antitumor activity of mIL12 mRNA did not require NK and NKT cells. mIL12 mRNA antitumor activity correlated with TH1 tumor microenvironment (TME) transformation. In a PD-L1 blockade monotherapy-resistant model, antitumor immunity induced by mIL12 mRNA was enhanced by anti-PD-L1. mIL12 mRNA also drove regression of uninjected distal lesions, and anti-PD-L1 potentiated this response. Importantly, intratumoral delivery of mRNA encoding membrane-tethered mIL12 also drove rejection of uninjected lesions with very limited circulating IL12p70, supporting the hypothesis that local IL12 could induce a systemic antitumor immune response against distal lesions. Furthermore, in ex vivo patient tumor slice cultures, human IL12 mRNA (MEDI1191) induced dose-dependent IL12 production, downstream IFNγ expression and TH1 gene expression. CONCLUSIONS: These data demonstrate the potential for intratumorally delivered IL12 mRNA to promote TH1 TME transformation and robust antitumor immunity.See related commentary by Cirella et al., p. 6080.

Durable anticancer immunity from intratumoral administration of IL-23, IL-36γ, and OX40L mRNAs.

Many solid cancers contain dysfunctional immune microenvironments. Immune system modulators that initiate responses to foreign pathogens could be promising candidates for reigniting productive responses toward tumors. Interleukin-1 (IL-1) and IL-12 cytokine family members cooperate at barrier tissues after microbial invasion, in human inflammatory diseases, and in antitumoral immunity. IL-36γ, in classic alarmin fashion, acts in damaged tissues, whereas IL-23 centrally coordinates immune responses to danger signals. In this study, direct intratumoral delivery of messenger RNAs (mRNAs) encoding these cytokines produced robust anticancer responses in a broad range of tumor microenvironments. The addition of mRNA encoding the T cell costimulator OX40L increased complete response rates in treated and untreated distal tumors compared to the cytokine mRNAs alone. Mice exhibiting complete responses were subsequently protected from tumor rechallenge. Treatments with these mRNA mixtures induced downstream cytokine and chemokine expression, and also activated multiple dendritic cell (DC) and T cell types. Consistent with this, efficacy was dependent on Batf3-dependent cross-presenting DCs and cytotoxic CD8+ T cells. IL-23/IL-36γ/OX40L triplet mRNA mixture triggered substantial immune cell recruitment into tumors, enabling effective tumor destruction irrespective of previous tumoral immune infiltrates. Last, combining triplet mRNA with checkpoint blockade led to efficacy in models otherwise resistant to systemic immune checkpoint inhibition. Human cell studies showed similar cytokine responses to the individual components of this mRNA mixture, suggesting translatability of immunomodulatory activity to human patients.

Role for cytoplasmic nucleotide hydrolysis in hepatic function and protein synthesis.

Nucleotide hydrolysis is essential for many aspects of cellular function. In the case of 3',5'-bisphosphorylated nucleotides, mammals possess two related 3'-nucleotidases, Golgi-resident 3'-phosphoadenosine 5'-phosphate (PAP) phosphatase (gPAPP) and Bisphosphate 3'-nucleotidase 1 (Bpnt1). gPAPP and Bpnt1 localize to distinct subcellular compartments and are members of a conserved family of metal-dependent lithium-sensitive enzymes. Although recent studies have demonstrated the importance of gPAPP for proper skeletal development in mice and humans, the role of Bpnt1 in mammals remains largely unknown. Here we report that mice deficient for Bpnt1 do not exhibit skeletal defects but instead develop severe liver pathologies, including hypoproteinemia, hepatocellular damage, and in severe cases, frank whole-body edema and death. Accompanying these phenotypes, we observed tissue-specific elevations of the substrate PAP, up to 50-fold in liver, repressed translation, and aberrant nucleolar architecture. Remarkably, the phenotypes of the Bpnt1 knockout are rescued by generating a double mutant mouse deficient for both PAP synthesis and hydrolysis, consistent with a mechanism in which PAP accumulation is toxic to tissue function independent of sulfation. Overall, our study defines a role for Bpnt1 in mammalian physiology and provides mechanistic insights into the importance of sulfur assimilation and cytoplasmic PAP hydrolysis to normal liver function.

A role for a lithium-inhibited Golgi nucleotidase in skeletal development and sulfation.

Sulfation is an important biological process that modulates the function of numerous molecules. It is directly mediated by cytosolic and Golgi sulfotransferases, which use 3'-phosphoadenosine 5'-phosphosulfate to produce sulfated acceptors and 3'-phosphoadenosine 5'-phosphate (PAP). Here, we identify a Golgi-resident PAP 3'-phosphatase (gPAPP) and demonstrate that its activity is potently inhibited by lithium in vitro. The inactivation of gPAPP in mice led to neonatal lethality, lung abnormalities resembling atelectasis, and dwarfism characterized by aberrant cartilage morphology. The phenotypic similarities of gPAPP mutant mice to chondrodysplastic models harboring mutations within components of the sulfation pathway lead to the discovery of undersulfated chondroitin in the absence of functional enzyme. Additionally, we observed loss of gPAPP leads to perturbations in the levels of heparan sulfate species in lung tissue and whole embryos. Our data are consistent with a model that clearance of the nucleotide product of sulfotransferases within the Golgi plays an important role in glycosaminoglycan sulfation, provide a unique genetic basis for chondrodysplasia, and define a function for gPAPP in the formation of skeletal elements derived through endochondral ossification.

An essential role for an inositol polyphosphate multikinase, Ipk2, in mouse embryogenesis and second messenger production.

Phospholipase C and several inositol polyphosphate kinase (IPK) activities generate a branched ensemble of inositol polyphosphate second messengers that regulate cellular signaling pathways in the nucleus and cytoplasm. Here, we report that mice deficient for Ipk2 (also known as inositol polyphosphate multikinase), an inositol trisphosphate and tetrakisphosphate 6/5/3-kinase active at several places in the inositol metabolic pathways, die around embryonic day 9.5 with multiple morphological defects, including abnormal folding of the neural tube. Metabolic analysis of Ipk2-deficient cells demonstrates that synthesis of the majority of inositol pentakisphosphate, hexakisphosphate and pyrophosphate species are disrupted, although the presence of 10% residual inositol hexakisphosphate indicates the existence of a minor alternative pathway. Agonist induced inositol tris- and bis-phosphate production and calcium release responses are present in homozygous mutant cells, indicating that the observed mouse phenotypes are a result of failure to produce higher inositol polyphosphates. Our data demonstrate that Ipk2 plays a major role in the synthesis of inositol polyphosphate messengers derived from inositol 1,4,5-trisphosphate and uncovers a role for their production in embryogenesis and normal development.

Casein kinase Iepsilon plays a functional role in the transforming growth factor-beta signaling pathway.

The transforming growth factor-beta (TGF-beta) signaling pathway is known to be involved in a wide range of biological events, including development, cellular differentiation, apoptosis, and oncogenesis. The TGF-beta signal is mediated by ligand binding to the type II receptor, leading to the recruitment and activation of the type I receptor, and subsequent activation of a family of intracellular signal transducing proteins called Smads. Here we report a regulatory role for casein kinase Iepsilon (CKIepsilon) in the TGF-beta signaling cascade. We find that CKIepsilon binds to all Smads and the cytoplasmic domains of the type I and type II receptors both in vitro and in vivo. The interaction of CKIepsilon with the type I and type II receptors is independent of TGF-beta stimulation, whereas the CKIepsilon/Smad interaction is transiently disrupted by ligand treatment. Additionally, CKIepsilon is able to phosphorylate the receptor-activated Smads (Smads 1-3 and 5) and the type II receptor in vitro. Transcriptional reporter assays reveal that transient overexpression of wild type CKIepsilon dramatically reduces basal reporter activity but enhances TGF-beta-stimulated transcription. Furthermore, overexpression of a kinase-dead mutant of CKIepsilon inhibits both basal and ligand-induced transcription, whereas inhibition of endogenous CKI catalytic activity with IC261 blocks only TGF-beta-stimulated reporter activity. Finally, knocking down CKIepsilon protein levels results in a significant increase in basal and TGF-beta-induced transcription. These results suggest that CKIepsilon plays a ligand-dependent, differential, and dual regulatory role within the TGF-beta signaling pathway.

Transforming growth factor beta-mediated transcriptional repression of c-myc is dependent on direct binding of Smad3 to a novel repressive Smad binding element.

Smad proteins are the most well-characterized intracellular effectors of the transforming growth factor beta (TGF-beta) signal. The ability of the Smads to act as transcriptional activators via TGF-beta-induced recruitment to Smad binding elements (SBE) within the promoters of TGF-beta target genes has been firmly established. However, the elucidation of the molecular mechanisms involved in TGF-beta-mediated transcriptional repression are only recently being uncovered. The proto-oncogene c-myc is repressed by TGF-beta, and this repression is required for the manifestation of the TGF-beta cytostatic program in specific cell types. We have shown that Smad3 is required for both TGF-beta-induced repression of c-myc and subsequent growth arrest in keratinocytes. The transcriptional repression of c-myc is dependent on direct Smad3 binding to a novel Smad binding site, termed a repressive Smad binding element (RSBE), within the TGF-beta inhibitory element (TIE) of the c-myc promoter. The c-myc TIE is a composite element, comprised of an overlapping RSBE and a consensus E2F site, that is capable of binding at least Smad3, Smad4, E2F-4, and p107. The RSBE is distinct from the previously defined SBE and may partially dictate, in conjunction with the promoter context of the overlapping E2F site, whether the Smad3-containing complex actively represses, as opposed to transactivates, the c-myc promoter.

Transforming growth factor-beta1 inhibition of vascular smooth muscle cell activation is mediated via Smad3.

Activation of vascular smooth muscle cells (VSMCs) by proinflammatory cytokines is a key feature of atherosclerotic lesion formation. Transforming growth factor (TGF)-beta1 is a pleiotropic growth factor that can modulate the inflammatory response in diverse cell types including VSMCs. However, the mechanisms by which TGF-beta1 is able to mediate these effects remains incompletely understood. We demonstrate here that the ability of TGF-beta1 to inhibit markers of VSMC activation, inducible nitric-oxide synthase (iNOS) and interleukin (IL)-6, is mediated through its downstream effector Smad3. In reporter gene transfection studies, we found that among a panel of Smads, Smad3 could inhibit iNOS induction in an analogous manner as exogenous TGF-beta1. Adenoviral overexpression of Smad3 potently repressed inducible expression of endogenous iNOS and IL-6. Conversely, TGF-beta1 inhibition of cytokine-mediated induction of iNOS and IL-6 expression was completely blocked in Smad3-deficient VSMCs. Previous studies demonstrate that CCAAT/enhancer-binding protein (C/EBP) and NF-kappaB sites are critical for cytokine induction of both the iNOS and IL-6 promoters. We demonstrate that the inhibitory effect of Smad3 occurs via a novel antagonistic effect of Smad3 on C/EBP DNA-protein binding and activity. Smad3 mediates this effect in part by inhibiting C/EBP-beta and C/EBP-delta through distinct mechanisms. Furthermore, we find that Smad3 prevents the cooperative induction of the iNOS promoter by C/EBP and NF-kappaB. These data demonstrate that Smad3 plays an essential role in mediating TGF-beta1 anti-inflammatory response in VSMCs.

Essential role for Smad3 in regulating MCP-1 expression and vascular inflammation.

Transforming growth factor (TGF)-beta(1) is a pleiotropic growth factor with known inhibitory effects on immune cell activation. However, the specific mechanism(s) and in vivo significance of the effectors of TGF-beta(1) modulation in the context of vascular inflammation are not well characterized. The chemokine monocyte chemoattractant protein (MCP)-1 is critical for the recruitment of macrophages in inflammatory disease states. In this study, we provide definitive evidence that the ability of TGF-beta(1) to inhibit MCP-1 expression is mediated via its effector Smad3. Adenoviral overexpression of Smad3 potently repressed inducible expression of endogenous MCP-1. Conversely, TGF-beta(1) inhibition of cytokine-mediated induction of MCP-1 expression was completely blocked in Smad3-deficient macrophages. Consistent with this impaired response, cardiac allografts in Smad3-deficient mice developed accelerated intimal hyperplasia with increased infiltration of adventitial macrophages expressing MCP-1. Previous studies show that MCP-1 inducibility is regulated by an AP-1 complex composed of c-Jun/c-Fos heterodimers. We demonstrate that the inhibitory effect of Smad3 occurs via a novel antagonistic effect of Smad3 on AP-1 DNA-protein binding and activity. Thus, Smad3 plays an essential role in modulating vascular inflammation characteristic of transplant-associated arteriopathy, is important in regulating MCP-1 expression, and plays a critical role in the ability of TGF-beta(1) to repress stimuli from a major inflammatory signaling pathway.

Beta-arrestin 2 mediates endocytosis of type III TGF-beta receptor and down-regulation of its signaling.

beta-Arrestins bind to activated seven transmembrane-spanning (7TMS) receptors (G protein-coupled receptors) after the receptors are phosphorylated by G protein-coupled receptor kinases (GRKs), thereby regulating their signaling and internalization. Here, we demonstrate an unexpected and analogous role of beta-arrestin 2 (betaarr2) for the single transmembrane-spanning type III transforming growth factor-beta (TGF-beta) receptor (TbetaRIII, also referred to as betaglycan). Binding of betaarr2 to TbetaRIII was also triggered by phosphorylation of the receptor on its cytoplasmic domain (likely at threonine 841). However, such phosphorylation was mediated by the type II TGF-beta receptor (TbetaRII), which is itself a kinase, rather than by a GRK. Association with betaarr2 led to internalization of both receptors and down-regulation of TGF-beta signaling. Thus, the regulatory actions of beta-arrestins are broader than previously appreciated, extending to the TGF-beta receptor family as well.

Smads "freeze" when they ski.

The transforming growth factor-beta (TGF-beta) signal is manifest through activated heteromeric Smad complex-mediated transcriptional modulation of target genes that translates into diverse, context-specific biologic effects, such as the potent TGF-beta-initiated cytostatic program. The TGF-beta pathway is effectively antagonized through the direct binding and subsequent repression of activated Smad heteromeric complexes by the Ski family of proto-oncoproteins.

Smad3 deficiency attenuates bleomycin-induced pulmonary fibrosis in mice.

Transforming growth factor-beta (TGF-beta) signaling plays an important regulatory role during lung fibrogenesis. Smad3 was identified in the pathway for transducing TGF-beta signals from the cell membrane to the nucleus. Using mice without Smad3 gene expression, we investigated whether Smad3 could regulate bleomycin-induced pulmonary fibrosis in vivo. Mice deficient in Smad3 demonstrated suppressed type I procollagen mRNA expression and reduced hydroxyproline content in the lungs compared with wild-type mice treated with bleomycin. Furthermore, loss of Smad3 greatly attenuated morphological fibrotic responses to bleomycin in the mouse lungs, suggesting that Smad3 is implicated in the pathogenesis of pulmonary fibrosis. These results show that Smad3 contributes to bleomycin-induced lung injury and that Smad3 may serve as a novel target for potential therapeutic treatment of lung fibrosis.