Transcription factor ZIC2 regulates the tumorigenic phenotypes associated with both bulk and cancer stem cells in epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is the most lethal gynecologic malignancy in North America. Current therapeutic regimens are ineffective against advanced EOC. A better understanding of the molecular mechanisms that regulate the biology of EOC will be a critical step toward developing more efficacious therapies against EOC. Herein, we demonstrate that elevated expression of transcription factor ZIC2 was associated with lower survival of EOC patients. Knockout of endogenous ZIC2 in EOC cells attenuated the tumorigenic phenotypes associated with both bulk and cancer stem cells in vitro and in vivo, indicating a pro-tumorigenic role of ZIC2 in EOC. On the other hand, however, overexpression of ZIC2 in EOC cells that do not express endogenous ZIC2 promoted cell migration and sphere formation, but inhibited cell growth and colony formation in vitro and tumor growth in vivo, indicating that the role for ZIC2 in EOC is context dependent. Our transcriptomic analysis showed that ZIC2-regulated genes were involved in multiple biological processes and signaling pathways associated with tumor progression. In conclusion, our findings reveal a context-dependent role for ZIC2 in regulating tumorigenic phenotypes in EOC, providing evidence that ZIC2 can be a potential therapeutic target for EOCs that express a high level of ZIC2.

Intraepithelial lymphocytes promote intestinal regeneration through CD160/HVEM signaling

Chemotherapy and radiotherapy frequently lead to intestinal damage. The mechanisms governing the repair or regeneration of intestinal damage are still not fully elucidated. Intraepithelial lymphocytes (IELs) are the primary immune cells residing in the intestinal epithelial layer. However, whether IELs are involved in intestinal epithelial injury repair remains unclear. Here, we found that IELs rapidly infiltrated the intestinal crypt region and are crucial for the recovery of the intestinal epithelium post-chemotherapy. Interestingly, IELs predominantly promoted intestinal regeneration by modulating the proliferation of transit-amplifying (TA) cells. Mechanistically, the expression of CD160 on IELs allows for interaction with herpes virus entry mediator (HVEM) on the intestinal epithelium, thereby activating downstream nuclear factor kappa (NF-κB) signaling and further promoting intestinal regeneration. Deficiency in either CD160 or HVEM resulted in reduced proliferation of intestinal progenitor cells, impaired intestinal damage repair, and increased mortality following chemotherapy. Remarkably, the adoptive transfer of CD160-sufficient IELs rescued the Rag1 deficient mice from chemotherapy-induced intestinal inflammation. Overall, our study underscores the critical role of IELs in intestinal regeneration and highlights the potential applications of targeting the CD160-HVEM axis for managing intestinal adverse events post-chemotherapy and radiotherapy.

Promises and challenges of organoids: From humanized to human derived

Kastenschmidt et al.1 present a groundbreaking organoid culture model for follicular lymphoma, which is capable of maintaining stable compositions of B and T cells. This model is utilized in testing bispecific antibodies in effective killing of tumor B cells with the activation of T cells.

Bacteria-derived nanovesicles enhance tumour vaccination by trained immunity

Trained immunity enhances the responsiveness of immune cells to subsequent infections or vaccinations. Here we demonstrate that pre-vaccination with bacteria-derived outer-membrane vesicles, which contain large amounts of pathogen-associated molecular patterns, can be used to potentiate, and enhance, tumour vaccination by trained immunity. Intraperitoneal administration of these outer-membrane vesicles to mice activates inflammasome signalling pathways and induces interleukin-1β secretion. The elevated interleukin-1β increases the generation of antigen-presenting cell progenitors. This results in increased immune response when tumour antigens are delivered, and increases tumour-antigen-specific T-cell activation. This trained immunity increased protection from tumour challenge in two distinct cancer models.

STING licensing of type I dendritic cells potentiates antitumor immunity

Stimulator of interferon genes (STING) is an immune adaptor protein that senses cyclic GMP-AMP in response to self or microbial cytosolic DNA as a danger signal. STING is ubiquitously expressed in diverse cell populations, including cancer cells, with distinct cellular functions, such as activation of type I interferons, autophagy induction, or triggering apoptosis. It is not well understood whether and which subsets of immune cells, stromal cells, or cancer cells are particularly important for STING-mediated antitumor immunity. Here, using a polymeric STING-activating nanoparticle (PolySTING) with a shock-and-lock dual activation mechanism, we show that conventional type 1 dendritic cells (cDC1s) are essential for STING-mediated rejection of multiple established and metastatic murine tumors. STING status in the host but not in the cancer cells (Tmem173-/-) is important for antitumor efficacy. Specific depletion of cDC1 (Batf3-/-) or STING deficiency in cDC1 (XCR1creSTINGfl/fl) abolished PolySTING efficacy, whereas depletion of other myeloid cells had little effect. Adoptive transfer of wild-type cDC1 in Batf3-/- mice restored antitumor efficacy, whereas transfer of cDC1 with STING or IRF3 deficiency failed to rescue. PolySTING induced a specific chemokine signature in wild-type but not Batf3-/- mice. Multiplexed immunohistochemistry analysis of STING-activating cDC1s in resected tumors correlates with patient survival. Furthermore, STING-cDC1 signature was increased after neoadjuvant pembrolizumab therapy in patients with non-small cell lung cancer. Therefore, we have defined that a subset of myeloid cells is essential for STING-mediated antitumor immunity with associated biomarkers for prognosis.

STING Licensing of Type I Dendritic Cells Potentiates Antitumor Immunity

Stimulator of interferon genes (STING) is an immune adaptor protein that senses cyclic GMP-AMP (cGAMP) in response to self or microbial cytosolic DNA as a danger signal. STING is ubiquitously expressed in diverse cell populations including cancer cells with distinct cellular functions such as activation of type I interferons, autophagy induction, or triggering apoptosis. It is not well understood whether and which subsets of immune cells, stromal cells, or cancer cells are particularly important for STING-mediated antitumor immunity. Here using a polymeric STING-activating nanoparticle (PolySTING) with a "shock-and-lock" dual activation mechanism, we show type 1 conventional dendritic cell (cDC1) is essential for STING-mediated rejection of multiple established and metastatic murine tumors. STING status in the host but not in the cancer cells ( Tmem173 -/- ) is important for antitumor efficacy. Specific depletion of cDC1 ( Batf3 -/- ) or STING deficiency in cDC1 ( XCR1 cre STING fl/fl ) abolished PolySTING efficacy, whereas depletion of other myeloid cells had little effect. Adoptive transfer of wildtype cDC1 in Batf3 -/- mice restored antitumor efficacy while transfer of cDC1 with STING or IRF3 deficiency failed to rescue. PolySTING induced a specific chemokine signature in wildtype but not Batf3 -/- mice. Multiplexed immunohistochemistry analysis of STING-activating cDC1s in resected tumors correlates with patient survival while also showing increased expressions after neoadjuvant pembrolizumab therapy in non-small cell lung cancer patients. Therefore, we have defined that a subset of myeloid cells is essential for STING-mediated antitumor immunity with associated biomarkers for prognosis.

One Sentence Summary

A "shock-and-lock" nanoparticle agonist induces direct STING signaling in type 1 conventional dendritic cells to drive antitumor immunity with defined biomarkers.

Facts and hopes on chimeric cytokine agents for cancer immunotherapy

Cytokines are key mediators of immune responses that can modulate the antitumor activity of immune cells. Cytokines have been explored as a promising cancer immunotherapy. However, there are several challenges to cytokine therapy, especially a lack of tumor targeting, resulting in high toxicity and limited efficacy. To overcome these limitations, novel approaches have been developed to engineer cytokines with improved properties, such as chimeric cytokines. Chimeric cytokines are fusion proteins that combine different cytokine domains or link cytokines to antibodies (immunocytokines) or other molecules that can target specific receptors or cells. Chimeric cytokines can enhance the selectivity and stability of cytokines, leading to reduced toxicity and improved efficacy. In this review, we focus on two promising cytokines, interleukin-2 (IL-2) and IL-15, and summarize the current advances and challenges of chimeric cytokine design and application for cancer immunotherapy. Most of the current approaches focus on increasing the potency of cytokines, but another important goal is to reduce toxicity. Cytokine engineering is promising for cancer immunotherapy as it can enhance tumor targeting while minimizing adverse effects.

Survey of NF1 inactivation by surrogate immunohistochemistry in ovarian carcinomas

OBJECTIVE

Inhibition of the MAPK pathway by MEK inhibitors (MEKi) is currently a therapeutic standard in several cancer types, including ovarian low-grade serous carcinoma (LGSC). A common MAPK pathway alteration in tubo-ovarian high-grade serous carcinoma (HGSC) is the genomic inactivation of neurofibromin 1 (NF1). The primary objectives of our study were to survey the prevalence of NF1 inactivation in the principal ovarian carcinoma histotype as well as to evaluate its associations with clinico-pathological parameters and key biomarkers including BRCA1/2 status in HGSC.

METHODS

A recently commercialized NF1 antibody (clone NFC) was orthogonally validated on an automated immunohistochemistry (IHC) platform and IHC was performed on tissue microarrays containing 2140 ovarian carcinoma cases. Expression was interpreted as loss/inactivated (complete or subclonal) versus normal/retained.

RESULTS

Loss of NF1 expression was detected in 250/1429 (17.4%) HGSC including 11% with subclonal loss. Survival of NF1-inactivated HGSC patients was intermediate between favorable BRCA1/2 mutated HGSC and unfavorable CCNE1 high-level amplified HGSC. NF1 inactivation was mutually exclusive with CCNE1 high-level amplifications, co-occurred with RB1 loss and occurred at similar frequencies in BRCA1/2 mutated versus wild-type HGSC. NF1 loss was found in 21/286 (7.3%) endometrioid carcinomas with a favorable prognostic association (p = 0.048), and in 4/64 (5.9%) LGSC, mutually exclusive with other driver events.

CONCLUSIONS

NF1 inactivation occurs in a significant subset of BRCA1/2 wild-type HGSC and a subset of LGSC. While the functional effects of NF1 inactivation need to be further characterized, this signifies a potential therapeutic opportunity to explore targeting NF1 inactivation in these tumors.

RNA cytosine methyltransferase NSUN5 promotes protein synthesis and tumorigenic phenotypes in glioblastoma

Glioblastoma (GBM) is the most common and aggressive malignant primary brain tumor in adults. The standard treatment achieves a median overall survival for GBM patients of only 15 months. Hence, novel therapies based on an increased understanding of the mechanistic underpinnings of GBM are desperately needed. In this study, we show that elevated expression of 28S rRNA (cytosine-C(5))-methyltransferase NSUN5, which methylates cytosine 3782 of 28S rRNA in GBM cells, is strongly associated with the poor survival of GBM patients. Moreover, we demonstrate that overexpression of NSUN5 increases protein synthesis in GBM cells. NSUN5 knockdown decreased protein synthesis, cell proliferation, sphere formation, migration, and resistance to temozolomide in GBM cell lines. NSUN5 knockdown also decreased the number and size of GBM neurospheres in vitro. As a corollary, mice harboring U251 tumors wherein NSUN5 was knocked down survived longer than mice harboring control tumors. Taken together, our results suggest that NSUN5 plays a protumorigenic role in GBM by enabling the enhanced protein synthesis requisite for tumor progression. Accordingly, NSUN5 may be a hitherto unappreciated target for the treatment of GBM.

DNAJA2 deficiency activates cGAS-STING pathway via the induction of aberrant mitosis and chromosome instability

Molecular chaperone HSP70s are attractive targets for cancer therapy, but their substrate broadness and functional non-specificity have limited their role in therapeutical success. Functioning as HSP70's cochaperones, HSP40s determine the client specificity of HSP70s, and could be better targets for cancer therapy. Here we show that tumors defective in HSP40 member DNAJA2 are benefitted from immune-checkpoint blockade (ICB) therapy. Mechanistically, DNAJA2 maintains centrosome homeostasis by timely degrading key centriolar satellite proteins PCM1 and CEP290 via HSC70 chaperone-mediated autophagy (CMA). Tumor cells depleted of DNAJA2 or CMA factor LAMP2A exhibit elevated levels of centriolar satellite proteins, which causes aberrant mitosis characterized by abnormal spindles, chromosome missegregation and micronuclei formation. This activates the cGAS-STING pathway to enhance ICB therapy response in tumors derived from DNAJA2-deficient cells. Our study reveals a role for DNAJA2 to regulate mitotic division and chromosome stability and suggests DNAJA2 as a potential target to enhance cancer immunotherapy, thereby providing strategies to advance HSPs-based cancer therapy.

Engineered anti-PDL1 with IFNα targets both immunoinhibitory and activating signals in the liver to break HBV immune tolerance

OBJECTIVE

The purpose of this study is to develop an anti-PDL1-based interferon (IFN) fusion protein to overcome the chronic hepatitis B virus (HBV)-induced immune tolerance, and combine this immunotherapy with a HBV vaccine to achieve the functional cure of chronic hepatitis B (CHB) infection.

DESIGN

We designed an anti-PDL1-IFNα heterodimeric fusion protein, in which one arm was derived from anti-PDL1 antibody and the other arm was IFNα, to allow targeted delivery of IFNα into the liver by anti-PDL1 antibody. The effect of the anti-PDL1-IFNα heterodimer on overcoming hepatitis B surface antigen (HBsAg) vaccine resistance was evaluated in chronic HBV carrier mice.

RESULTS

The anti-PDL1-IFNα heterodimer preferentially targeted the liver and resulted in viral suppression, the PD1/PDL1 immune checkpoint blockade and dendritic cell activation/antigen presentation to activate HBsAg-specific T cells, thus breaking immune tolerance in chronic HBV carrier mice. When an HBsAg vaccine was administered soon after anti-PDL1-IFNα heterodimer treatment, we observed strong anti-HBsAg antibody and HBsAg-specific T cell responses for efficient HBsAg clearance in chronic HBV carrier mice that received the combination treatment but not in those that received either single treatment.

CONCLUSIONS

Targeting the liver with an engineered anti-PDL1-IFNα heterodimer can break HBV-induced immune tolerance to an HBsAg vaccine, offering a promising translatable therapeutic strategy for the functional cure of CHB.

Blockade of trans PD-L1 interaction with CD80 augments antitumor immunity

PD-L1 has two receptors: PD-1 and CD80. Previous reports assumed that PD-L1 and CD80 interacted in trans, but recent reports showed that only cis PD-L1/CD80 interactions existed, and prevention of cis PD-L1/CD80 interactions on antigen-presenting cells (APCs) reduced antitumor immunity via augmenting PD-L1/PD-1 and CD80/CTLA4 interactions between T and APCs. Here, using tumor-bearing mice capable of cis and trans or trans only PD-L1/CD80 interactions, we show that trans PD-L1/CD80 interactions do exist between tumor and T cells, and the effects of trans PD-L1/CD80 interactions require tumor cell expression of MHC-I and T cell expression of CD28. The blockade of PD-L1/CD80 interactions in mice with both cis and trans interactions or with only trans interactions augments antitumor immunity by expanding IFN-γ-producing CD8⁺ T cells and IFN-γ-dependent NOS2-expressing tumor-associated macrophages. Our studies indicate that although cis and trans PD-L1/CD80 interactions may have opposite effects on antitumor immunity, the net effect of blocking PD-L1/CD80 interactions in vivo augments CD8⁺ T cell-mediated antitumor immunity.

An engineered concealed IL-15-R elicits tumor-specific CD8+T cell responses through PD-1-cis delivery

Checkpoint blockade immunotherapy releases the inhibition of tumor-infiltrating lymphocytes (TILs) but weakly induces TIL proliferation. Exogenous IL-15 could further expand TILs and thus synergize with αPD-L1 therapy. However, systemic delivery of IL-15 extensively expands peripheral NK cells, causing severe toxicity. To redirect IL-15 to intratumoral PD-1+CD8+T effector cells instead of NK cells for better tumor control and lower toxicity, we engineered an anti-PD-1 fusion with IL-15-IL-15Rα, whose activity was geographically concealed by immunoglobulin Fc region with an engineered linker (αPD-1-IL-15-R) to bypass systemic NK cells. Systematic administration of αPD-1-IL-15-R elicited extraordinary antitumor efficacy with undetectable toxicity. Mechanistically, cis-delivery of αPD-1-IL-15-R vastly expands tumor-specific CD8+T cells for tumor rejection. Additionally, αPD-1-IL-15-R upregulated PD-1 and IL-15Rβ on T cells to create a feedforward activation loop, thus rejuvenating TILs, not only resulting in tumor control in situ, but also suppressing tumor metastasis. Collectively, renavigating IL-15 to tumor-specific PD-1+CD8+T cells, αPD-1-IL-15-R elicits effective systemic antitumor immunity.

Zinc cyclic di-AMP nanoparticles target and suppress tumours via endothelial STING activation and tumour-associated macrophage reinvigoration

The clinical utility of stimulator of interferon genes (STING) agonists has been limited due to poor tumour-targeting and unwanted toxicity following systemic delivery. Here we describe a robust tumour-targeted STING agonist, ZnCDA, formed by the encapsulation of bacterial-derived cyclic dimeric adenosine monophosphate (CDA) in nanoscale coordination polymers. Intravenously injected ZnCDA prolongs CDA circulation and efficiently targets tumours, mediating robust anti-tumour effects in a diverse set of preclinical cancer models at a single dose. Our findings reveal that ZnCDA enhances tumour accumulation by disrupting endothelial cells in the tumour vasculature. ZnCDA preferentially targets tumour-associated macrophages to modulate antigen processing and presentation and subsequent priming of an anti-tumour T-cell response. ZnCDA reinvigorates the anti-tumour activity of both radiotherapy and immune checkpoint inhibitors in immunologically 'cold' pancreatic and glioma tumour models, offering a promising combination strategy for the treatment of intractable human cancers.

IL-2 delivery by engineered mesenchymal stem cells re-invigorates CD8+ T cells to overcome immunotherapy resistance in cancer

Immune checkpoint blockade (ICB)-based immunotherapy depends on functional tumour-infiltrating lymphocytes (TILs), but essential cytokines are less understood. Here we uncover an essential role of endogenous IL-2 for ICB responsiveness and the correlation between insufficient IL-2 signalling and T-cell exhaustion as tumours progress. To determine if exogenous IL-2 in the tumour microenvironment can overcome ICB resistance, we engineered mesenchymal stem cells (MSCs) to successfully deliver IL-2 mutein dimer (SIL2-EMSC) to TILs. While MSCs have been used to suppress inflammation, SIL2-EMSCs elicit anti-tumour immunity and overcome ICB resistance without toxicity. Mechanistically, SIL2-EMSCs activate and expand pre-existing CD8⁺ TILs, sufficient for tumour control and induction of systemic anti-tumour effects. Furthermore, engineered MSCs create synergy of innate and adaptive immunity. The therapeutic benefits of SIL2-EMSCs were also observed in humanized mouse models. Overall, engineered MSCs rejuvenate CD8⁺ TILs and thus potentiate ICB and chemotherapy.

KP372-1-Induced AKT Hyperactivation Blocks DNA Repair to Synergize With PARP Inhibitor Rucaparib via Inhibiting FOXO3a/GADD45α Pathway

Poly (ADP-ribose) polymerase (PARP) inhibitors (PARPi) have exhibited great promise in the treatment of tumors with homologous recombination (HR) deficiency, however, PARPi resistance, which ultimately recovers DNA repair and cell progress, has become an enormous clinical challenge. Recently, KP372-1 was identified as a novel potential anticancer agent that targeted the redox enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1), to induce extensive reactive oxygen species (ROS) generation that amplified DNA damage, leading to cancer cell death. To overcome PARPi resistance and expand its therapeutic utility, we investigated whether a combination therapy of a sublethal dose of KP372-1 with a nontoxic dose of PARPi rucaparib would synergize and enhance lethality in NQO1 over-expressing cancers. We reported that the combination treatment of KP372-1 and rucaparib induced a transient and dramatic AKT hyperactivation that inhibited DNA repair by regulating FOXO3a/GADD45α pathway, which enhanced PARPi lethality and overcame PARPi resistance. We further found that PARP inhibition blocked KP372-1-induced PARP1 hyperactivation to reverse NAD⁺/ATP loss that promoted Ca²⁺-dependent autophagy and apoptosis. Moreover, pretreatment of cells with BAPTA-AM, a cytosolic Ca²⁺ chelator, dramatically rescued KP372-1- or combination treatment-induced lethality and significantly suppressed PAR formation and γH2AX activation. Finally, we demonstrated that this combination therapy enhanced accumulation of both agents in mouse tumor tissues and synergistically suppressed tumor growth in orthotopic pancreatic and non-small-cell lung cancer xenograft models. Together, our study provides novel preclinical evidence for new combination therapy in NQO1⁺ solid tumors that may broaden the clinical utility of PARPi.

Exogenous signaling repairs defective T cell signaling inside the tumor microenvironment for better immunity

It is known that tumor-reactive T cells are initially activated in the draining lymph node, but it is not well known whether and how tumor-infiltrating lymphocytes (TILs) are reactivated in the tumor microenvironment (TME). We hypothesize that defective T cell receptor (TCR) signaling and cosignals in the TME limit T cell reactivation. To address this, we designed a mesenchymal stromal cell–based delivery of local membrane-bound anti-CD3 and/or cosignals to explore their contribution to reactivate T cells inside the TME. Combined anti-CD3 and CD40L rather than CD80 led to superior antitumor efficacy compared with either alone. Mechanistically, TCR activation of preexisting CD8⁺ T cells synergized with CD40L activation of DCs inside the TME for optimum tumor control. Exogenous TCR signals could better reactivate TILs that then exited to attack distal tumors. This study supplies further evidence that TCR signaling for T cell reactivation in the TME is defective but can be rescued by proper exogenous signals.

Lactate increases stemness of CD8 + T cells to augment anti-tumor immunity

Lactate is a key metabolite produced from glycolytic metabolism of glucose molecules, yet it also serves as a primary carbon fuel source for many cell types. In the tumor-immune microenvironment, effect of lactate on cancer and immune cells can be highly complex and hard to decipher, which is further confounded by acidic protons, a co-product of glycolysis. Here we show that lactate is able to increase stemness of CD8+ T cells and augments anti-tumor immunity. Subcutaneous administration of sodium lactate but not glucose to mice bearing transplanted MC38 tumors results in CD8+ T cell-dependent tumor growth inhibition. Single cell transcriptomics analysis reveals increased proportion of stem-like TCF-1-expressing CD8+ T cells among intra-tumoral CD3+ cells, a phenotype validated by in vitro lactate treatment of T cells. Mechanistically, lactate inhibits histone deacetylase activity, which results in increased acetylation at H3K27 of the Tcf7 super enhancer locus, leading to increased Tcf7 gene expression. CD8+ T cells in vitro pre-treated with lactate efficiently inhibit tumor growth upon adoptive transfer to tumor-bearing mice. Our results provide evidence for an intrinsic role of lactate in anti-tumor immunity independent of the pH-dependent effect of lactic acid, and might advance cancer immune therapy.

T cell receptor β-chain-targeting chimeric antigen receptor T cells against T cell malignancies

The success of chimeric antigen receptor (CAR) T cells in treating B cell malignancies comes at the price of eradicating normal B cells. Even though T cell malignancies are aggressive and treatment options are limited, similar strategies for T cell malignancies are constrained by the severe immune suppression arising from bystander T cell aplasia. Here, we show the selective killing of malignant T cells without affecting normal T cell-mediated immune responses in vitro and in a mouse model of disseminated leukemia. Further, we develop a CAR construct that carries the single chain variable fragment of a subtype-specific antibody against the variable TCR β-chain region. We demonstrate that these anti-Vβ8 CAR-T cells are able to recognize and kill all Vβ8⁺ malignant T cells that arise from clonal expansion while sparing malignant or healthy Vβ8⁻ T cells, allowing sufficient T cell-mediated cellular immunity. In summary, we present a proof of concept for a selective CAR-T cell therapy to eradicate T cell malignancies while maintaining functional adaptive immunity, which opens the possibility for clinical development.

Healthy T cells are polyclonal, while malignant T cells are developing via clonal expansion. Here authors show that T cell tumours could be eradicated by chimeric antigen receptor T cells targeting the T cell receptor (TCR) β-chain that is specific to malignant T cells, while healthy T cells using diverse TCR β-chains are spared.

A Heterologous V-01 or Variant-Matched Bivalent V-01D-351 Booster following Primary Series of Inactivated Vaccine Enhances the Neutralizing Capacity against SARS-CoV-2 Delta and Omicron Strains

Immune escape of emerging SARS-CoV-2 variants of concern (VOCs) and waning immunity over time following the primary series suggest the importance and necessity of booster shot of COVID-19 vaccines. With the aim to preliminarily evaluate the potential of heterologous boosting, we conducted two pilot studies to evaluate the safety and immunogenicity of the V-01 or a bivalent V-01D-351 (targeting Delta and Beta strain) booster after 5–7 months of the primary series of inactivated COVID-9 vaccine (ICV). A total of 77 participants were enrolled, with 20 participants in the V-01D-351 booster study, and 27, 30 participants in the age stratified participants of V-01 booster study. The safety results showed that V-01 or V-01D-351 was safe and well-tolerated as a heterologous booster shot, with overall adverse reactions predominantly being absent or mild in severity. The immunogenicity results showed that the heterologous prime–boost immunization with V-01 or bivalent V-01D-351 booster induced stronger humoral immune response as compared with the homologous booster with ICV. In particular, V-01D-351 booster showed the highest pseudovirus neutralizing antibody titers against prototype SARS-CoV-2, Delta and Omicron BA.1 strains at day 14 post boosting, with GMTs 22.7, 18.3, 14.3 times higher than ICV booster, 6.2, 6.1, 3.8 times higher than V-01 booster (10 μg), and 5.2, 3.8, 3.5 times higher than V-01 booster (25 μg), respectively. The heterologous V-01 booster also achieved a favorable safety and immunogenicity profile in older participants. Our study has provided evidence for a flexible roll-out of heterologous boosters and referential approaches for variant-specific vaccine boosters, with rationally conserved but diversified epitopes relative to primary series, to build herd immunity against the ongoing pandemic.

Epigenetic Repression of STING by MYC Promotes Immune Evasion and Resistance to Immune Checkpoint Inhibitors in Triple-Negative Breast Cancer

The MYC oncogene is frequently amplified in triple-negative breast cancer (TNBC). Here, we show that MYC suppression induces immune-related hallmark gene set expression and tumor-infiltrating T cells in MYC-hyperactivated TNBCs. Mechanistically, MYC repressed stimulator of interferon genes (STING) expression via direct binding to the STING1 enhancer region, resulting in downregulation of the T-cell chemokines CCL5, CXCL10, and CXCL11. In primary and metastatic TNBC cohorts, tumors with high MYC expression or activity exhibited low STING expression. Using a CRISPR-mediated enhancer perturbation approach, we demonstrated that MYC-driven immune evasion is mediated by STING repression. STING repression induced resistance to PD-L1 blockade in mouse models of TNBC. Finally, a small-molecule inhibitor of MYC combined with PD-L1 blockade elicited a durable response in immune-cold TNBC with high MYC expression, suggesting a strategy to restore PD-L1 inhibitor sensitivity in MYC-overexpressing TNBC.

Suppression of local IFN-I by commensal microbiota-derived butyrate impairs antitumor effects of ionizing radiation

The antitumor effects of ionizing radiation (IR) are mediated in part through activation of innate and adaptive immunity. Here, we report that gut microbiota influences tumor control following IR. Vancomycin decreased the abundance of butyrate-producing gut bacteria, accompanied with reduction of butyric acid in circulation and tumor tissues, and enhanced antitumor responses to IR. Oral administration of Lachnospiraceae, a family of vancomycin-sensitive bacteria, associated with increased systemic and intratumoral butyric acid levels and impaired the efficacy of IR in germ-free (GF) mice. Local butyrate inhibited STING-activated type I IFN expression in dendritic cells (DCs) through blockade of TBK 1 and IRF3 phosphorylation, which abrogated IR-induced tumor-specific cytotoxic T cell immune responses without directly protecting tumor cells from radiation. Our findings demonstrate that the selective targeting of butyrate-producing microbiota may provide a novel therapeutic option to enhance tumor radiation sensitivity.

This work was supported by a grant from the Ludwig Foundation to R.R. Weichselbaum, and National Institutes of Health/National Cancer Institute Provocative Questions grants R21 CA227528 and R21 CA231273-01 (R.R. Weichselbaum).

Concurrent delivery of immune checkpoint blockade modulates T cell dynamics to enhance neoantigen vaccine-generated antitumor immunity

Neoantigen vaccines aiming to induce tumor-specific T cell responses have achieved promising antitumor effects in early clinical trials. However, the underlying mechanism regarding response or resistance to this treatment is unclear. Here we observe that neoantigen vaccine-generated T cells can synergize with the immune checkpoint blockade for effective tumor control. Specifically, we performed single-cell sequencing on over 100,000 T cells and uncovered that combined therapy induces an antigen-specific CD8 T cell population with active chemokine signaling (Cxcr3+/Ccl5+), lower co-inhibitory receptor expression (Lag3-/Havcr2-) and higher cytotoxicity (Fasl+/Gzma+). Furthermore, generation of neoantigen-specific T cells in the draining lymph node is required for combination treatment. Signature genes of this unique population are associated with T cell clonal frequency and better survival in humans. Our study profiles the dynamics of tumor-infiltrating T cells during neoantigen vaccine and immune checkpoint blockade treatments and high-dimensionally identifies neoantigen-reactive T cell signatures for future development of therapeutic strategies.

AXL targeting restores PD-1 blockade sensitivity of STK11/LKB1 mutant NSCLC through expansion of TCF1+ CD8 T cells

Mutations in STK11/LKB1 in non-small cell lung cancer (NSCLC) are associated with poor patient responses to immune checkpoint blockade (ICB), and introduction of a Stk11/Lkb1 (L) mutation into murine lung adenocarcinomas driven by mutant Kras and Trp53 loss (KP) resulted in an ICB refractory syngeneic KPL tumor. Mechanistically this occurred because KPL mutant NSCLCs lacked TCF1-expressing CD8 T cells, a phenotype recapitulated in human STK11/LKB1 mutant NSCLCs. Systemic inhibition of Axl results in increased type I interferon secretion from dendritic cells that expanded tumor-associated TCF1+PD-1+CD8 T cells, restoring therapeutic response to PD-1 ICB in KPL tumors. This was observed in syngeneic immunocompetent mouse models and in humanized mice bearing STK11/LKB1 mutant NSCLC human tumor xenografts. NSCLC-affected individuals with identified STK11/LKB1 mutations receiving bemcentinib and pembrolizumab demonstrated objective clinical response to combination therapy. We conclude that AXL is a critical targetable driver of immune suppression in STK11/LKB1 mutant NSCLC.

Selective delivery of low-affinity IL-2 to PD-1+ T cells rejuvenates antitumor immunity with reduced toxicity

PD-1 signaling on T cells is the major pathway that limits T cell immunity, but the efficacy of anti–PD-1 therapy has been limited to a small proportion of patients with advanced cancers. We fortuitously observed that anti–PD-1 therapy depends on IL-2 signaling, which raises the possibility that a lack of IL-2 limits anti–PD-1–induced effector T cell expansion. To selectively deliver IL-2 to PD-1⁺CD8⁺ tumor-infiltrating lymphocytes (TILs), we engineered a low-affinity IL-2 paired with anti–PD-1 (PD-1–laIL-2), which reduced affinity to peripheral Treg cells but enhanced avidity to PD-1⁺CD8⁺ TILs. PD-1–laIL-2 exerted better tumor control and lower toxicity than single or mixed treatments. Mechanistically, PD-1–laIL-2 could effectively expand dysfunctional and tumor-specific CD8⁺ T cells. Furthermore, we discovered that presumably dysfunctional PD-1⁺TIM3⁺ TILs are the dominant tumor-specific T cells responding to PD-1–laIL-2. Collectively, these results highlight that PD-1–laIL-2 can target and reactivate tumor-specific TILs for tumor regression as a unique strategy with stronger efficacy and lower toxicity.

A tumor-specific pro-IL-12 activates preexisting cytotoxic T cells to control established tumors

[Figure: see text].

Sequential immunization with SARS-CoV-2 RBD vaccine induces potent and broad neutralization against variants in mice

The current COVID-19 pandemic caused by constantly emerging SARS-CoV-2 variants still poses a threat to public health worldwide. Effective next-generation vaccines and optimized booster vaccination strategies are urgently needed. Here, we sequentially immunized mice with a SARS-CoV-2 wild-type inactivated vaccine and a heterologous mutant RBD vaccine, and then evaluated their neutralizing antibody responses against variants including Beta, Delta, Alpha, Iota, Kappa, and A.23.1. These data showed that a third booster dose of heterologous RBD vaccine especially after two doses of inactivated vaccines significantly enhanced the GMTs of nAbs against all SARS-CoV-2 variants we tested. In addition, the WT and variants all displayed good cross-immunogenicity and might be applied in the design of booster vaccines to induce broadly neutralizing antibodies.

Abstract P058: Tumor-targeted IL-2 by engineered mesenchymal stem cells reinvigorates CD8+ T cells

Tumor microenvironment (TME) generates immunosuppressive niche to induce CD8+ tumor infiltrating lymphocytes (TILs) exhaustion. Therapeutic targeting to functionally reinvigorate CD8+ T cells is a promising strategy to enhance antitumor immunity. While interleukin-2 (IL-2) based therapies cause potent T cell activation and proliferation, the clinical application remains challenging due to short half-life and severe toxicity at therapeutic doses. To address this, we engineered mesenchymal stem cells (MSCs) to successfully proliferate and turn on or off CD8 T cell-preferential IL-2 mutein/Fc fusion protein (SIL2-EMSC) to target cytotoxic T cells in the TME. Peritumoral administration of SIL2-EMSCs permits local production of sufficient SIL2 inside the TME and induces complete tumor regression without adverse toxicity. Mechanistically, SIL2-EMSC remodels the TME that activates and expands preexisting CD8+ TILs. Furthermore, local treatment of SIL2-EMSC elicits systemic antitumor responses for the clearance of distal tumor and metastasis. In advanced tumors, SIL2-EMSCs can overcome resistance to immune check blockade (ICB) and β-lapachone (β-lap) chemotherapy. The therapeutic benefits of SIL2-EMSC were also observed in humanized mouse models. Overall, tumor-targeted delivery of cytokines by next generation of MSCs reverses immunosuppressive environment, improves antitumor effects, and synergize with various therapies without adverse toxicity.

Citation Format: Joonbeom Bae, Longchao Liu, Casey Timmerman, Eric Hsu, Anli Zhang, Jiankun Zhu, Yang-Xin Fu. Tumor-targeted IL-2 by engineered mesenchymal stem cells reinvigorates CD8+ T cells [abstract]. In: Abstracts: AACR Virtual Special Conference: Tumor Immunology and Immunotherapy; 2021 Oct 5-6. Philadelphia (PA): AACR; Cancer Immunol Res 2022;10(1 Suppl):Abstract nr P058.

Outcome and Immune Correlates of a Phase II Trial of High-Dose Interleukin-2 and Stereotactic Ablative Radiotherapy for Metastatic Renal Cell Carcinoma

PURPOSE

This phase II clinical trial evaluated whether the addition of stereotactic ablative radiotherapy (SAbR), which may promote tumor antigen presentation, improves the overall response rate (ORR) to high-dose IL2 (HD IL2) in metastatic renal cell carcinoma (mRCC).

PATIENTS AND METHODS

Patients with pathologic evidence of clear cell renal cell carcinoma (RCC) and radiographic evidence of metastasis were enrolled in this single-arm trial and were treated with SAbR, followed by HD IL2. ORR was assessed based on nonirradiated metastases. Secondary endpoints included overall survival (OS), progression-free survival (PFS), toxicity, and treatment-related tumor-specific immune response. Correlative studies involved whole-exome and transcriptome sequencing, T-cell receptor sequencing, cytokine analysis, and mass cytometry on patient samples.

RESULTS

Thirty ethnically diverse mRCC patients were enrolled. A median of two metastases were treated with SAbR. Among 25 patients evaluable by RECIST v1.1, ORR was 16% with 8% complete responses. Median OS was 37 months. Treatment-related adverse events (AE) included 22 grade ≥3 events that were not dissimilar from HD IL2 alone. There were no grade 5 AEs. A correlation was observed between SAbR to lung metastases and improved PFS (P = 0.0165). Clinical benefit correlated with frameshift mutational load, mast cell tumor infiltration, decreased circulating tumor-associated T-cell clones, and T-cell clonal expansion. Higher regulatory/CD8⁺ T-cell ratios at baseline in the tumor and periphery correlated with no clinical benefit.

CONCLUSIONS

Adding SAbR did not improve the response rate to HD IL2 in patients with mRCC in this study. Tissue analyses suggest a possible correlation between frameshift mutation load as well as tumor immune infiltrates and clinical outcomes.

Rejuvenation of tumour-specific T cells through bispecific antibodies targeting PD-L1 on dendritic cells

Bispecific T-cell engagers (BiTEs) preferentially targeting tumour-associated antigens and stimulating CD3-mediated signalling are being used in patients to treat acute B-cell lymphoblastic leukemia. However, the potency of BiTEs in solid tumours is limited by their short half-life and their severe toxicity at relevant therapeutic doses. Here we report the design and in vivo performance of a bispecific antibody that simultaneously targets the murine T-cell co-receptor CD3ε and the murine immune checkpoint programmed-death ligand 1 (PD-L1). In multiple syngeneic tumour models, the bispecific antibody generated higher antitumour immune responses than conventional BiTEs targeting tumour-associated antigens and CD3ε. We found that the durable antigen-specific T-cell responses resulted from the rejuvenation of CD8 T cells, owing to the blockade of PD-L1 on dendritic cells (but not on tumour cells) and co-stimulation by B7-1&2 (a peripheral membrane protein on dendritic cells). Bispecific T-cell engagers targeting dendritic cells rather than tumour cells may represent a general means of T-cell rejuvenation for durable cancer immunotherapy.

800 Dual targeting of CTLA-4 and CD47 on Treg cells rejuvenates immunity against solid tumors

Background

Although approved by FDA, anti-CTLA-4 treatment has severe side effect that limits its clinical usage. Blockade of CD47, the “don't eat me” signal, has limited effects in solid tumors despite its potent anti-tumor effects in hematopoietic malignancies. Targeted delivery of immune blockers into tumor tissues are desireble.

Methods

Taking advantage of the high expression of CTLA-4 on Treg cells and abundant Fc receptor+ active phagocytes inside the tumor microenvironment (TME), we design and test an anti-CTLA-4×SIRPα (CD47 ligand)-Fc heterodimer that selectively blocks CD47 on intratumoral Treg cells and increases antibody-dependent cellular phagocytosis (the “eat me” signal).

Results

Anti-CTLA-4×SIRPα preferentially depletes ICOShigh immunosuppressive Treg cells in the TME (figure 1–3) and enhances immunity against solid tumors. Mechanistically, we discovered that CD47 expression on Treg cells limits anti-CTLA-4 mediated depletion while Fc on the heterodimer enhances the depletion. Furthermore, anti-human CTLA-4×SIRPα depletes tumor Treg cells (figure 4–6) and exhibits less toxicity than anti-human CTLA-4 in a humanized mouse model.

Conclusions

Collectively, these results highlight coordinatively modulating “eat me” and “don't eat me” signals for depleting Treg cells inside the TME as a unique strategy for solid tumor treatment.

Abstract 800 Figure 1

Anti-CTLA-4×SIRPα selectively targets intratumor Treg. (A) Expression of CTLA-4 transcripts in colorectal cancer patient tissues based on single cell sequencing online database (29). (B and C) CTLA-4 expression on Treg cells from PBMC, spleen and tumor cells in MC38 tumor-bearing mice on day 14. (D) Schematic diagram of anti-CTLA-4×SIRPα heterodimer. (E) Kinetic association (ka), dissociation (kd), and calculated affinity (KD) for binding of the indicated analyte to mouse CTLA-4 or CD47 antigen were measured by surface plasmon resonance using OpenSPR instrument. (F) Binding of SIRPα, CTLA-4 and anti-CTLA-4×SIRPα to RBC from C57BL/6 mice, n=4. (G) Anti-CTLA-4×SIRPα binding on Treg of PBMC and tumor cells from MC38 tumor-bearing mice. (H) C57BL/6 mice were inoculated with 5 × 105 MC38 tumor cells. After 13 days, 20 µg anti-CTLA-4×SIRPα was injected intraperitoneally. Five days later, mice were perfused with PBS, and tumor and other tissues were harvested and homogenized. Anti-CTLA-4×SIRPα protein abundance was determined with ELISA, n=4.

Abstract 800 Figure 2

Anti-CTLA-4×SIRPα preferentially depletes ICOShi Treg. (A–C) C57BL/6 mice (n=4) were inoculated with 5 × 105 MC38 tumor cells and treated with Combo or anti-CTLA-4×SIRPα on day 13. Five days later, Treg cells from tumor, spleen and draining lymph node (dLN) were analyzed. The representative flow cytometric gating was shown in (A). Treg cells frequency from different groups was shown in (B). The ratio of CD8+ T cells to Treg was shown in (C). (D–F) Foxp3-EGFP reporter mice (n=3) were inoculated with 5 × 105 MC38 tumor cells and treated with Combo or anti-CTLA-4×SIRPα on day 13. Five days later, Foxp3-EGFP+ cells from tumor, spleen and dLN were analyzed. The representative flow cytometric gating was shown in (D). Foxp3-EGFP+ cell frequency from different groups was shown in (E). The ratio of CD8+ T cells to Foxp3-EGFP+ cells was shown in (F). (G–I) Same experiment scheme as (A–F). Representative ICOS expression on Treg cells was shown in (G). (H) ICOS++ frequency among Treg cells (H) and ICOS++ frequency among YFP+ cells (I) were shown.

Abstract 800 Figure 3

Anti-CTLA-4×SIRPα reduces tumor in T cell dependent way. (A) C57BL/6 mice were inoculated with 5 × 105 MC38 tumor cells and treated with equal moles of anti-CTLA-4 plus SIRPα (Combo, 12 µg + 8 µg) or anti-CTLA-4×SIRPα (20 µg) on day 14. Tumor growth was measured every 3 days, n=5. (B) BALB/C mice were inoculated with 5 × 105 CT26 tumor cells and treated with Combo (30 µg+ 20 µg) or anti-CTLA-4×SIRPα (50 µg) on day 6. Tumor growth was measured every 3 days, n=5. (C) Rag1-/- mice were inoculated with 1 × 105 MC38 tumor cells and treated with Combo (12 µg+ 8 µg) or anti-CTLA-4×SIRPα (20 µg) on day 13. Tumor growth was measured every 3 days, n=5. (D) MuMT mice were inoculated with 1.5 × 106 MC38 tumor cells and treated with anti-CTLA-4×SIRPα (20 µg) on day 14. Tumor growth was measured every 3 days, n=4. (E and F) C57BL/6 mice were inoculated with 5 × 105 MC38 tumor cells and treated with anti-CTLA-4×SIRPα on day 13. 200 μg of anti-CD4 (E) or anti-CD8 (F) was administrated one day before treatment initiation and then twice a week for 2 weeks. Tumor growth was measured every 3 days, n=5. (G–I) C57BL/6 mice (n=4) were inoculated with 5 × 105 MC38 tumor cells and treated with Combo or anti-CTLA-4×SIRPα on day 14. Five days later, tumor-infiltrating lymphocytes (TILs) were analyzed for total CD45 in tumor (E), Ki67 expression on CD4 and CD8 T cells from different groups (F and G) after treatment.

Abstract 800 Figure 4

Anti-CTLA-4×SIR enhances tumor-specific T cell IFN-gamma. (A) C57BL/6 mice (n=4) were inoculated with 5 × 105 MC38 tumor cells and treated with Combo or anti-CTLA-4×SIRPα on day 13. Five days later, TILs were analyzed for tumor specific T cells. (B and C) C57BL/6 mice (n=4) were inoculated with 5 × 105 MC38 tumor cells and treated with Combo or anti-CTLA-4×SIRPα on day 13. Five days later, TILs were purified with CD45+ positive selection magnetic beads. TILs (A) and dLN (B) were re-stimulated with irradiated MC38 tumor cells or irrelevant control Lewis lung cancer (LLC) cells for 48 h. IFN-γ producing cells were determined by ELISPOT assay. (D) WT or Ifng-/- C57BL/6 mice were inoculated with 5 × 105 MC38 tumor cells and treated with anti-CTLA-4×SIRPα on day 13. Tumor growth was measured every 3 days, n=4. (E) C57BL/6 mice were inoculated with 5 × 105 MC38 tumor cells and treated with anti-CTLA-4×SIRPα on day 13. 150 μg of anti-IFN-γ was administrated one day before treatment initiation and then twice a week for 2 weeks. Tumor growth was measured every 3 days, n=5. (F and G) C57BL/6 mice were inoculated with 5 × 105 MC38 tumor cells and treated with anti-CTLA-4×SIRPα on day 14. Six weeks later, anti-CTLA-4×SIRPα cured mice and control naïve mice were re-challenged with 5 × 106 MC38 tumor cells on the left flank (opposite to the original injection flank) (F), and 5 × 105 LLC tumor cells were injected on the right flank (G). Tumor growth was measured every 3 days, n=5.

Abstract 800 Figure 5

CD47 expression on Treg cells is essential. (A) Cd47-/- tumor bearing C57BL/6 mice were treated with Combo or anti-CTLA-4×SIRPα on day 13. Tumor growth was measured every 3 days, n=5. (B) WT or Cd47-/- C57BL/6 mice were inoculated with 5 × 105 MC38 tumor cells and treated with anti-CTLA-4×SIRPα on day 14. Tumor growth was measured every 3 days, n=5. (C) WT or Cd47-/- T cells were purified by negative selection magnetic beads and intravenously transferred to Rag1-/- mice. 2 × 105 MC38 tumor cells were inoculated into the recipient mice the next day. Mice were treated with 40 µg anti-CTLA-4×SIRPα on day 7 and day 12. Experiment scheme was shown in upper panel and tumor growth was shown in lower panel, n=5. (D) C57BL/6 mice were inoculated with 5 × 105 MC38-cEGFR tumor cells and treated with 30 µg anti-EGFR×SIRPα or anti-CTLA-4×SIRPα on day 14. Tumor growth was measured every 3 days, n=3–4. (E) WT or Fcer1g-/- C57BL/6 mice were inoculated with 1 × 105 MC38 tumor cells and treated with anti-CTLA-4×SIRPα on day 13. Tumor growth was measured every 3 days, n=5. (F) WT C57BL/6 mice were inoculated with 5 × 105 MC38 tumor cells and treated with anti-CTLA-4×SIRPα or anti-CTLA-4×SIRPα with mutant Fc (Anti-CTLA-4×SIRPα-InFc) on day 14. Tumor growth was measured every 3 days, n=5. (G) Bone marrow derived macrophages from WT or Fcer1g-/-mice were mixed with CFSE labelled in vitro differentiated Treg cells from WT or Cd47-/- mice for 3 h. Phagocytosis was determined with flow cytometry. Phagocytosis index was defined as the percentage of CFSE+ macrophages among total macrophages.

Abstract 800 Figure 6

A human version anti-CTLA-4×SIRPα heterodimer depletes Treg. (A and B) CD47 and CTLA-4 expression level on Treg cells of PBMC and tumor from NSCLC patients. The representative flow cytometric gating was shown in (A), pooled data from different patients was show in (B). (C) Anti-hCTLA-4, SIRPα and anti-hCTLA-4×SIRPα binding on Jurkat and Jurkat-hCTLA-4 expressing cells. (D) Comparison of anti-hCTLA-4×SIRPα binding on Jurkat and Jurkat-hCTLA-4 cells based on (C). (E and F) PBMC-humanized NSG mice were inoculated with 2.5 × 106 A549 tumor cells and treated with anti-hCTLA-4 plus SIRPα (h-Combo, 18 µg +12 µg) or anti-hCTLA-4×SIRPα (30 µg) on day 12. Two days later, the frequency of tumor-infiltrating Treg cells (G) and ICOS expression level on Treg cells (F) were analyzed, n=4. (G) PBMC-humanized NSG mice were treated with 200 μg anti-hCTLA-4 or anti-hCTLA-4×SIRPα twice a week for 4 times. Mouse body weight was monitored every 3 days, n=5. Data are shown as mean ± SEM from two independent experiments. P value was determined by paired t test (B), unpaired t test (E and F) and two-way ANOVA with Geisser-Greenhouse's correction (G). The normality of data was confirmed by Shapiro-Wilk test.

602 AXL targeting with bemcentinb restores PD-1 blockade sensitivity of STK11/LKB1 mutant NSCLC through innate immune cell mediated expansion of TCF1+ CD8 T cells

Background

Mutations in tumor suppressor STK11/LKB1 are associated with negative predictive and prognostic impact in NSCLC patients receiving immune checkpoint inhibitors (CPI) in several published cohorts, although there have been some conflicting reports on the association of such mutations with patient outcomes in this setting [1–9]. STK11/LKB1 tumors are characterized by a suppressive tumor micro-environment devoid of cytotoxic T cells, and we hypothesized that targeting the receptor tyrosine kinase AXL, a known driver of an innate immune suppressive microenvironment, would restore sensitivity to PD-1 in syngeneic pre-clinical models as well as in patients harboring STK11/LKB1 mutated NSCLC.

Methods

Stk11/Lkb1 (L) mutation was introduced by CRISPR technology into murine lung adenocarcinomas driven by mutant Kras and Trp53 loss (KP). Sensitivity towards anti-PD-1 was evaluated in the absence and presence of the small molecule AXL inhibitor bemcentinib in the KPL model and in a human NSCLC xenograft model carrying a STK11/LKB1 mutation. The immune tumor landscape was mapped following introduction of the Stk11/Lkb1 mutation and therapeutic intervention with anti-PD-1/pembrolizumab and bemcentinib. FFPE fine-needle aspirate biopsies of target lesions were acquired from patients at screening immediately prior to enrollment in BGBC008, a PhII single-arm, 2-stage study with bemcentinib (200mg/d) and pembrolizumab (200 mg/q3wk) for previously-treated stage IV lung adenocarcinoma patients who were CPI naïve or CPI refractory. Patients were assessed for response according to RECIST1.1 criteria at scheduled scan intervals.

Results

Introduction of a STK11/LKB1 mutation into murine lung adenocarcinomas driven by mutant Kras and Trp53 loss resulted in a PD-1 refractory syngeneic KPL tumor. Mechanistically this occurred because KPL mutant NSCLCs lacked TCF1-expressing CD8 T cells, a phenotype that was recapitulated in human STK11/LKB1 mutant NSCLCs. Systemic inhibition of AXL with bemcentinib resulted in increased type I interferon secretion from dendritic cells resulting in expansion of tumor-associated TCF1+PD-1+CD8 T cells and restored therapeutic response to PD-1. This effect was observed in a syngeneic immunocompetent mouse model and in humanized mice bearing STK11/LKB1 mutant NSCLC human tumor xenografts.In an ongoing clinical trial (NCT03184571), 3 evaluable NSCLC patients with identified STK11/LKB1 mutations demonstrated objective clinical response/clinical benefit to the combination of AXL inhibitor bemcentinib and pembrolizumab

Conclusions

In these models, AXL is a critical targetable driver of immune suppression in STK11/LKB1 mutant NSCLC contributing to CPI resistance. Our results show that inhibition of AXL rescues this deficit and represents a new clinical strategy in combination with anti-PD-1 therapy in NSCLC patients carrying a STK11/LKB1 mutation

Acknowledgements

The authors would like to thank all patients and their caretakers for participating in this trial.

Trial Registration

Patients treated with bemcentinib and pembrolizumab combination therapy were enrolled in the BGBC008 clinical trial (BerGenBio ASA and Merck & Co., Inc., Kenilworth NJ, USA, NCT03184571)

References

Gu M, Xu T, Chang P. KRAS/LKB1 and KRAS/TP53 co-mutations create divergent immune signatures in lung adenocarcinomas. Ther Adv Med Oncol. 2021;13:17588359211006950.

Cho BC, Lopes G, Kowalski DM. Relationship between STK11 and KEAP1 mutational status and efficacy in KEYNOTE-042: pembrolizumab monotherapy as first-line therapy for PD-L1 positive advanced NSCLC. Cancer Res. 2020;80(16 Supplement):CT084.

Aredo JV, Padda SK, Kunder CA. Impact of KRAS mutation subtype and concurrent pathogenic mutations on non-small cell lung cancer outcomes. Lung Cancer. 2019;133:144–150.

Kwack WG, Shin SY, Lee SH. Primary Resistance to Immune Checkpoint Blockade in an STK11/TP53/KRAS-Mutant Lung Adenocarcinoma with High PD-L1 Expression. Oncol Targets Ther. 2020;13:8901–8905.

Shire NJ, Klein AB, Golozar A. STK11 (LKB1) mutations in metastatic NSCLC: Prognostic value in the real world. PLoS One. 2020;15(9):e0238358. 6. Skoulidis F, Goldberg ME, Greenawalt DM. STK11/LKB1 Mutations and PD-1 Inhibitor Resistance in KRAS-Mutant Lung Adenocarcinoma. Cancer Discov. 2018;8(7):822–835. 7. Wang H, Guo J, Shang X. Less immune cell infiltration and worse prognosis after immunotherapy for patients with lung adenocarcinoma who harbored STK11 mutation. Int. Immunopharmacol. 2020;84:106574. 8. Kitajima S, Ivanova E, Gou S. Suppression of STING Associated with LKB1 Loss in KRAS-Driven Lung Cancer. Cancer Discov. 2019;9(1):34–45. 9. Mograbi B, Heeke S, Hofman P. The Importance of STK11/LKB1 Assessment in Non-Small Cell Lung Carcinomas. Diagnostics (Basel). 2021;11(2):196.

Ethics Approval

This study was approved by the following ethical committees: Use of human cord blood: UT Southwestern (UTSW) Parkland Hospital, STU 112010-047Animal studies: UTSW Medical Center, Institutional Animal Care and Use Committee, APN 2015-100921Clinical study: London Bridge Research Ethics Committee (UK): 17/LO/0418; REC-South East (Norway): 2017/473; Drug Research Ethics Committee of the University Hospital Clinic of Barcelona (Spain): BGBC008/MK-3475_PN-531; Medical College of Wisconsin Institutional Review Board #4 (USA): PRO00029453

Dual targeting of CTLA-4 and CD47 on Treg cells promotes immunity against solid tumors

Blockade of CD47, the "do not eat me" signal, has limited effects in solid tumors despite its potent antitumor effects in hematopoietic malignancies. Taking advantage of the high expression of cytotoxic T lymphocyte-associated protein 4 (CTLA-4) on T_reg cells and abundant Fc receptor-expressing active phagocytes inside the tumor microenvironment (TME), we designed and tested a heterodimer combining an anti-CTLA-4 antibody, which targets T_reg cells, with the CD47 ligand, signal regulatory protein α (SIRPα), to selectively block CD47 on intratumoral T_reg cells. We hypothesized that heterodimer treatment would increase antibody-dependent cellular phagocytosis of the targeted T_reg cells. We found that anti-CTLA-4×SIRPα preferentially depleted ICOS^high immunosuppressive T_reg cells in the TME and enhanced immunity against solid tumors, including MC38 and CT26 murine colon cancers. Mechanistically, we found that CD47 expression on T_reg cells limited anti-CTLA-4-mediated depletion and Fc on the heterodimer-enhanced depletion. Furthermore, anti-human CTLA-4×SIRPα depleted tumor T_reg cells and exhibits less toxicity than anti-human CTLA-4 in a humanized mouse model. Collectively, these results demonstrate that simultaneously modulating both "eat me" and do not eat me signals induces T_reg cell depletion inside the TME and may be an effective strategy for treating solid tumors.

Tumor-conditional IL-15 pro-cytokine reactivates anti-tumor immunity with limited toxicity

IL-15 is a promising cytokine to expand NK and CD8⁺ T cells for cancer immunotherapy, but its application is limited by dose-limiting, on-target off-tumor toxicity. Here, we have developed a next-generation IL-15 that is activated inside the tumor microenvironment (TME). This pro-IL-15 has the extracellular domain of IL-15Rβ fused to the N-terminus of sIL-15-Fc through a tumor-enriched Matrix Metalloproteinase (MMP) cleavable peptide linker to block its activity. Unlike sIL-15-Fc, pro-IL-15 does not activate the peripheral expansion of NK cells and T cells, thus reducing systemic toxicity, but it still preserves efficient anti-tumor abilities. In various mouse tumors, the anti-tumor effect of pro-IL-15 depends on intratumoral CD8⁺ T cells and IFN-γ. Pro-IL-15 increases the stem-like TCF1⁺Tim-3^-CD8⁺ T cells within tumor tissue and helps overcome immune checkpoint blockade (ICB) resistance. Moreover, pro-IL-15 synergizes with current tyrosine kinase inhibitor (TKI) targeted-therapy in a poorly inflamed TUBO tumor model, suggesting that pro-IL-15 helps overcome targeted-therapy resistance. Our results demonstrate a next-generation IL-15 cytokine that can stimulate potent anti-tumor activity without severe toxicity.

Immune mechanisms orchestrate tertiary lymphoid structures in tumors via cancer-associated fibroblasts

Tumor-associated tertiary lymphoid structures (TA-TLS) are associated with enhanced patient survival and responsiveness to cancer therapies, but the mechanisms underlying their development are unknown. We show here that TA-TLS development in murine melanoma is orchestrated by cancer-associated fibroblasts (CAF) with characteristics of lymphoid tissue organizer cells that are induced by tumor necrosis factor receptor signaling. CAF organization into reticular networks is mediated by CD8 T cells, while CAF accumulation and TA-TLS expansion depend on CXCL13-mediated recruitment of B cells expressing lymphotoxin-α1β2. Some of these elements are also overrepresented in human TA-TLS. Additionally, we demonstrate that immunotherapy induces more and larger TA-TLS that are more often organized with discrete T and B cell zones, and that TA-TLS presence, number, and size are correlated with reduced tumor size and overall response to checkpoint immunotherapy. This work provides a platform for manipulating TA-TLS development as a cancer immunotherapy strategy.

Radiotherapy and immunotherapy converge on elimination of tumor-promoting erythroid progenitor cells through adaptive immunity

Tumor-induced CD45^-Ter119⁺CD71⁺ erythroid progenitor cells, termed "Ter cells," promote tumor progression by secreting artemin (ARTN), a neurotrophic peptide that activates REarranged during Transfection (RET) signaling. We demonstrate that both local tumor ionizing radiation (IR) and anti-programmed death ligand 1 (PD-L1) treatment decreased tumor-induced Ter cell abundance in the mouse spleen and ARTN secretion outside the irradiation field in an interferon- and CD8⁺ T cell-dependent manner. Recombinant erythropoietin promoted resistance to radiotherapy or anti-PD-L1 therapies by restoring Ter cell numbers and serum ARTN concentration. Blockade of ARTN or potential ARTN signaling partners, or depletion of Ter cells augmented the antitumor effects of both IR and anti-PD-L1 therapies in mice. Analysis of samples from patients who received radioimmunotherapy demonstrated that IR-mediated reduction of Ter cells, ARTN, and GFRα3, an ARTN signaling partner, were each associated with tumor regression. Patients with melanoma who received immunotherapy exhibited favorable outcomes associated with decreased expression of GFRα3. These findings demonstrate an out-of-field, or "abscopal," effect mediated by adaptive immunity, which is induced during local tumor irradiation. This effect, in turn, governs the therapeutic effects of radiation and immunotherapy. Therefore, our results identify multiple targets to potentially improve outcomes after radiotherapy and immunotherapy.

A chimeric antigen receptor with antigen-independent OX40 signaling mediates potent antitumor activity

Although chimeric antigen receptor (CAR)-modified T cells have shown great success in the treatment of B cell malignancies, this approach has limited efficacy in patients with solid tumors. Various modifications in CAR structure have been explored to improve this efficacy, including the incorporation of two costimulatory domains. Because costimulatory signals are transduced together with T cell receptor signals during T cell activation, we engineered a type of CAR-T cells with a costimulatory signal that was activated independently from the tumor antigen to recapitulate physiological stimulation. We screened 12 costimulatory receptors to identify OX40 as the most effective CAR-T function enhancer. Our data indicated that these new CAR-T cells showed superior proliferation capability compared to current second-generation CAR-T cells. OX40 signaling reduced CAR-T cell apoptosis through up-regulation of genes encoding Bcl-2 family members and enhanced proliferation through increased activation of the NF-κB (nuclear factor κB), MAPK (mitogen-activated protein kinase), and PI3K-AKT (phosphoinositide 3-kinase to the kinase AKT) pathways. OX40 signaling not only enhanced the cytotoxicity of CAR-T cells but also reduced exhaustion markers, thereby maintaining their function in immunosuppressive tumor microenvironments. In mouse tumor models and in patients with metastatic lymphoma, these CAR-T cells exhibited robust amplification and antitumor activity. Our findings provide an alternative option for CAR-T optimization with the potential to overcome the challenge of treating solid tumors.

Abstract 3180: Blockade of PD-L1 interaction with CD80 in trans augments anti-tumor immunity by increasing NOS2 in tumor-associated macrophages

Programmed death ligand 1(PD-L1) has two receptors: programmed death receptor 1 (PD-1) and CD80. Both PD-L1 and CD80 are expressed by activated T-cells, antigen presenting cells (APCs) and tumor cells. Although the role of PD-L1/PD-1 interaction in regulation of tumor immunity has been well characterized, role of PD-L1/CD80 interaction remains largely unknown. The interaction mode of PD-L1 with CD80 is also controversial. Our previous studies showed that in murine model of acute graft versus host disease, PD-L1 interact with CD80 on different cells (Deng et al: J. Immunol. 2015); but a recent report showed that PD-L1 interacts with CD80 in cis on the same cell (Sugiura et al: Science 2019). In the current studies, we tested the role of PD-L1/CD80 interaction in trans in regulation of tumor immunity. WT, PD-L1-/-, and CD80-/- C57BL/6 mice were inoculated with WT or PD-L1-/- MC38 tumor cells and intraperitoneally injected with 200μg anti-PD-L1(43H12) that specifically block PD-L1/CD80 interactions or control IgG, starting on D7 after tumor inoculation, every 3 days, total of 5 times. Tumor volume was monitored every 3 days for up to D20. Tumor and tumor draining lymph nodes were harvested on D14 or D15 after tumor inoculation for mechanism studies. We observed that administration of 43H12 resulted in inhibition of tumor growth in WT MC38→WT Rec model; as well as in models of WT MC38→PD-L1-/- Rec (no PD-L1 on APCs or T cells), WT MC38→CD80-/- Rec (no CD80 on APCs or T cells), and PD-L1-/-MC38→CD80-/- Rec (no PD-L1 on tumor cells and no CD80 on APCs or T cells, truly PD-L1 interaction with CD80 in trans). These results indicate that blockade of PD-L1 interaction with CD80 in trans inhibits tumor growth. Furthermore, we found that blockade of PD-L1/CD80 interaction by 43H12 mAb increased percentage of CD8+ effector memory T (Tem) that produce IFN-γ and tumor-associated macrophages (TAMs) that express NOS2. Administration of anti-IFN-γ eliminated increase of NOS2 and anti-tumor effect, and administration of NOS2 inhibitor (1400W) also eliminated the anti-tumor effect mediated by injection of 43H12 mAb. Therefore, PD-L1 interaction with CD80 in trans regulate tumor immunity; and blockade of this interaction augments anti-tumor immunity via augmenting CD8+ Tem expansion and their production of IFN-γ, and subsequently augmenting tumoricidal NOS2 expressed in TAMs.

Citation Format: Yuankun Zhang, Qingxiao Song, Michael Lee, Haidong Tang, Kaniel Cassady, Yang-Xin Fu, Dustin E. Schones, Arthur Riggs, Ru Feng, Defu Zeng. Blockade of PD-L1 interaction with CD80 in trans augments anti-tumor immunity by increasing NOS2 in tumor-associated macrophages [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3180.

Next-generation cytokines for cancer immunotherapy

Most studies focus on the first and second signals of T cell activation. However, the roles of cytokines in immunotherapy are not fully understood, and cytokines have not been widely used in patient care. Clinical application of cytokines is limited due to their short half-life in vivo, severe toxicity at therapeutic doses, and overall lack of efficacy. Several modifications have been engineered to extend their half-life and increase tumor targeting, including polyethylene glycol conjugation, fusion to tumor-targeting antibodies, and alteration of cytokine/cell receptor-binding affinity. These modifications demonstrate an improvement in either increased antitumor efficacy or reduced toxicity. However, these cytokine engineering strategies may still be improved further, as each strategy poses advantages and disadvantages in the delicate balance of targeting tumor cells, tumor-infiltrating lymphocytes, and peripheral immune cells. This review focuses on selected cytokines, including interferon-α, interleukin (IL)-2, IL-15, IL-21, and IL-12, in both preclinical studies and clinical applications. We review next-generation designs of these cytokines that improve half-life, tumor targeting, and antitumor efficacy. We also present our perspectives on the development of new strategies to potentiate cytokine-based immunotherapy.

De novo prediction of cancer-associated T cell receptors for noninvasive cancer detection

The adaptive immune system recognizes tumor antigens at an early stage to eradicate cancer cells. This process is accompanied by systemic proliferation of the tumor antigen-specific T lymphocytes. While detection of asymptomatic early-stage cancers is challenging due to small tumor size and limited somatic alterations, tracking peripheral T cell repertoire changes may provide an attractive solution to cancer diagnosis. Here, we developed a deep learning method called DeepCAT to enable de novo prediction of cancer-associated T cell receptors (TCRs). We validated DeepCAT using cancer-specific or non-cancer TCRs obtained from multiple major histocompatibility complex I (MHC-I) multimer-sorting experiments and demonstrated its prediction power for TCRs specific to cancer antigens. We blindly applied DeepCAT to distinguish over 250 patients with cancer from over 600 healthy individuals using blood TCR sequences and observed high prediction accuracy, with area under the curve (AUC) ≥ 0.95 for multiple early-stage cancers. This work sets the stage for using the peripheral blood TCR repertoire for noninvasive cancer detection.

All-trans retinoic acid overcomes solid tumor radioresistance by inducing inflammatory macrophages

Radiotherapy (RT) is an important anti-cancer treatment modality that activates innate and adaptive immune responses. When all-trans retinoic acid (RA) was administered with radiation, we observed superior antitumor responses compared to ionizing radiation (IR) alone or RA alone. The superior antitumor effects of combination treatment were accompanied by a dramatic increase of TNF-α- and inducible nitric oxide synthase (iNOS)-producing inflammatory macrophages in local and distal non-irradiated (distal) tumors. Inflammatory macrophages are essential for the therapeutic efficacy of combination treatment by inducing effector T cell infiltration and enhancing the effector T cell to regulatory T cell ratio in local and distal tumors. T cells and T cell-derived IFN-γ are crucial for increasing inflammatory macrophage levels in IR and RA treated tumors. Notably, whereas CD8⁺ T cells are required for the antitumor response to IR, CD4⁺ T cells are required for the effectiveness of the IR and RA combination. Combination treatment with RA enhanced the abscopal response when radiation and PD-L1 blockade were used together. The synergistic positive feedback loop of inflammatory macrophages and adaptive immunity is required for the antitumor efficacy of IR plus RA combination treatment. Our findings provide a translational and relatively nontoxic strategy for enhancing the local and systemic antitumor effects of IR.

The AIM2 and NLRP3 inflammasomes trigger IL-1-mediated antitumor effects during radiation

The inflammasome promotes inflammation-associated diseases, including cancer, and contributes to the radiation-induced tissue damage. However, the role of inflammasome in radiation-induced antitumor effects is unclear. We observed that tumors transplanted in Casp1-/- mice were resistant to radiation treatment compared with tumors in wild-type (WT) mice. To map out which molecule in the inflammasome pathway contributed to this resistant, we investigated the antitumor effect of radiation in several inflammasome-deficient mice. Tumors grown in either Aim2-/- or Nlrp3-/- mice remained sensitive to radiation, like WT mice, whereas Aim2-/-Nlrp3-/- mice showed radioresistance. Mechanistically, extracellular vesicles (EVs) and EV-free supernatant derived from irradiated tumors activated both Aim2 and Nlrp3 inflammasomes in macrophages, leading to the production of interleukin-1β (IL-1β). IL-1β treatment helped overcome the radioresistance of tumors growing in Casp1-/- and Aim2-/-Nlrp3-/- mice. IL-1 signaling in dendritic cells (DCs) promoted radiation-induced antitumor immunity by enhancing the cross-priming activity of DCs. Overall, we demonstrated that radiation-induced activation of the AIM2 and NLRP3 inflammasomes coordinate to induce some of the antitumor effects of radiation by triggering IL-1 signaling in DCs, leading to their activation and cross-priming.