Personalized neoantigen vaccine and pembrolizumab in advanced hepatocellular carcinoma: a phase 1/2 trial

Programmed cell death protein 1 (PD-1) inhibitors have modest efficacy as a monotherapy in hepatocellular carcinoma (HCC). A personalized therapeutic cancer vaccine (PTCV) may enhance responses to PD-1 inhibitors through the induction of tumor-specific immunity. We present results from a single-arm, open-label, phase 1/2 study of a DNA plasmid PTCV (GNOS-PV02) encoding up to 40 neoantigens coadministered with plasmid-encoded interleukin-12 plus pembrolizumab in patients with advanced HCC previously treated with a multityrosine kinase inhibitor. Safety and immunogenicity were assessed as primary endpoints, and treatment efficacy and feasibility were evaluated as secondary endpoints. The most common treatment-related adverse events were injection-site reactions, observed in 15 of 36 (41.6%) patients. No dose-limiting toxicities or treatment-related grade ≥3 events were observed. The objective response rate (modified intention-to-treat) per Response Evaluation Criteria in Solid Tumors 1.1 was 30.6% (11 of 36 patients), with 8.3% (3 of 36) of patients achieving a complete response. Clinical responses were associated with the number of neoantigens encoded in the vaccine. Neoantigen-specific T cell responses were confirmed in 19 of 22 (86.4%) evaluable patients by enzyme-linked immunosorbent spot assays. Multiparametric cellular profiling revealed active, proliferative and cytolytic vaccine-specific CD4+ and CD8+ effector T cells. T cell receptor β-chain (TCRβ) bulk sequencing results demonstrated vaccination-enriched T cell clone expansion and tumor infiltration. Single-cell analysis revealed posttreatment T cell clonal expansion of cytotoxic T cell phenotypes. TCR complementarity-determining region cloning of expanded T cell clones in the tumors following vaccination confirmed reactivity against vaccine-encoded neoantigens. Our results support the PTCV's mechanism of action based on the induction of antitumor T cells and show that a PTCV plus pembrolizumab has clinical activity in advanced HCC. ClinicalTrials.gov identifier: NCT04251117 .

Teclistamab impairs humoral immunity in patients with heavily pretreated myeloma: importance of immunoglobulin supplementation

ABSTRACT

Teclistamab and other B-cell maturation antigen (BCMA)-targeting bispecific antibodies (BsAbs) have substantial activity in patients with heavily pretreated multiple myeloma (MM) but are associated with a high rate of infections. BCMA is also expressed on normal plasma cells and mature B cells, which are essential for the generation of a humoral immune response. The aim of this study was to improve the understanding of the impact of BCMA-targeting BsAbs on humoral immunity. The impact of teclistamab on polyclonal immunoglobulins and B cell counts was evaluated in patients with MM who received once-weekly teclistamab 1.5 mg/kg subcutaneously. Vaccination responses were assessed in a subset of patients. Teclistamabinduced rapid depletion of peripheral blood B cells in patients with MM and eliminated normal plasma cells in ex vivo assays. In addition, teclistamab reduced the levels of polyclonal immunoglobulins (immunoglobulin G [IgG], IgA, IgE, and IgM), without recovery over time while receiving teclistamab therapy. Furthermore, response to vaccines against Streptococcus pneumoniae, Haemophilus influenzae type B, and severe acute respiratory syndrome coronavirus 2 was severely impaired in patients treated with teclistamab compared with vaccination responses observed in patients with newly diagnosed MM or relapsed/refractory MM. Intravenous immunoglobulin (IVIG) use was associated with a significantly lower risk of serious infections among patients treated with teclistamab (cumulative incidence of infections at 6 months: 5.3% with IVIG vs 54.8% with observation only [P < .001]). In conclusion, our data show severe defects in humoral immunity induced by teclistamab, the impact of which can be mitigated by the use of immunoglobulin supplementation. This trial was registered at www.ClinicalTrials.gov as #NCT04557098.

Siglec-7 glyco-immune binding mAbs or NK cell engager biologics induce potent antitumor immunity against ovarian cancers

Ovarian cancer (OC) is a lethal gynecologic malignancy, with modest responses to CPI. Engagement of additional immune arms, such as NK cells, may be of value. We focused on Siglec-7 as a surface antigen for engaging this population. Human antibodies against Siglec-7 were developed and characterized. Coculture of OC cells with PBMCs/NKs and Siglec-7 binding antibodies showed NK-mediated killing of OC lines. Anti-Siglec-7 mAb (DB7.2) enhanced survival in OC-challenged mice. In addition, the combination of DB7.2 and anti-PD-1 demonstrated further improved OC killing in vitro. To use Siglec-7 engagement as an OC-specific strategy, we engineered an NK cell engager (NKCE) to simultaneously engage NK cells through Siglec-7, and OC targets through FSHR. The NKCE demonstrated robust in vitro killing of FSHR+ OC, controlled tumors, and improved survival in OC-challenged mice. These studies support additional investigation of the Siglec-7 targeting approaches as important tools for OC and other recalcitrant cancers.

Multivalent in vivo delivery of DNA-encoded bispecific T cell engagers effectively controls heterogeneous GBM tumors and mitigates immune escape

Glioblastoma multiforme (GBM) is among the most difficult cancers to treat with a 5-year survival rate less than 5%. An immunotherapeutic vaccine approach targeting GBM-specific antigen, EGFRvIII, previously demonstrated important clinical impact. However, immune escape variants were reported in the trial, suggesting that multivalent approaches targeting GBM-associated antigens may be of importance. Here we focused on multivalent in vivo delivery of synthetic DNA-encoded bispecific T cell engagers (DBTEs) targeting two GBM-associated antigens, EGFRvIII and HER2. We designed and optimized an EGFRvIII-DBTE that induced T cell-mediated cytotoxicity against EGFRvIII-expressing tumor cells. In vivo delivery in a single administration of EGFRvIII-DBTE resulted in durable expression over several months in NSG mice and potent tumor control and clearance in both peripheral and orthotopic animal models of GBM. Next, we combined delivery of EGFRvIII-DBTEs with an HER2-targeting DBTE to treat heterogeneous GBM tumors. In vivo delivery of dual DBTEs targeting these two GBM-associated antigens exhibited enhanced tumor control and clearance in a heterogeneous orthotopic GBM challenge, while treatment with single-target DBTE ultimately allowed for tumor escape. These studies support that combined delivery of DBTEs, targeting both EGFRvIII and HER2, can potentially improve outcomes of GBM immunotherapy, and such multivalent approaches deserve additional study.

A mAb against surface-expressed FSHR engineered to engage adaptive immunity for ovarian cancer immunotherapy

Despite advances in ovarian cancer (OC) therapy, recurrent OC remains a poor-prognosis disease. Because of the close interaction between OC cells and the tumor microenvironment (TME), it is important to develop strategies that target tumor cells and engage components of the TME. A major obstacle in the development of OC therapies is the identification of targets with expression limited to tumor surface to avoid off-target interactions. The follicle-stimulating hormone receptor (FSHR) has selective expression on ovarian granulosa cells and is expressed on 50%-70% of serous OCs. We generated mAbs targeting the external domain of FSHR using in vivo-expressed FSHR vector. By high-throughput flow analysis, we identified multiple clones and downselected D2AP11, a potent FSHR surface-targeted mAb. D2AP11 identifies important OC cell lines derived from tumors with different mutations, including BRCA1/2, and lines resistant to a wide range of therapies. We used D2AP11 to develop a bispecific T cell engager. In vitro addition of PBMCs and T cells to D2AP11-TCE induced specific and potent killing of different genetic and immune escape OC lines, with EC50s in the ng/ml range, and attenuated tumor burden in OC-challenged mouse models. These studies demonstrate the potential utility of biologics targeting FSHR for OC and perhaps other FSHR-positive cancers.

Abstract 3573: DNA immunotherapy targeting BARF1 demonstrates therapeutic impact in novel murine carcinoma models expressing EBV latent antigens

Epstein Barr Virus (EBV) latent infection is associated with multiple types of cancer. Several clinical studies have targeted EBV antigens as immune therapeutic targets with limited efficacy of EBV+ malignancies, suggesting additional targets might be important. BamHI-A rightward frame 1 (BARF1) is an EBV antigen that is highly expressed in EBV-associated gastric carcinoma (EBVaGC) and EBV+ nasopharyngeal carcinoma (NPC) and has not been evaluated as an antigen in the context of therapeutic immunization. Here, we developed a synthetic DNA-based expression cassette as immunotherapy targeting BARF1 (pBARF1). Immunization with pBARF1 induced potent antigen-specific humoral and polyfunctional effector T cell responses in vivo. We observed significant antigen-specific increases of IFN-γ+, IFN-γ+ TNF-α+, and IFN-γ+ TNF-α+ IL-2+ populations in CD8+ T cells from the pBARF1 immunized animals in both C57BL/6 and BALB/c mice. Novel BARF1 expressing carcinoma lines that grow in immune-competent animals were developed as surrogates for human EBV+ tumors. We confirmed that BARF1 expression in these new cancer cell lines, MC38-BARF1 and CT26-BARF1, was within the range of human EBV+ cancer cell lines, SNU719 and C666-1. Immunization with pBARF1 plasmid demonstrated impact of tumor progression through induction of CD8+ T cell in these BARF1+ carcinoma models. We also observed long-term antitumor immunity, at least up to 446 days, against BARF1 in a CT26-BARF1 rechallenge study. Using IVIS in vivo imaging, we observed that pBARF1 immunized animals rapidly controlled and cleared cancer cells. These studies demonstrate the potential for pBARF1 immunity to induce antigen-specific immune responses impacting tumor progression. Further study of this immune target and these EBV+ tumor models is likely important as part of therapeutic approaches for EBV+ malignancies.

Citation Format: Xizhou Zhu, Alfredo Perales-Puchalt, Krzysztof Wojtak, Ziyang Xu, Kun Yun, Pratik S. Bhojnagarwala, Devivasha Bordoloi, Daniel H. Park, Kevin Liaw, Mamadou A. Bah, Paul M. Lieberman, Ebony N. Gary, Ami Patel, David B. Weiner. DNA immunotherapy targeting BARF1 demonstrates therapeutic impact in novel murine carcinoma models expressing EBV latent antigens [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3573.

Abstract 4262: Immunotherapy of ovarian cancer targeting FSHR by innate and adaptive immunity

Ovarian cancer (OC) represents the deadliest gynecologic malignancy. Despite important advances in the field of OC therapy, recurrent OC still has very poor prognosis with a median survival of 1 year. Due to the close interaction between the ovarian cancer cells and tumor microenvironment, development of treatment strategies which not only target the tumor cells but also the components of the tumor microenvironment hold significance. Notably, a prime obstacle in the development of therapies is to identify targets with specific expression limited to the tumor surface and not the healthy tissues. The follicle-stimulating hormone receptor (FSHR) is one such target with selective expression in ovarian granulosa cells and thus, a potentially important therapeutic target in OC. Therefore, we developed monoclonal antibodies against FSHR and focused on studies of the most potent of these reagents. Anti-FSHR antibody bound to diverse FSHR expressing ovarian serous and clear cell adenocarcinoma cells suggesting these antibodies could be used to specifically target OC. We then designed a novel DNA encoded bispecific T cell engager targeting FSHR (FSHRxCD3) and evaluated this bispecific in therapeutic models for the treatment of OC. FSHRxCD3 bispecific in the presence of human PBMCs was highly specific in killing FSHR positive ovarian tumor lines. However, T cell approaches alone may not be fully effective in treating OC, referred as Immunologically “Cold” Tumors. Hence, we hypothesized that engaging the other components of immune system, would provide better tumor control. Increasing lines of evidence suggest that OC is receptive to Natural killer (NK) cell attack. We designed antibodies against human Siglec-7, an inhibitory receptor present on human NK cells and showed they could bind to NK cells. We then used these to create a novel class of bispecific NK engager (NKE) that simultaneously targets both Siglec-7 and FSHR (Siglec-7xFSHR). This NKE was potent at killing FSHR positive OC targets in both in vitro and in vivo assays. Multiple Ovarian tumors including BRCA mutated and PARPi resistant ovarian cancer cells could be targeted by this immune therapy. Our data demonstrate the therapeutic potential of these two novel bispecific molecules and initial studies suggest that their combination may be valuable in patients with OC.

Citation Format: Devivasha Bordoloi, Pratik Bhojnagarwala, Abhijeet J. Kulkarni, Opeyemi S. Adeniji, Alfredo Perales-Puchalt, Ryan P. O’Connell, Xizhou Zhu, Elizabeth M. Parzych, Rugang Zhang, Mohamed Abdel-Mohsen, David B. Weiner. Immunotherapy of ovarian cancer targeting FSHR by innate and adaptive immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 4262.

Personalized neoantigen DNA vaccines expand tumor-specific T cells in the periphery which infiltrate the tumor in hepatocellular carcinoma

2638

Background: Tumor neoantigens are epitopes derived from tumor-specific mutations that can be incorporated in personalized vaccines to prime T cell responses. DNA vaccines delivered with electroporation have recently shown strong CD8 and CD4 T cell responses in clinical trials. In preclinical studies, DNA-encoded neoantigen vaccines have shown induction of CD8 T cells against 50% of predicted high affinity epitopes with the ability to impact tumor growth. Methods: Paired blood and tumor biopsy samples were collected from a patient with hepatocellular carcinoma before and after treatment with GNOS-PV02 (DNA neoantigen targeted vaccine) + plasmid IL-12 + pembrolizumab. Treatment resulted in a partial response with a decrease in tumor size of 44% by RECIST (168 mm to 94 mm). TCRbeta sequencing was performed on all 4 samples and single cell TCR and transcriptome sequencing was performed from T cells isolated from the post-treatment blood sample. Newly identified TCRs in blood and tumor after vaccination were inserted into an expression vector and used to generate engineered TCR T cells. Engineered TCR T cells were tested against the neoantigens included in the vaccine and their responses characterized by flow cytometry. Results: We identified 67,893 new clones in PBMC after vaccination, 3 of which comprised between 0.1 to 1% of the total T cell clones. Moreover, we identified 5126 new clones in the tumor post vaccination, out of these, 3878 (75.68%) were not found within the patient’s pre vaccination PBMCs and 556 (10.86%) were identified within the pre vaccination PBMC pool. Importantly, of the newly identified T cells infiltrating the tumor post vaccination, we observed high frequency TCR clones of which 44 and 7 clones were above 0.1% and 1%, respectively. The majority of the newly identified T cell clones were CD8 T cells (68.75%) with an activated phenotype. Importantly, the 6 most expanded clones in blood were identified to be activated CD8+CD69+ T cells (81.82%). Engineered TCR T cells generated encoding the TCRs of these newly identified CD8 T cells showed activation when exposed to the tumor neoantigens encoded in the neoantigen DNA vaccine GNOS-PV02. Conclusions: GNOS-PV02, a neoantigen DNA vaccine, in combination with plasmid IL-12 and pembrolizumab resulted in expansion of newly identified T cells, primarily activated CD8, which trafficked to the tumor. These new tumor infiltrating T cells showed TCR specificity against tumor neoantigens encoded in GNOS-PV02 and may account for the observed objective decrease in tumor size.

DNA immunotherapy targeting BARF1 induces potent anti-tumor responses against Epstein-Barr-virus-associated carcinomas

Latent Epstein-Barr virus (EBV) infection is associated with several types of cancer. Several clinical studies have targeted EBV antigens as immune therapeutic targets with limited efficacy of EBV malignancies, suggesting that additional targets might be important. BamHI-A rightward frame 1 (BARF1) is an EBV antigen that is highly expressed in EBV⁺ nasopharyngeal carcinoma (NPC) and EBV-associated gastric carcinoma (EBVaGC). BARF1 antigen can transform human epithelial cells in vivo. BARF1-specific antibodies and cytotoxic T cells were detected in some EBV⁺ NPC patients. However, BARF1 has not been evaluated as an antigen in the context of therapeutic immunization. Its possible importance in this context is unclear. Here, we developed a synthetic-DNA-based expression cassette as immunotherapy targeting BARF1 (pBARF1). Immunization with pBARF1 induced potent antigen-specific humoral and T cell responses in vivo. Immunization with pBARF1 plasmid impacted tumor progression through the induction of CD8⁺ T cells in novel BARF1⁺ carcinoma models. Using an in vivo imaging system, we observed that pBARF1-immunized animals rapidly cleared cancer cells. We demonstrated that pBARF1 can induce antigen-specific immune responses that can impact cancer progression. Further study of this immune target is likely important as part of therapeutic approaches for EBV⁺ malignancies.

453 Personalized DNA neoantigen vaccine (GNOS-PV02) in combination with plasmid IL-12 and pembrolizumab for the treatment of patients with advanced hepatocellular carcinoma

Background

Hepatocellular carcinoma (HCC) is the fourth most common cause of cancer-related death. Immune checkpoint inhibitors targeting PD-1 have limited activity in HCC as monotherapy, with response rates ranging from 14–17%. Tumor neoantigens derived from tumor-specific mutations can be incorporated into personalized therapeutic cancer vaccines to generate tumor-specific T cell immunity, potentially priming the immune system for anti-PD1 therapy. DNA vaccines have been shown to elicit strong CD8 and CD4 T cell responses in preclinical and clinical trials. GNOS-PV02 is a personalized DNA vaccine, encoding up to 40 patient-specific neoantigens. In the GT-30 trial, it is used in combination with INO-9012 (plasmid-encoded IL-12) and pembrolizumab for the treatment of advanced HCC.

Methods

GT-30 is a single-arm phase I/II clinical trial to assess the safety, immunogenicity, and preliminary efficacy of GNOS-PV02 in combination with INO-9012 and pembrolizumab in patients with advanced HCC. Twenty-four patients are anticipated to be enrolled. Patients are recruited upon diagnosis or during first-line treatment with tyrosine kinase inhibitors (TKI). Tumors are biopsied for exome and transcriptome sequencing, and peripheral blood collected for germline sequencing and histogenetics. The tumor specific vaccine is designed, optimized and manufactured during first-line therapy. Each vaccine encodes up to 40 neoantigens. After progression or intolerance with first-line therapy, patients commence concurrent personalized vaccine and pembrolizumab. GNOS-PV02 + INO-9012 are administered Q3w for the first 4 doses and Q9w thereafter. Pembrolizumab is delivered Q3w.

Results

We performed a data cut-off on the first 12 patients. The median age was 66 years (range 55–75 years). GNOS-PV02 + INO-9012 with pembrolizumab has had no reported DLTs or drug related SAEs. The most common treatment-related AE were grade 1 fatigue (25%) and grade 1 injection site reactions (17%). By including up to 40 epitopes in the vaccine we were able to target all neoantigens present in 83% of the patients. The objective response rate was 25% (3/12 partial response, 5/12 stable disease, 4/12 progressive disease). Analysis of the TCR repertoire in peripheral blood and tumor tissue identified novel and significantly expanded T cell clones post-vaccination in all patients analyzed. Many of the novel peripheral T cell clones were also identified to have trafficked to the TME at week 9, potentially mediating the observed tumor regressions.

Conclusions

These data demonstrate the potential of GNOS-PV02 + INO-9012 with pembrolizumab to target multiple neoepitopes, and provide initial support for the safety and efficacy of this regimen in patients with advanced HCC.

Trial Registration

NCT04251117

Ethics Approval

The study obtained IRB approval (IRB) and all patients signed informed consent prior to taking part in the clinical trial. NZCR EC: 20/NTA/6; JHU: IRB00227771; Mount Sinai: HS#: 20–00076

777 Personalized DNA vaccine in combination with plasmid encoded IL-12 for the treatment of a patient with anaplastic astrocytoma

Background

Tumor neoantigens are epitopes derived from tumor-specific mutations. Such mutations can be incorporated in personalized vaccines to prime T cell responses against tumor specific antigens. DNA vaccines delivered with electroporation have recently shown strong CD8 and CD4 T cell responses in clinical trials. In preclinical studies, DNA-encoded neoantigen vaccines have shown induction of CD8 T cells against 50% of predicted high affinity epitopes with the ability to impact tumor growth.

Methods

Two resection samples from a patient with IDH+ MGMT-methylated anaplastic astrocytoma were subject to whole exome and transcriptome sequencing. Epitopes derived from 27 neoantigens and 3 shared tumor-associated antigens were prioritized and included in a personalized vaccine. The patient was treated with surgery, radiotherapy and temozolomide starting June 2018 and received the first dose of the personalized vaccine in June 2019 under a compassionate use single patient IND application with the FDA.

Results

As of July 23rd, 2021, the patient has received 11 doses of the DNA personalized vaccine. No serious adverse events have been reported. Related adverse events are limited to grade 1 injection site reactions. The patient remains progression-free 37 months after surgery and 25 months after starting vaccination. Three weeks following the 3rd dose, a hyperintense image on the tumor bed was identified, which disappeared on the following MRI, 2 weeks following dose 5, being catalogued as pseudo progression. Ex vivo ELISpot have identified T cell responses to 28/30 epitopes (93.3%), including 25/27 (92.6%) neoantigens and 3/3 (100%) shared antigens. Flow cytometry analysis has determined that T cell responses are 92.3% CD8 and 69.2% CD4 (30.8% CD8 only; 61.5% both CD8 and CD4; and 7.7% CD4 only).

Conclusions

This compassionate use treatment in an adjuvant setting demonstrates manufacturing feasibility, safety, tolerability, immunogenicity, and suggests potential for persistent clinical response of DNA encoded personalized vaccines. The data supports further investigation of DNA-encoded personalized vaccines into newly diagnosed high-grade gliomas.

Ethics Approval

The study was approved by Washington University's IRB. The participant gave informed consent before taking part in the study.

A synDNA vaccine delivering neoAg collections controls heterogenous, multifocal murine lung and ovarian tumors via robust T cell generation

Neoantigens are tumor-specific antigens that arise due to somatic mutations in the DNA of tumor cells. They represent ideal targets for cancer immunotherapy since there is minimal risk for on-target, off-tumor toxicities. Additionally, these are foreign antigens that should be immunogenic due to lack of central immune tolerance. Tumor neoantigens are predominantly passenger mutations, which do not contribute to tumorigenesis. In cases of multi-focal or metastatic tumors, different foci can have significantly different mutation profiles. This suggests that it is important to target as many neoantigens as possible to better control tumors and target multi-focal tumors within the same patient. Herein, we report a study targeting up to 40 neoantigens using a single DNA plasmid. We observed significant plasticity in the epitope strings arranged in the vaccine with regard to immune induction and tumor control. Different vaccines elicited T cell responses against multiple epitopes on the vaccine string and controlled growth of multi-focal, heterogeneous tumors in a therapeutic tumor challenge. Additionally, the multi-epitope antigens induced long-term immunity and rejected a tumor re-challenge several weeks after the final vaccination. These data provide evidence that DNA-encoded long antigen strings can be an important tool for immunotherapeutic vaccination against neoantigens with implications for other in vivo-delivered antigen strings.

Personalized DNA neoantigen vaccine in combination with plasmid IL-12 and pembrolizumab for the treatment of patients with advanced hepatocellular carcinoma

TPS2680

Background: Hepatocellular carcinoma (HCC) is the fourth most common cause of cancer-related death. Immune checkpoint inhibitors targeting PD-1 have limited activity in HCC as monotherapy, with response rates ranging from 14-17%. Tumor neoantigens derived from tumor-specific mutations can be incorporated into personalized therapeutic cancer vaccines to prime T cell responses, potentially enhancing responses to anti-PD1 therapy. DNA vaccines have been shown to elicit strong CD8 and CD4 T cell responses in preclinical and clinical trials. In preclinical studies, DNA-encoded neoantigen vaccines have shown induction of CD8 T cells against 50% of predicted high affinity epitopes with the ability to impact tumor growth. GNOS-PV02 is a personalized DNA vaccine, encoding up to 40 patient-specific neoantigens. In the GT-30 trial, it is used in combination with INO-9012 (plasmid-encoded IL-12) and pembrolizumab for the treatment of advanced HCC. Methods: The GT-30 trial (NCT04251117) is a single-arm phase I/II clinical trial to assess the safety, immunogenicity, and preliminary efficacy of GNOS-PV02 in combination with INO-9012 and pembrolizumab in patients with advanced HCC. Twenty-four patients are anticipated to be enrolled. Patients are recruited upon diagnosis or during first-line treatment with tyrosine kinase inhibitors (TKI). Tumors are biopsied for exome and transcriptome sequencing. The tumor specific vaccine is designed, optimized and manufactured during first-line therapy. Each vaccine encodes up to 40 neoantigens, which includes all detected neoantigens for the majority of HCC patients. After progression or intolerance with first-line therapy, patients can commence trial therapy with concurrent personalized vaccine and pembrolizumab. GNOS-PV02 + INO-9012 are administered Q3w for the first 4 doses and Q9w thereafter until disease progression. Pembrolizumab is delivered Q3w until disease progression. Immunogenicity of each of the vaccine epitopes will be determined by ex vivo ELISpot and flow cytometry. Clinical activity is assessed by RECIST1.1 at baseline and every 9 weeks. Serial biopsies will be obtained at 9 weeks and upon disease progression to evaluate changes in the exome, transcriptome and changes to the tumor microenvironment. Clinical trial information: NCT04251117.

Personalized DNA neoantigen vaccine in combination with plasmid IL-12 for the treatment of a patient with anaplastic astrocytoma

e14561

Background: Tumor neoantigens are epitopes derived from tumor-specific mutations that may be incorporated in personalized vaccines to prime T cell responses. DNA vaccines delivered with electroporation have recently shown strong CD8 and CD4 T cell responses in clinical trials. In preclinical studies, DNA-encoded neoantigen vaccines have shown induction of CD8 T cells against 50% of predicted high affinity epitopes with the ability to impact tumor growth. Methods: Two resection samples from a patient with IDH+ MGMT-methylated anaplastic astrocytoma were subject to whole exome and transcriptome sequencing. Epitopes derived from 27 neoantigens and 3 shared tumor-associated antigens were prioritized and included in a personalized vaccine. The patient was treated with surgery, radiotherapy and temozolomide starting June 2018 and received the first dose of the personalized vaccine in June 2019 under a compassionate use single patient IND application with the FDA. Results: As of February 10, 2021, the patient has received 10 doses of the DNA personalized vaccine. No serious adverse events have been reported. Related adverse events are limited to grade 1 injection site reactions. The patient remains progression-free 32 months after surgery and 20 months after starting vaccination. Three weeks following the third dose, a hyperintense image on the tumor bed was identified, which disappeared on the following MRI, 2 weeks following dose 5, being catalogued as pseudo progression. Ex vivo ELISpot have identified T cell responses to 21/30 epitopes (70%), including 18/27 (67%) neoantigens and 3/3 (100%) shared antigens. Flow cytometry analysis has determined that T cell responses are 92.3% CD8 and 69.2% CD4 (30.8% CD8 only; 61.5% both CD8 and CD4; and 7.7% CD4 only). Conclusions: This compassionate use treatment in an adjuvant setting demonstrates manufacturing feasibility, safety, tolerability, immunogenicity, and suggests potential for persistent clinical response of DNA encoded personalized vaccines. The data supports further investigation of DNA-encoded personalized vaccines into newly diagnosed high-grade gliomas.

Immunotherapy of prostate cancer using novel synthetic DNA vaccines targeting multiple tumor antigens

Prostate cancer is a prevalent cancer in men and consists of both indolent and aggressive phenotypes. While active surveillance is recommended for the former, current treatments for the latter include surgery, radiation, chemo and hormonal therapy. It has been observed that the recurrence in the treated patients is high and results in castration resistant prostate cancer for which treatment options are limited. This scenario has prompted us to consider immunotherapy with synthetic DNA vaccines, as this approach can generate antigen-specific tumor-killing immune cells. Given the multifocal and heterogeneous nature of prostate cancer, we hypothesized that synthetic DNA vaccines targeting different prostate specific antigens are likely to induce broader and improved immunity who are at high risk as well as advanced clinical stage of prostate cancer, compared to a single antigen approach. Utilizing a bioinformatics approach, synthetic enhanced DNA vaccine (SEV) constructs were generated against STEAP1, PAP, PARM1, PSCA, PCTA and PSP94. Synthetic enhanced vaccines for prostate cancer antigens were shown to elicit antigen-specific immune responses in mice and the anti-tumor activity was evident in a prostate tumor challenge mouse model. These studies support further evaluation of the DNA tools for immunotherapy of prostate cancer and perhaps other cancers.

BTN3A1 governs antitumor responses by coordinating αβ and γδ T cells

Gamma delta (γδ) T cells infiltrate most human tumors, but current immunotherapies fail to exploit their in situ major histocompatibility complex-independent tumoricidal potential. Activation of γδ T cells can be elicited by butyrophilin and butyrophilin-like molecules that are structurally similar to the immunosuppressive B7 family members, yet how they regulate and coordinate αβ and γδ T cell responses remains unknown. Here, we report that the butyrophilin BTN3A1 inhibits tumor-reactive αβ T cell receptor activation by preventing segregation of N-glycosylated CD45 from the immune synapse. Notably, CD277-specific antibodies elicit coordinated restoration of αβ T cell effector activity and BTN2A1-dependent γδ lymphocyte cytotoxicity against BTN3A1⁺ cancer cells, abrogating malignant progression. Targeting BTN3A1 therefore orchestrates cooperative killing of established tumors by αβ and γδ T cells and may present a treatment strategy for tumors resistant to existing immunotherapies.

Synthetic DNA Delivery of an Engineered Arginase Enzyme Can Modulate Specific Immunity In Vivo

Arginase is a complex and unique enzyme that plays diverse roles in health and disease. By metabolizing arginine, it can shape the outcome of innate and adaptive immune responses. The immunomodulatory capabilities of arginase could potentially be applied for local immunosuppression or induction of immune tolerance. With the use of an enhanced DNA delivery approach, we designed and studied a DNA-encoded secretable arginase enzyme as a tool for immune modulation and evaluated its immunomodulatory function in vivo. Strong immunosuppression of cluster of differentiation 4 (CD4) and CD8 T cells, as well as macrophages and dendritic cells, was observed in vitro in the presence of an arginase-rich supernatant. To further evaluate the efficacy of DNA-encoded arginase on in vivo immunosuppression against an antigen, a cancer antigen vaccine model was used in the presence or absence of DNA-encoded arginase. Significant in vivo immunosuppression was observed in the presence of DNA-encoded arginase. The efficacy of this DNA-encoded arginase delivery was examined in a local, imiquimod-induced, psoriasis-like, skin-inflammation model. Pretreatment of animals with the synthetic DNA-encoded arginase led to significant decreases in skin acanthosis, proinflammatory cytokines, and costimulatory molecules in extracted macrophages and dendritic cells. These results draw attention to the potential of direct in vivo-delivered arginase to function as an immunomodulatory agent for treatment of local inflammation or autoimmune diseases.

Neutralization of hepatitis B virus by a novel DNA-encoded monoclonal antibody

Hepatitis B virus (HBV) causes a potentially life-threatening liver infection that frequently results in life-long chronic infection. HBV is responsible for 887,000 deaths each year, most resulting from chronic liver diseases and hepatocellular carcinoma. Presently, there are 250 million chronic HBV carriers worldwide who are at a high risk for developing cirrhosis and hepatocellular carcinoma (HCC). HCC is the most common type of liver cancer with a strong association with HBV infection. HBV transmission through blood transfusions and perinatal transfer from infected mother to child have been common routes of infection. In the present study, we describe the development of a synthetic DNA plasmid encoding an anti-HBV human monoclonal antibody specific for the common “a determinant region” of HBsAg of hepatitis B virus and demonstrate the ability of this platform at directing in vivo antibody expression. In vivo delivery of this DNA encoded monoclonal antibody (DMAb) plasmid in mice resulted in expression of human IgG over a period of one month following a single injection. Serum antibody was found to recognize the relevant conformational epitope from plasma purified native HBsAg as well as bound HBV in HepG2.2.15 cells. The serum DMAb efficiently neutralized HBV and prevented infection of HepaRG cells in vitro. Additional study of these HBV-DMAb as a possible therapy or immunoprophylaxis for HBV infection is warranted.

Abstract B67: Synthetic DNA multi-neoantigen vaccine drives predominately MHC class I CD8+ T cell-mediated effector immunity impacting tumor challenge

T-cell recognition of cancer neoantigens is important for effective immune checkpoint blockade therapy, and there is increasing interest in developing personalized tumor neoantigen vaccines. Previous studies utilizing RNA and synthetic long peptide neoantigen vaccines in preclinical and early-phase clinical studies have shown immune responses predominantly driven by MHC class II CD4+ T cells. Although it has been established that CD4+ T cells are able to recognize tumor neoantigens, the majority of naturally occurring tumor antigen-specific killer T cells identified in patients have been of CD8+ origin, indicating that additional immunization strategies aimed to stimulate neoantigen-specific CD8+ T cells may be useful. Here, we report the first preclinical study utilizing a synthetic DNA vaccine platform to target tumor neoantigens in mice. For this study, we identified neoepitopes by sequencing syngeneic mouse tumors, and designed optimized DNA plasmids encoding long strings of neoepitopes separated by highly efficient cleavage sites preserving epitope integrity. We tested the immunogenicity of 84 independent neoepitopes encoded into optimized DNA plasmids delivered by adaptive electroporation in mice in vivo. We observed that this approach generated robust T-cell immunity against a similar proportion of epitopes compared to other vaccine platforms (20/84, 24%). Strikingly, however, the synthetic neoantigen DNA vaccine platform generated a much larger proportion of CD8+ T-cell responses compared to the prior studies. Synthetic neoantigen DNA vaccines generated 75% CD8+ only or CD4/CD8+ T-cell responses, and 25% CD4+ only T-cell responses, showing a dramatic and important CD8+ T-cell bias. Inclusion of only high-affinity MHC class I (&lt;500nM) epitopes selected for a larger proportion of immunogenic epitopes, and for 100% CD8+ or CD8+/CD4+ T-cell epitopes. These neoantigen vaccines were able to control tumor growth therapeutically in vivo in both lung and ovarian cancer models, and T cells expanded from immunized mice were able to kill tumor cells ex vivo. Because of the potential for rapid synthesis of vaccine constructs, the capacity to deliver a large number of neoepitopes simultaneously, and the potent CD8+ stimulatory capacity, this advanced DNA vaccine platform represents a likely important new approach for cancer immunotherapy.

Citation Format: Elizabeth K. Duperret, Alfredo Perales-Puchalt, Regina Stoltz, G.H. Hiranjith, Nitin Mandloi, James Barlow, Amitabha Chaudhuri, Niranjan Y. Sardesai, David B. Weiner. Synthetic DNA multi-neoantigen vaccine drives predominately MHC class I CD8+ T cell-mediated effector immunity impacting tumor challenge [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology and Immunotherapy; 2018 Nov 27-30; Miami Beach, FL. Philadelphia (PA): AACR; Cancer Immunol Res 2020;8(4 Suppl):Abstract nr B67.

Abstract 1547: DNA-encoded bispecific T-cell engagers and antibodies present long-term antitumor activity

Specific antibody therapy, including monoclonal antibodies and bispecific T cell engagers (BiTEs), are important new tools for cancer immunotherapy. However, these approaches are slow to develop and may be limited in their production thus restricting the patients who can access these treatments. BiTEs exhibit a particularly short half-life and difficult production. The development of an approach allowing simplified development, delivery and in vivo production would be an important advance. Here we describe development of a designed synthetic DNA plasmid, which we optimized to permit high expression of an anti-HER2 antibody (HER2DMAb) and delivered it into animals through adaptive electroporation. HER2DMAb was efficiently expressed in vitro and in vivo, reaching levels of 50ug/ml in mouse sera. Mechanistically, HER2DMAb blocked HER2 signaling and induced antibody-dependent cytotoxicity. HER2DMAb delayed tumor progression for HER2-expressing ovarian and breast cancer models. We next used the HER2DMAb scFv portion to engineer a DNA-encoded BiTE. This HER2DBiTE was expressed in vivo for approximately 4 months after a single administration. The HER2DBiTE was highly cytolytic and delayed cancer progression in mice. These studies illustrate a novel approach to generate DBiTEs in vivo which represent promising immunotherapies for HER2+ tumors including ovarian and potentially other cancers.

Citation Format: Alfredo Perales-Puchalt, Elizabeth K. Duperret, Kar Muthumani, David B. Weiner, Xue Yang, Xizhou Zhu, Krzysztof Wojtak, Edgar Tello-Ruiz, Megan C. Wise. DNA-encoded bispecific T-cell engagers and antibodies present long-term antitumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1547.

Novel Synthetic DNA Immunogens Targeting Latent Expressed Antigens of Epstein-Barr Virus Elicit Potent Cellular Responses and Inhibit Tumor Growth

Infectious diseases are linked to 15%-20% of cancers worldwide. Among them, Epstein-Barr virus (EBV) is an oncogenic herpesvirus that chronically infects over 90% of the adult population, with over 200,000 cases of cancer and 150,000 cancer-related deaths attributed to it yearly. Acute EBV infection can present as infectious mononucleosis, and lead to the future onset of multiple cancers, including Burkitt lymphoma, Hodgkin lymphoma, nasopharyngeal carcinoma, and gastric carcinoma. Many of these cancers express latent viral genes, including Epstein-Barr virus nuclear antigen 1 (EBNA1) and latent membrane proteins 1 and 2 (LMP1 and LMP2). Previous attempts to create potent immunogens against EBV have been reported but generated mixed success. We designed novel Synthetic Consensus (SynCon) DNA vaccines against EBNA1, LMP1 and LMP2 to improve on the immune potency targeting important antigens expressed in latently infected cells. These EBV tumor antigens are hypothesized to be useful targets for potential immunotherapy of EBV-driven cancers. We optimized the genetic sequences for these three antigens, studied them for expression, and examined their immune profiles in vivo. We observed that these immunogens generated unique profiles based on which antigen was delivered as the vaccine target. EBNA1vax and LMP2Avax generated the most robust T cell immunity. Interestingly, LMP1vax was a very weak immunogen, generating very low levels of CD8 T cell immunity both as a standalone vaccine and as part of a trivalent vaccine cocktail. LMP2Avax was able to drive immunity that impacted EBV-antigen-positive tumor growth. These studies suggest that engineered EBV latent protein vaccines deserve additional study as potential agents for immunotherapy of EBV-driven cancers.

Butyrophilin 3A1 is a Dynamic T Cell Regulator in Ovarian Cancer

Ovarian carcinoma microenvironmental T cells exert clinically relevant pressure against malignant progression; however current immunotherapies rarely induce ovarian cancer regression. Here we investigate CD277-containing butyrophilin 3A1 (BTN3A1), a poorly investigated immunoregulatory pathway driven by myeloid and tumor cells in ovarian tumor beds. We show that BTN3A1 is overexpressed in ovarian cancer and is associated with a significant survival disadvantage in these patients (n=200). Concomitantly, ectopic expression of BTN3A1 on APCs inhibits αβ T cell proliferation and Th1 cytokine production. Proteomic analyses and binding assays demonstrate that BTN3A1 interacts with the CD45 phosphatase and elements of the TCR. Consequently, TCR ligation in the presence of BTN3A1 inhibits the segregation of CD45 from the immune synapse and blunts downstream signaling by antagonizing the phosphorylation of CD3Zeta, Lck, and Zap70. We developed fully human αCD277 antibodies which rescue αβ T cell proliferation and Th1 cytokine responses, while driving the infiltration of T cells into tumor beds, delaying ovarian tumor progression in novel BTN3A1+ humanized mice and xenograft studies. Paradoxically, αCD277 antibodies promote the activation of γδ T cells by driving a conformational transformation of BTN3A1. Thus, co-transfer of γδ and Ag-specific αβ T cells in the presence of αCD277 antibodies synergize to further impair malignant progression in vivo. Overall, we show that BTN3A1 drives αβ T cell dysfunction in ovarian cancer, while αCD277 antibodies transform this molecule from immunosuppressive to immunostimulatory by rescuing αβ T cells and activating γδ T cells, thus dynamically unleashing T cell-driven antitumor immunity.

Satb1 deficiency licenses TFH-differentiation

T Follicular Helper cells (TFH) provide both co-stimulation and stimulatory cytokines to B cells to facilitate affinity maturation, class switch recombination, and plasma cell differentiation within the germinal center. However, is not clear how TFH differentiation is regulated. We found that deficiency of the chromatin organizer Satb1 results in increased TFH formation in CD4Cre+Satb1flx/flx mice through up-regulation of the canonical TFH markers ICOS and PD-1 and suppression of Foxp3+PD-1highCXCR5+ T follicular regulatory (TFR) cells as well. Accordingly, CD4Cre+Satb1flx/flx mice, or RAG1−/− mice transferred with Satb1-deficient CD4+ T cells showed a dramatic accumulation of CD4+CXCR5+PD-1high upon ovarian tumor challenge, compared to their Satb1+ counterparts, which was associated with reduced tumor growth. Importantly, intratumoral administration of Satb1-deficient CD4+ T cells re-directed to target ovarian cancer cells through chimeric receptors, but not their Satb1+ counterparts, induce the formation of Tertiary Lymphoid Structures in most tumors.

Conclusion

Satb1 controls three mechanisms relevant for TFH differentiation and, subsequently, antigen-specific humoral responses; namely, PD- 1 expression, ICOS de-repression and TFR formation. Our results suggest a novel role for Satb1 as a major regulator of TFH differentiation and TLS during tumor formation.

DNA-encoded bispecific T cell engagers and antibodies present long-term antitumor activity

Specific antibody therapy, including mAbs and bispecific T cell engagers (BiTEs), are important new tools for cancer immunotherapy. However, these approaches are slow to develop and may be limited in their production, thus restricting the patients who can access these treatments. BiTEs exhibit a particularly short half-life and difficult production. The development of an approach allowing simplified development, delivery, and in vivo production would be an important advance. Here we describe the development of a designed synthetic DNA plasmid, which we optimized to permit high expression of an anti-HER2 antibody (HER2dMAb) and delivered it into animals through adaptive electroporation. HER2dMAb was efficiently expressed in vitro and in vivo, reaching levels of 50 μg/ml in mouse sera. Mechanistically, HER2dMAb blocked HER2 signaling and induced antibody-dependent cytotoxicity. HER2dMAb delayed tumor progression for HER2-expressing ovarian and breast cancer models. We next used the HER2dMAb single-chain variable fragment portion to engineer a DNA-encoded BiTE (DBiTE). This HER2DBiTE was expressed in vivo for approximately 4 months after a single administration. The HER2DBiTE was highly cytolytic and delayed cancer progression in mice. These studies illustrate an approach to generate DBiTEs in vivo, which represent promising immunotherapies for HER2+ tumors, including ovarian and potentially other cancers.

Engineered transfer RNAs for suppression of premature termination codons

Premature termination codons (PTCs) are responsible for 10–15% of all inherited disease. PTC suppression during translation offers a promising approach to treat a variety of genetic disorders, yet small molecules that promote PTC read-through have yielded mixed performance in clinical trials. Here we present a high-throughput, cell-based assay to identify anticodon engineered transfer RNAs (ACE-tRNA) which can effectively suppress in-frame PTCs and faithfully encode their cognate amino acid. In total, we identify ACE-tRNA with a high degree of suppression activity targeting the most common human disease-causing nonsense codons. Genome-wide transcriptome ribosome profiling of cells expressing ACE-tRNA at levels which repair PTC indicate that there are limited interactions with translation termination codons. These ACE-tRNAs display high suppression potency in mammalian cells, Xenopus oocytes and mice in vivo, producing PTC repair in multiple genes, including disease causing mutations within cystic fibrosis transmembrane conductance regulator (CFTR).

Premature termination codon suppression therapy could be used to treat a range of genetic disorders. Here the authors present a high-throughput cell-based assay to identify anticodon engineered tRNAs with high suppression activity.

Engineered DNA Vaccination against Follicle-Stimulating Hormone Receptor Delays Ovarian Cancer Progression in Animal Models

Ovarian cancer presents in 80% of patients as a metastatic disease, which confers it with dismal prognosis despite surgery and chemotherapy. However, it is an immunogenic disease, and the presence of intratumoral T cells is a major prognostic factor for survival. We used a synthetic consensus (SynCon) approach to generate a novel DNA vaccine that breaks immune tolerance to follicle-stimulating hormone receptor (FSHR), present in 50% of ovarian cancers but confined to the ovary in healthy tissues. SynCon FSHR DNA vaccine generated robust CD8⁺ and CD4⁺ cellular immune responses and FSHR-redirected antibodies. The SynCon FSHR DNA vaccine delayed the progression of a highly aggressive ovarian cancer model with peritoneal carcinomatosis in immunocompetent mice, and it increased the infiltration of anti-tumor CD8⁺ T cells in the tumor microenvironment. Anti-tumor activity of this FSHR vaccine was confirmed in a syngeneic murine FSHR-expressing prostate cancer model. Furthermore, adoptive transfer of vaccine-primed CD8⁺ T cells after ex vivo expansion delayed ovarian cancer progression. In conclusion, the SynCon FSHR vaccine was able to break immune tolerance and elicit an effective anti-tumor response associated with an increase in tumor-infiltrating T cells. FSHR DNA vaccination could help current ovarian cancer therapy after first-line treatment of FSHR⁺ tumors to prevent tumor recurrence.

A Synthetic DNA, Multi-Neoantigen Vaccine Drives Predominately MHC Class I CD8+ T-cell Responses, Impacting Tumor Challenge

T-cell recognition of cancer neoantigens is important for effective immune-checkpoint blockade therapy, and an increasing interest exists in developing personalized tumor neoantigen vaccines. Previous studies utilizing RNA and long-peptide neoantigen vaccines in preclinical and early-phase clinical studies have shown immune responses predominantly driven by MHC class II CD4⁺ T cells. Here, we report on a preclinical study utilizing a DNA vaccine platform to target tumor neoantigens. We showed that optimized strings of tumor neoantigens, when delivered by potent electroporation-mediated DNA delivery, were immunogenic and generated predominantly MHC class I-restricted, CD8⁺ T-cell responses. High MHC class I affinity was associated specifically with immunogenic CD8⁺ T-cell epitopes. These DNA neoantigen vaccines induced a therapeutic antitumor response in vivo, and neoantigen-specific T cells expanded from immunized mice directly killed tumor cells ex vivo These data illustrate a unique advantage of this DNA platform to drive CD8⁺ T-cell immunity for neoantigen immunotherapy.

Simplifying checkpoint inhibitor delivery through in vivo generation of synthetic DNA-encoded monoclonal antibodies (DMAbs)

Checkpoint inhibitors (CPI) have revolutionized the treatment of many solid tumors. However, difficulties in production, stability, the requirement of frequent high doses for antibody administration and long intravenous administration are recurring issues. Synthetically designed DNA-encoded monoclonal antibodies (DMAbs) are a novel delivery method for antibody therapy which could potentially address many of these issues, simplifying design and implementation of MAb-based therapies. DMAbs delivered through plasmid DNA injection and electroporation have been used in preclinical models for the treatment or prophylaxis of infectious diseases, cancer and cardiovascular disease. Our group has recently reported that immune checkpoint blockers can be optimized and delivered in vivo advancing further DMAb technology by optimization, expression and in vivo functional characterization of anti-CTLA4 antibodies. Here we report optimization, expression and binding of DMAbs based on anti-PD1 CPI and discuss the potential of DMAbs in checkpoint immunotherapy.

Maternal telomere length is shorter in intrauterine growth restriction versus uncomplicated pregnancies, but not in the offspring or in IVF-conceived newborns

RESEARCH QUESTION

The study aimed to determine whether IVF or intrauterine growth restriction (IUGR) result in short neonatal telomeres, which could explain the higher risk of cardiovascular and metabolic disease described in these populations.

DESIGN

This was an observational, analytical, cross-sectional, prospective study with controls in a tertiary hospital. The main outcome was to determine the leukocyte telomere length in 126 newborns and their mothers (n = 109). Newborns were conceived spontaneously or by IVF, and uncomplicated and IUGR pregnancies were studied. Telomere lengths were measured using high-throughput telomere quantitative fluorescent in-situ hybridization.

RESULTS

There was no difference in average telomere length between newborns conceived by IVF or those with IUGR and spontaneously conceived healthy newborns (P = 0.466 and P = 0.732, respectively); this remained after controlling for confounders (P = 0.218 and P = 0.991, respectively). Mothers of newborns with IUGR had a shorter average telomere length than women with uncomplicated pregnancies (P = 0.023), which was confirmed after controlling for age, body mass index and smoking habit (P = 0.034).

CONCLUSIONS

The results support the safety of IVF and IUGR in terms of the postnatal health of the newborns. The shorter telomeres of IUGR mothers may represent a higher cardiovascular risk, which would have clinical implications under the stress of pregnancy in otherwise healthy adults.

A Designer Cross-reactive DNA Immunotherapeutic Vaccine that Targets Multiple MAGE-A Family Members Simultaneously for Cancer Therapy

PURPOSE

Cancer/testis antigens have emerged as attractive targets for cancer immunotherapy. Clinical studies have targeted MAGE-A3, a prototype antigen that is a member of the MAGE-A family of antigens, in melanoma and lung carcinoma. However, these studies have not yet had a significant impact due to poor CD8⁺ T-cell immunogenicity, platform toxicity, or perhaps limited target antigen availability. In this study, we develop an improved MAGE-A immunogen with cross-reactivity to multiple family members.

EXPERIMENTAL DESIGN

In this study, we analyzed MAGE-A expression in The Cancer Genome Atlas and observed that many patients express multiple MAGE-A isoforms, not limited to MAGE-A3, simultaneously in diverse tumors. On the basis of this, we designed an optimized consensus MAGE-A DNA vaccine capable of cross-reacting with many MAGE-A isoforms, and tested immunogenicity and antitumor activity of this vaccine in a relevant autochthonous melanoma model.

RESULTS

Immunization of this MAGE-A vaccine by electroporation in C57Bl/6 mice generated robust IFNγ and TNFα CD8⁺ T-cell responses as well as cytotoxic CD107a/IFNγ/T-bet triple-positive responses against multiple isoforms. Furthermore, this MAGE-A DNA immunogen generated a cross-reactive immune response in 14 of 15 genetically diverse, outbred mice. We tested the antitumor activity of this MAGE-A DNA vaccine in Tyr::CreER;BRAF^Ca/+;Pten^lox/lox transgenic mice that develop melanoma upon tamoxifen induction. The MAGE-A DNA therapeutic vaccine significantly slowed tumor growth and doubled median mouse survival.

CONCLUSIONS

These results support the clinical use of consensus MAGE-A immunogens with the capacity to target multiple MAGE-A family members to prevent tumor immune escape.

Synthetic DNA-Encoded Monoclonal Antibody Delivery of Anti-CTLA-4 Antibodies Induces Tumor Shrinkage In Vivo

Antibody-based immune therapies targeting the T-cell checkpoint molecules CTLA-4 and PD-1 have affected cancer therapy. However, this immune therapy requires complex manufacturing and frequent dosing, limiting the global use of this treatment. Here, we focused on the development of a DNA-encoded monoclonal antibody (DMAb) approach for delivery of anti-CTLA-4 monoclonal antibodies in vivo With this technology, engineered and formulated DMAb plasmids encoding IgG inserts were directly injected into muscle and delivered intracellularly by electroporation, leading to in vivo expression and secretion of the encoded IgG. DMAb expression from a single dose can continue for several months without the need for repeated administration. Delivery of an optimized DMAb encoding anti-mouse CTLA-4 IgG resulted in high serum levels of the antibody as well as tumor regression in Sa1N and CT26 tumor models. DNA-delivery of the anti-human CTLA-4 antibodies ipilimumab and tremelimumab in mice achieved potent peak levels of approximately 85 and 58 μg/mL, respectively. These DMAb exhibited prolonged expression, with maintenance of serum levels at or above 15 μg/mL for over a year. Anti-human CTLA-4 DMAbs produced in vivo bound to human CTLA-4 protein expressed on stimulated human peripheral blood mononuclear cells and induced T-cell activation in a functional assay ex vivo In summary, direct in vivo expression of DMAb encoding checkpoint inhibitors serves as a novel tool for immunotherapy that could significantly improve availability and provide broader access to such therapies.Significance: DNA-encoded monoclonal antibodies represent a novel technology for delivery and expression of immune checkpoint blockade antibodies, thus expanding patient access to, and possible clinical applications of, these therapies. Cancer Res; 78(22); 6363-70. ©2018 AACR.

IL-33 delays metastatic peritoneal cancer progression inducing an allergic microenvironment

Ovarian cancer is frequently diagnosed as peritoneal carcinomatosis. Unlike other tumor locations, the peritoneal cavity is commonly exposed to gut-breaching and ascending genital microorganisms and has a unique immune environment. IL-33 is a local cytokine that can activate innate and adaptive immunity. We studied the effectiveness of local IL-33 delivery in the treatment of cancer that has metastasized to the peritoneal cavity. Direct peritoneal administration of IL-33 delayed the progression of metastatic peritoneal cancer. Prolongation in survival was not associated with a direct effect of IL-33 on tumor cells, but with major changes in the immune microenvironment of the tumor. IL-33 promoted a significant increase in the leukocyte compartment of the tumor immunoenvironment and an allergic cytokine profile. We observed a substantial increase in the number of activated CD4⁺ T-cells accompanied by peritoneal eosinophil infiltration, B-cell activation and activation of peritoneal macrophages which displayed tumoricidal capacity. Depletion of CD4⁺ cells, eosinophils or macrophages reduced the anti-tumor effects of IL-33 but none of these alone were sufficient to completely abrogate its positive benefit. In conclusion, local administration of IL-33 generates an allergic tumor environment resulting in a novel approach for treatment of metastatic peritoneal malignancies, such as advanced ovarian cancer.

Synthetic DNA delivery by electroporation promotes robust in vivo sulfation of broadly neutralizing anti-HIV immunoadhesin eCD4-Ig

BACKGROUND

Despite vigorous and ongoing efforts, active immunizations have yet to induce broadly neutralizing antibodies (bNAbs) against HIV-1. An alternative approach is to achieve prophylaxis with long-term expression of potent biologic HIV-1 inhibitors with Adeno-associated Virus (AAV), which could however be limited by hosts' humoral and cellular responses. An approach that facilitates in vivo production of these complex molecules independent of viral-vectored delivery will be a major advantage.

METHODS

We used synthetic DNA and electroporation (DNA/EP) to deliver an anti-HIV-1 immunoadhesin eCD4-Ig in vivo. In addition, we engineered a TPST2 enzyme variant (IgE-TPST2), characterized its intracellular trafficking patterns and determined its ability to post-translationally sulfate eCD4-Ig in vivo.

FINDINGS

With a single round of DNA injection, a peak expression level of 80-100μg/mL was observed in mice 14 days post injection (d.p.i). The engineered IgE-TPST2 enzyme trafficked efficiently to the Trans-Golgi Network (TGN). Co-administrating low dose of plasmid IgE-TPST2 with plasmid eCD4-Ig enhanced the potency of eCD4-Ig by three-fold in the ex vivo neutralization assay against the global panel of HIV-1 pseudoviruses.

INTERPRETATION

This work provides a proof-of-concept for delivering anti-HIV-1 immunoadhesins by advanced nucleic acid technology and modulating protein functions in vivo with targeted enzyme-mediated post-translational modifications.

FUNDING

This work is supported by NIH IPCAVD Grant U19 Al109646-04, Martin Delaney Collaboration for HIV Cure Research and W.W. Smith Charitable Trust.

Abstract SY01-02: Blockade of estrogen signaling boosts antitumor immunity by dwindling cancer-promoting myelopoiesis

Although the role of estrogen signaling in the progression of breast tumors and a subset of ovarian cancer patients has been underscored by the clinical use of ER antagonists, how estrogens impact the orchestration and maintenance of protective antitumor immunity remains elusive. Here we show that estrogen signaling accelerates the progression of different estrogen-insensitive tumor models by contributing to tumor-promoting, expanded myelopoiesis. This results in increased mobilization of myeloid-derived suppressor cells (MDSCs) and also the augmentation of their intrinsic immunosuppressive activity on a per cell basis, in vivo in the bone marrow of tumor-bearing hosts. Accordingly, estrogens had a profound effect on T cell-dependent antitumor immunity and tumor-promoting inflammation, independently of the sensitivity of tumor cells to estrogen signaling. Differences in tumor growth in the presence of estrogen-insensitive tumor cells are dependent on blunted antitumor immunity and, correspondingly, disappear in immunodeficient hosts and also upon MDSC depletion. Mechanistically, estrogen receptor alpha activates the STAT3 pathway in human and mouse bone marrow myeloid precursors by enhancing JAK2 and SRC activity. Consequently, fulvestrant had significant effects in delaying the progression of estrogen-insensitive tumors, providing a rationale for blocking estrogen signals to boost the effectiveness of anticancer immunotherapies, which is currently being tested at our institution in breast cancer patients. Our data therefore provide novel mechanistic insight into how enhanced estrogenic activity contributes to malignant progression in established tumors by driving pathologic, tumor-promoting myelopoiesis. Our work suggests that new antiestrogen drugs that have no agonistic effects (different from tamoxifen) could have benefits to boost protective immunity in a wide range of cancers, while augmented estrogenic activity could contribute to tumor initiation and/or malignant progression.

Citation Format: Nikolaos Svoronos, Alfredo Perales-Puchalt, Jose R. Conejo-Garcia. Blockade of estrogen signaling boosts antitumor immunity by dwindling cancer-promoting myelopoiesis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr SY01-02.

Frontline Science: Microbiota reconstitution restores intestinal integrity after cisplatin therapy

Due to their cytotoxic activities, many anticancer drugs cause extensive damage to the intestinal mucosa and have antibiotic activities. Here, we show that cisplatin induces significant changes in the repertoire of intestinal commensal bacteria that exacerbate mucosal damage. Restoration of the microbiota through fecal-pellet gavage drives healing of cisplatin-induced intestinal damage. Bacterial translocation to the blood stream is correspondingly abrogated, resulting in a significant reduction in systemic inflammation, as evidenced by decreased serum IL-6 and reduced mobilization of granulocytes. Mechanistically, reversal of dysbiosis in response to fecal gavage results in the production of protective mucins and mobilization of CD11b+ myeloid cells to the intestinal mucosa, which promotes angiogenesis. Administration of Ruminococcus gnavus, a bacterial strain selectively depleted by cisplatin treatment, could only partially restore the integrity of the intestinal mucosa and reduce systemic inflammation, without measurable increases in the accumulation of mucin proteins. Together, our results indicate that reconstitution of the full repertoire of intestinal bacteria altered by cisplatin treatment accelerates healing of the intestinal epithelium and ameliorates systemic inflammation. Therefore, fecal microbiota transplant could paradoxically prevent life-threatening bacteremia in cancer patients treated with chemotherapy.

Alteration of the Tumor Stroma Using a Consensus DNA Vaccine Targeting Fibroblast Activation Protein (FAP) Synergizes with Antitumor Vaccine Therapy in Mice

Purpose: Fibroblast activation protein (FAP) is overexpressed in cancer-associated fibroblasts and is an interesting target for cancer immune therapy, with prior studies indicating a potential to affect the tumor stroma. Our aim was to extend this earlier work through the development of a novel FAP immunogen with improved capacity to break tolerance for use in combination with tumor antigen vaccines.Experimental Design: We used a synthetic consensus (SynCon) sequence approach to provide MHC class II help to support breaking of tolerance. We evaluated immune responses and antitumor activity of this novel FAP vaccine in preclinical studies, and correlated these findings to patient data.Results: This SynCon FAP DNA vaccine was capable of breaking tolerance and inducing both CD8⁺ and CD4⁺ immune responses. In genetically diverse, outbred mice, the SynCon FAP DNA vaccine was superior at breaking tolerance compared with a native mouse FAP immunogen. In several tumor models, the SynCon FAP DNA vaccine synergized with other tumor antigen-specific DNA vaccines to enhance antitumor immunity. Evaluation of the tumor microenvironment showed increased CD8⁺ T-cell infiltration and a decreased macrophage infiltration driven by FAP immunization. We extended this to patient data from The Cancer Genome Atlas, where we find high FAP expression correlates with high macrophage and low CD8⁺ T-cell infiltration.Conclusions: These results suggest that immune therapy targeting tumor antigens in combination with a microconsensus FAP vaccine provides two-fisted punch-inducing responses that target both the tumor microenvironment and tumor cells directly. Clin Cancer Res; 24(5); 1190-201. ©2018 AACR.

SATB1 Expression Governs Epigenetic Repression of PD-1 in Tumor-Reactive T Cells

Despite the importance of programmed cell death-1 (PD-1) in inhibiting T cell effector activity, the mechanisms regulating its expression remain poorly defined. We found that the chromatin organizer special AT-rich sequence-binding protein-1 (Satb1) restrains PD-1 expression induced upon T cell activation by recruiting a nucleosome remodeling deacetylase (NuRD) complex to Pdcd1 regulatory regions. Satb1 deficienct T cells exhibited a 40-fold increase in PD-1 expression. Tumor-derived transforming growth factor β (Tgf-β) decreased Satb1 expression through binding of Smad proteins to the Satb1 promoter. Smad proteins also competed with the Satb1-NuRD complex for binding to Pdcd1 enhancers, releasing Pdcd1 expression from Satb1-mediated repression, Satb1-deficient tumor-reactive T cells lost effector activity more rapidly than wild-type lymphocytes at tumor beds expressing PD-1 ligand (CD274), and these differences were abrogated by sustained CD274 blockade. Our findings suggest that Satb1 functions to prevent premature T cell exhaustion by regulating Pdcd1 expression upon T cell activation. Dysregulation of this pathway in tumor-infiltrating T cells results in diminished anti-tumor immunity.

Trametinib Drives T-cell-Dependent Control of KRAS-Mutated Tumors by Inhibiting Pathological Myelopoiesis

Targeted therapies elicit seemingly paradoxical and poorly understood effects on tumor immunity. Here, we show that the MEK inhibitor trametinib abrogates cytokine-driven expansion of monocytic myeloid-derived suppressor cells (mMDSC) from human or mouse myeloid progenitors. MEK inhibition also reduced the production of the mMDSC chemotactic factor osteopontin by tumor cells. Together, these effects reduced mMDSC accumulation in tumor-bearing hosts, limiting the outgrowth of KRas-driven breast tumors, even though trametinib largely failed to directly inhibit tumor cell proliferation. Accordingly, trametinib impeded tumor progression in vivo through a mechanism requiring CD8⁺ T cells, which was paradoxical given the drug's reported ability to inhibit effector lymphocytes. Confirming our observations, adoptive transfer of tumor-derived mMDSC reversed the ability of trametinib to control tumor growth. Overall, our work showed how the effects of trametinib on immune cells could partly explain its effectiveness, distinct from its activity on tumor cells themselves. More broadly, by providing a more incisive view into how MEK inhibitors may act against tumors, our findings expand their potential uses to generally block mMDSC expansion, which occurs widely in cancers to drive their growth and progression. Cancer Res; 76(21); 6253-65. ©2016 AACR.

The chromatin organizer SATB1 governs the epigenetic repression of the co-inhibitory receptor PD-1 in T cells

Despite the importance of Programmed Cell Death-1 (PDCD1/PD-1) in inhibiting T-cell effector activity, the mechanisms regulating its expression in anti-tumor lymphocytes remain poorly defined. Here we show that the chromatin organizer Special AT-rich Sequence-Binding Protein-1 (Satb1) is required to restrain activation-induced PD-1 expression. We demonstrate that, mechanistically, Satb1 physically interacts with a nucleosome remodeling deacetylase (NuRD) complex, which it recruits to Pdcd1 regulatory regions. This molecular complex thus drives histone de-acetylation and results in PD-1 repression in T cells. Accordingly, T-cell-specific Satb1 deficiency results in a 40-fold increase in PD-1 expression. Intriguingly, tumor-derived Transforming growth factor (Tgf)-β decreases Satb1 expression in T cells through binding of Smad Family Member (Smad) proteins to the Satb1 promoter, while Smad also competes with Satb1/NuRD for binding to Pdcd1 enhancers, cooperatively unleashing PD-1 expression in a Satb1-dependent manner. Consequently, Satb1-deficient tumor-reactive T cells lose their effector activity more rapidly than wild-type T cells at PD-L1+ tumor beds, but these differences are abrogated by sustained PD-L1 blockade. Therefore, we demonstrate that Satb1 is an epigenetic controller of PD-1 expression, and that Tgf-β signaling contributes to T cell dysfunction within the tumor microenvironment by inhibiting Satb1-mediated repression of PD-1.

Tumor Cell-Independent Estrogen Signaling Drives Disease Progression through Mobilization of Myeloid-Derived Suppressor Cells

The role of estrogens in antitumor immunity remains poorly understood. Here, we show that estrogen signaling accelerates the progression of different estrogen-insensitive tumor models by contributing to deregulated myelopoiesis by both driving the mobilization of myeloid-derived suppressor cells (MDSC) and enhancing their intrinsic immunosuppressive activity in vivo Differences in tumor growth are dependent on blunted antitumor immunity and, correspondingly, disappear in immunodeficient hosts and upon MDSC depletion. Mechanistically, estrogen receptor alpha activates the STAT3 pathway in human and mouse bone marrow myeloid precursors by enhancing JAK2 and SRC activity. Therefore, estrogen signaling is a crucial mechanism underlying pathologic myelopoiesis in cancer. Our work suggests that new antiestrogen drugs that have no agonistic effects may have benefits in a wide range of cancers, independently of the expression of estrogen receptors in tumor cells, and may synergize with immunotherapies to significantly extend survival.

SIGNIFICANCE

Ablating estrogenic activity delays malignant progression independently of the tumor cell responsiveness, owing to a decrease in the mobilization and immunosuppressive activity of MDSCs, which boosts T-cell-dependent antitumor immunity. Our results provide a mechanistic rationale to block estrogen signaling with newer antagonists to boost the effectiveness of anticancer immunotherapies. Cancer Discov; 7(1); 72-85. ©2016 AACR.See related commentary by Welte et al., p. 17This article is highlighted in the In This Issue feature, p. 1.

Follicle-Stimulating Hormone Receptor Is Expressed by Most Ovarian Cancer Subtypes and Is a Safe and Effective Immunotherapeutic Target

PURPOSE

To define the safety and effectiveness of T cells redirected against follicle-stimulating hormone receptor (FSHR)-expressing ovarian cancer cells.

EXPERIMENTAL DESIGN

FSHR expression was determined by Western blotting, immunohistochemistry, and qPCR in 77 human ovarian cancer specimens from 6 different histologic subtypes and 20 human healthy tissues. The effectiveness of human T cells targeted with full-length FSH in vivo was determined against a panel of patient-derived xenografts. Safety and effectiveness were confirmed in immunocompetent tumor-bearing mice, using constructs targeting murine FSHR and syngeneic T cells.

RESULTS

FSHR is expressed in gynecologic malignancies of different histologic types but not in nonovarian healthy tissues. Accordingly, T cells expressing full-length FSHR-redirected chimeric receptors mediate significant therapeutic effects (including tumor rejection) against a panel of patient-derived tumors in vivo In immunocompetent mice growing syngeneic, orthotopic, and aggressive ovarian tumors, fully murine FSHR-targeted T cells also increased survival without any measurable toxicity. Notably, chimeric receptors enhanced the ability of endogenous tumor-reactive T cells to abrogate malignant progression upon adoptive transfer into naïve recipients subsequently challenged with the same tumor. Interestingly, FSHR-targeted T cells persisted as memory lymphocytes without noticeable PD-1-dependent exhaustion during end-stage disease, in the absence of tumor cell immunoediting. However, exosomes in advanced tumor ascites diverted the effector activity of this and other chimeric receptor-transduced T cells away from targeted tumor cells.

CONCLUSIONS

T cells redirected against FSHR⁺ tumor cells with full-length FSH represent a promising therapeutic alternative against a broad range of ovarian malignancies, with negligible toxicity even in the presence of cognate targets in tumor-free ovaries. Clin Cancer Res; 23(2); 441-53. ©2016 AACR.

Good prognosis of cerclage in cases of cervical insufficiency when intra-amniotic inflammation/infection is ruled out

OBJECTIVE

To determine if absence of sub-clinical intra-amniotic inflammation improves the prognosis of rescue cerclage in cases of bulging membranes.

METHODS

Cohort study with all women with bulging membranes admitted into our hospital between 2009 and 2013. Patients underwent amniocentesis to quantify amniotic glucose, leukocytes, IL-6 and leukocyte esterase levels and for microbiological culture. All patients without intra-amniotic inflammation or sub-clinical chorioamnionitis were proposed a physical examination-indicated cervical cerclage. Those who did not accept were treated with bed rest.

RESULTS

We enrolled 31 women. Median gestational age at diagnosis was 23 + 1 (21–25 + 4) weeks. Median interval until delivery was 12 (3–52.5) d. IL-6 had the highest diagnostic accuracy for good prognosis. Patients with IL6 <2.90 ng/ml were diagnosed later in pregnancy and presented a longer interval until delivery (89 versus 4 d), higher gestational age at delivery (35 + 1 versus 23 + 3 weeks) and a lower rate of prematurity (54.5% versus 100%) and perinatal mortality (0% versus 80%) than those with IL-6 ≥2.90 ng/ml. Rescue cerclage and low Il-6 were the best predictors of good outcome.

CONCLUSION

IL-6 levels in amniotic fluid may be of clinical value for individualizing the management of patients with bulging membranes for placement of rescue cerclage.

MEK inhibition by trametinib impairs the mobilization of monocytic MDSCs to facilitate anti-tumor T cell immunity

The MEK inhibitor trametinib is approved for clinical use in melanoma and being investigated in many other solid tumors, yet the effects of trametinib on non-tumor cells in the cancer microenvironment remain understudied. Although MEK inhibition potently suppresses T cells in vitro, cytotoxic T cell activity is unaffected in trametinib-treated mice. In a preclinical Kras-driven breast cancer model we found that the anti-tumor activity of trametinib requires CD8+ T cells and occurs even in the absence of direct inhibition of tumor cell proliferation. Instead, trametinib selectively impairs the mobilization of Ly6C+ Myeloid-Derived Suppressor Cells (MDSCs) from myeloid precursors and also abrogates the production of MDSC-chemotactic osteopontin by tumor cells. These combined effects reduce MDSC accumulation at tumor beds, enhancing T cell-mediated protection. Our results demonstrate that the combined anti-inflammatory activity of trametinib on multiple cell types, even without direct influence on tumor cell proliferation, could be responsible for its anti-tumor effects.

IL15 Agonists Overcome the Immunosuppressive Effects of MEK Inhibitors

Many signal transduction inhibitors are being developed for cancer therapy target pathways that are also important for the proper function of antitumor lymphocytes, possibly weakening their therapeutic effects. Here we show that most inhibitors targeting multiple signaling pathways have especially strong negative effects on T-cell activation at their active doses on cancer cells. In particular, we found that recently approved MEK inhibitors displayed potent suppressive effects on T cells in vitro However, these effects could be attenuated by certain cytokines that can be administered to cancer patients. Among them, clinically available IL15 superagonists, which can activate PI3K selectively in T lymphocytes, synergized with MEK inhibitors in vivo to elicit potent and durable antitumor responses, including by a vaccine-like effect that generated resistance to tumor rechallenge. Our work identifies a clinically actionable approach to overcome the T-cell-suppressive effects of MEK inhibitors and illustrates how to reconcile the deficiencies of signal transduction inhibitors, which impede desired immunologic effects in vivo Cancer Res; 76(9); 2561-72. ©2016 AACR.

Risk factors for vertical transmission of hepatitis C virus: a single center experience with 710 HCV-infected mothers

OBJECTIVE

The aim of this study was to analyze the risk factors on the perinatal transmission of hepatitis C virus (HCV).

STUDY DESIGN

A retrospective cohort study with 711 infants born to 710 HCV-infected mothers was conducted at the Hospital La Fe, in Valencia, Spain, from 1986 to 2011. As potential risk factors for transmission we analyzed: maternal age, mode of acquisition of HCV infection, HIV co-infection, antiretroviral treatment against HIV, CD4 cell count, HIV and HCV viral load, liver enzyme levels during pregnancy, smoking habit, gestational age, intrapartum invasive procedures, length of rupture of membranes, length of labor, mode of delivery, episiotomy, birth weight, newborn gender and type of feeding.

RESULTS

Overall perinatal HCV transmission rate was 2.4%. The significant risk factors related with HCV transmission were maternal virus load >615copies/mL (OR 9.3 [95% CI 1.11-78.72]), intrapartum invasive procedures (OR 10.1 [95% CI 2.6-39.02]) and episiotomy (OR 4.2 [95% CI 1.2-14.16]). HIV co-infection and newborn female were near significance (p=0.081 and 0.075, respectively).

CONCLUSIONS

Invasive procedures as fetal scalp blood sampling or internal electrode and episiotomy increase vertical transmission of HCV, especially in patients with positive HCV RNA virus load at delivery.

ER Stress Sensor XBP1 Controls Anti-tumor Immunity by Disrupting Dendritic Cell Homeostasis

Dendritic cells (DCs) are required to initiate and sustain T cell-dependent anti-cancer immunity. However, tumors often evade immune control by crippling normal DC function. The endoplasmic reticulum (ER) stress response factor XBP1 promotes intrinsic tumor growth directly, but whether it also regulates the host anti-tumor immune response is not known. Here we show that constitutive activation of XBP1 in tumor-associated DCs (tDCs) drives ovarian cancer (OvCa) progression by blunting anti-tumor immunity. XBP1 activation, fueled by lipid peroxidation byproducts, induced a triglyceride biosynthetic program in tDCs leading to abnormal lipid accumulation and subsequent inhibition of tDC capacity to support anti-tumor T cells. Accordingly, DC-specific XBP1 deletion or selective nanoparticle-mediated XBP1 silencing in tDCs restored their immunostimulatory activity in situ and extended survival by evoking protective type 1 anti-tumor responses. Targeting the ER stress response should concomitantly inhibit tumor growth and enhance anti-cancer immunity, thus offering a unique approach to cancer immunotherapy.

The Tumor Macroenvironment: Cancer-Promoting Networks Beyond Tumor Beds

During tumor progression, alterations within the systemic tumor environment, or macroenvironment, result in the promotion of tumor growth, tumor invasion to distal organs, and eventual metastatic disease. Distally produced hormones, commensal microbiota residing within mucosal surfaces, myeloid cells and even the bone marrow impact the systemic immune system, tumor growth, and metastatic spread. Understanding the reciprocal interactions between the cells and soluble factors within the macroenvironment and the primary tumor will enable the design of specific therapies that have the potential to prevent dissemination and metastatic spread. This chapter will summarize recent findings detailing how the primary tumor and systemic tumor macroenvironment coordinate malignant progression.

Microbially driven TLR5-dependent signaling governs distal malignant progression through tumor-promoting inflammation

The dominant TLR5(R392X) polymorphism abrogates flagellin responses in >7% of humans. We report that TLR5-dependent commensal bacteria drive malignant progression at extramucosal locations by increasing systemic IL-6, which drives mobilization of myeloid-derived suppressor cells (MDSCs). Mechanistically, expanded granulocytic MDSCs cause γδ lymphocytes in TLR5-responsive tumors to secrete galectin-1, dampening antitumor immunity and accelerating malignant progression. In contrast, IL-17 is consistently upregulated in TLR5-unresponsive tumor-bearing mice but only accelerates malignant progression in IL-6-unresponsive tumors. Importantly, depletion of commensal bacteria abrogates TLR5-dependent differences in tumor growth. Contrasting differences in inflammatory cytokines and malignant evolution are recapitulated in TLR5-responsive/unresponsive ovarian and breast cancer patients. Therefore, inflammation, antitumor immunity, and the clinical outcome of cancer patients are influenced by a common TLR5 polymorphism.

Transforming growth factor β-mediated suppression of antitumor T cells requires FoxP1 transcription factor expression

Tumor-reactive T cells become unresponsive in advanced tumors. Here we have characterized a common mechanism of T cell unresponsiveness in cancer driven by the upregulation of the transcription factor Forkhead box protein P1 (Foxp1), which prevents CD8⁺ T cells from proliferating and upregulating Granzyme-B and interferon-γ in response to tumor antigens. Accordingly, Foxp1-deficient lymphocytes induced rejection of incurable tumors and promoted protection against tumor rechallenge. Mechanistically, Foxp1 interacted with the transcription factors Smad2 and Smad3 in preactivated CD8⁺ T cells in response to microenvironmental transforming growth factor-β (TGF-β), and was essential for its suppressive activity. Therefore, Smad2 and Smad3-mediated c-Myc repression requires Foxp1 expression in T cells. Furthermore, Foxp1 directly mediated TGF-β-induced c-Jun transcriptional repression, which abrogated T cell activity. Our results unveil a fundamental mechanism of T cell unresponsiveness different from anergy or exhaustion, driven by TGF-β signaling on tumor-associated lymphocytes undergoing Foxp1-dependent transcriptional regulation.

Transforming growth factor β-mediated suppression of antitumor T cells requires FoxP1 transcription factor expression

Tumor-reactive T cells become unresponsive in advanced tumors. Here we have characterized a common mechanism of T cell unresponsiveness in cancer driven by the upregulation of the transcription factor Forkhead box protein P1 (Foxp1), which prevents CD8⁺ T cells from proliferating and upregulating Granzyme-B and interferon-γ in response to tumor antigens. Accordingly, Foxp1-deficient lymphocytes induced rejection of incurable tumors and promoted protection against tumor rechallenge. Mechanistically, Foxp1 interacted with the transcription factors Smad2 and Smad3 in preactivated CD8⁺ T cells in response to microenvironmental transforming growth factor-β (TGF-β), and was essential for its suppressive activity. Therefore, Smad2 and Smad3-mediated c-Myc repression requires Foxp1 expression in T cells. Furthermore, Foxp1 directly mediated TGF-β-induced c-Jun transcriptional repression, which abrogated T cell activity. Our results unveil a fundamental mechanism of T cell unresponsiveness different from anergy or exhaustion, driven by TGF-β signaling on tumor-associated lymphocytes undergoing Foxp1-dependent transcriptional regulation.