Summary Restoration of anti-tumor immunity by blocking PD-L1 signaling using antibodies has proven to be beneficial in cancer therapy. Here we show that BET bromodomain inhibition suppresses PD-L1 expression and limits tumor progression in ovarian cancer. CD274 (encoding PD-L1) is a direct target of BRD4-mediated gene transcription. In mouse models, treatment with the BET inhibitor JQ1 significantly reduced PD-L1 expression on tumor cells and tumor-associated dendritic cells and macrophages, which correlated with an increase in the activity of anti-tumor cytotoxic T cells. The BET inhibitor limited tumor progression in a cytotoxic T cell dependent manner. Together, these data demonstrate a small molecule approach to block PD-L1 signaling. Given the fact that BET inhibitors have been proven safe with manageable reversible toxicity in clinical trials, our findings indicate that pharmacological BET inhibitors represent a treatment strategy for targeting PD-L1 expression.

The dominant TLR5R392X polymorphism abrogates flagellin responses in >7% of humans. We report that TLR5-dependent commensal bacteria drive malignant progression at extra-mucosal 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 anti-tumor immunity and accelerating malignant progression. In contrast, IL-17 is consistently up-regulated 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, anti-tumor immunity and the clinical outcome of cancer patients are influenced by a common TLR5 polymorphism.

We have shown that the aged microenvironment increases melanoma metastasis, and decreases response to targeted therapy, and here we queried response to anti-PD1. We analyzed the relationship between age, response to anti-PD1, and prior therapy in 538 patients. We used mouse models of melanoma, to analyze the intratumoral immune microenvironment in young versus aged mice and confirmed our findings in human melanoma biopsies. Patients over the age of 60 responded more efficiently to anti-PD-1, and likelihood of response to anti-PD-1 increased with age, even when we controlled for prior MAPKi therapy. Placing genetically identical tumors in aged mice (52 weeks) significantly increased their response to anti-PD1 as compared with the same tumors in young mice (8 weeks). These data suggest that this increased response in aged patients occurs even in the absence of a more complex mutational landscape. Next, we found that young mice had a significantly higher population of regulatory T cells (Tregs), skewing the CD8:Treg ratio. FOXP3 staining of human melanoma biopsies revealed similar increases in Tregs in young patients. Depletion of Tregs using anti-CD25 increased the response to anti-PD1 in young mice. While there are obvious limitations to our study, including our inability to conduct a meta-analysis due to a lack of available data, and our inability to control for mutational burden, there is a remarkable consistency in these data from over 500 patients across 8 different institutes worldwide. These results stress the importance of considering age as a factor for immunotherapy response. .

Purpose: Whole tumor lysates are promising antigen sources for dendritic cell (DC) therapy as they contain many relevant immunogenic epitopes to help prevent tumor escape. Two common methods of tumor lysate preparations are freeze-thaw processing and UVB irradiation to induce necrosis and apoptosis, respectively. Hypochlorous acid (HOCl) oxidation is a new method for inducing primary necrosis and enhancing the immunogenicity of tumor cells.Experimental Design: We compared the ability of DCs to engulf three different tumor lysate preparations, produce T-helper 1 (T H 1)-priming cytokines and chemokines, stimulate mixed leukocyte reactions (MLR), and finally elicit T-cell responses capable of controlling tumor growth in vivo.Results: We showed that DCs engulfed HOCl-oxidized lysate most efficiently stimulated robust MLRs, and elicited strong tumor-specific IFN-g secretions in autologous T cells. These DCs produced the highest levels of T H 1-priming cytokines and chemokines, including interleukin (IL)-12. Mice vaccinated with HOCl-oxidized ID8-ova lysate-pulsed DCs developed T-cell responses that effectively controlled tumor growth. Safety, immunogenicity of autologous DCs pulsed with HOCl-oxidized autologous tumor lysate (OCDC vaccine), clinical efficacy, and progression-free survival (PFS) were evaluated in a pilot study of five subjects with recurrent ovarian cancer. OCDC vaccination produced few grade 1 toxicities and elicited potent T-cell responses against known ovarian tumor antigens. Circulating regulatory T cells and serum IL-10 were also reduced. Two subjects experienced durable PFS of 24 months or more after OCDC.Conclusions: This is the first study showing the potential efficacy of a DC vaccine pulsed with HOCloxidized tumor lysate, a novel approach in preparing DC vaccine that is potentially applicable to many cancers.

The role of estrogens in anti-tumor 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 (MDSCs) and enhancing their intrinsic immunosuppressive activity in vivo. Differences in tumor growth are dependent on blunted anti-tumor 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 pathological myelopoiesis in cancer. Our work suggests that new anti-estrogen 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.

Studies on gene therapy for hemophilia B (HB) using adeno-associated viral (AAV) vectors showed that the safety of a given strategy is directly related to the vector dose. To overcome this limitation, we sought to test the efficacy and the risk of immunogenicity of a novel factor IX (FIX) R338L associated with ϳ 8-fold increased specific activity. Muscle-directed expression of canine FIX-R338L by AAV vectors was carried out in HB dogs. Therapeutic levels of circulating canine FIX activity (3.5%-8%) showed 8-to 9-fold increased specific activity, similar to humans with FIX-R338L. IntroductionHemophilia B (HB) is an X-linked bleeding disorder resulting from a deficiency of coagulation factor IX (FIX). Gene therapy is an attractive strategy for the treatment of the disease because continuous maintenance of FIX levels as low as 1%-5% of normal have been shown to substantially ameliorate the bleeding phenotype in both preclinical and clinical models. [1][2][3][4][5][6] Studies using adeno-associated viral (AAV) vectors showed that the safety profile is vector dose-dependent. 3,4 In a liver-directed approach, immune responses to AAV-capsid proteins at the highest dose tested (2 ϫ 10 12 vg/kg) required transient immunosuppression for sustained transgene expression. 3,4 In a study on direct intramuscular AAV-FIX, the safety profile was excellent 2 and the local transgene expression of FIX in the injected muscle persisted for 3.7 and 10 years in 2 human subjects tested. 7,8 However, all doses tested in the intramuscular study resulted in subtherapeutic circulating FIX levels. 2 The use of FIX variants with gain of function offers the opportunity to enhance the efficacy of genebased approaches for HB without increasing the vector doses. In an early study, we demonstrated that replacement of arginine 338 by alanine (R338A) was associated with an ϳ 3-fold increase in the protein specific activity in murine models of HB receiving AAV-FIX-R338A 9 as later confirmed in other models. 10,11 Recently, we described a naturally occurring gain-of-function mutation in humans characterized by leucine at position 338 (R338L), which exhibits normal antigen levels, but an ϳ 8-fold higher specific activity. 12 Notably, the arginine at position 338 in FIX is conserved among mammals, and this region of the enzyme appears to be part of the substrate exosite for factor X. 13 Here we report, for the first time, the use of the homologous FIX-R338L in a large and immunocompetent canine model of severe HB (Ͻ 1% of normal).

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Purpose Define the safety and effectiveness of T-cells re-directed against Follicle-Stimulating Hormone Receptor (FSHR)-expressing ovarian cancer cells. Experimental Design FSHR expression was determined by Western-blot, immunohistochemistry and Q-PCR in 77 human ovarian cancer specimens from 6 different histological 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 histological types, but not in non-ovarian healthy tissues. Accordingly, T-cells expressing full-length FSHR-re-directed 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.