Stephen J. Blake

Suppression of Metastases Using a New Lymphocyte Checkpoint Target for Cancer Immunotherapy

UNLABELLED CD96 has recently been shown as a negative regulator of mouse natural killer (NK)-cell activity, with Cd96(-/-)mice displaying hyperresponsive NK cells upon immune challenge. In this study, we have demonstrated that blocking CD96 with a monoclonal antibody inhibited experimental metastases in three different tumor models. The antimetastatic activity of anti-CD96 was dependent on NK cells, CD226 (DNAM-1), and IFNγ, but independent of activating Fc receptors. Anti-CD96 was more effective in combination with anti-CTLA-4, anti-PD-1, or doxorubicin chemotherapy. Blocking CD96 in Tigit(-/-)mice significantly reduced experimental and spontaneous metastases compared with its activity in wild-type mice. Co-blockade of CD96 and PD-1 potently inhibited lung metastases, with the combination increasing local NK-cell IFNγ production and infiltration. Overall, these data demonstrate that blocking CD96 is a new and complementary immunotherapeutic strategy to reduce tumor metastases. SIGNIFICANCE This article illustrates the antimetastatic activity and mechanism of action of an anti-CD96 antibody that inhibits the CD96-CD155 interaction and stimulates NK-cell function. Targeting host CD96 is shown to complement surgery and conventional immune checkpoint blockade.

Tumor immunoevasion by the conversion of effector NK cells into type 1 innate lymphoid cells

Avoiding destruction by immune cells is a hallmark of cancer, yet how tumors ultimately evade control by natural killer (NK) cells remains incompletely defined. Using global transcriptomic and flow-cytometry analyses and genetically engineered mouse models, we identified the cytokine-TGF-β-signaling-dependent conversion of NK cells (CD49a−CD49b+Eomes+) into intermediate type 1 innate lymphoid cell (intILC1) (CD49a+CD49b+Eomes+) populations and ILC1 (CD49a+CD49b−Eomesint) populations in the tumor microenvironment. Strikingly, intILC1s and ILC1s were unable to control local tumor growth and metastasis, whereas NK cells favored tumor immunosurveillance. Experiments with an antibody that neutralizes the cytokine TNF suggested that escape from the innate immune system was partially mediated by TNF-producing ILC1s. Our findings provide new insight into the plasticity of group 1 ILCs in the tumor microenvironment and suggest that the TGF-β-driven conversion of NK cells into ILC1s is a previously unknown mechanism by which tumors escape surveillance by the innate immune system.

Improved Efficacy of Neoadjuvant Compared to Adjuvant Immunotherapy to Eradicate Metastatic Disease

Immunotherapy has recently entered a renaissance phase with the approval of multiple agents for the treatment of cancer. Immunotherapy stands ready to join traditional modalities, including surgery, chemotherapy, radiation, and hormone therapy, as a pillar of cancer treatment. Although immunotherapy has begun to have success in advanced cancer treatment, its scheduling and efficacy with surgery to treat earlier stages of cancer and prevent distant metastases has not been systematically examined. Here, we have used two models of spontaneously metastatic breast cancers in mice, to illustrate the significantly greater therapeutic power of neoadjuvant, compared with adjuvant immunotherapies in the context of primary tumor resection. Elevated and sustained peripheral tumor-specific immune responses underpinned the outcome, and blood sampling of tumor-specific CD8+ T cells immediately prior and post surgery may provide a predictor of outcome. These data now provide strong rationale to extensively test and compare neoadjuvant immunotherapy in humans.

Molecular Pathways: Targeting CD96 and TIGIT for Cancer Immunotherapy.

The receptors CD96 and TIGIT are expressed on the surface of T and natural killer (NK) cells, and recent studies suggest both play important inhibitory roles in immune function. CD96 has been shown to modulate immune cell activity in mice, with Cd96−/− mice displaying hypersensitive NK-cell responses to immune challenge and significant tumor resistance. TIGIT overexpression has been shown to reduce NK-cell–mediated cytotoxicity. TIGIT is also upregulated on T cells during cancer and chronic viral infection, with expression associated with effector T-cell exhaustion and increased regulatory T-cell suppression. The counterbalance between the putative inhibitory CD96 and TIGIT receptors and the activating receptor, CD226, offers unique strategies for immuno-oncology drug development. Blocking CD96 or TIGIT with mAbs has been shown to improve tumor control in mice, in particular when used in combination with PD-1/PD-L1 blockade. These results have highlighted these pathways as promising new targets for immune modulation. This review will examine the rationale behind targeting CD96 and TIGIT, and discuss the potential approaches in translating these preclinical findings into novel clinical agents. Clin Cancer Res; 22(21); 5183–8. ©2016 AACR.

Improved mouse models to assess tumour immunity and irAEs after combination cancer immunotherapies

The current excitement surrounding cancer immunotherapy stems particularly from clinical data involving agents mediating immune checkpoint receptor blockade, which have induced unprecedented efficacy against a range of tumours compared with previous immunotherapeutic approaches. However, an important consideration in targeting checkpoint receptors has been the emergence of associated toxicities termed immune‐related adverse events (irAEs). In light of the clinical benefits observed after co‐blockade of checkpoint receptors and data from preclinical mouse models, there is now a strong rationale to combine different checkpoint receptors together, with other immunotherapies or more conventional therapies to assess if clinical benefits to cancer patients can be further improved. However, one may predict the frequency and severity of irAEs will increase with combinations, which may result in premature therapy cessation, thus limiting the realization of such an approach. In addition, there is a limit to how many different combination therapies that can be tested in a timely manner given the legal, regulatory and budgetary issues associated with conducting clinical trials. Thus, there is a need to develop preclinical mouse models that more accurately inform us as to which immunotherapies might combine best to provide the optimal therapeutic index (maximal anti‐tumour efficacy and low level irAEs) in different cancer settings. In this review we will discuss the irAEs observed in patients after checkpoint blockade and discuss which mouse models of cancer can be appropriate to assess the development of tumour immunity and irAEs following combination cancer immunotherapies.

Assessing Immune-Related Adverse Events of Efficacious Combination Immunotherapies in Preclinical Models of Cancer

New combination immunotherapies are displaying both efficacy and immune-related adverse events (irAE) in humans. However, grade 3/4 irAEs occur in a high proportion, which can lead to discontinuation of treatment and can result in fatalities if not promptly treated. Prolonged T regulatory cell (Treg) depletion in tumor-bearing Foxp3-DTR mice using diphtheria toxin (DT) mirrored the spectrum of antitumor responses and severity of irAEs that can occur in ipilimumab/nivolumab-treated patients. In contrast, transient Treg depletion or anti-CTLA-4/PD-1 therapy had equivalent effects in mice, lowering the immune tolerance threshold and allowing irAEs to be more easily induced following treatment with additional immunomodulatory antibodies. Transient Treg depletion of DT in combination with anti-PD-1 or anti-TIM-3 monoclonal antibodies had a high therapeutic window compared with DT plus anti-CD137. In contrast, DT plus anti-CD137-treated mice developed severe irAEs similar to grade 3/4 clinical symptoms. These irAEs appeared because of an infiltration of activated proliferating effector T cells in the tissues producing IFNγ and TNF; however, TNF blockade decreased irAEs severity without impacting on tumor growth. Cancer Res; 76(18); 5288-301. ©2016 AACR.

Autophagy-dependent regulatory T cells are critical for the control of graft-versus-host disease

Regulatory T cells (Tregs) play a crucial role in the maintenance of peripheral tolerance. Quantitative and/or qualitative defects in Tregs result in diseases such as autoimmunity, allergy, malignancy, and graft-versus-host disease (GVHD), a serious complication of allogeneic stem cell transplantation (SCT). We recently reported increased expression of autophagy-related genes (Atg) in association with enhanced survival of Tregs after SCT. Autophagy is a self-degradative process for cytosolic components that promotes cell homeostasis and survival. Here, we demonstrate that the disruption of autophagy within FoxP3+ Tregs (B6.Atg7fl/fl-FoxP3cre+ ) resulted in a profound loss of Tregs, particularly within the bone marrow (BM). This resulted in dysregulated effector T cell activation and expansion, and the development of enterocolitis and scleroderma in aged mice. We show that the BM compartment is highly enriched in TIGIT+ Tregs and that this subset is differentially depleted in the absence of autophagy. Moreover, following allogeneic SCT, recipients of grafts from B6.Atg7fl/fl-FoxP3cre+ donors exhibited reduced Treg reconstitution, exacerbated GVHD, and reduced survival compared with recipients of B6.WT-FoxP3cre+ grafts. Collectively, these data indicate that autophagy-dependent Tregs are critical for the maintenance of tolerance after SCT and that the promotion of autophagy represents an attractive immune-restorative therapeutic strategy after allogeneic SCT.

Agonistic CD40 mAb-Driven IL12 Reverses Resistance to Anti-PD1 in a T-cell–Rich Tumor

The durability and efficacy of anti-human PD1 monoclonal antibodies (PD1 mAb) vary across different malignancies. Although an absence of tumor-infiltrating cytotoxic T lymphocytes has been identified as a cause for resistance to PD1 mAb, the presence of intratumor exhausted PD1hi T cells also contributes to insensitivity to this immune checkpoint therapy. In this study, we used mouse tumor models of PD1 mAb resistance that harbored PD1hi T cells and flow cytometry analysis of tumor-infiltrating leukocytes immediately post-therapy as a screening platform to identify agents that could resensitize T cells to PD1 blockade. We showed that an agonistic anti-CD40 mAb converted PD1hi T cells into PD1lo T cells, reversing phenotypic T-cell exhaustion and allowing the anti-PD1 refractory tumors to respond to anti-PD1 therapy. PD1 downmodulation by anti-CD40 mAb relied upon IL12 but not IL23, CD80/CD86/CD28, or CD70/CD27. Consistent with a role for regulatory T cells (Treg) in promoting T-cell exhaustion, we also showed that intratumor Treg presented with a less activated and attenuated suppressive phenotype, marked by reductions in CTLA4 and PD1. Similar to anti-CD40 mAb, anti-CTLA4 mAb also lowered intratumor T-cell PD1 expression. Our study provides a proof-of-principle framework to systematically identify immune conditioning agents able to convert PD1hi T cells to PD1lo T cells, with clinical implications in the management of anti-PD1 refractory patients. Cancer Res; 76(21); 6266-77. ©2016 AACR.

Role of IL-17 and IL-22 in autoimmunity and cancer

The dysregulation of inflammatory cytokines can cause a variety of diseases, such as autoimmunity and cancer. Since their identification in 2005, Th17 cells and its signature cytokine IL-17, have been implicated in the pathogenesis of autoimmune diseases such as psoriasis and rheumatoid arthritis (RA), and inflammatory associated cancers such as colorectal carcinoma (CRC). Recently, IL-22 a Th17 related cytokine has been shown to be pathogenic in psoriasis and RA. In this review, we will summarize the biological functions of IL-17 and IL-22, their role in autoimmune diseases and briefly review results from clinical trials targeting IL-17 or its receptor for the treatment of autoimmune diseases. Next, we will discuss pre-clinical and clinical data supporting the rationale of targeting other cytokines implicated in the Th17/IL-17 pathway, such as IL-22 and IL-23. Finally, we discuss the role of IL-17, and in particularly IL-22 in tumour immunity and possible therapeutic interventions.

Anti-CD137 enhances anti-CD20 therapy of systemic B-cell lymphoma with altered immune homeostasis but negligible toxicity.

ABSTRACT Studies of sequential anti-CD137/anti-CD20 therapy have previously shown that the efficacy of anti-CD20 was heavily reliant upon anti-CD137; however, the exact mechanism of the anti-B-cell lymphoma efficacy, and whether this correlates with enhanced adverse effects or toxicity, had not been elucidated. Here, we observed that sequential anti-CD137 administration with anti-CD20 resulted in a synergistic therapy, largely dependent upon Fc receptors (FcR), to prolong survival in an experimental B-cell lymphoma therapy model. Tumor suppression was accompanied by B cell depletion, which was not dependent on one activating FcR. Surprisingly, the B-cell activating factor (BAFF) was elevated in the plasma of mice receiving anti-CD137 alone or in combination with anti-CD20, while a selective increase in some plasma cytokines was also noted and triggered by anti-CD137. These effects were independent of activating FcR. Sustained treatment of advanced lymphoma revealed increased lymphocyte infiltrates into the liver and a significant decrease in the metabolic capability of the liver in mice receiving anti-CD137. Importantly, these effects were not exacerbated in mice receiving the anti-CD20/CD137 combination, and elevations in classical liver damage markers such as alanine aminotransferase (ALT) were less than that caused by the lymphoma itself. Thus, combined anti-CD20/anti-CD137 treatment increases the therapeutic index of anti-CD20 or anti-CD137 alone. These mouse data were corroborated by ongoing clinical development studies to assess safety, tolerability and pharmacodynamic activity of human patients treated by this approach. Together, these data support the use of this sequential antibody therapeutic strategy to improve the efficacy of rituximab in B-cell lymphoma patients.