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

The structure, expression, and multifaceted role of immune-checkpoint protein VISTA as a critical regulator of anti-tumor immunity, autoimmunity, and inflammation

Among various immunoregulatory molecules, the B7 family of immune-checkpoint receptors consists of highly valuable targets for cancer immunotherapy. Antibodies targeting two B7 family co-inhibitory receptors, CTLA-4 and PD-1, have elicited long-term clinical outcomes in previously refractory cancer types and are considered a breakthrough in cancer therapy. Despite the success, the relatively low response rate (20-30%) warrants efforts to identify and overcome additional immune-suppressive pathways. Among the expanding list of T cell inhibitory regulators, V domain immunoglobulin suppressor of T cell activation (VISTA) is a unique B7 family checkpoint that regulates a broad spectrum of immune responses. Here, we summarize recent advances that highlight the structure, expression, and multi-faceted immunomodulatory mechanisms of VISTA in the context of autoimmunity, inflammation, and anti-tumor immunity.

PD-1/PD-L1 Blockade: Have We Found the Key to Unleash the Antitumor Immune Response?

PD-1–PD-L1 interaction is known to drive T cell dysfunction, which can be blocked by anti-PD-1/PD-L1 antibodies. However, studies have also shown that the function of the PD-1–PD-L1 axis is affected by the complex immunologic regulation network, and some CD8⁺ T cells can enter an irreversible dysfunctional state that cannot be rescued by PD-1/PD-L1 blockade. In most advanced cancers, except Hodgkin lymphoma (which has high PD-L1/L2 expression) and melanoma (which has high tumor mutational burden), the objective response rate with anti-PD-1/PD-L1 monotherapy is only ~20%, and immune-related toxicities and hyperprogression can occur in a small subset of patients during PD-1/PD-L1 blockade therapy. The lack of efficacy in up to 80% of patients was not necessarily associated with negative PD-1 and PD-L1 expression, suggesting that the roles of PD-1/PD-L1 in immune suppression and the mechanisms of action of antibodies remain to be better defined. In addition, important immune regulatory mechanisms within or outside of the PD-1/PD-L1 network need to be discovered and targeted to increase the response rate and to reduce the toxicities of immune checkpoint blockade therapies. This paper reviews the major functional and clinical studies of PD-1/PD-L1, including those with discrepancies in the pathologic and biomarker role of PD-1 and PD-L1 and the effectiveness of PD-1/PD-L1 blockade. The goal is to improve understanding of the efficacy of PD-1/PD-L1 blockade immunotherapy, as well as enhance the development of therapeutic strategies to overcome the resistance mechanisms and unleash the antitumor immune response to combat cancer.

Modulation of antitumor immunity with histone deacetylase inhibitors

Histone deacetylase inhibitors possess a broad array of antitumor activities; however, their net impact on the evolving antitumor immune response is highly dependent on the inhibitors used and the histone deacetylases they target. Herein, we sequentially focus on each stage of the antitumor immune response - from dendritic cell activation and migration, antigen uptake and presentation, T-cell activation and differentiation and the enactment of antitumor effector functions within the tumor microenvironment. In particular, we will discuss how various inhibitors have different effects depending on cellular activation, experimental design and specific histone deacetylases being targeted - and how these changes impact the outcome of an antitumor immune response. At last, we consider the impact these inhibitors may have on T-cell exhaustion and implications for combination with other immunomodulating therapies.

Satb1: Restraining PD1 and T Cell Exhaustion

Mechanisms that govern PD1 expression and exhaustion in T cells are not fully understood. In this issue of Immunity, Stephen et al. (2017) uncover a key role for the genome organizer Satb1 in restraining PD1 expression and promoting tumor immunity.

PD-1 related transcriptome profile and clinical outcome in diffuse gliomas

Background: PD-1 plays a critical part in control of immune response to malignancy. Anti-PD-1 treatment is a hopeful strategy to improve the dismal prognosis of gliomas. To characterize the role of PD-1 in diffuse gliomas, we investigated its related biological process at transcriptome level and its clinical prognostic value. Method and patients: Through Chinese Glioma Genome Atlas and TCGA datasets, we systematically reviewed a total of 994 cases with RNA-seq data and analyzed the functional annotation of PD-1 by Gene ontology (GO) analysis. Univariate and multivariate survival analysis were performed in 907 patients with survival data. Results: We found PD-1 was significantly upregulated in glioblastoma and isocitrate dehydrogenase wild type tumors. According to TCGA transcriptional classification scheme, PD-1 expression was higher in tumors of mesenchymal subtype than other subtypes, and shown good predictive value to mesenchymal subtype. GO analysis revealed that genes significantly correlated with PD-1 were involved in essential functions associated with anti-tumor immune process. Through screening transcriptomic data, we found a strong correlation between PD-1 and immune cell populations especially for T cells. In addition, we investigated the association between PD-1 and genes related to its function, and found that PD-1 was significantly correlated with genes including TGFB1, IDO1, CD40, ICOS and SATB1, and other immune checkpoint molecules including CTLA4, LAG3, TIM3 and CD276. Survival analysis suggested that higher PD-1 expression was independently associated with worse prognosis of patients with diffuse gliomas. Conclusion: Our results indicated that PD-1 was involved in key steps of anti-tumor immune process and independently predicted worse prognosis in diffuse gliomas. These findings may expend our understanding of potential anti-PD-1 treatments.

Immunotherapy for Breast Cancer: Current and Future Strategies

Purpose of Review

The breast tumor microenvironment is immunosuppressive and is increasingly recognized to play a significant role in tumorigenesis. A deeper understanding of normal and aberrant interactions between malignant and immune cells has allowed researchers to harness the immune system with novel immunotherapy strategies, many of which have shown promise in breast cancer. This review discusses the application of immunotherapy to the treatment of breast cancer.

Recent Findings

Both basic science and clinical trial data are rapidly developing in the use of immunotherapy for breast cancer. The current clinical trial landscape includes therapeutic vaccines, immune checkpoint blockade, antibodies, cytokines, and adoptive cell therapy.

Summary

Despite early failures, the application of immunotherapeutic strategies to the treatment of breast cancer holds promise.

An immunogenic personal neoantigen vaccine for patients with melanoma

Effective anti-tumour immunity in humans has been associated with the presence of T cells directed at cancer neoantigens, a class of HLA-bound peptides that arise from tumour-specific mutations. They are highly immunogenic because they are not present in normal tissues and hence bypass central thymic tolerance. Although neoantigens were long-envisioned as optimal targets for an anti-tumour immune response, their systematic discovery and evaluation only became feasible with the recent availability of massively parallel sequencing for detection of all coding mutations within tumours, and of machine learning approaches to reliably predict those mutated peptides with high-affinity binding of autologous human leukocyte antigen (HLA) molecules. We hypothesized that vaccination with neoantigens can both expand pre-existing neoantigen-specific T-cell populations and induce a broader repertoire of new T-cell specificities in cancer patients, tipping the intra-tumoural balance in favour of enhanced tumour control. Here we demonstrate the feasibility, safety, and immunogenicity of a vaccine that targets up to 20 predicted personal tumour neoantigens. Vaccine-induced polyfunctional CD4+ and CD8+ T cells targeted 58 (60%) and 15 (16%) of the 97 unique neoantigens used across patients, respectively. These T cells discriminated mutated from wild-type antigens, and in some cases directly recognized autologous tumour. Of six vaccinated patients, four had no recurrence at 25 months after vaccination, while two with recurrent disease were subsequently treated with anti-PD-1 (anti-programmed cell death-1) therapy and experienced complete tumour regression, with expansion of the repertoire of neoantigen-specific T cells. These data provide a strong rationale for further development of this approach, alone and in combination with checkpoint blockade or other immunotherapies.

Expression and clinical significance of SATB1 and TLR4 in breast cancer

This study investigated the expression of special AT-rich sequence-binding protein 1 (SATB1) and toll-like receptor 4 (TLR4) protein in breast cancer and its clinical significance. We collected breast cancer tissues from 120 patients and adjacent non-cancerous tissue from 53 patients. SATB1 was expressed in 89 cases of breast cancer (74.17%) and in 7 cases of adjacent non-cancerous tissue (13.21%). TLR4 was expressed in 70 cases of breast cancer tissues (58.33%) and in 48 cases of adjacent non-cancerous tissue (90.57%). The differences of SATB and TLR4 in breast cancer and adjacent non-cancerous tissue were statistically significant. We found a negative correlation between the expression of SATB1 and TLR4 (r=−0.624, P<0.05). The expression of SATB1 and TLR4 were not significantly correlated with age, menopause, and PR and HER-2 protein expression, but were significantly correlated with tumor size, local lymphatic metastasis, histopathological grade, tumor stage, and ER protein expression (P<0.05). Overall, SATB1 and TLR4 proteins are involved in the development of breast cancer, a finding of great significance to identify therapeutic targets and prognosis markers for breast cancer.

Epigenetic modulation in cancer immunotherapy

The success of immune checkpoint inhibitors in cancer immunotherapy has been widely heralded. However many cancer patients do not respond to immune checkpoint therapy and some relapse due to acquired tumor resistance. Epigenetic targeting may be beneficial in cancer immunotherapy by reversing immune avoidance and escape mechanisms employed by cancer cells, as well as by modulating immune cell differentiation and function. In this manuscript we review recent findings suggesting how epigenetics may be used to improve cancer immunotherapy. We focus on the inhibitors of the CTLA4 and PD1 immune checkpoints and epigenetic modifiers of histone acetylation and methylation and DNA methylation.