TSG-6+ cancer-associated fibroblasts modulate myeloid cell responses and impair anti-tumor response to immune checkpoint therapy in pancreatic cancer.

Resistance to immune checkpoint therapy (ICT) presents a growing clinical challenge. The tumor microenvironment (TME) and its components, namely tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs), play a pivotal role in ICT resistance; however, the underlying mechanisms remain under investigation. In this study, we identify expression of TNF-Stimulated Factor 6 (TSG-6) in ICT-resistant pancreatic tumors, compared to ICT-sensitive melanoma tumors, both in mouse and human. TSG-6 is expressed by CAFs within the TME, where suppressive macrophages expressing Arg1, Mafb, and Mrc1, along with TSG-6 ligand Cd44, predominate. Furthermore, TSG-6 expressing CAFs co-localize with the CD44 expressing macrophages in the TME. TSG-6 inhibition in combination with ICT improves therapy response and survival in pancreatic tumor-bearing mice by reducing macrophages expressing immunosuppressive phenotypes and increasing CD8 T cells. Overall, our findings propose TSG-6 as a therapeutic target to enhance ICT response in non-responsive tumors.

Identification of human regulatory T cells in the setting of T-cell activation and anti-CTLA-4 immunotherapy on the basis of expression of latency-associated peptide.

UNLABELLED: Effector and regulatory T cells (Treg) share multiple markers that make it difficult to discern differences in these populations in humans. The transcription factor FoxP3 has been shown to identify Tregs. However, the detection of FoxP3 requires cell permeabilization, thereby preventing isolation of viable Tregs. Subsequently, the extracellular marker CD127 was established for the identification of Tregs. However, these studies were not conducted in the setting of immunotherapy. Here, we conducted studies to analyze CD127 and FoxP3 expression on T cells before and after in vitro activation as well as in the setting of patients treated with antibodies directed against cytotoxic T-lymphocyte antigen-4 (CTLA-4). We show that latency-associated peptide (LAP), as opposed to CD127, was capable of identifying Tregs after in vitro activation as well as after treatment with anti-CTLA-4. Therefore, we propose that LAP should be used as a marker of Tregs for immune monitoring studies in patients treated with active immunotherapy such as anti-CTLA-4. SIGNIFICANCE: Tregs play an important role in human diseases, including cancer and autoimmunity; however, it has been difficult to study these cells because of a lack of an appropriate marker. Here, we propose LAP as a marker that can be used to identify Tregs in patients treated with immunotherapy, thereby permitting isolation of these cells for functional studies and for ex vivo expansion.

NY-ESO-1 DNA vaccine induces T-cell responses that are suppressed by regulatory T cells.

PURPOSE: Different vaccination strategies against the NY-ESO-1 antigen have been employed in an attempt to induce antitumor immune responses. Antigen-specific effector T-cell responses have been reported in a subset of vaccinated patients; however, these responses have not consistently correlated with disease regression. Here, we report for the first time clinical and immune responses generated by the NY-ESO-1 DNA vaccine administered by particle-mediated epidermal delivery to cancer patients. EXPERIMENTAL DESIGN: Eligible patients received treatment with the NY-ESO-1 DNA vaccine. Clinical outcomes and immune responses were assessed. RESULTS: The NY-ESO-1 DNA vaccine was safely administered and induced both antigen-specific effector CD4 and/or CD8 T-cell responses in 93% (14 of 15) of patients who did not have detectable pre-vaccine immune responses. Despite the induction of antigen-specific T-cell responses, clinical outcomes consisted predominantly of progressive disease. Detectable effector T-cell responses were inconsistent and did not persist in all patients after completion of the scheduled vaccinations. However, high-avidity CD4 T-cell responses that were either undetectable pre-vaccine or found to be diminished at a later time during the clinical trial were detected in certain patients' samples after in vitro depletion of regulatory T cells. CONCLUSIONS: Regulatory T cells play a role in diminishing vaccine-induced antigen-specific effector T-cell responses in cancer patients. The NY-ESO-1 DNA vaccine represents a feasible immunotherapeutic strategy to induce antigen-specific T-cell responses. Counteracting regulatory T-cell activity before vaccination may lead to prolonged effector T-cell responses and possibly antitumor responses in cancer patients.

Anti-CTLA-4 therapy results in higher CD4+ICOShi T cell frequency and IFN-gamma levels in both nonmalignant and malignant prostate tissues.

Cytotoxic lymphocyte antigen-4 (CTLA-4) blockade is an active immunotherapeutic strategy that is currently in clinical trials in cancer. There are several ongoing trials of anti-CTLA-4 in the metastatic setting of prostate cancer patients with reported clinical responses consisting of decreases in the prostate specific antigen (PSA) tumor marker for some patients. Immunologic markers that correlate with these clinical responses are necessary to guide further development of anti-CTLA-4 therapy in the treatment of cancer patients. We recently reported that CD4(+) inducible co-stimulator (ICOS)(hi) T cells that produce interferon-gamma (IFN-gamma) are increased in the peripheral blood and tumor tissues of bladder cancer patients treated with anti-CTLA-4 antibody. Here we present data from the same clinical trial in bladder cancer patients demonstrating a higher frequency of CD4(+)ICOS(hi) T cells and IFN-gamma mRNA levels in nonmalignant prostate tissues and incidental prostate tumor tissues removed at the time of radical cystoprostatectomy. Our data suggest immunologic markers that can be used to monitor prostate cancer patients who receive anti-CTLA-4 therapy and indicate that the immunologic impact of anti-CTLA-4 antibody can occur in both tumor and nonmalignant tissues. These data should be taken into consideration for evaluation of efficacy as well as immune-related adverse events associated with anti-CTLA-4 therapy.

CTLA-4 blockade increases IFNgamma-producing CD4+ICOShi cells to shift the ratio of effector to regulatory T cells in cancer patients.

Significant anti-tumor responses have been reported in a small subset of cancer patients treated with the immunotherapeutic agent anti-CTLA-4 antibody. All clinical trials to date, comprising over 3,000 patients, have been conducted in the metastatic disease setting, which allows for correlation of drug administration with clinical outcome but has limited analyses of intermediate biomarkers to indicate whether the drug has impacted human immune responses within the tumor microenvironment. We conducted a pre-surgical clinical trial in six patients with localized bladder cancer, which allowed for correlation of drug administration with biomarkers in both blood and tumor tissues but did not permit correlation with clinical outcome. We found that CD4 T cells from peripheral blood and tumor tissues of all treated patients had markedly increased expression of inducible costimulator (ICOS). These CD4(+)ICOS(hi) T cells produced IFN-gamma (IFNgamma) and could recognize the tumor antigen NY-ESO-1. Increase in CD4(+)ICOS(hi) cells led to an increase in the ratio of effector to regulatory T cells. To our knowledge, these are the first immunologic changes reported in both tumor tissues and peripheral blood as a result of treatment with anti-CTLA-4 antibody, and they may be used to guide dosing and scheduling of this agent to improve clinical responses.