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The combination of anti-VEGF blockade (bevacizumab) with immune checkpoint anti–CTLA-4 blockade (ipilimumab) in a phase I study showed tumor endothelial activation and immune cell infiltration that were associated with favorable clinical outcomes in patients with metastatic melanoma. To identify potential immune targets responsible for these observations, posttreatment plasma from long-term responding patients were used to screen human protein arrays. We reported that ipilimumab plus bevacizumab therapy elicited humoral immune responses to galectin-1 (Gal-1), which exhibits protumor, proangiogenesis, and immunosuppressive activities in 37.2% of treated patients. Gal-1 antibodies purified from posttreatment plasma suppressed the binding of Gal-1 to CD45, a T-cell surface receptor that transduces apoptotic signals upon binding to extracellular Gal-1. Antibody responses to Gal-1 were found more frequently in the group of patients with therapeutic responses and correlated with improved overall survival. In contrast, another subgroup of treated patients had increased circulating Gal-1 protein instead, and they had reduced overall survival. Our findings suggest that humoral immunity to Gal-1 may contribute to the efficacy of anti-VEGF and anti–CTLA-4 combination therapy. Gal-1 may offer an additional therapeutic target linking anti-angiogenesis and immune checkpoint blockade. Cancer Immunol Res; 5(6); 446–54. ©2017 AACR.

Blockade of the pathway including programmed death-ligand 1 (PD-L1) and its receptor programmed cell death protein 1 (PD-1) has produced clinical benefits in patients with a variety of cancers. Elevated levels of soluble PD-L1 (sPD-L1) have been associated with worse prognosis in renal cell carcinoma and multiple myeloma. However, the regulatory roles and function of sPD-L1 particularly in connection with immune checkpoint blockade treatment are not fully understood. We identified four splice variants of PD-L1 in melanoma cells, and all of them are secreted. Secretion of sPD-L1 resulted from alternate splicing activities, cytokine induction, cell stress, cell injury, and cell death in melanoma cells. Pretreatment levels of sPD-L1 were elevated in stage IV melanoma patient sera compared with healthy donors. High pretreatment levels of sPD-L1 were associated with increased likelihood of progressive disease in patients treated by CTLA-4 or PD-1 blockade. Although changes in circulating sPD-L1 early after treatment could not distinguish responders from those with progressive disease, after five months of treatment by CTLA-4 or PD-1 blockade patients who had increased circulating sPD-L1 had greater likelihood of developing a partial response. Induction of sPD-L1 was associated with increased circulating cytokines after CTLA-4 blockade but not following PD-1 blockade. Circulating sPD-L1 is a prognostic biomarker that may predict outcomes for subgroups of patients receiving checkpoint inhibitors. Cancer Immunol Res; 5(6); 480–92. ©2017 AACR.

Immune checkpoint therapies targeting CTLA-4 and PD-1 have proven effective in cancer treatment. However, the identification of biomarkers for predicting clinical outcomes and mechanisms to overcome resistance remain as critical needs. Angiogenesis is increasingly appreciated as an immune modulator with potential for combinatorial use with checkpoint blockade. Angiopoietin-2 (ANGPT2) is an immune target in patients and is involved in resistance to anti-VEGF treatment with the monoclonal antibody bevacizumab. We investigated the predictive and prognostic value of circulating ANGPT2 in metastatic melanoma patients receiving immune checkpoint therapy. High pretreatment serum ANGPT2 was associated with reduced overall survival in CTLA-4 and PD-1 blockade–treated patients. These treatments also increased serum ANGPT2 in many patients early after treatment initiation, whereas ipilimumab plus bevacizumab treatment decreased serum concentrations. ANGPT2 increases were associated with reduced response and/or overall survival. Ipilimumab increased, and ipilimumab plus bevacizumab decreased, tumor vascular ANGPT2 expression in a subset of patients, which was associated with increased and decreased tumor infiltration by CD68+ and CD163+ macrophages, respectively. In vitro, bevacizumab blocked VEGF-induced ANGPT2 expression in tumor-associated endothelial cells, whereas ANGPT2 increased PD-L1 expression on M2-polarized macrophages. Treatments elicited long-lasting and functional antibody responses to ANGPT2 in a subset of patients receiving clinical benefit. Our findings suggest that serum ANGPT2 may be considered as a predictive and prognostic biomarker for immune checkpoint therapy and may contribute to treatment resistance via increasing proangiogenic and immunosuppressive activities in the tumor microenvironment. Targeting ANGPT2 provides a rational combinatorial approach to improve the efficacy of immune therapy. Cancer Immunol Res; 5(1); 17–28. ©2016 AACR.

PD-L1 immunohistochemical staining does not always predict whether a cancer will respond to treatment with PD-1 inhibitors. We sought to characterize immune cell infiltrates and the expression of T-cell inhibitor markers in PD-L1–positive and PD-L1–negative malignant pleural mesothelioma samples. We developed a method for immune cell phenotyping using flow cytometry on solid tumors that have been dissociated into single-cell suspensions and applied this technique to analyze 43 resected malignant pleural mesothelioma specimens. Compared with PD-L1–negative tumors, PD-L1–positive tumors had significantly more infiltrating CD45+ immune cells, a significantly higher proportion of infiltrating CD3+ T cells, and a significantly higher percentage of CD3+ cells displaying the activated HLA-DR+/CD38+ phenotype. PD-L1–positive tumors also had a significantly higher proportion of proliferating CD8+ T cells, a higher fraction of FOXP3+/CD4+ Tregs, and increased expression of PD-1 and TIM-3 on CD4+ and CD8+ T cells. Double-positive PD-1+/TIM-3+ CD8+ T cells were more commonly found on PD-L1–positive tumors. Compared with epithelioid tumors, sarcomatoid and biphasic mesothelioma samples were significantly more likely to be PD-L1 positive and showed more infiltration with CD3+ T cells and PD-1+/TIM-3+ CD8+ T cells. Immunologic phenotypes in mesothelioma differ based on PD-L1 status and histologic subtype. Successful incorporation of comprehensive immune profiling by flow cytometry into prospective clinical trials could refine our ability to predict which patients will respond to specific immune checkpoint blockade strategies. Cancer Immunol Res; 4(12); 1038–48. ©2016 AACR.

Blocking the programmed death-1 (PD-1) pathway has clinical benefit in metastatic cancer and has led to the approval of the mAbs pembrolizumab and nivolumab to treat melanoma and nivolumab for non–small cell lung cancer. Expression of PD-L1 on the cell surface of either tumor cells or infiltrating immune cells is associated with a higher likelihood of response to PD-1 blockade in multiple studies. Most mAbs to PD-L1 in use are directed to its extracellular domain and immunohistochemically stain tumor tissue with a mixture of cytoplasmic and membrane staining. Cytoplasmic staining obscures the interpretation of a positive reaction on the tumor cell membrane, and thus affects the accuracy of PD-L1 scoring systems. We developed a mAb to the cytoplasmic domain of PD-L1, 405.9A11 (9A11), which is both more selective for membranous PD-L1 and more sensitive in IHC and Western blotting, compared with previous mAbs specific for the PD-L1 extracellular domain. Here, we compare immunohistochemical staining patterns of PD-L1 expression in five types of tumors, using five PD-L1 mAbs: 9A11, 7G11, and three commercially available mAbs. We demonstrate that 9A11, as well as two other cytoplasmic domain-specific mAbs, E1L3N and SP142, can clearly delineate the membrane of PD-L1–positive cells in formalin-fixed paraffin-embedded tissue and facilitate interpretation of staining results. Cancer Immunol Res; 3(12); 1308–15. ©2015 AACR.

Esophageal adenocarcinoma is an increasingly common disease with a dismal 5-year survival rate of 10% to 15%. In the first systematic evaluation of the PD-1 pathway in esophageal adenocarcinoma, we identify expression of PD-L2 in cancer cells in 51.7% of esophageal adenocarcinomas. Epithelial PD-L1 was expressed on only 2% of cases, although PD-L1+ immune cells were observed in 18% of esophageal adenocarcinomas. We also evaluated expression in the precursor lesion of esophageal adenocarcinoma, Barrett's esophagus, which emerges following gastric reflux–induced esophageal inflammation, and found PD-L2 expression in Barrett's esophagus but not in non–Barrett's esophagus esophagitis. Because the progression from squamous esophagitis to Barrett's esophagus is accompanied by a transition from a TH1 to TH2 immune response, we hypothesized that the TH2 cytokines IL4/IL13 could contribute to PD-L2 induction. We confirmed that these cytokines can augment PD-L2 expression in esophageal adenocarcinoma cell lines. These results suggest that the inflammatory environment in Barrett's esophagus and esophageal adenocarcinoma may contribute to the expression of PD-L2. Furthermore, the potential for PD-1 receptor blockade to be effective in esophageal adenocarcinomas with epithelial PD-L2 or immune cell PD-L1 expression should be evaluated in clinical trials. Cancer Immunol Res; 3(10); 1123–9. ©2015 AACR.

Inhibition of immune checkpoints, including cytotoxic T-lymphocyte antigen-4 (CTLA-4), programmed death-1 (PD-1), and its ligand PD-L1, has demonstrated exciting and durable remissions across a spectrum of malignancies. Combinatorial regimens blocking complementary immune checkpoints further enhance the therapeutic benefit. The activity of these agents for patients with glioblastoma, a generally lethal primary brain tumor associated with significant systemic and microenvironmental immunosuppression, is not known. We therefore systematically evaluated the antitumor efficacy of murine antibodies targeting a broad panel of immune checkpoint molecules, including CTLA-4, PD-1, PD-L1, and PD-L2 when administered as single-agent therapy and in combinatorial regimens against an orthotopic, immunocompetent murine glioblastoma model. In these experiments, we observed long-term tumor-free survival following single-agent anti–PD-1, anti–PD-L1, or anti–CTLA-4 therapy in 50%, 20%, and 15% of treated animals, respectively. Combination therapy of anti–CTLA-4 plus anti–PD-1 cured 75% of the animals, even against advanced, later-stage tumors. In long-term survivors, tumor growth was not seen upon intracranial tumor rechallenge, suggesting that tumor-specific immune memory responses were generated. Inhibitory immune checkpoint blockade quantitatively increased activated CD8+ and natural killer cells and decreased suppressive immune cells in the tumor microenvironment and draining cervical lymph nodes. Our results support prioritizing the clinical evaluation of PD-1, PD-L1, and CTLA-4 single-agent targeted therapy as well as combination therapy of CTLA-4 plus PD-1 blockade for patients with glioblastoma. Cancer Immunol Res; 4(2); 124–35. ©2015 AACR.