Good bacteria help fight cancer: Resident gut bacteria can affect patient responses to cancer immunotherapy (see the Perspective by Jobin). Routy et al. show that antibiotic consumption is associated with poor response to immunotherapeutic PD-1 blockade. They profiled samples from patients with lung and kidney cancers and found that nonresponding patients had low levels of the bacterium Akkermansia muciniphila . Oral supplementation of the bacteria to antibiotic-treated mice restored the response to immunotherapy. Matson et al. and Gopalakrishnan et al. studied melanoma patients receiving PD-1 blockade and found a greater abundance of “good” bacteria in the guts of responding patients. Nonresponders had an imbalance in gut flora composition, which correlated with impaired immune cell activity. Thus, maintaining healthy gut flora could help patients combat cancer. Science , this issue p. 91 , p. 104 , p. 97 ; see also p. 32

Here, we describe a multiplexed immunohistochemical platform with computational image processing workflows, including image cytometry, enabling simultaneous evaluation of 12 biomarkers in one formalin-fixed paraffin-embedded tissue section. To validate this platform, we used tissue microarrays containing 38 archival head and neck squamous cell carcinomas and revealed differential immune profiles based on lymphoid and myeloid cell densities, correlating with human papilloma virus status and prognosis. Based on these results, we investigated 24 pancreatic ductal adenocarcinomas from patients who received neoadjuvant GVAX vaccination and revealed that response to therapy correlated with degree of mono-myelocytic cell density and percentages of CD8+ T cells expressing T cell exhaustion markers. These data highlight the utility of in situ immune monitoring for patient stratification and provide digital image processing pipelines to the community for examining immune complexity in precious tissue sections, where phenotype and tissue architecture are preserved to improve biomarker discovery and assessment.

Pancreas ductal adenocarcinoma (PDAC) has one of the worst 5-year survival rates of all solid tumors, and thus new treatment strategies are urgently needed. Here, we report that targeting Bruton tyrosine kinase (BTK), a key B-cell and macrophage kinase, restores T cell–dependent antitumor immune responses, thereby inhibiting PDAC growth and improving responsiveness to standard-of-care chemotherapy. We report that PDAC tumor growth depends on cross-talk between B cells and FcRγ⁺ tumor–associated macrophages, resulting in T_H2-type macrophage programming via BTK activation in a PI3Kγ-dependent manner. Treatment of PDAC-bearing mice with the BTK inhibitor PCI32765 (ibrutinib) or by PI3Kγ inhibition reprogrammed macrophages toward a T_H1 phenotype that fostered CD8⁺ T-cell cytotoxicity, and suppressed PDAC growth, indicating that BTK signaling mediates PDAC immunosuppression. These data indicate that pharmacologic inhibition of BTK in PDAC can reactivate adaptive immune responses, presenting a new therapeutic modality for this devastating tumor type. Significance: We report that BTK regulates B-cell and macrophage-mediated T-cell suppression in pancreas adenocarcinomas. Inhibition of BTK with the FDA-approved inhibitor ibrutinib restores T cell–dependent antitumor immune responses to inhibit PDAC growth and improves responsiveness to chemotherapy, presenting a new therapeutic modality for pancreas cancer. Cancer Discov; 6(3); 270–85. ©2015 AACR. See related commentary by Roghanian et al., p. 230. See related article by Pylayeva-Gupta et al., p. 247. See related article by Lee et al., p. 256. This article is highlighted in the In This Issue feature, p. 217

Mechanisms of immune suppression in peripheral tissues counteract protective immunity to prevent immunopathology and are coopted by tumors for immune evasion. While lymphatic vessels facilitate T cell priming, they also exert immune suppressive effects in lymph nodes at steady-state. Therefore, we hypothesized that peripheral lymphatic vessels acquire suppressive mechanisms to limit local effector CD8⁺ T cell accumulation in murine skin. We demonstrate that nonhematopoietic PD-L1 is largely expressed by lymphatic and blood endothelial cells and limits CD8⁺ T cell accumulation in tumor microenvironments. IFNγ produced by tissue-infiltrating, antigen-specific CD8⁺ T cells, which are in close proximity to tumor-associated lymphatic vessels, is sufficient to induce lymphatic vessel PD-L1 expression. Disruption of IFNγ-dependent crosstalk through lymphatic-specific loss of IFNγR boosts T cell accumulation in infected and malignant skin leading to increased viral pathology and tumor control, respectively. Consequently, we identify IFNγR as an immunological switch in lymphatic vessels that balances protective immunity and immunopathology leading to adaptive immune resistance in melanoma. Graphical Abstract

Purpose: Two studies in previously treated metastatic pancreatic cancer have been completed combining GVAX pancreas vaccine (GM-CSF–secreting allogeneic pancreatic tumor cells) with cyclophosphamide (Cy) and CRS-207 (live, attenuated Listeria monocytogenes–expressing mesothelin). In the current study, we compared Cy/GVAX followed by CRS-207 with (Arm A) or without nivolumab (Arm B). Patients and Methods: Patients with pancreatic adenocarcinoma who received one prior therapy for metastatic disease and RECIST measurable disease were randomized 1:1 to receive treatment on Arm A or Arm B. The primary objective was to compare overall survival (OS) between the arms. Additional objectives included assessment of progression-free survival, safety, tumor responses, CA19-9 responses, and immunologic correlates. Results: Ninety-three patients were treated (Arm A, 51; Arm B, 42). The median OS in Arms A and B were 5.9 [95% confidence interval (CI), 4.7–8.6] and 6.1 (95% CI, 3.5–7.0) months, respectively, with an HR of 0.86 (95% CI, 0.55–1.34). Objective responses were seen in 3 patients using immune-related response criteria (4%, 2/51, Arm A; 2%, 1/42, Arm B). The grade ≥3 related adverse event rate, whereas higher in Arm A (35.3% vs. 11.9%) was manageable. Changes in the microenvironment, including increase in CD8⁺ T cells and a decrease in CD68⁺ myeloid cells, were observed in long-term survivors in Arm A only. Conclusions: Although the study did not meet its primary endpoint of improvement in OS of Arm A over Arm B, the OS was comparable with standard therapy. Objective responses and immunologic changes in the tumor microenvironment were evident.

Purpose: Malignant pleural mesothelioma (MPM) is an aggressive cancer associated with poor prognosis. CRS-207 is a live-attenuated Listeria monocytogenes engineered to express mesothelin, a tumor-associated antigen highly expressed in MPM. CRS-207 induces antitumor immune responses and increases susceptibility of neoplastic cells to immune-mediated killing. Patients and Methods: Patients with unresectable MPM, ECOG 0 or 1, and adequate organ and pulmonary function were enrolled in this multicenter, open-label phase Ib study. They received two priming infusions of 1 × 10⁹ CFU CRS-207, followed by pemetrexed/cisplatin chemotherapy, and CRS-207 booster infusions. Primary objectives were safety and induction of immune response. Secondary/exploratory objectives included tumor response, progression-free survival (PFS), overall survival (OS), immune subset analysis, and gene-expression profiling of tumor. Results: Of 35 evaluable patients, 89% (31/35) had disease control with one complete response (3%), 19 partial responses (54%), and 10 stable disease (29%). The estimated median duration of response was 5.0 months (95% CI, 3.9–11.5). The median PFS and OS were 7.5 (95% CI, 7.0–9.9) and 14.7 (95% CI, 11.2–21.9) months, respectively. Tumor size reduction was observed post–CRS-207 infusion prior to chemotherapy in 11 of 35 (31%) patients. No unexpected treatment-related serious adverse events or deaths were observed. IHC analysis of pre- and post–CRS-207 treatment tumor biopsies revealed possible reinvigoration and proliferation of T cells, increased infiltration of dendritic and natural killer cells, increased CD8:T_reg ratio, and a shift from immunosuppressive M2-like to proinflammatory M1-like macrophages following CRS-207 administration. Conclusions: Combination of CRS-207 and chemotherapy induced significant changes in the local tumor microenvironment and objective tumor responses in a majority of treated patients.