Hepatocytes coordinate immune evasion in cancer via release of serum amyloid A proteins

T cell infiltration into tumors is a favorable prognostic feature, but most solid tumors lack productive T cell responses. Mechanisms that coordinate T cell exclusion are incompletely understood. Here we identify hepatocyte activation via interleukin-6/STAT3 and secretion of serum amyloid A (SAA) proteins 1 and 2 as important regulators of T cell surveillance of extrahepatic tumors. Loss of STAT3 in hepatocytes or SAA remodeled the tumor microenvironment with infiltration by CD8+ T cells, while interleukin-6 overexpression in hepatocytes and SAA signaling via Toll-like receptor 2 reduced the number of intratumoral dendritic cells and, in doing so, inhibited T cell tumor infiltration. Genetic ablation of SAA enhanced survival after tumor resection in a T cell-dependent manner. Likewise, in individuals with pancreatic ductal adenocarcinoma, long-term survivors after surgery demonstrated lower serum SAA levels than short-term survivors. Taken together, these data define a fundamental link between liver and tumor immunobiology wherein hepatocytes govern productive T cell surveillance in cancer.

Multimodal immune phenotyping reveals microbial-T cell interactions that shape pancreatic cancer

Microbes are an integral component of the tumor microenvironment. However, determinants of microbial presence remain ill-defined. Here, using spatial-profiling technologies, we show that bacterial and immune cell heterogeneity are spatially coupled. Mouse models of pancreatic cancer recapitulate the immune-microbial spatial coupling seen in humans. Distinct intra-tumoral niches are defined by T cells, with T cell-enriched and T cell-poor regions displaying unique bacterial communities that are associated with immunologically active and quiescent phenotypes, respectively, but are independent of the gut microbiome. Depletion of intra-tumoral bacteria slows tumor growth in T cell-poor tumors and alters the phenotype and presence of myeloid and B cells in T cell-enriched tumors but does not affect T cell infiltration. In contrast, T cell depletion disrupts the immunological state of tumors and reduces intra-tumoral bacteria. Our results establish a coupling between microbes and T cells in cancer wherein spatially defined immune-microbial communities differentially influence tumor biology.

Cancer immunotherapy via synergistic coactivation of myeloid receptors CD40 and Dectin-1

Myeloid cells facilitate T cell immune evasion in cancer yet are pliable and have antitumor potential. Here, by cotargeting myeloid activation molecules, we leveraged the myeloid compartment as a therapeutic vulnerability in mouse models of pancreatic cancer. Myeloid cells in solid tumors expressed activation receptors including the pattern recognition receptor Dectin-1 and the TNF receptor superfamily member CD40. In mouse models of checkpoint inhibitor-resistant pancreatic cancer, coactivation of Dectin-1, via systemic β-glucan therapy, and CD40, with agonist antibody treatment, eradicated established tumors and induced immunological memory. Antitumor activity was dependent on cDC1s and T cells but did not require classical T cell-mediated cytotoxicity or blockade of checkpoint molecules. Rather, targeting CD40 drove T cell-mediated IFN-γ signaling, which converged with Dectin-1 activation to program distinct macrophage subsets to facilitate tumor responses. Thus, productive cancer immune surveillance in pancreatic tumors resistant to checkpoint inhibition can be invoked by coactivation of complementary myeloid signaling pathways.

Kupffer cells prevent pancreatic ductal adenocarcinoma metastasis to the liver in mice

Although macrophages contribute to cancer cell dissemination, immune evasion, and metastatic outgrowth, they have also been reported to coordinate tumor-specific immune responses. We therefore hypothesized that macrophage polarization could be modulated therapeutically to prevent metastasis. Here, we show that macrophages respond to β-glucan (odetiglucan) treatment by inhibiting liver metastasis. β-glucan activated liver-resident macrophages (Kupffer cells), suppressed cancer cell proliferation, and invoked productive T cell-mediated responses against liver metastasis in pancreatic cancer mouse models. Although excluded from metastatic lesions, Kupffer cells were critical for the anti-metastatic activity of β-glucan, which also required T cells. Furthermore, β-glucan drove T cell activation and macrophage re-polarization in liver metastases in mice and humans and sensitized metastatic lesions to anti-PD1 therapy. These findings demonstrate the significance of macrophage function in metastasis and identify Kupffer cells as a potential therapeutic target against pancreatic cancer metastasis to the liver.

Abstract 2888: Hepatocytes coordinate immune evasion in cancer via release of serum amyloid A proteins

INTRODUCTION: Pancreatic ductal adenocarcinoma (PDAC) is a lethal disease for which the 5-year survival rate is about 10%. Rare long-term survivors after surgical resection have been characterized as having high quality immune responses to primary tumors. However, the mechanisms that regulate immune surveillance in PDAC remain ill-defined.

METHODS: Here, we used patient data and genetic mouse models to study potential determinants of T cell surveillance in PDAC.

SUMMARY: Long-term survivors (>3 years) compared to short-term survivors (>3 months and <1 year) after resection of treatment-naïve PDAC had increased CD8+ T cell infiltration into tumors and lower systemic inflammation as measured by neutrophil-to-lymphocyte ratio (NLR). In a panel of 10 PDAC cell lines orthotopically injected into mice, higher NLR correlated with decreased T cell infiltration into tumors and increased liver inflammation. Specifically, IL-6/STAT3 signaling was enriched in livers of mice with tumors with fewer T cells. Based on these observations, we hypothesized that pancreatic cancer development triggers liver-directed immunosuppression that restrains productive anti-tumor T cell surveillance. To test this hypothesis, we overexpressed IL-6 in hepatocytes, which was sufficient to convert a primary tumor with a T cell “inflamed” phenotype to T cell “non-inflamed”. This biology was dependent on STAT3 signaling in hepatocytes. To this end, loss of STAT3 specifically in hepatocytes drove an influx of CD8+ T cells into non-inflamed primary tumors. We next identified acute phase reactants serum amyloid A proteins 1 and 2 (SAA) as necessary for the inhibition of T cell infiltration by hepatocytes. In mice lacking SAA, tumor-specific T cell infiltration was increased, T cells in tumors expressed activation markers, and tumor growth was inhibited. In patients, we similarly found that high levels of SAA correlated with a decrease in T cells and an increase in monocytes in the peripheral blood; furthermore, long-term survivors after tumor resection had significantly lower SAA levels than short-term survivors. To test the direct role of SAA in survival after tumor resection, we developed a novel mouse model of distal pancreatectomy/splenectomy, which recapitulated observations from patients that higher T cell infiltration into tumors associates with improved survival. Further, mice lacking SAA survived significantly longer after surgery in a T cell-dependent manner.

CONCLUSIONS: Our findings define a pivotal role for hepatocytes in regulating productive T cell surveillance in cancer. Specifically, our data show that IL-6 can activate STAT3 in hepatocytes to release SAA which then suppress productive T cell surveillance. Taken together, these data suggest that activation of hepatocytes and their release of SAA are novel therapeutic targets for improving the productivity of cancer immunity and patient outcomes after surgery.

Citation Format: Meredith L. Stone, Jesse Lee, Jae W. Lee, Heather Coho, Max M. Wattenberg, Hana Choi, Veronica M. Hererra, Yuqing Xue, Shaanti Choi-Bose, Vinod Balachandran, Gregory L. Beatty. Hepatocytes coordinate immune evasion in cancer via release of serum amyloid A proteins [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2888.

Abstract C018: Co-activation of myeloid signaling pathways for pancreatic cancer immunotherapy

Pancreatic ductal adenocarcinoma (PDA) is characterized by a robust myeloid cell infiltrate. Although myeloid cells in PDA most commonly associate with immunosuppression, they also show plasticity and possess the capacity to engage productive anti-tumor immunity, thereby providing a potential therapeutic vulnerability. Here, we show that distinct myeloid cell subsets infiltrating human PDA express non-redundant activating receptors. Among the most highly expressed receptors was the pattern recognition receptor CLEC7A, which was expressed by macrophages, monocytes, and immature myeloid cells. In contrast, the TNF superfamily member CD40, was expressed by dendritic cells (DC) and SPP1+ macrophages. We hypothesized that combinatory targeting of myeloid activating receptors might be needed to restore productive immunosurveillance in PDA. In immune checkpoint blockade-resistant mouse models of PDA, pharmacologic activation of CLEC7A, using beta glucan (BG) therapy was associated with upregulation of the CXCL2/3-CXCR2 axis and triggered increases in intra-tumoral macrophages and granulocytes. Conversely, CD40 agonist therapy induced activity of the CXCL9-CXCR3 axis and drove conventional DC type 1-dependent infiltration of CD4+ and CD8+ T cells into tumors. Neither myeloid agonist alone, though, was sufficient to trigger durable anti-tumor immunity. By contrast, induction of both myeloid and lymphoid immunosurveillance by co-activation of CLEC7A/CD40 pathways caused tumor eradication, durable tumor control and T cell dependent immunological memory. Depletion of CSF1R+ myeloid cells or T cells significantly reduced the anti-tumor activity of treatment thereby highlighting the cooperativity of innate and adaptive immunity for anti-tumor activity. Moreover, the efficacy of CLEC7A and CD40 co-activation was independent of immune checkpoint blockade. Thus, beyond inhibitory checkpoint molecules on T cells, combinatory activation of non-redundant myeloid signaling pathways can be leveraged to trigger durable anti-tumor immunity, suggesting a new immunotherapy paradigm. A clinical trial of CLEC7A and CD40 agonist therapy for the treatment of patients with PDA is under development.

Citation Format: Max M. Wattenberg, Heather Coho, Veronica M. Herrera, Kathleen Graham, Meredith L. Stone, Yuqing Xue, Renee B. Chang, Christopher Cassella, Mingen Liu, Shaanti Choi-Bose, Stacy K. Thomas, Hana Choi, Yan Li, Lauren Melendez, Michael Giannone, Nandita Bose, Gregory L. Beatty. Co-activation of myeloid signaling pathways for pancreatic cancer immunotherapy [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr C018.

Abstract 5633: Beta-Glucan treatment restricts liver metastasis in pancreatic cancer

Introduction: For most patients with pancreatic ductal adenocarcinoma (PDAC), metastatic disease is the main cause of mortality with the liver being the most common site of metastasis. In the liver, macrophages are the most abundant immune cell subset, yet their role in regulating liver metastasis remains poorly understood. Two distinct macrophage populations exist in the liver: liver-resident Clec4f+F4/80+ Kupffer cells (KCs) and Clec4fnegF4/80+ bone marrow derived macrophages (BMDMs). Here, we sought to understand the impact of these macrophage subsets on liver metastasis and the ability of a myeloid agonist, a β-glucan (BG), to skew macrophages towards an anti-metastatic phenotype.

Methods: C57BL/6 mice were given an intraportal (iPo) injection of an LSL-KrasG12D/+;LSL-Trp53R172H/+;Pdx-1-Cre;LSL-Rosa26-Yfp (KPCY) cell line to model liver metastasis. Mice were necropsied 2 days later to measure metastatic seeding of cancer cells or 12-14 days later to assess metastatic lesion outgrowth. Liver metastatic burden and immune cell populations were analyzed by flow cytometry and immunohistochemistry. In macrophage depletion experiments, liver macrophages were depleted using clodronate encapsulated liposomes (CEL) delivered intraperitoneally. In studies involving BG treatment, weekly intravenous administration of BG began 2 days prior to iPo injection of cancer cells.

Results: Liver macrophage depletion did not influence metastatic seeding in the liver; but, did inhibit the outgrowth of established metastatic colonies. Histological analysis showed that Clec4f+ KCs were excluded from metastatic lesions, whereas BMDMs actively infiltrated. BMDM infiltration into lesions was also largely unaffected by CEL treatment. To stimulate macrophages with anti-metastatic activity, BG was administered systemically and found to bind to >95% of KCs but only 30% of BMDMs and 20-35% of other immune cell populations. BG treatment attenuated liver metastasis when given during both the seeding and outgrowth phases of metastasis (mean metastatic burden as % live cells in liver: 1%, BG vs 6.5%, control, p<0.0001). Analysis of metastatic lesions in BG treated mice by histology showed smaller lesions (mean size: 0.9mm2, BG vs 1.5mm2, control, p=0.09), decreased proliferating cancer cells (mean # of proliferating cancer cells per unit metastatic area: 480, BG vs 810, control, p<0.0001), and increased numbers of CD3+ T cells at the periphery of lesions compared to lesions from control mice (mean # of T cells per mm2 metastatic area: 300, BG vs 135, control, p<0.0001). The efficacy of BG to restrict liver metastasis was dependent on liver macrophages.

Conclusions: Taken together, these findings suggest that, while liver macrophages can be coopted to support metastatic outgrowth, treatment with a β-glucan, as a myeloid agonist is a novel strategy to engender liver macrophages with anti-metastatic activity.

Citation Format: Stacy K. Thomas, Shaanti Choi-Bose, Heather Coho, Christopher Casella, Meredith L. Stone, Max M. Wattenberg, Gregory L. Beatty. Beta-Glucan treatment restricts liver metastasis in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 5633.

TNF blockade uncouples toxicity from antitumor efficacy induced with CD40 chemoimmunotherapy

Agonist CD40 antibodies are under clinical development in combination with chemotherapy as an approach to prime for antitumor T cell immunity. However, treatment with anti-CD40 is commonly accompanied by both systemic cytokine release and liver transaminase elevations, which together account for the most common dose-limiting toxicities. Moreover, anti-CD40 treatment increases the potential for chemotherapy-induced hepatotoxicity. Here, we report a mechanistic link between cytokine release and hepatotoxicity induced by anti-CD40 when combined with chemotherapy and show that toxicity can be suppressed without impairing therapeutic efficacy. We demonstrate in mice and humans that anti-CD40 triggers transient hepatotoxicity marked by increased serum transaminase levels. In doing so, anti-CD40 sensitizes the liver to drug-induced toxicity. Unexpectedly, this biology is not blocked by the depletion of multiple myeloid cell subsets, including macrophages, inflammatory monocytes, and granulocytes. Transcriptional profiling of the liver after anti-CD40 revealed activation of multiple cytokine pathways including TNF and IL-6. Neutralization of TNF, but not IL-6, prevented sensitization of the liver to hepatotoxicity induced with anti-CD40 in combination with chemotherapy without impacting antitumor efficacy. Our findings reveal a clinically feasible approach to mitigate toxicity without impairing efficacy in the use of agonist CD40 antibodies for cancer immunotherapy.