Oncogenic KRAS-dependent stromal interleukin-33 directs the pancreatic microenvironment to promote tumor growth.

Pancreatic cancer is characterized by an extensive fibroinflammatory microenvironment. During carcinogenesis, normal stromal cells are converted to cytokine-high cancer associated fibroblasts (CAFs). The mechanisms underlying this conversion, including regulation and function of fibroblast-derived cytokines, are poorly understood. Thus, efforts to target CAFs therapeutically have so far failed. Here, we show that signals from epithelial cells expressing oncogenic KRAS -a hallmark pancreatic cancer mutation- activate fibroblast autocrine signaling, which drives expression of the cytokine interleukin-33 (IL-33). Stromal IL-33 expression remains high and dependent on epithelial KRAS throughout carcinogenesis; in turn, environmental stress induces IL-33 secretion. Using compartment-specific IL-33 knockout mice, we observed that lack of stromal IL-33 leads to profound reprogramming of multiple components of the pancreatic tumor microenvironment, including CAFs, myeloid cells and lymphocytes. Notably, loss of stromal IL-33 leads to an increase in CD8+ T cell infiltration and activation, and, ultimately, reduced tumor growth.

Arginase 1 is a key driver of immune suppression in pancreatic cancer.

An extensive fibroinflammatory stroma rich in macrophages is a hallmark of pancreatic cancer. In this disease, it is well appreciated that macrophages are immunosuppressive and contribute to the poor response to immunotherapy; however, the mechanisms of immune suppression are complex and not fully understood. Immunosuppressive macrophages are classically defined by the expression of the enzyme Arginase 1 (ARG1), which we demonstrated is potently expressed in pancreatic tumor-associated macrophages from both human patients and mouse models. While routinely used as a polarization marker, ARG1 also catabolizes arginine, an amino acid required for T cell activation and proliferation. To investigate this metabolic function, we used a genetic and a pharmacologic approach to target Arg1 in pancreatic cancer. Genetic inactivation of Arg1 in macrophages, using a dual recombinase genetically engineered mouse model of pancreatic cancer, delayed formation of invasive disease, while increasing CD8+ T cell infiltration. Additionally, Arg1 deletion induced compensatory mechanisms, including Arg1 overexpression in epithelial cells, namely Tuft cells, and Arg2 overexpression in a subset of macrophages. To overcome these compensatory mechanisms, we used a pharmacological approach to inhibit arginase. Treatment of established tumors with the arginase inhibitor CB-1158 exhibited further increased CD8+ T cell infiltration, beyond that seen with the macrophage-specific knockout, and sensitized the tumors to anti-PD1 immune checkpoint blockade. Our data demonstrate that Arg1 drives immune suppression in pancreatic cancer by depleting arginine and inhibiting T cell activation.

WNT signaling in the tumor microenvironment promotes immunosuppression in murine pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDA) is associated with activation of WNT signaling. Whether this signaling pathway regulates the tumor microenvironment has remained unexplored. Through single-cell RNA sequencing of human pancreatic cancer, we discovered that tumor-infiltrating CD4+ T cells express TCF7, encoding for the transcription factor TCF1. We conditionally inactivated Tcf7 in CD4 expressing T cells in a mouse model of pancreatic cancer and observed changes in the tumor immune microenvironment, including more CD8+ T cells and fewer regulatory T cells, but also compensatory upregulation of PD-L1. We then used a clinically available inhibitor of Porcupine, a key component of WNT signaling, and observed similar reprogramming of the immune response. WNT signaling inhibition has limited therapeutic window due to toxicity, and PD-L1 blockade has been ineffective in PDA. Here, we show that combination targeting reduces pancreatic cancer growth in an experimental model and might benefit the treatment of pancreatic cancer.

Combinatorial Gli activity directs immune infiltration and tumor growth in pancreatic cancer.

Proper Hedgehog (HH) signaling is essential for embryonic development, while aberrant HH signaling drives pediatric and adult cancers. HH signaling is frequently dysregulated in pancreatic cancer, yet its role remains controversial, with both tumor-promoting and tumor-restraining functions reported. Notably, the GLI family of HH transcription factors (GLI1, GLI2, GLI3), remain largely unexplored in pancreatic cancer. We therefore investigated the individual and combined contributions of GLI1-3 to pancreatic cancer progression. At pre-cancerous stages, fibroblast-specific Gli2/Gli3 deletion decreases immunosuppressive macrophage infiltration and promotes T cell infiltration. Strikingly, combined loss of Gli1/Gli2/Gli3 promotes macrophage infiltration, indicating that subtle changes in Gli expression differentially regulate immune infiltration. In invasive tumors, Gli2/Gli3 KO fibroblasts exclude immunosuppressive myeloid cells and suppress tumor growth by recruiting natural killer cells. Finally, we demonstrate that fibroblasts directly regulate macrophage and T cell migration through the expression of Gli-dependent cytokines. Thus, the coordinated activity of GLI1-3 directs the fibroinflammatory response throughout pancreatic cancer progression.

Extrinsic KRAS Signaling Shapes the Pancreatic Microenvironment Through Fibroblast Reprogramming.

BACKGROUND & AIMS: Oncogenic Kirsten Rat Sarcoma virus (KRAS) is the hallmark mutation of human pancreatic cancer and a driver of tumorigenesis in genetically engineered mouse models of the disease. Although the tumor cell-intrinsic effects of oncogenic Kras expression have been widely studied, its role in regulating the extensive pancreatic tumor microenvironment is less understood. METHODS: Using a genetically engineered mouse model of inducible and reversible oncogenic Kras expression and a combination of approaches that include mass cytometry and single-cell RNA sequencing we studied the effect of oncogenic KRAS in the tumor microenvironment. RESULTS: We have discovered that non-cell autonomous (ie, extrinsic) oncogenic KRAS signaling reprograms pancreatic fibroblasts, activating an inflammatory gene expression program. As a result, fibroblasts become a hub of extracellular signaling, and the main source of cytokines mediating the polarization of protumorigenic macrophages while also preventing tissue repair. CONCLUSIONS: Our study provides fundamental knowledge on the mechanisms underlying the formation of the fibroinflammatory stroma in pancreatic cancer and highlights stromal pathways with the potential to be exploited therapeutically.

Apolipoprotein E Promotes Immune Suppression in Pancreatic Cancer through NF-κB-Mediated Production of CXCL1.

Pancreatic ductal adenocarcinoma (PDAC) is a lethal malignancy with few effective therapeutic options. PDAC is characterized by an extensive fibroinflammatory stroma that includes abundant infiltrating immune cells. Tumor-associated macrophages (TAM) are prevalent within the stroma and are key drivers of immunosuppression. TAMs in human and murine PDAC are characterized by elevated expression of apolipoprotein E (ApoE), an apolipoprotein that mediates cholesterol metabolism and has known roles in cardiovascular and Alzheimer's disease but no known role in PDAC. We report here that ApoE is also elevated in peripheral blood monocytes in PDAC patients, and plasma ApoE protein levels stratify patient survival. Orthotopic implantation of mouse PDAC cells into syngeneic wild-type or in ApoE-/- mice showed reduced tumor growth in ApoE-/- mice. Histologic and mass cytometric (CyTOF) analysis of these tumors showed an increase in CD8+ T cells in tumors in ApoE-/- mice. Mechanistically, ApoE induced pancreatic tumor cell expression of Cxcl1 and Cxcl5, known immunosuppressive factors, through LDL receptor and NF-κB signaling. Taken together, this study reveals a novel immunosuppressive role of ApoE in the PDAC microenvironment. SIGNIFICANCE: This study shows that elevated apolipoprotein E in PDAC mediates immune suppression and high serum apolipoprotein E levels correlate with poor patient survival.See related commentary by Sherman, p. 4186.

Association between Tunneled Pleural Catheter Use and Infection in Patients Immunosuppressed from Antineoplastic Therapy. A Multicenter Study.

Rationale: Patients with malignant or paramalignant pleural effusions (MPEs or PMPEs) may have tunneled pleural catheter (TPC) management withheld because of infection concerns from immunosuppression associated with antineoplastic therapy.Objectives: To determine the rate of infections related to TPC use and to determine the relationship to antineoplastic therapy, immune system competency, and overall survival (OS).Methods: We performed an international, multiinstitutional study of patients with MPEs or PMPEs undergoing TPC management from 2008 to 2016. Patients were stratified by whether or not they underwent antineoplastic therapy and/or whether or not they were immunocompromised. Cumulative incidence functions and multivariable competing risk regression analyses were performed to identify independent predictors of TPC-related infection. Kaplan-Meier method and multivariable Cox proportional hazards modeling were performed to examine for independent effects on OS.Results: A total of 1,408 TPCs were placed in 1,318 patients. Patients had a high frequency of overlap between antineoplastic therapy and an immunocompromised state (75-83%). No difference in the overall (6-7%), deep pleural (3-5%), or superficial (3-4%) TPC-related infection rates between subsets of patients stratified by antineoplastic therapy or immune status was observed. The median time to infection was 41 (interquartile range, 19-87) days after TPC insertion. Multivariable competing risk analyses demonstrated that longer TPC duration was associated with a higher risk of TPC-related infection (subdistribution hazard ratio, 1.03; 95% confidence interval [CI], 1.00-1.06; P = 0.028). Cox proportional hazards analysis showed antineoplastic therapy was associated with better OS (hazard ratio, 0.84; 95% CI, 0.73-0.97; P = 0.015).Conclusions: The risk of TPC-related infection does not appear to be increased by antineoplastic therapy use or an immunocompromised state. The overall rates of infection are low and comparable with those of immunocompetent patients with no relevant antineoplastic therapy. These results support TPC palliation for MPE or PMPEs regardless of plans for antineoplastic therapy.

Pleural plaques by inhalation of asbestos fibers.

INTRODUCTION: Asbestos fiber pleural plaque is characterized by lesions composed of fibrous tissue that are located in the parietal pleura. They usually appear in up to 3 to 58% of workers who were exposed to asbestos fiber, and 0.5 to 8% in the general population. The objective of this article is to present a case report of a patient whose chest x-ray showed pleural changes associated with exposure to asbestos fibers. CASE REPORT: A 49-year-old male patient, construction worker with a history of exposure to asbestos fibers, underwent a chest x-ray performed according to International Labor Organization (ILO) standards, which revealed focal pleural changes. Subsequently, the presence of pleural plaques was confirmed by computed tomography (CT) scan of the chest. DISCUSSION: Chest x-ray with ILO technique is the basic instrument for the identification of diseases related to asbestos fiber exposure. The study should be completed with a CT scan of the chest, whose sensitivity is greater, allowing early detection of pleural abnormalities. It is essential to obtain a detailed occupational history, since it is the most reliable and practical method to measure asbestos fiber exposure.

Regulatory T-cell Depletion Alters the Tumor Microenvironment and Accelerates Pancreatic Carcinogenesis.

Regulatory T cells (Treg) are abundant in human and mouse pancreatic cancer. To understand the contribution to the immunosuppressive microenvironment, we depleted Tregs in a mouse model of pancreatic cancer. Contrary to our expectations, Treg depletion failed to relieve immunosuppression and led to accelerated tumor progression. We show that Tregs are a key source of TGFß ligands and, accordingly, their depletion reprogramed the fibroblast population, with loss of tumor-restraining, smooth muscle actin-expressing fibroblasts. Conversely, we observed an increase in chemokines Ccl3, Ccl6, and Ccl8 leading to increased myeloid cell recruitment, restoration of immune suppression, and promotion of carcinogenesis, an effect that was inhibited by blockade of the common CCL3/6/8 receptor CCR1. Further, Treg depletion unleashed pathologic CD4+ T-cell responses. Our data point to new mechanisms regulating fibroblast differentiation in pancreatic cancer and support the notion that fibroblasts are a heterogeneous population with different and opposing functions in pancreatic carcinogenesis. SIGNIFICANCE: Here, we describe an unexpected cross-talk between Tregs and fibroblasts in pancreatic cancer. Treg depletion resulted in differentiation of inflammatory fibroblast subsets, in turn driving infiltration of myeloid cells through CCR1, thus uncovering a potentially new therapeutic approach to relieve immunosuppression in pancreatic cancer.See related commentary by Aykut et al., p. 345.This article is highlighted in the In This Issue feature, p. 327.

Electromagnetic Transthoracic Nodule Localization for Minimally Invasive Pulmonary Resection.

BACKGROUND: Increased use of chest computed tomography and the institution of lung cancer screening have increased the detection of ground-glass and small pulmonary nodules. Intraoperative localization of these lesions via a minimally invasive thoracoscopic approach can be challenging. We present the feasibility of perioperative transthoracic percutaneous nodule localization using a novel electromagnetic navigation platform. METHODS: This is a multicenter retrospective analysis of a prospectively collected database of patients who underwent perioperative electromagnetic transthoracic nodule localization before attempted minimally invasive resection between July 2016 and March 2018. Localization was performed using methylene blue or a mixture of methylene blue and the patient's blood (1:1 ratio). Patient, nodule, and procedure characteristics were collected and reported. RESULTS: Thirty-one nodules were resected from 30 patients. Twenty-nine of 31 nodules (94%) were successfully localized. Minimally invasive resection was successful in 93% of patients (28/30); 7% (2/30) required conversion to thoracotomy. The median nodule size was 13 mm (interquartile range 25%-75%, 9.5-15.5), and the median depth from the surface of the visceral pleura to the nodule was 10 mm (interquartile range 25%-75%, 5.0-15.9). Seventy-one percent (22/31) of nodules were malignant. No complications associated with nodule localization were reported. CONCLUSIONS: The use of intraoperative electromagnetic transthoracic nodule localization before thoracoscopic resection of small and/or difficult to palpate lung nodules is safe and effective, potentially eliminating the need for direct nodule palpation. Use of this technique aids in minimally invasive localization and resection of small, deep, and/or ground-glass lung nodules.

Myeloid cells are required for PD-1/PD-L1 checkpoint activation and the establishment of an immunosuppressive environment in pancreatic cancer.

BACKGROUND: Pancreatic cancer is characterised by the accumulation of a fibro-inflammatory stroma. Within this stromal reaction, myeloid cells are a predominant population. Distinct myeloid subsets have been correlated with tumour promotion and unmasking of anti-tumour immunity. OBJECTIVE: The goal of this study was to determine the effect of myeloid cell depletion on the onset and progression of pancreatic cancer and to understand the relationship between myeloid cells and T cell-mediated immunity within the pancreatic cancer microenvironment. METHODS: Primary mouse pancreatic cancer cells were transplanted into CD11b-diphtheria toxin receptor (DTR) mice. Alternatively, the iKras* mouse model of pancreatic cancer was crossed into CD11b-DTR mice. CD11b+ cells (mostly myeloid cell population) were depleted by diphtheria toxin treatment during tumour initiation or in established tumours. RESULTS: Depletion of myeloid cells prevented KrasG12D-driven pancreatic cancer initiation. In pre-established tumours, myeloid cell depletion arrested tumour growth and in some cases, induced tumour regressions that were dependent on CD8+ T cells. We found that myeloid cells inhibited CD8+ T-cell anti-tumour activity by inducing the expression of programmed cell death-ligand 1 (PD-L1) in tumour cells in an epidermal growth factor receptor (EGFR)/mitogen-activated protein kinases (MAPK)-dependent manner. CONCLUSION: Our results show that myeloid cells support immune evasion in pancreatic cancer through EGFR/MAPK-dependent regulation of PD-L1 expression on tumour cells. Derailing this crosstalk between myeloid cells and tumour cells is sufficient to restore anti-tumour immunity mediated by CD8+ T cells, a finding with implications for the design of immune therapies for pancreatic cancer.

Professional Caregivers' Oral Care Practices and Beliefs for Elderly Clients Aging In Place.

PURPOSE: As recently as the 1990s long-term care facilities (LTCFs) were the main housing option for semi- or fully-dependent elders. Today, 90% of those 65 and older want to "age in place." The growth of the elderly population that want to "age in place" will require increasing numbers of professional caregivers to assist in oral care practices. The purpose of this study was to address the gap in the knowledge about the oral care practices and beliefs of professional caregivers who work for non-medical in-home care companies charged in the care of "aging in place" elders. METHODS: The Nursing Dental Coping Belief Scale was used in a descriptive cross-sectional study. Professional caregivers (n=67) employed by 3 non-medical in-home care companies in South Texas completed the survey. The survey gathered demographic information, oral care practice questions and oral health belief questions. Statistics used for data analysis included chi-square contingency table analysis. The level of significance was set at p<0.05 for all analyses. RESULTS: Non-medical in-home care companies are not mandated by law to provide training, yet professional caregivers wanted more training in brushing and flossing (85%). A majority (60%) reported being trained. Most (85%) looked inside their client's mouth yet nearly 18% did not floss their client's teeth and only 31% knew if their clients wore dentures. CONCLUSION: While this was a small study, it provides preliminary information that professional caregivers, who serve clients aging in place, want more oral care training. Professional caregivers would be better served if there were more thorough and frequent training provided with managerial oversight.