Vishnu R. Mani

The necrosome promotes pancreatic oncogenesis via CXCL1 and Mincle-induced immune suppression

Neoplastic pancreatic epithelial cells are believed to die through caspase 8-dependent apoptotic cell death, and chemotherapy is thought to promote tumour apoptosis. Conversely, cancer cells often disrupt apoptosis to survive. Another type of programmed cell death is necroptosis (programmed necrosis), but its role in pancreatic ductal adenocarcinoma (PDA) is unclear. There are many potential inducers of necroptosis in PDA, including ligation of tumour necrosis factor receptor 1 (TNFR1), CD95, TNF-related apoptosis-inducing ligand (TRAIL) receptors, Toll-like receptors, reactive oxygen species, and chemotherapeutic drugs. Here we report that the principal components of the necrosome, receptor-interacting protein (RIP)1 and RIP3, are highly expressed in PDA and are further upregulated by the chemotherapy drug gemcitabine. Blockade of the necrosome in vitro promoted cancer cell proliferation and induced an aggressive oncogenic phenotype. By contrast, in vivo deletion of RIP3 or inhibition of RIP1 protected against oncogenic progression in mice and was associated with the development of a highly immunogenic myeloid and T cell infiltrate. The immune-suppressive tumour microenvironment associated with intact RIP1/RIP3 signalling depended in part on necroptosis-induced expression of the chemokine attractant CXCL1, and CXCL1 blockade protected against PDA. Moreover, cytoplasmic SAP130 (a subunit of the histone deacetylase complex) was expressed in PDA in a RIP1/RIP3-dependent manner, and Mincle—its cognate receptor—was upregulated in tumour-infiltrating myeloid cells. Ligation of Mincle by SAP130 promoted oncogenesis, whereas deletion of Mincle protected against oncogenesis and phenocopied the immunogenic reprogramming of the tumour microenvironment that was induced by RIP3 deletion. Cellular depletion suggested that whereas inhibitory macrophages promote tumorigenesis in PDA, they lose their immune-suppressive effects when RIP3 or Mincle is deleted. Accordingly, T cells, which are not protective against PDA progression in mice with intact RIP3 or Mincle signalling, are reprogrammed into indispensable mediators of anti-tumour immunity in the absence of RIP3 or Mincle. Our work describes parallel networks of necroptosis-induced CXCL1 and Mincle signalling that promote macrophage-induced adaptive immune suppression and thereby enable PDA progression.

Dectin 1 activation on macrophages by galectin 9 promotes pancreatic carcinoma and peritumoral immune tolerance

The progression of pancreatic oncogenesis requires immune-suppressive inflammation in cooperation with oncogenic mutations. However, the drivers of intratumoral immune tolerance are uncertain. Dectin 1 is an innate immune receptor crucial for anti-fungal immunity, but its role in sterile inflammation and oncogenesis has not been well defined. Furthermore, non-pathogen-derived ligands for dectin 1 have not been characterized. We found that dectin 1 is highly expressed on macrophages in pancreatic ductal adenocarcinoma (PDA). Dectin 1 ligation accelerated the progression of PDA in mice, whereas deletion of Clec7a—the gene encoding dectin 1—or blockade of dectin 1 downstream signaling was protective. We found that dectin 1 can ligate the lectin galectin 9 in mouse and human PDA, which results in tolerogenic macrophage programming and adaptive immune suppression. Upon disruption of the dectin 1–galectin 9 axis, CD4+ and CD8+ T cells, which are dispensable for PDA progression in hosts with an intact signaling axis, become reprogrammed into indispensable mediators of anti-tumor immunity. These data suggest that targeting dectin 1 signaling is an attractive strategy for developing an immunotherapy for PDA.

Radiation Therapy Induces Macrophages to Suppress T-Cell Responses Against Pancreatic Tumors in Mice.

BACKGROUND & AIMS The role of radiation therapy in the treatment of patients with pancreatic ductal adenocarcinoma (PDA) is controversial. Randomized controlled trials investigating the efficacy of radiation therapy in patients with locally advanced unresectable PDA have reported mixed results, with effects ranging from modest benefit to worse outcomes compared with control therapies. We investigated whether radiation causes inflammatory cells to acquire an immune-suppressive phenotype that limits the therapeutic effects of radiation on invasive PDAs and accelerates progression of preinvasive foci. METHODS We investigated the effects of radiation therapy in p48(Cre);LSL-Kras(G12D) (KC) and p48(Cre);LSLKras(G12D);LSL-Trp53(R172H) (KPC) mice, as well as in C57BL/6 mice with orthotopic tumors grown from FC1242 cells derived from KPC mice. Some mice were given neutralizing antibodies against macrophage colony-stimulating factor 1 (CSF1 or MCSF) or F4/80. Pancreata were exposed to doses of radiation ranging from 2 to 12 Gy and analyzed by flow cytometry. RESULTS Pancreata of KC mice exposed to radiation had a higher frequency of advanced pancreatic intraepithelial lesions and more foci of invasive cancer than pancreata of unexposed mice (controls); radiation reduced survival time by more than 6 months. A greater proportion of macrophages from radiation treated invasive and preinvasive pancreatic tumors had an immune-suppressive, M2-like phenotype compared with control mice. Pancreata from mice exposed to radiation had fewer CD8(+) T cells than controls, and greater numbers of CD4(+) T cells of T-helper 2 and T-regulatory cell phenotypes. Adoptive transfer of T cells from irradiated PDA to tumors of control mice accelerated tumor growth. Radiation induced production of MCSF by PDA cells. A neutralizing antibody against MCSF prevented radiation from altering the phenotype of macrophages in tumors, increasing the anti-tumor T-cell response and slowing tumor growth. CONCLUSIONS Radiation treatment causes macrophages murine PDA to acquire an immune-suppressive phenotype and disabled T-cell-mediated anti-tumor responses. MCSF blockade negates this effect, allowing radiation to have increased efficacy in slowing tumor growth.

NLRP3 signaling drives macrophage-induced adaptive immune suppression in pancreatic carcinoma.

The tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDA) is characterized by immune tolerance, which enables disease to progress unabated by adaptive immunity. However, the drivers of this tolerogenic program are incompletely defined. In this study, we found that NLRP3 promotes expansion of immune-suppressive macrophages in PDA. NLRP3 signaling in macrophages drives the differentiation of CD4+ T cells into tumor-promoting T helper type 2 cell (Th2 cell), Th17 cell, and regulatory T cell populations while suppressing Th1 cell polarization and cytotoxic CD8+ T cell activation. The suppressive effects of NLRP3 signaling were IL-10 dependent. Pharmacological inhibition or deletion of NLRP3, ASC (apoptosis-associated speck-like protein containing a CARD complex), or caspase-1 protected against PDA and was associated with immunogenic reprogramming of innate and adaptive immunity within the TME. Similarly, transfer of PDA-entrained macrophages or T cells from NLRP3−/− hosts was protective. These data suggest that targeting NLRP3 holds the promise for the immunotherapy of PDA.

Mincle suppresses Toll-like receptor 4 activation

Regulation of Toll‐like receptor responses is critical for limiting tissue injury and autoimmunity in both sepsis and sterile inflammation. We found that Mincle, a C‐type lectin receptor, regulates proinflammatory Toll‐like receptor 4 signaling. Specifically, Mincle ligation diminishes Toll‐like receptor 4–mediated inflammation, whereas Mincle deletion or knockdown results in marked hyperresponsiveness to lipopolysaccharide in vitro, as well as overwhelming lipopolysaccharide‐mediated inflammation in vivo. Mechanistically, Mincle deletion does not up‐regulate Toll‐like receptor 4 expression or reduce interleukin 10 production after Toll‐like receptor 4 ligation; however, Mincle deletion decreases production of the p38 mitogen‐activated protein kinase‐dependent inhibitory intermediate suppressor of cytokine signaling 1, A20, and ABIN3 and increases expression of the Toll‐like receptor 4 coreceptor CD14. Blockade of CD14 mitigates the increased sensitivity of Mincle−/− leukocytes to Toll‐like receptor 4 ligation. Collectively, we describe a major role for Mincle in suppressing Toll‐like receptor 4 responses and implicate its importance in nonmycobacterial models of inflammation.

Mincle Signaling Promotes Con A Hepatitis

Con A hepatitis is regarded as a T cell–mediated model of acute liver injury. Mincle is a C-type lectin receptor that is critical in the immune response to mycobacteria and fungi but does not have a well-defined role in preclinical models of non-pathogen–mediated inflammation. Because Mincle can ligate the cell death ligand SAP130, we postulated that Mincle signaling drives intrahepatic inflammation and liver injury in Con A hepatitis. Acute liver injury was assessed in the murine Con A hepatitis model using C57BL/6, Mincle−/−, and Dectin-1−/− mice. The role of C/EBPβ and hypoxia-inducible factor-1α (HIF-1α) signaling was assessed using selective inhibitors. We found that Mincle was highly expressed in hepatic innate inflammatory cells and endothelial cells in both mice and humans. Furthermore, sterile Mincle ligands and Mincle signaling intermediates were increased in the murine liver in Con A hepatitis. Most significantly, Mincle deletion or blockade protected against Con A hepatitis, whereas Mincle ligation exacerbated disease. Bone marrow chimeric and adoptive transfer experiments suggested that Mincle signaling in infiltrating myeloid cells dictates disease phenotype. Conversely, signaling via other C-type lectin receptors did not alter disease course. Mechanistically, we found that Mincle blockade decreased the NF-κβ–related signaling intermediates C/EBPβ and HIF-1α, both of which are necessary in macrophage-mediated inflammatory responses. Accordingly, Mincle deletion lowered production of nitrites in Con A hepatitis and inhibition of both C/EBPβ and HIF-1α reduced the severity of liver disease. Our work implicates a novel innate immune driver of Con A hepatitis and, more broadly, suggests a potential role for Mincle in diseases governed by sterile inflammation.

Surgical resection of a giant primary liposarcoma of the anterior mediastinum.

This case describes the incidental finding and surgical removal of an 1.8-kg liposarcoma in the anterior mediastinum. These tumors are very rare and would normally present with symptoms of intrathoracic compression; however, this patient was completely asymptomatic. The case presentation and treatment rationale are described along with a brief review of existing literature.

Inverted Meckel’s Diverticulum: Rare Etiology of an Intestinal Obstruction

Acute gastrointestinal obstruction can have a varied spectrum of clinical presentation and etiologies. It has been studied in detail and the management criteria have been well defined for the most part in our era. The etiologies are usually well defined. However, acute small bowel obstruction (SBO) due to intussusception caused by an inverted Meckels diverticulum is a rare phenomenon that is often times missed on initial presentation and/or consequently until resected and visualized on pathological examination. We present a case of a 34-year-old presenting with symptoms and signs of acute intestinal obstruction and radiographic exam showing ileo-ileal intussusception. The patient failed to improve initially following conservative management and was taken to the operating room for small bowel resection which then revealed an inverted Meckel’s diverticulum.

Acute Pancreatitis with Splenic Infarction as Early Postoperative Complication following Laparoscopic Sleeve Gastrectomy

Obesity is becoming a global health burden along with its comorbidities. It imposes tremendous financial burden and health costs worldwide. Surgery has emerged as the definitive treatment option for morbidly obese patients with comorbidities. Laparoscopic sleeve gastrectomy is performed now more than ever making it imperative for physicians and surgeons to recognize both the common and the uncommon risks and complications associated with it. In this report we describe a rare early life-threatening postoperative complication following laparoscopic sleeve gastrectomy. From our extensive review of literature, there is no existing report of acute pancreatitis with splenic infarction postsleeve gastrectomy to this date.

A Rare Case of Diffuse Idiopathic Pulmonary Neuroendocrine Cell Hyperplasia

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a rare clinical condition with only about 100 cases reported in the literature. It is characterized by primary hyperplasia of pulmonary neuroendocrine cells (PNECs) which are specialized epithelial cells located throughout the entire respiratory tract, from the trachea to the terminal airways. DIPNECH appears in various forms that include diffuse proliferation of scattered neuroendocrine cells, small nodules, or a linear proliferation. It is usually seen in middle-aged, nonsmoking women with symptoms of cough, dyspnea, and wheezing. We present a 45-year-old, nonsmoking woman who presented with symptoms of DIPNECH associated with bilateral pulmonary nodules and left hilar adenopathy. Of interest, DIPNECH in our patient was associated with metastatic pulmonary carcinoids, papillary carcinoma of the left breast, oncocytoma and angiomyolipoma of her left kidney, and cortical nodules suggestive of tuberous sclerosis. She had video assisted thoracoscopic surgery (VATS), modified radical mastectomy with reconstruction, and radical nephrectomy. She is currently symptom-free most of the time with over two years of follow-up.