An iron-rich subset of macrophages promotes tumor growth through a Bach1-Ednrb axis.

We define a subset of macrophages in the tumor microenvironment characterized by high intracellular iron and enrichment of heme and iron metabolism genes. These iron-rich tumor-associated macrophages (iTAMs) supported angiogenesis and immunosuppression in the tumor microenvironment and were conserved between mice and humans. iTAMs comprise two additional subsets based on gene expression profile and location-perivascular (pviTAM) and stromal (stiTAM). We identified the endothelin receptor type B (Ednrb) as a specific marker of iTAMs and found myeloid-specific deletion of Ednrb to reduce tumor growth and vascular density. Further studies identified the transcription factor Bach1 as a repressor of the iTAM transcriptional program, including Ednrb expression. Heme is a known inhibitor of Bach1, and, correspondingly, heme exposure induced Ednrb and iTAM signature genes in macrophages. Thus, iTAMs are a distinct macrophage subset regulated by the transcription factor Bach1 and characterized by Ednrb-mediated immunosuppressive and angiogenic functions.

Mapping and modeling human colorectal carcinoma interactions with the tumor microenvironment.

The initiation and progression of cancer are intricately linked to the tumor microenvironment (TME). Understanding the function of specific cancer-TME interactions poses a major challenge due in part to the complexity of the in vivo microenvironment. Here we predict cancer-TME interactions from single cell transcriptomic maps of both human colorectal cancers (CRCs) and mouse CRC models, ask how these interactions are altered in human tumor organoid (tumoroid) cultures, and functionally recapitulate human myeloid-carcinoma interactions in vitro. Tumoroid cultures suppress gene expression programs involved in inflammation and immune cell migration, providing a reductive platform for re-establishing carcinoma-immune cell interactions in vitro. Introduction of human monocyte-derived macrophages into tumoroid cultures instructs macrophages to acquire immunosuppressive and pro-tumorigenic gene expression programs similar to those observed in vivo. This includes hallmark induction of SPP1, encoding Osteopontin, an extracellular CD44 ligand with established oncogenic effects. Taken together, these findings offer a framework for understanding CRC-TME interactions and provide a reductionist tool for modeling specific aspects of these interactions.

MYC Levels Regulate Metastatic Heterogeneity in Pancreatic Adenocarcinoma.

The degree of metastatic disease varies widely among patients with cancer and affects clinical outcomes. However, the biological and functional differences that drive the extent of metastasis are poorly understood. We analyzed primary tumors and paired metastases using a multifluorescent lineage-labeled mouse model of pancreatic ductal adenocarcinoma (PDAC)-a tumor type in which most patients present with metastases. Genomic and transcriptomic analysis revealed an association between metastatic burden and gene amplification or transcriptional upregulation of MYC and its downstream targets. Functional experiments showed that MYC promotes metastasis by recruiting tumor-associated macrophages, leading to greater bloodstream intravasation. Consistent with these findings, metastatic progression in human PDAC was associated with activation of MYC signaling pathways and enrichment for MYC amplifications specifically in metastatic patients. Collectively, these results implicate MYC activity as a major determinant of metastatic burden in advanced PDAC. SIGNIFICANCE: Here, we investigate metastatic variation seen clinically in patients with PDAC and murine PDAC tumors and identify MYC as a major driver of this heterogeneity.This article is highlighted in the In This Issue feature, p. 275.

Calcium signaling induces a partial EMT.

Epithelial plasticity, or epithelial-to-mesenchymal transition (EMT), is a well-recognized form of cellular plasticity, which endows tumor cells with invasive properties and alters their sensitivity to various agents, thus representing a major challenge to cancer therapy. It is increasingly accepted that carcinoma cells exist along a continuum of hybrid epithelial-mesenchymal (E-M) states and that cells exhibiting such partial EMT (P-EMT) states have greater metastatic competence than those characterized by either extreme (E or M). We described recently a P-EMT program operating in vivo by which carcinoma cells lose their epithelial state through post-translational programs. Here, we investigate the underlying mechanisms and report that prolonged calcium signaling induces a P-EMT characterized by the internalization of membrane-associated E-cadherin (ECAD) and other epithelial proteins as well as an increase in cellular migration and invasion. Signaling through Gαq-associated G-protein-coupled receptors (GPCRs) recapitulates these effects, which operate through the downstream activation of calmodulin-Camk2b signaling. These results implicate calcium signaling as a trigger for the acquisition of hybrid/partial epithelial-mesenchymal states in carcinoma cells.

Macrophages in SHH subgroup medulloblastoma display dynamic heterogeneity that varies with treatment modality.

Tumor-associated macrophages (TAMs) play an important role in tumor immunity and comprise of subsets that have distinct phenotype, function, and ontology. Transcriptomic analyses of human medulloblastoma, the most common malignant pediatric brain cancer, showed that medulloblastomas (MBs) with activated sonic hedgehog signaling (SHH-MB) have significantly more TAMs than other MB subtypes. Therefore, we examined MB-associated TAMs by single-cell RNA sequencing of autochthonous murine SHH-MB at steady state and under two distinct treatment modalities: molecular-targeted inhibitor and radiation. Our analyses reveal significant TAM heterogeneity, identify markers of ontologically distinct TAM subsets, and show the impact of brain microenvironment on the differentiation of tumor-infiltrating monocytes. TAM composition undergoes dramatic changes with treatment and differs significantly between molecular-targeted and radiation therapy. We identify an immunosuppressive monocyte-derived TAM subset that emerges with radiation therapy and demonstrate its role in regulating T cell and neutrophil infiltration in MB.

Counter Regulation of Spic by NF-κB and STAT Signaling Controls Inflammation and Iron Metabolism in Macrophages.

Activated macrophages must carefully calibrate their inflammatory responses to balance efficient pathogen control with inflammation-mediated tissue damage, but the molecular underpinnings of this "balancing act" remain unclear. Using genetically engineered mouse models and primary macrophage cultures, we show that Toll-like receptor (TLR) signaling induces the expression of the transcription factor Spic selectively in patrolling monocytes and tissue macrophages by a nuclear factor κB (NF-κB)-dependent mechanism. Functionally, Spic downregulates pro-inflammatory cytokines and promotes iron efflux by regulating ferroportin expression in activated macrophages. Notably, interferon-gamma blocks Spic expression in a STAT1-dependent manner. High levels of interferon-gamma are indicative of ongoing infection, and in its absence, activated macrophages appear to engage a "default" Spic-dependent anti-inflammatory pathway. We also provide evidence for the engagement of this pathway in sterile inflammation. Taken together, our findings uncover a pathway wherein counter-regulation of Spic by NF-κB and STATs attune inflammatory responses and iron metabolism in macrophages.

Tumor-Derived Retinoic Acid Regulates Intratumoral Monocyte Differentiation to Promote Immune Suppression.

The immunosuppressive tumor microenvironment (TME) is a major barrier to immunotherapy. Within solid tumors, why monocytes preferentially differentiate into immunosuppressive tumor-associated macrophages (TAMs) rather than immunostimulatory dendritic cells (DCs) remains unclear. Using multiple murine sarcoma models, we find that the TME induces tumor cells to produce retinoic acid (RA), which polarizes intratumoral monocyte differentiation toward TAMs and away from DCs via suppression of DC-promoting transcription factor Irf4. Genetic inhibition of RA production in tumor cells or pharmacologic inhibition of RA signaling within TME increases stimulatory monocyte-derived cells, enhances T cell-dependent anti-tumor immunity, and synergizes with immune checkpoint blockade. Furthermore, an RA-responsive gene signature in human monocytes correlates with an immunosuppressive TME in multiple human tumors. RA has been considered as an anti-cancer agent, whereas our work demonstrates its tumorigenic capability via myeloid-mediated immune suppression and provides proof of concept for targeting this pathway for tumor immunotherapy.

Grade is a Dominant Risk Factor for Metastasis in Patients with Rectal Neuroendocrine Tumors.

BACKGROUND: Small (< 2 cm) and diminutive (< 1 cm) rectal neuroendocrine tumors (RNETs) are often described as indolent lesions. A large single-center experience was reviewed to determine the incidence of metastasis and the risk factors for its occurrence. METHODS: Cases of RNET between 2010 and 2017 at a single institution were retrospectively reviewed. The rate of metastasis was determined, and outcomes were stratified by tumor size and grade. Uni- and multivariable predictors of metastasis were identified, and a classification and regression tree analysis was used to stratify the risk for distant metastasis. RESULTS: The study identified 98 patients with RNET. The median follow-up period was 28 months. Of the 98 patients, 79 had primary tumors smaller than 1 cm, 8 had tumors 1 to 2 cm in size, and 11 had tumors 2 cm in size or larger. In terms of grade, 86 patients had grade 1 (G1) tumors, 8 patients had grade 2 (G2) tumors, and 4 patients had grade 3 (G3) tumors. Twelve patients developed metastatic disease. Both size and grade were associated with distant metastasis in the uni- and multivariable analyses, but when stratified by grade, size was predictive of metastasis only for G1 tumors (p < 0.001). Among the 12 patients with metastatic disease, 3 (25%) had diminutive primary tumors, and 9 (75%) had primary tumors 2 cm in size or larger. Diminutive tumors that metastasized were all G2. CONCLUSIONS: Patients with diminutive and small RNETs are at risk for metastatic disease. Tumor grade is a dominant predictor of dissemination. More rigorous staging, closer surveillance, or more aggressive initial management may be warranted for patients with G2 tumors, irrespective of size.

Primary Bone Tumors: Challenges and Opportunities for CAR-T Therapies.

Primary malignant bone tumors are rare, occur in all age groups, and include distinct entities such as osteosarcoma, Ewing sarcoma, and chondrosarcoma. Traditional treatment with some combination of chemotherapy, surgery, and radiation has reached the limit of efficacy, with substantial room for improvement in patient outcome. Furthermore, genomic characterization of these tumors reveals a paucity of actionable molecular targets. Against this backdrop, recent advances in cancer immunotherapy represent a silver lining in the treatment of primary bone cancer. Major strategies in cancer immunotherapy include stimulating naturally occurring anti-tumor T cells and adoptive transfer of tumor-specific cytotoxic T cells. Chimeric antigen receptor T cells (CAR-T cells) belong to the latter strategy and are an impressive application of both insights into T cell biology and advances in genetic engineering. In this review, we briefly describe the CAR-T approach and discuss its applications in primary bone tumors. © 2019 American Society for Bone and Mineral Research.

Predictors of Metastases in Rectal Neuroendocrine Tumors: Results of a National Cohort Study.

BACKGROUND: Rectal neuroendocrine tumors are often found incidentally. Local excision alone has been advocated for lesions ≤2 cm; however, the evidence base for this approach is limited. OBJECTIVE: Associations among tumor size, degree of differentiation, and presence of distant metastatic disease were examined. DESIGN: This was a retrospective cohort study. SETTINGS: This study was conducted using a nationwide cohort. PATIENTS: A total of 4893 patients with rectal neuroendocrine tumors were identified in the National Cancer Database (2006-2015). MAIN OUTCOME MEASURES: Logistic regression analyses were used to evaluate associations among tumor size, degree of differentiation, and presence of regional and distant metastatic disease. Cut point analysis was performed to identify an optimal size threshold predictive of distant metastatic disease. RESULTS: Of patients included for analysis, 3880 (79.3%) had well-differentiated tumors, 540 (11.0%) had moderately differentiated tumors, and 473 (9.7%) had poorly differentiated tumors. On logistic regression, increasing size was associated with a higher likelihood of pathologically confirmed lymph node involvement (among patients undergoing proctectomy), and both size and degree of differentiation were independently associated with a higher likelihood of distant metastatic disease. The association between tumor size and distant metastatic disease was stronger for well-differentiated and moderately differentiated tumors (OR = 1.4; p < 0.001 for both) than for poorly differentiated tumors (OR = 1.1; p = 0.010). For well-differentiated tumors, the optimal cut point for the presence of distant metastatic disease was 1.15 cm (area under the curve = 0.88; 88% sensitive and 88% specific). Tumors ≥1.15 cm in diameter were associated with a substantially increased incidence of distant metastatic disease (72/449 (13.8%)). For moderately differentiated tumors, the optimal cut point was also 1.15 cm (area under the curve = 0.87, 100% sensitive and 75% specific). LIMITATIONS: This study was limited by its retrospective design. CONCLUSIONS: Tumor size and degree of differentiation are predictive of regional and distant metastatic disease in rectal neuroendocrine tumors. Patients with tumors >1.15 cm are at substantial risk of distant metastasis and should be staged and managed accordingly. See Video Abstract at http://links.lww.com/DCR/A778.

Malignant Bowel Obstruction: Reappraising the Value of Surgery.

Urgent palliative surgery in the setting of advanced malignancy is associated with significant morbidity, mortality, and cost. Malignant bowel obstruction is the most frequent indication for such intervention. Traditional surgical dogma is often invoked to justify associated risks and cost, but little evidence exists to support surgical over nonsurgical approaches. Evolving evidence may provide more meaningful guidance for treatment selection.

Impact of acute postoperative limb ischemia after cardiac and thoracic aortic surgery.

OBJECTIVE: Acute limb ischemia (ALI) is the cause of significant morbidity and mortality. Although ALI after cardiac surgery is associated with high rates of morbidity and mortality, there are no robust, controlled analyses of the risk factors and outcomes of ALI in this setting. We aimed to identify risk factors for and to delineate outcomes after ALI in patients undergoing cardiac surgery. METHODS: We performed a retrospective review of prospectively collected data on patients undergoing cardiac surgery at our institution between 2002 and 2012. RESULTS: Between 2002 and 2012, there were 11,343 patients who underwent major open cardiac surgery, with 156 cases of ALI for an incidence of 1.4%. In a multivariable model, significant risk factors for ALI included body surface area (odds ratio [OR], 0.41; 95% confidence interval [CI], 0.18-0.92), current smoking status (OR, 2.2; 95% CI, 1.3-3.7), peripheral arterial disease (OR, 2.5; 95% CI, 1.6-3.7), nonelective operative status (OR, 1.9-5.0; 95% CI, 1.2-19.7), use of extracorporeal membrane oxygenation (OR, 5.6; 95% CI, 2.5-11.6) or intra-aortic balloon pump (OR, 4.7; 95% CI, 2.9-7.5), and valve operation (OR, 2.1; 95% CI, 1.1-4.0). There were 105 (67%) patients who developed ALI who required an operation, and 27 (17%) required an amputation on the index admission. ALI was associated with a significant reduction in long-term survival (hazard ratio, 3.72; 95% CI, 2.97-4.65; P < .0001). CONCLUSIONS: ALI is associated with significant morbidity and mortality, and it is also associated with reduced long-term survival. Those patients with the risk factors described require extra vigilance to limit the risk of ALI and should be managed in accordance with the patient's overall clinical condition and goals of care.

Value in palliative cancer surgery: A critical assessment.

Emergency operations are associated with increased morbidity, mortality, and cost compared to elective operations. Palliative and emergent surgery for patients with advanced malignancies is associated with additional risk and remains controversial. Emergent or palliative interventions can be broadly categorized according to indication. Tumor related complications (bleeding, obstruction, or perforation) merit specific consideration, as do specific presentations such as pneumoperitoneum, pneumatosis intestinalis, or peritonitis from other causes that may arise during active therapy for malignancies. Although nonoperative, endoscopic, and interventional treatment modalities are frequently available, surgery remains the only effective therapy in selected situations such as small intestinal obstruction and tumor perforation. Selection of patients for surgery requires consideration of factors including overall prognosis, performance status, and patients' priorities. Selection and risk assessment tools underscore the limited capacity of patients' with higher risk features for durable recovery but do not supplant nuanced clinical judgment. J. Surg. Oncol. 2016;114:311-315. © 2016 Wiley Periodicals, Inc.

Multidisciplinary management of nonfunctional neuroendocrine tumor of the pancreas.

Pancreatic neuroendocrine tumors (PNETs) are a rare and diverse group of tumors; nonfunctional (NF) PNETs account for the majority of cases. Most patients with NF-PNETs have metastatic disease at the time of presentation. A variety of treatment modalities exist, including medical, liver directed, and surgical treatments. Aggressive surgical management is associated with prolonged survival, however available data are limited by selection bias and the frequent combination of PNETs with carcinoid tumors. Although few patients with metastatic disease will be cured, application of currently available therapies in a multidisciplinary setting can lead to excellent outcomes with prolonged patient survival.