TREM2 macrophages drive NK cell paucity and dysfunction in lung cancer

Natural killer (NK) cells are commonly reduced in human tumors, enabling many to evade surveillance. Here, we sought to identify cues that alter NK cell activity in tumors. We found that, in human lung cancer, the presence of NK cells inversely correlated with that of monocyte-derived macrophages (mo-macs). In a murine model of lung adenocarcinoma, we show that engulfment of tumor debris by mo-macs triggers a pro-tumorigenic program governed by triggering receptor expressed on myeloid cells 2 (TREM2). Genetic deletion of Trem2 rescued NK cell accumulation and enabled an NK cell-mediated regression of lung tumors. TREM2+ mo-macs reduced NK cell activity by modulating interleukin (IL)-18/IL-18BP decoy interactions and IL-15 production. Notably, TREM2 blockade synergized with an NK cell-activating agent to further inhibit tumor growth. Altogether, our findings identify a new axis, in which TREM2+ mo-macs suppress NK cell accumulation and cytolytic activity. Dual targeting of macrophages and NK cells represents a new strategy to boost antitumor immunity.

Spatial Positioning and Matrix Programs of Cancer-Associated Fibroblasts Promote T-cell Exclusion in Human Lung Tumors

It is currently accepted that cancer-associated fibroblasts (CAF) participate in T-cell exclusion from tumor nests. To unbiasedly test this, we used single-cell RNA sequencing coupled with multiplex imaging on a large cohort of lung tumors. We identified four main CAF populations, two of which are associated with T-cell exclusion: (i) MYH11+αSMA+ CAF, which are present in early-stage tumors and form a single cell layer lining cancer aggregates, and (ii) FAP+αSMA+ CAF, which appear in more advanced tumors and organize in patches within the stroma or in multiple layers around tumor nests. Both populations orchestrate a particular structural tissue organization through dense and aligned fiber deposition compared with T cell-permissive CAF. Yet they produce distinct matrix molecules, including collagen IV (MYH11+αSMA+ CAF) and collagen XI/XII (FAP+αSMA+ CAF). Hereby, we uncovered unique molecular programs of CAF driving T-cell marginalization, whose targeting should increase immunotherapy efficacy in patients bearing T cell-excluded tumors.

SIGNIFICANCE

The cellular and molecular programs driving T-cell marginalization in solid tumors remain unclear. Here, we describe two CAF populations associated with T-cell exclusion in human lung tumors. We demonstrate the importance of pairing molecular and spatial analysis of the tumor microenvironment, a prerequisite to developing new strategies targeting T cell-excluding CAF. See related commentary by Sherman, p. 2501. This article is highlighted in the In This Issue feature, p. 2483.

Single-cell analysis of human non-small cell lung cancer lesions refines tumor classification and patient stratification

Immunotherapy is a mainstay of non-small cell lung cancer (NSCLC) management. While tumor mutational burden (TMB) correlates with response to immunotherapy, little is known about the relationship between the baseline immune response and tumor genotype. Using single-cell RNA sequencing, we profiled 361,929 cells from 35 early-stage NSCLC lesions. We identified a cellular module consisting of PDCD1⁺CXCL13⁺ activated T cells, IgG⁺ plasma cells, and SPP1⁺ macrophages, referred to as the lung cancer activation module (LCAM^hi). We confirmed LCAM^hi enrichment in multiple NSCLC cohorts, and paired CITE-seq established an antibody panel to identify LCAM^hi lesions. LCAM presence was found to be independent of overall immune cell content and correlated with TMB, cancer testis antigens, and TP53 mutations. High baseline LCAM scores correlated with enhanced NSCLC response to immunotherapy even in patients with above median TMB, suggesting that immune cell composition, while correlated with TMB, may be a nonredundant biomarker of response to immunotherapy.

MDSC: Markers, development, states, and unaddressed complexity

Myeloid-derived suppressor cells (MDSCs) are one of the most discussed biological entities in immunology. While the context and classification of this group of cells has evolved, MDSCs most commonly describe cells arising during chronic inflammation, especially late-stage cancers, and are defined by their T cell immunosuppressive functions. This MDSC concept has helped explain myeloid phenomena associated with disease outcome, but currently lacks clear definitions and a unifying framework across pathologies. Here, we propose such a framework to classify MDSCs as discrete cell states based on activation signals in myeloid populations leading to suppressive modes characterized by specific, measurable effects. Developing this level of knowledge of myeloid states across pathological conditions may ultimately transform how disparate diseases are grouped and treated.

"America First" Will Destroy U.S. Science

The U.S. government has sought to restrict immigration under the “America First” doctrine. These policies severely harm American science by stripping it of talent and eliminating a major driver of its innovation engine. We urge scientists to work to reverse these policies and forcefully condemn anti-immigrant sentiments.

Author Correction: A conserved dendritic-cell regulatory program limits antitumour immunity

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A conserved dendritic-cell regulatory program limits antitumour immunity

Checkpoint blockade therapies have improved cancer treatment, but such immunotherapy regimens fail in a large subset of patients. Conventional type 1 dendritic cells (DC1s) control the response to checkpoint blockade in preclinical models and are associated with better overall survival in patients with cancer, reflecting the specialized ability of these cells to prime the responses of CD8⁺ T cells^1-3. Paradoxically, however, DC1s can be found in tumours that resist checkpoint blockade, suggesting that the functions of these cells may be altered in some lesions. Here, using single-cell RNA sequencing in human and mouse non-small-cell lung cancers, we identify a cluster of dendritic cells (DCs) that we name 'mature DCs enriched in immunoregulatory molecules' (mregDCs), owing to their coexpression of immunoregulatory genes (Cd274, Pdcd1lg2 and Cd200) and maturation genes (Cd40, Ccr7 and Il12b). We find that the mregDC program is expressed by canonical DC1s and DC2s upon uptake of tumour antigens. We further find that upregulation of the programmed death ligand 1 protein-a key checkpoint molecule-in mregDCs is induced by the receptor tyrosine kinase AXL, while upregulation of interleukin (IL)-12 depends strictly on interferon-γ and is controlled negatively by IL-4 signalling. Blocking IL-4 enhances IL-12 production by tumour-antigen-bearing mregDC1s, expands the pool of tumour-infiltrating effector T cells and reduces tumour burden. We have therefore uncovered a regulatory module associated with tumour-antigen uptake that reduces DC1 functionality in human and mouse cancers.

An Innovative Consulting Group for Sharing Expertise on Launching and Sustaining Student-Run Free Clinics: A Model for Building Student-Run Endeavors

Student-run, physician-supervised free clinics (SRFCs) provide essential healthcare services for many uninsured and underinsured patients in the USA. While SRFCs serve diverse populations and offer distinct services, they face many similar barriers to successful clinic operation. Historically, the sharing of best practices and development strategies across SRFCs has been limited and insufficient for both new and emerging free clinics. To address these challenges, in 2015, the East Harlem Health Outreach Program (EHHOP) at the Icahn School of Medicine at Mount Sinai formed the EHHOP Consulting Group (ECG), with the goal of providing client SRFCs individualized support from medical students. ECG draws from the experience of EHHOP and other veteran SRFCs to provide customized solutions to best address client SRFC needs. Here, we describe ECG's inception, structure, and consulting work with client SRFCs. We propose that this interactive, longitudinal model can be adapted to other healthcare trainee initiatives where cross-institutional collaboration could prove beneficial.