Lung tumor MHCII immunity depends on in situ antigen presentation by fibroblasts

CAF-mediated tumor vascularization: From mechanistic insights to targeted therapies

Cancer-associated fibroblasts (CAFs) are a major component of the tumor microenvironment (TME) and play a crucial role in tumor progression. The biological properties of tumors, such as drug resistance, vascularization, immunosuppression, and metastasis are closely associated with CAFs. During tumor development, CAFs contribute to tumor progression by remodeling the extracellular matrix (ECM), inhibiting immune cell function, promoting angiogenesis, and facilitating tumor cell growth, invasion, and metastasis. Studies have shown that CAFs can promote endothelial cell proliferation by directly secreting cytokines such as vascular endothelial growth factor (VEGF) and fibroblast Growth Factor (FGF), as well as through exosomes. CAFs also secrete the chemokine stromal cell-derived factor 1 (SDF-1) to recruit endothelial progenitor cells (EPCs) into the peripheral blood and guide their migration to the tumor periphery. Additionally, CAFs can induce tumor cells to transform into "endothelial cells" that participate in vascular wall formation. However, the precise mechanisms remain to be further investigated. Due to their widespread presence in various solid tumors and their tumor-promoting function, CAFs are emerging as therapeutic targets. In this review, we summarize the specific mechanisms through which CAFs promote angiogenesis and outline current therapeutic strategies targeting CAF-induced vascularization, ongoing clinical trials targeting CAFs, and discuss potential future treatment approaches. We hope this will contribute to the advancement of CAF-targeted tumor treatment strategies.

Stromal heterogeneity in the adult lung delineated by single-cell genomics

Stromal cells in the lung provide structural support to other cells and play critical roles in inflammation, repair, and fibrosis after injury. Recent technological advancements in single-cell genomics have tremendously improved our knowledge of stromal heterogeneity in the lung. Stromal heterogeneity in single-cell RNA sequencing data is often conserved across different studies despite the different annotation strategies. Spatial analyses suggest that each stromal subset is characterized by unique anatomic locations in the adult lung. This review overviews the stromal heterogeneity delineated by single-cell RNA sequencing studies and highlights the functional characteristics and locations of each population.

Pluripotent stem cell-derived mesenchymal stem cells for therapeutic applications, developmental study, and cancer research

Human mesenchymal stem cells (MSCs) have been widely studied and applied for the treatment of various diseases due to their crucial role in tissue repair and regeneration. Compared to MSCs isolated from somatic tissues, MSCs differentiated from human pluripotent stem cells (ps-MSCs) have demonstrated similar therapeutic effects while possessing some advantages in quality control and assurance, given their unlimited and consistent supply of source cells. This makes ps-MSCs highly druggable and promising for therapeutic applications. In this minireview, we introduce the latest progress in ps-MSC research, focusing on the therapeutic properties, origin, in vivo development, and application of ps-MSCs in cancer research. We will also discuss the perspectives and challenges of this relatively new source of MSCs.

Fibroblasts in immune responses, inflammatory diseases and therapeutic implications

Once regarded as passive bystander cells of the tissue stroma, fibroblasts have emerged as active orchestrators of tissue homeostasis and disease. From regulating immunity and controlling tissue remodelling to governing cell growth and differentiation, fibroblasts assume myriad roles in guiding normal tissue development, maintenance and repair. By comparison, in chronic inflammatory diseases such as rheumatoid arthritis, fibroblasts recruit and sustain inflammatory leukocytes, become dominant producers of pro-inflammatory factors and catalyse tissue destruction. In other disease contexts, fibroblasts promote fibrosis and impair host control of cancer. Single-cell studies have uncovered striking transcriptional and functional heterogeneity exhibited by fibroblasts in both normal tissues and diseased tissues. In particular, advances in the understanding of fibroblast pathology in rheumatoid arthritis have shed light on pathogenic fibroblast states in other chronic diseases. The differentiation and activation of these fibroblast states is driven by diverse physical and chemical cues within the tissue microenvironment and by cell-intrinsic signalling and epigenetic mechanisms. These insights into fibroblast behaviour and regulation have illuminated therapeutic opportunities for the targeted deletion or modulation of pathogenic fibroblasts across many diseases.

CD4+T and CD8+T cells profile in lung inflammation and fibrosis: targets and potential therapeutic drugs

Pulmonary fibrosis is an interstitial lung disease characterized by chronic progressive fibrosis. It is associated with fibrocyte proliferation and collagen deposition, leading to severe, irreversible lung function decline. Despite extensive research, the diagnosis and treatment of pulmonary fibrosis are complicated and have no effective treatment. During the formation of pulmonary fibrosis, immune dysregulation by inflammatory cell infiltration is the key driver of pulmonary fibrosis. Recently, single-cell sequencing analysis of silicosis mice showed that various cells in the alveolar immune microenvironment are involved in forming pulmonary fibrosis, such as macrophages, fibroblasts, epithelial cells, etc. Among them, T cell subpopulations in silicosis mice were significantly activated, indicating that T lymphocyte subsets play an essential role in the process of pulmonary fibrosis. More and more pulmonary clinical studies show that T lymphocytes in the lung immune microenvironment play an important and multifaceted role. This article summarizes the role of CD4+T cells and CD8+T cells in pulmonary fibrosis. This article provides some new insight into the potential therapy target that can delay the process of pulmonary fibrosis by regulating the proportions of different subpopulations of T lymphocytes and some related signaling pathways.

Evoking the Cancer-immunity cycle by targeting the tumor-specific antigens in Cancer immunotherapy

Cancer-related deaths continue to rise, largely due to the suboptimal efficacy of current treatments. Fortunately, immunotherapy has emerged as a promising alternative, offering new hope for cancer patients. Among various immunotherapy approaches, targeting tumor-specific antigens (TSAs) has gained particular attention due to its demonstrated success in clinical settings. Despite these advancements, there are still gaps in our understanding of TSAs. Therefore, this review explores the life cycle of TSAs in cancer, the methods used to identify them, and recent advances in TSAs-targeted cancer therapies. Enhancing medical professionals' understanding of TSAs will help facilitate the development of more effective TSAs-based cancer treatments.

Reciprocal Modulation of Tumour and Immune Cell Motility: Uncovering Dynamic Interplays and Therapeutic Approaches

Dysregulated cell movement is a hallmark of cancer progression and metastasis, the leading cause of cancer-related mortality. The metastatic cascade involves tumour cell migration, invasion, intravasation, dissemination, and colonisation of distant organs. These processes are influenced by reciprocal interactions between cancer cells and the tumour microenvironment (TME), including immune cells, stromal components, and extracellular matrix proteins. The epithelial-mesenchymal transition (EMT) plays a crucial role in providing cancer cells with invasive and stem-like properties, promoting dissemination and resistance to apoptosis. Conversely, the mesenchymal-epithelial transition (MET) facilitates metastatic colonisation and tumour re-initiation. Immune cells within the TME contribute to either anti-tumour response or immune evasion. These cells secrete cytokines, chemokines, and growth factors that shape the immune landscape and influence responses to immunotherapy. Notably, immune checkpoint blockade (ICB) has transformed cancer treatment, yet its efficacy is often dictated by the immune composition of the tumour site. Elucidating the molecular cross-talk between immune and cancer cells, identifying predictive biomarkers for ICB response, and developing strategies to convert cold tumours into immune-active environments is critical to overcoming resistance to immunotherapy and improving patient survival.

Transcriptome Landscape of Cancer-Associated Fibroblasts in Human PDAC

Cancer-associated fibroblasts (CAFs) play a crucial role in the progression of pancreatic ductal adenocarcinoma (PDAC). Here, integrated single-cell RNA sequencing analysis is utilized to comprehensively map CAFs in the human PDAC tumor microenvironment (TME). Normal fibroblasts (NFs) and nine distinct CAF subtypes are identified including newly identified CAF subtypes, CDCP1+FTL+ CAFs, transitional CAFs (tCAFs), interferon simulated genes (ISG)+ myofibroblastic CAFs (myCAFs), and proliferative CAFs (pCAFs). CDCP1+FTL+ CAFs, pCAFs, and ISG+ myCAFs are associated with unfavorable clinical outcomes. CDCP1+FTL+ CAFs exhibit enhanced glycolysis and iron metabolism, resisting ferroptosis. The antigen-presenting CAFs (apCAFs) show high heterogeneity, consisting of multiple subtypes expressing distinct immune cell signatures. The CAF subtypes display differentiation plasticity, transitioning from early normal-like CAFs (nCAFs) to inflammatory CAFs (iCAFs) and myCAFs, ultimately leading to more invasive pCAFs. AP-1 family members FOS and JUN regulate the malignant phenotype conversion of NFs to nCAFs, while transforming growth factor-β (TGFβ) and interferon-γ (IFNγ) signals trigger the interconversion between classic myCAFs and iCAFs, respectively. A close interaction between CAFs and myeloid cells (especially neutrophils) is further observed in PDAC-TME, mainly mediated by CXCR4-CXCL12 chemotaxis. This work depicts a detailed CAF map and its dynamic interconvertible shift, providing important insights for combined targeted CAFs therapy.

Single-cell analysis and machine learning-based integration develop an immune-responsive signature of antigen-presenting cancer-associated fibroblasts in lung adenocarcinoma

Background

Cancer-associated fibroblasts (CAFs) are pivotal regulators of the tumor immune microenvironment, shaping immune responses and influencing therapeutic outcomes. While previous studies have predominantly focused on CAF subpopulations that impair responses to immune checkpoint inhibitors (ICIs), CAF subsets associated with favorable ICIs responses in lung adenocarcinoma (LUAD) remain underexplored. In this study, we integrated bulk RNA and single-cell RNA sequencing data from LUAD samples to identify CAF subpopulations relevant to ICIs efficacy.

Methods

Using a machine learning-driven approach, we developed a robust immune response signature based on this antigen-presenting CAFs (apCAFs) subset to predict ICIs responses.

Results

We uncovered a novel subset of apCAFs exhibiting macrophage-like features, characterized by the expression of major histocompatibility complex (MHC) class II, CD74, and costimulatory molecules (CD80, CD86, CD83, and CD40). This subset, distinct from classic apCAFs described in other cancer types, is strongly associated with favorable ICIs responses across multiple datasets. Notably, these macrophage-like apCAFs are present in LUAD samples prior to treatment, although their abundance varies among individuals. Patients classified as high-risk using signature calculated by a machine learning-driven approach exhibited lower overall survival rates and diminished immune cell infiltration following ICIs therapy.

Conclusions

Collectively, our findings establish a critical link between macrophage-like apCAFs and ICIs efficacy, offering a clinically applicable signature for patient stratification and guiding therapeutic strategies targeting the tumor microenvironment.

Cancer-associated fibroblasts as a potential novel liquid biopsy marker in cancer patients

Cancer-associated fibroblasts (CAFs) are tissue residing cells within the tumor microenvironment (TME). Stromal CAFs have been shown to be associated with poor prognosis and tumor progression in several solid tumor entities. Although the molecular mechanisms are not fully understood yet, a critical role within the TME through direct interaction with the tumor cells as well as other cells has been proposed. While most studies on CAFs focus on stromal CAFs, recent reports highlight the possibility of detecting circulating CAFs (cCAFs) in the blood. In contrast to invasive tissue biopsies for stromal CAF characterization, liquid biopsy allows a minimally invasive isolation of cCAFs. Furthermore, liquid biopsy methods could enable continuous monitoring of cCAFs in cancer patients and therefore may present a novel biomarker for solid tumors. In this work, we present an overview of cCAF studies currently available and summarize the liquid biopsy techniques for cCAF isolation and detection. Moreover, the future research directions in the emerging field are highlighted and the potential applications of cCAFs as novel biomarkers for solid tumor patients discussed.

Cancer-associated fibroblasts in breast cancer in the single-cell era: Opportunities and challenges

Breast cancer is a leading cause of morbidity and mortality in women, and its progression is closely linked to the tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs), key components of the TME, play a crucial role in promoting tumor growth by driving cancer cell proliferation, invasion, extracellular matrix (ECM) remodeling, inflammation, chemoresistance, and immunosuppression. CAFs exhibit considerable heterogeneity and are classified into subgroups based on different combinations of biomarkers. Single-cell RNA sequencing (scRNA-seq) enables high-throughput and high-resolution analysis of individual cells. Relying on this technology, it is possible to cluster complex CAFs according to different biomarkers to analyze the specific phenotypes and functions of different subpopulations. This review explores CAF clusters in breast cancer and their associated biomarkers, highlighting their roles in disease progression and potential for targeted therapies.

The role of TIGIT-CD226-PVR axis in mediating T cell exhaustion and apoptosis in NSCLC

The treatment of non-small cell lung cancer (NSCLC) remains a critical challenge in oncology, primarily due to the dysfunction and exhaustion of T cells within the tumor microenvironment, which greatly limits the effectiveness of immunotherapy. This study investigates the regulatory role of the T cell immunoglobulin and ITIM domain (TIGIT)-CD226-PVR signaling axis in the exhaustion and apoptosis of cluster of differentiation (CD)27+/CD127+T cells in NSCLC. Utilizing single-cell sequencing technology, we conducted a comprehensive gene expression analysis of T cells in a mouse model of NSCLC. Bioinformatics analysis revealed that the TIGIT-CD226-PVR signaling axis is highly active in the CD27+/CD127+T cell subset and is closely associated with their functional decline and exhaustion. In vitro experiments further demonstrated that inhibiting the TIGIT-PVR pathway while activating the CD226-PVR pathway significantly restored T cell proliferation and effector function. Importantly, in vivo studies showed that targeting this axis can significantly alleviate T cell exhaustion, enhance their cytotoxicity against NSCLC cells, and promote apoptosis, thereby improving the efficacy of immunotherapy.

The tumor microenvironment is an ecosystem sustained by metabolic interactions

Cancer-associated fibroblasts (CAFs) and immune cells make up two major components of the tumor microenvironment (TME), contributing to an ecosystem that can either support or restrain cancer progression. Metabolism is a key regulator of the TME, providing a means for cells to communicate with and influence each other, modulating tumor progression and anti-tumor immunity. Cells of the TME can metabolically interact directly through metabolite secretion and consumption or by influencing other aspects of the TME that, in turn, stimulate metabolic rewiring in target cells. Recent advances in understanding the subtypes and plasticity of cells in the TME both open up new avenues and create challenges for metabolically targeting the TME to hamper tumor growth and improve response to therapy. This perspective explores ways in which the CAF and immune components of the TME could metabolically influence each other, based on current knowledge of their metabolic states, interactions, and subpopulations.

Risk factors and management of lung cancer in idiopathic pulmonary fibrosis: A comprehensive review

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease. Lung cancer (LC) is among the most crucial comorbidity factors in patients with IPF. IPF patients that are diagnosed with LC have a reduced mean survival time. Therapeutic strategies for LC in patients with IPF need to be adapted according to the individual treatment risk. Life-threatening acute exacerbation (AE) of IPF may occur in association with cancer treatment, thereby severely restricting the therapeutic options for IPF-associated LC. Because LC and anticancer treatments can worsen the prognosis of IPF, the prevention of LC is as critical as managing patients with IPF.

Interferon-γ-stimulated antigen-presenting cancer-associated fibroblasts hinder neoadjuvant chemoimmunotherapy efficacy in lung cancer

Conventional neoadjuvant chemotherapy provides limited benefit for patients with resectable non-small cell lung cancer (NSCLC). Recently, neoadjuvant chemoimmunotherapy (NCIT) has transformed the perioperative management of NSCLC by priming systemic anti-tumor immunity before surgery, yet it remains ineffective for at least 50% of patients. Through single-cell sequencing analysis of our NCIT cohort, we identify that antigen-presenting cancer-associated fibroblasts (apCAFs) can impede the efficacy of NCIT. Using a custom cancer-associated fibroblast biobank, we uncover that interferon (IFN)-γ stimulates apCAF expansion via the JAK1/2-STAT1-IFI6/27 pathway. Mechanistically, apCAFs significantly contribute to PD-L2 expression in the tumor microenvironment (TME), triggering the accumulation of FOXP1+regulatory T cells (Tregs) through the PD-L2-RGMB axis. Reprogramming apCAFs by inhibiting the IFN-γ pathway or blocking the PD-L2-RGMB axis substantially mitigates apCAFs-mediated FOXP1+Tregs' expansion. In summary, we reveal the role of apCAFs in compromising NCIT efficacy and propose applications for anti-PD-L2/RGMB regimens to synergize with anti-PD1 therapies by targeting apCAFs.

Single-cell RNA sequencing and spatial transcriptomics reveal the heterogeneity and intercellular communication of cancer-associated fibroblasts in gastric cancer

BACKGROUND

Gastric cancer is a highly aggressive malignancy characterized by a complex tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs), which are a key component of the TME, exhibit significant heterogeneity and play crucial roles in tumor progression. Therefore, a comprehensive understanding of CAFs is essential for developing novel therapeutic strategies for gastric cancer.

METHODS

This study investigates the characteristics and functional information of CAF subtypes and explores the intercellular communication between CAFs and malignant epithelial cells (ECs) in gastric cancer by analyzing single-cell sequencing data from 24 gastric cancer samples. CellChat was employed to map intercellular communication, and Seurat was used to integrate single-cell sequencing data with spatial transcriptome data to reconstruct a comprehensive single-cell spatial map. The spatial relationship between apCAFs and cancer cells was analyzed using multicolor immunohistochemistry.

RESULTS

Cells were categorized into nine distinct categories, revealing a positive correlation between the proportions of epithelial cells (ECs) and fibroblasts. Furthermore, six fibroblast subpopulations were identified: inflammatory (iCAFs), pericytes, matrix (mCAFs), antigen-presenting (apCAFs), smooth muscle cells (SMCs), and proliferative CAFs (pCAFs). Each of these subpopulations was linked to various biological processes and immune responses. Malignant ECs exhibited heightened intercellular communication, particularly with CAF subpopulations, through specific ligand-receptor interactions. High-density regions of CAF subpopulations displayed spatial exclusivity, with pericytes serving as a source for iCAFs, mCAFs, and apCAFs. Notably, malignant ECs and apCAFs showed increased interactions, with certain ligand-receptor pairs potentially impacting the prognosis of gastric cancer. Multiplex immunohistochemistry (mIHC) confirmed the close spatial proximity of apCAFs to cancer cells in gastric cancer.

CONCLUSION

Our study provided a comprehensive characterization of CAF heterogeneity in gastric cancer and revealed the intricate intercellular networks within the TME. The identified CAF subpopulations and their interactions with malignant cells could serve as potential therapeutic targets.

Antigen-presenting cancer associated fibroblasts enhance antitumor immunity and predict immunotherapy response

Cancer-associated fibroblasts (CAF) play a crucial role in tumor progression and immune regulation. However, the functional heterogeneity of CAFs remains unclear. Here, we identify antigen-presenting CAFs (apCAF), characterized by high MHC II expression, in gastric cancer (GC) tumors and find that apCAFs are preferentially located near tertiary lymphoid structures. Both in vivo and in vitro experiments demonstrate that apCAFs promote T cell activation and enhances its cytotoxic and proliferative capacities, thereby strengthening T cell-mediated anti-tumor immunity. Additionally, apCAFs facilitate the polarization of macrophages toward a pro-inflammatory phenotype. These polarized macrophages, in turn, promote the formation of apCAFs, creating a positive feedback loop that amplifies anti-tumor immune responses. Notably, baseline tumors in immunotherapy responders across various cancer types exhibit higher levels of apCAFs infiltration. This study advances the understanding of CAFs heterogeneity in GC and highlights apCAFs as a potential biomarker for predicting immunotherapy response in pan-cancer.

Advances in nanotechnology for targeting cancer-associated fibroblasts: A review of multi-strategy drug delivery and preclinical insights

Cancer-associated fibroblasts (CAFs) play a crucial role in the tumor microenvironment by promoting tumor growth, immune evasion, and metastasis. Recently, drug delivery systems targeting CAFs have emerged as a promising long-term and effective approach to cancer treatment. Advances in nanotechnology, in particular, have led to the development of nanomedicine delivery systems designed specifically to target CAFs, offering new possibilities for precise and personalized cancer therapies. This article reviews recent progress in drug delivery using nanocarriers that target CAFs. Additionally, we explore the potential of combining multiple therapies, such as chemotherapy and immunotherapy, with nanocarriers to enhance efficacy and overcome drug resistance. Although many preclinical studies show promise, the clinical application of nanomedicine still faces considerable challenges, especially in terms of drug penetration and large-scale production. Therefore, this review aims to provide a fresh perspective on CAF-targeted drug delivery systems and highlight potential future research directions and clinical applications.

Integration of single-cell and spatial transcriptomics reveals fibroblast subtypes in hepatocellular carcinoma: spatial distribution, differentiation trajectories, and therapeutic potential

BACKGROUND

Cancer-associated fibroblasts (CAFs) are key components of the hepatocellular carcinoma (HCC) tumor microenvironment (TME). regulating tumor proliferation, metastasis, therapy resistance, immune evasion via diverse mechanisms. A deeper understanding of the l diversity of CAFs is essential for predicting patient prognosis and guiding treatment strategies.

METHODS

We examined the diversity of CAFs in HCC by integrating single-cell, bulk, and spatial transcriptome analyses.

RESULTS

Using a training cohort of 88 HCC single-cell RNA sequencing (scRNA-seq) samples and a validation cohort of 94 samples, encompassing over 1.2 million cells, we classified three fibroblast subpopulations in HCC: HLA-DRB1 + CAF, MMP11 + CAF, and VEGFA + CAF based on highly expressed genes of which, which are primarily located in normal tissue, tumor boundaries, and tumor interiors, respectively. Cell trajectory analysis revealed that VEGFA + CAFs are at the terminal stage of differentiation, which, notably, is tumor-specific. VEGFA + CAFs were significantly associated with patient survival, and the hypoxic microenvironment was found to be a major factor inducing VEGFA + CAFs. Through cellular communication with capillary endothelial cells (CapECs), VEGFA + CAFs promoted intra-tumoral angiogenesis, facilitating tumor progression and metastasis. Additionally, a machine learning model developed using high-expression genes from VEGFA + CAFs demonstrated high accuracy in predicting prognosis and sorafenib response in HCC patients.

CONCLUSIONS

We characterized three fibroblast subpopulations in HCC and revealed their distinct spatial distributions within the tumor. VEGFA + CAFs, which was induced by hypoxic TME, were associated with poorer prognosis, as they promote tumor angiogenesis through cellular communication with CapECs. Our findings provide novel insights and pave the way for individualized therapy in HCC patients.

Antigen-presenting fibroblasts: emerging players in immune modulation and therapeutic targets

Antigen-presenting fibroblasts are a newly recognized subset that challenges the traditional view of these cells as mere structural components. Under pathological or environmental stimuli, fibroblasts acquire antigen-presenting capabilities through the expression of MHC-II molecules and co-stimulatory factors, enabling them to interact with T cells and modulate immune responses. These specialized fibroblasts have been identified across various tissues and diseases, where they play context-dependent roles, either amplifying immune dysregulation or contributing to immune homeostasis. This review synthesizes recent advances in understanding the origins, activation, and functions of antigen-presenting fibroblasts. It highlights their role in promoting pathogenic immune responses and offering therapeutic opportunities through targeted modulation. Advancing our understanding of antigen-presenting fibroblasts holds great promise for developing innovative approaches to immune modulation and therapy across a range of diseases.

Functional heterogeneity of fibroblasts in primary tumors and metastases

Cancer-associated fibroblasts (CAFs) are abundant components of the tumor microenvironment (TME) of most solid malignancies and have emerged as key regulators of cancer progression and therapy response. Although recent technological advances have uncovered substantial CAF molecular heterogeneity at the single-cell level, defining functional roles for most described CAF populations remains challenging. With the aim of bridging CAF molecular and functional heterogeneity, this review focuses on recently identified functional interactions of CAF subtypes with malignant cells, immune cells, and other stromal cells in primary tumors and metastases. Dissecting the heterogeneous functional crosstalk of specific CAF populations with other components is starting to uncover candidate combinatorial strategies for therapeutically targeting the TME and cancer progression.

Myeloid cell-derived apCAFs promote HNSCC progression by regulating proportion of CD4+ and CD8+ T cells

It is well-known that cancer-associated fibroblasts (CAFs) are involved in the desmoplastic responses in Head and Neck Squamous Cell Carcinoma (HNSCC). CAFs are pivotal in the tumor microenvironment (TME) molding, and exert a profound influence on tumor development. The origin and roles of CAFs, however, are still unclear in the HNSCC, especially antigen-presenting cancer-associated fibroblasts (apCAFs). Our current study tried to explore the origin, mechanism, and function of the apCAFs in the HNSCC. Data from single-cell transcriptomics elucidated the presence of apCAFs in the HNSCC. Leveraging cell trajectory and Cellchat analysis along with robust lineage-tracing assays revealed that apCAFs were primarily derived from myeloid cells. This transdifferentiation was propelled by the macrophage migration inhibitory factor (MIF), which was secreted by tumor cells and activated the JAK/STAT3 signaling pathway. Analysis of the TCGA database has revealed that markers of apCAFs were inversely correlated with survival rates in patients with HNSCC. In vivo experiments have demonstrated that apCAFs could facilitate tumor progression. Furthermore, apCAFs could modulate ratio of CD4+ T cells/CD8+ T cells, such as higher ratio of CD4+ T cells/CD8+ T cells could promote tumor progression. Most importantly, data from in vivo assays revealed that inhibitors of MIF and p-STAT3 could significantly inhibit the OSCC growth. Therefore, our findings show potential innovative therapeutic approaches for the HNSCC.Significance: ApCAFs derived from myeloid cells promote the progression of HNSCC by increasing the ratio of CD4+/CD8+ cells, indicating potential novel targets to be used to treat the human HNSCC.

Fibroblastic reticular cells generate protective intratumoral T cell environments in lung cancer

Stringent control of T cell activity in the tumor microenvironment is essential for the generation of protective antitumor immunity. However, the identity, differentiation, and functions of the cells that create critical fibroblastic niches promoting tumor-infiltrating T cells remain elusive. Here, we show that CCL19-expressing fibroblastic reticular cells (FRCs) generate interconnected T cell environments (TEs) in human non-small cell lung cancer, including tertiary lymphoid structures and T cell tracks. Analysis of the FRC-T cell interactome in TEs indicated molecular networks regulating niche-specific differentiation of CCL19-expressing fibroblasts and T cell activation pathways. Single-cell transcriptomics and cell fate-mapping analyses in mice confirmed that FRCs in TEs originate from mural and adventitial progenitors. Ablation of intratumoral FRC precursors decreased antitumor T cell activity, resulting in reduced tumor control during coronavirus vector-based immunotherapy. In summary, specialized FRC niches in the tumor microenvironment govern the quality and extent of antitumor T cell immunity.

MHC class II of different non-professional antigen-presenting cells mediate multiple effects of crosstalk with CD4+T cells in lung diseases

The respiratory system is continuously exposed to the outside world, making it vulnerable to airborne particles and harmful pathogens like bacteria and viruses that can enter through breathing. Antigen presenting cells (APCs) have a vital function in the innate immune response as they present antigens to T cells and initiate the response of adaptive immune cells. Professional APCs engulf foreign microorganisms and display their peptides to T lymphocytes using MHC molecules. MHC II on their cell surface and potentially present antigen to CD4+T cells. Furthermore, various other types of cells have similar function that can also serve as APCs by expressing MHC II, thus impacting the progression of lung diseases, such as alveolar epithelial cells (AECs), endothelial cells (ECs), fibroblasts, innate lymphoid cells (ILCs), eosinophils, interstitial cells, mast cells, etc. express MHC II and present antigen. The non-professional APCs type and the extra signals it provides have a direct impact on CD4+T cell programming and downstream effector mechanisms. Here, we summarize the existing research on the expression of MHC II on non-professional APCs in different lung diseases and its influence on CD4+T differentiation types and disease outcomes, in order to further clarify the role of MHC II of different non-professional APCs in lung diseases, such as asthma, chronic obstructive pulmonary disease (COPD), etc.

Harnessing the tumor microenvironment: targeted cancer therapies through modulation of epithelial-mesenchymal transition

The tumor microenvironment (TME) is integral to cancer progression, impacting metastasis and treatment response. It consists of diverse cell types, extracellular matrix components, and signaling molecules that interact to promote tumor growth and therapeutic resistance. Elucidating the intricate interactions between cancer cells and the TME is crucial in understanding cancer progression and therapeutic challenges. A critical process induced by TME signaling is the epithelial-mesenchymal transition (EMT), wherein epithelial cells acquire mesenchymal traits, which enhance their motility and invasiveness and promote metastasis and cancer progression. By targeting various components of the TME, novel investigational strategies aim to disrupt the TME's contribution to the EMT, thereby improving treatment efficacy, addressing therapeutic resistance, and offering a nuanced approach to cancer therapy. This review scrutinizes the key players in the TME and the TME's contribution to the EMT, emphasizing avenues to therapeutically disrupt the interactions between the various TME components. Moreover, the article discusses the TME's implications for resistance mechanisms and highlights the current therapeutic strategies toward TME modulation along with potential caveats.

Cancer-associated fibroblasts as therapeutic targets for cancer: advances, challenges, and future prospects

Research into cancer treatment has been mainly focused on developing therapies to directly target cancer cells. Over the past decade, extensive studies have revealed critical roles of the tumour microenvironment (TME) in cancer initiation, progression, and drug resistance. Notably, cancer-associated fibroblasts (CAFs) have emerged as one of the primary contributors in shaping TME, creating a favourable environment for cancer development. Many preclinical studies have identified promising targets on CAFs, demonstrating remarkable efficacy of some CAF-targeted treatments in preclinical models. Encouraged by these compelling findings, therapeutic strategies have now advanced into clinical evaluation. We aim to provide a comprehensive review of relevant subjects on CAFs, including CAF-related markers and targets, their multifaceted roles, and current landscape of ongoing clinical trials. This knowledge can guide future research on CAFs and advocate for clinical investigations targeting CAFs.

Crosstalk between cancer-associated fibroblasts and non-neuroendocrine tumor cells in small cell lung cancer involves in glycolysis and antigen-presenting features

BACKGROUND

Small cell lung cancer (SCLC) is a highly fatal malignancy, the complex tumor microenvironment (TME) is a critical factor affecting SCLC progression. Cancer-associated fibroblasts (CAFs) are crucial components of TME, yet their role in SCLC and the underlying mechanisms during their interaction with SCLC cells remain to be determined.

METHODS

Microenvironmental cell components were estimated using transcriptome data from SCLC tissue available in public databases, analyzed with bioinformatic algorithms. A co-culture system comprising MRC5 fibroblasts and SCLC cell lines was constructed. RNA sequencing (RNA-seq) was performed on co-cultured and separately cultured MRC5 and H196 cells to identify differentially expressed genes (DEGs) and enriched signaling pathways. Glycolysis and STING signaling in SCLC cells were assessed using glucose uptake assays, qRT-PCR, and Western blot analysis. Immunohistochemical staining of SCLC tissue arrays quantified α-SMA, HLA-DRA and CD8 expression.

RESULTS

Non-neuroendocrine (non-NE) SCLC-derived CAFs exhibited more abundance and DEGs than NE SCLC-derived CAFs did, which interact with non-NE SCLC cells can induce the enrichment of glycolysis-related genes, increasement of glucose uptake, upregulation of glycolytic signaling proteins in non-NE SCLC cells and accumulation of lactate in the extracellular environment, confirming CAF-mediated glycolysis promotion. Additionally, glycolysis-induced ATP production activated STING signaling in non-NE SCLC cells, which upregulated T cell chemo-attractants. However, CAF abundance did not correlate with CD8 + T cell numbers in SCLC tissues. Additionally, non-NE SCLC cell-educated CAFs exhibited features of antigen-presenting CAFs (apCAFs), as indicated by the expression of major histocompatibility complex (MHC) molecules. Co-localization of HLA-DRA and α-SMA signals in SCLC tissues confirmed apCAF presence. The apCAFs and CD8 + T cells were co-located in the SCLC stroma, and there was a positive correlation between CAFs and regulatory T cell (Treg) abundance.

CONCLUSION

Our findings suggest that crosstalk between CAFs and non-NE SCLC cells promotes glycolysis in non-NE SCLC cells, thereby increase T cell chemo-attractant expression via activating STING signaling. On the other hand, it promotes the presence of apCAFs, which probably contributes to CD8 + T cell trapping and Treg differentiation. This study emphasizes the pro-tumor function of CAFs in SCLC by promoting glycolysis and impairing T cell function, providing direction for the development of novel therapeutic approaches targeting CAF in SCLC.

Wound healing: insights into autoimmunity, ageing, and cancer ecosystems through inflammation and IL-6 modulation

Wound healing represents a complex and evolutionarily conserved process across vertebrates, encompassing a series of life-rescuing events. The healing process runs in three main phases: inflammation, proliferation, and maturation/remodelling. While acute inflammation is indispensable for cleansing the wound, removing infection, and eliminating dead tissue characterised by the prevalence of neutrophils, the proliferation phase is characterised by transition into the inflammatory cell profile, shifting towards the prevalence of macrophages. The proliferation phase involves development of granulation tissue, comprising fibroblasts, activated myofibroblasts, and inflammatory and endothelial cells. Communication among these cellular components occurs through intercellular contacts, extracellular matrix secretion, as well as paracrine production of bioactive factors and proteolytic enzymes. The proliferation phase of healing is intricately regulated by inflammation, particularly interleukin-6. Prolonged inflammation results in dysregulations during the granulation tissue formation and may lead to the development of chronic wounds or hypertrophic/keloid scars. Notably, pathological processes such as autoimmune chronic inflammation, organ fibrosis, the tumour microenvironment, and impaired repair following viral infections notably share morphological and functional similarities with granulation tissue. Consequently, wound healing emerges as a prototype for understanding these diverse pathological processes. The prospect of gaining a comprehensive understanding of wound healing holds the potential to furnish fundamental insights into modulation of the intricate dialogue between cancer cells and non-cancer cells within the cancer ecosystem. This knowledge may pave the way for innovative approaches to cancer diagnostics, disease monitoring, and anticancer therapy.

Single-cell resolution spatial analysis of antigen-presenting cancer-associated fibroblast niches

Recent studies have identified a unique subtype of cancer-associated fibroblasts (CAFs) termed antigen-presenting CAFs (apCAFs), which remain the least understood CAF subtype. To gain a comprehensive understanding of the origin and function apCAFs, we construct a fibroblast molecular atlas across 14 types of solid tumors. Our integration study unexpectedly reveals two distinct apCAF lineages present in most cancer types: one associated with mesothelial-like cells and the other with fibrocytes. Using a high-resolution single-cell spatial imaging platform, we characterize the spatial niches of these apCAF lineages. We find that mesothelial-like apCAFs are located near cancer cells, while fibrocyte-like apCAFs are associated with tertiary lymphoid structures. Additionally, we discover that both apCAF lineages can up-regulate the secreted protein SPP1, which facilitates primary tumor formation and peritoneal metastasis. Taken together, this study offers an unprecedented resolution in analyzing apCAF lineages and their spatial niches.

Understanding and measuring mechanical signals in the tumor stroma

The tumor microenvironment (TME) is well known for its immune suppressive role, especially in solid tumors which are characterized by a thick, dense stroma. Apart from cell-cell interactions and biochemical signals, the tumor stroma is also characterized by its distinct mechanical properties, which are dictated by the composition and architecture of its extracellular matrix (ECM). Cancer-associated fibroblasts (CAFs) are the main producers and remodelers of the stromal ECM, and their heterogeneity has recently become a focus of intense research. This review describes recent findings highlighting CAF subtypes and their specific functions, as well as the development of 3D models to study tumor stroma mechanics in vitro. Finally, we discuss the quantitative techniques used to measure tissue mechanical properties at different scales. Given the diagnostic and prognostic value of stroma stiffness and composition, and the recent development of anti-tumor therapeutic strategies targeting the stroma, understanding and measuring tumor stroma mechanical properties has never been more timely or relevant.

Depicting the cellular complexity of pancreatic adenocarcinoma by Imaging Mass Cytometry: focus on cancer-associated fibroblasts

Introduction

Pancreatic ductal adenocarcinoma (PDAC) represents the complexity of interaction between cancer and cells of the tumor microenvironment (TME). Immune cells affect tumor cell behavior, thus driving cancer progression. Cancer-associated fibroblasts (CAFs) are responsible of the desmoplastic and fibrotic reaction by regulating deposition and remodeling of extracellular matrix (ECM). As tumor-promoting cells abundant in PDAC ECM, CAFs represent promising targets for novel anticancer interventions. However, relevant clinical trials are hampered by the lack of specific markers and elusive differences among CAF subtypes. Indeed, while single-cell transcriptomic analyses have provided important information on the cellular constituents of PDACs and related molecular pathways, studies based on the identification of protein markers in tissues aimed at identifying CAF subtypes and new molecular targets result incomplete.

Methods

Herein, we applied multiplexed Imaging Mass Cytometry (IMC) at single-cell resolution on 8 human PDAC tissues to depict the PDAC composing cells, and profiling immune cells, endothelial cells (ECs), as well as endocrine cells and tumor cells.

Results

We focused on CAFs by characterizing up to 19 clusters distinguished by phenotype, spatiality, and interaction with immune and tumor cells. We report evidence that specific subtypes of CAFs (CAFs 10 and 11) predominantly are enriched at the tumor-stroma interface and closely associated with tumor cells. CAFs expressing different combinations of FAP, podoplanin and cadherin-11, were associated with a higher level of CA19-9. Moreover, we identified specific subsets of FAP+ and podoplanin+/cadherin-11+ CAFs enriched in patients with negative prognosis.

Discussion

The present study provides new general insights into the complexity of the PDAC microenvironment by defining phenotypic heterogeneities and spatial distributions of CAFs, thus suggesting different functions of their subtypes in the PDAC microenvironment.

Cross-tissue human fibroblast atlas reveals myofibroblast subtypes with distinct roles in immune modulation

Fibroblasts, known for their functional diversity, play crucial roles in inflammation and cancer. In this study, we conduct comprehensive single-cell RNA sequencing analyses on fibroblast cells from 517 human samples, spanning 11 tissue types and diverse pathological states. We identify distinct fibroblast subpopulations with universal and tissue-specific characteristics. Pathological conditions lead to significant shifts in fibroblast compositions, including the expansion of immune-modulating fibroblasts during inflammation and tissue-remodeling myofibroblasts in cancer. Within the myofibroblast category, we identify four transcriptionally distinct subpopulations originating from different developmental origins, with LRRC15+ myofibroblasts displaying terminally differentiated features. Both LRRC15+ and MMP1+ myofibroblasts demonstrate pro-tumor potential that contribute to the immune-excluded and immune-suppressive tumor microenvironments (TMEs), whereas PI16+ fibroblasts show potential anti-tumor functions in adjacent non-cancerous regions. Fibroblast-subtype compositions define patient subtypes with distinct clinical outcomes. This study advances our understanding of fibroblast biology and suggests potential therapeutic strategies for targeting specific fibroblast subsets in cancer treatment.

Impact of mitochondrial dysfunction on the antitumor effects of immune cells

Mitochondrial dysfunction, a hallmark of immune cell failure, affects the antitumor effects of immune cells through metabolic reprogramming, fission, fusion, biogenesis, and immune checkpoint signal transduction of mitochondria. According to researchers, restoring damaged mitochondrial function can enhance the efficacy of immune cells. Nevertheless, the mechanism of mitochondrial dysfunction in immune cells in patients with cancer is unclear. In this review, we recapitulate the impact of mitochondrial dysfunction on the antitumor effects of T cells, natural killer cells, dendritic cells, and tumor-associated macrophage and propose that targeting mitochondria can provide new strategies for antitumor therapy.

CD4+ T cells in antitumor immunity

Advances in cancer immunotherapy have transformed cancer care and realized unprecedented responses in many patients. The growing arsenal of novel therapeutics - including immune checkpoint inhibition (ICI), adoptive T cell therapies (ACTs), and cancer vaccines - reflects the success of cancer immunotherapy. The therapeutic benefits of these treatment modalities are generally attributed to the enhanced quantity and quality of antitumor CD8+ T cell responses. Nevertheless, CD4+ T cells are now recognized to play key roles in both the priming and effector phases of the antitumor immune response. In addition to providing T cell help through co-stimulation and cytokine production, CD4+ T cells can also possess cytotoxicity either directly on MHC class II-expressing tumor cells or to other cells within the tumor microenvironment (TME). The presence of specific populations of CD4+ T cells, and their intrinsic plasticity, within the TME can represent an important determinant of clinical response to immune checkpoint inhibitors, vaccines, and chimeric antigen receptor (CAR) T cell therapies. Understanding how the antitumor functions of specific CD4+ T cell types are induced while limiting their protumorigenic attributes will enable more successful immunotherapies.

CAF-induced physical constraints controlling T cell state and localization in solid tumours

Solid tumours comprise cancer cells that engage in continuous interactions with non-malignant cells and with acellular components, forming the tumour microenvironment (TME). The TME has crucial and diverse roles in tumour progression and metastasis, and substantial efforts have been dedicated into understanding the functions of different cell types within the TME. These efforts highlighted the importance of non-cell-autonomous signalling in cancer, mediating interactions between the cancer cells, the immune microenvironment and the non-immune stroma. Much of this non-cell-autonomous signalling is mediated through acellular components of the TME, known as the extracellular matrix (ECM), and controlled by the cells that secrete and remodel the ECM - the cancer-associated fibroblasts (CAFs). In this Review, we delve into the complex crosstalk among cancer cells, CAFs and immune cells, highlighting the effects of CAF-induced ECM remodelling on T cell functions and offering insights into the potential of targeting ECM components to improve cancer therapies.

Macrophages Promote Atherosclerosis Development by Inhibiting CD8T Cell Apoptosis

Background

Atherosclerosis is an inflammatory cardiovascular disease. However, whether the association of immune cells in plaques promotes the progression of this disease has not yet been completely elucidated.

Materials and Methods

Thus, this study aimed to investigate the relationship between C1q+ macrophages and CD8T cells through scRNA-seq data reanalysis, quantitative real-time PCR, and flow cytometry. Chromatin immunoprecipitation-quantitative polymerase chain reaction, western blot, and antibody-blocking experiments were performed to investigate the role of macrophage-CD8T interaction in atherosclerosis. An atherosclerotic mouse model was developed to confirm our findings.

Results

Mechanistically, Spi1 expression induced by granulocyte-macrophage colony-stimulating factor promoted C1q expression in the macrophages. Moreover, C1q+ macrophages suppressed CD8T cell apoptosis by upregulating Slc7a7 expression to enhance the L-arginine uptake of CD8T cells. CD8T-derived interferon-γ promoted macrophage activation to induce atherosclerosis. Blockade of the C1q-C1qbp axis attenuated atherosclerosis.

Conclusion

In conclusion, macrophages interacting with CD8T promote atherosclerosis development via the C1q-C1qbp axis.

Phenotypic and spatial heterogeneity of CD8+ tumour infiltrating lymphocytes

CD8+ T cells are the workhorses executing adaptive anti-tumour response, and targets of various cancer immunotherapies. Latest advances have unearthed the sheer heterogeneity of CD8+ tumour infiltrating lymphocytes, and made it increasingly clear that the bulk of the endogenous and therapeutically induced tumour-suppressive momentum hinges on a particular selection of CD8+ T cells with advantageous attributes, namely the memory and stem-like exhausted subsets. A scrutiny of the contemporary perception of CD8+ T cells in cancer and the subgroups of interest along with the factors arbitrating their infiltration contextures, presented herein, may serve as the groundwork for future endeavours to probe further into the regulatory networks underlying their differentiation and migration, and optimise T cell-based immunotherapies accordingly.

CAFs vs. TECs: when blood feuds fuel cancer progression, dissemination and therapeutic resistance

Neoplastic progression involves complex interactions between cancer cells and the surrounding stromal milieu, fostering microenvironments that crucially drive tumor progression and dissemination. Of these stromal constituents, cancer-associated fibroblasts (CAFs) emerge as predominant inhabitants within the tumor microenvironment (TME), actively shaping multiple facets of tumorigenesis, including cancer cell proliferation, invasiveness, and immune evasion. Notably, CAFs also orchestrate the production of pro-angiogenic factors, fueling neovascularization to sustain the metabolic demands of proliferating cancer cells. Moreover, CAFs may also directly or indirectly affect endothelial cell behavior and vascular architecture, which may impact in tumor progression and responses to anti-cancer interventions. Conversely, tumor endothelial cells (TECs) exhibit a corrupted state that has been shown to affect cancer cell growth and inflammation. Both CAFs and TECs are emerging as pivotal regulators of the TME, engaging in multifaceted biological processes that significantly impact cancer progression, dissemination, and therapeutic responses. Yet, the intricate interplay between these stromal components and the orchestrated functions of each cell type remains incompletely elucidated. In this review, we summarize the current understanding of the dynamic interrelationships between CAFs and TECs, discussing the challenges and prospects for leveraging their interactions towards therapeutic advancements in cancer.

Targeting the devil: Strategies against cancer-associated fibroblasts in colorectal cancer

Cancer-associated fibroblasts (CAFs), as significant constituents of the tumor microenvironment (TME), play a pivotal role in the progression of cancers, including colorectal cancer (CRC). In this comprehensive review, we presented the origins and activation mechanisms of CAFs in CRC, elaborating on how CAFs drive tumor progression through their interactions with CRC cells, immune cells, vascular endothelial cells, and the extracellular matrix within the TME. We systematically outline the intricate web of interactions among CAFs, tumor cells, and other TME components, and based on this complex interplay, we summarize various therapeutic strategies designed to target CAFs in CRC. It is also essential to recognize that CAFs represent a highly heterogeneous group, encompassing various subtypes such as myofibroblastic CAF (myCAF), inflammatory CAF (iCAF), antigen-presenting CAF (apCAF), vessel-associated CAF (vCAF). Herein, we provide a summary of studies investigating the heterogeneity of CAFs in CRC and the characteristic expression patterns of each subtype. While the majority of CAFs contribute to the exacerbation of CRC malignancy, recent findings have revealed specific subtypes that exert inhibitory effects on CRC progression. Nevertheless, the comprehensive landscape of CAF heterogeneity still awaits exploration. We also highlight pivotal unanswered questions that need to be addressed before CAFs can be recognized as feasible targets for cancer treatment. In conclusion, the aim of our review is to elucidate the significance and challenges of advancing in-depth research on CAFs, while outlining the pathway to uncover the complex roles of CAFs in CRC and underscore their significant potential as therapeutic targets.

CAFs and T cells interplay: The emergence of a new arena in cancer combat

The interaction between the immune system and the tumor matrix has a huge impact on the progression and treatment of cancer. This paper summarizes and discusses the crosstalk between T cells and cancer-associated fibroblasts (CAFs). CAFs can also produce inhibitors that counteract the function of T cells and promote tumor immune escape, while T cells can also engage in complex two-way interactions with CAFs through direct cell contact, the exchange of soluble factors such as cytokines, and the remodeling of the extracellular matrix. Precise targeted intervention can effectively reverse tumor-promoting crosstalk between T cells and CAFs, improve anti-tumor immune response, and provide a new perspective for cancer treatment. Therefore, it is important to deeply understand the mechanism of crosstalk between T cells and CAFs. This review aims to outline the underlying mechanisms of these interactions and discuss potential therapeutic strategies that may become fundamental tools in the treatment of cancer, especially hard-to-cure cancers.

Deciphering CD4+ T cell-mediated responses against cancer

It's been long thought that CD8+ cytotoxic T cells play a major role in T cell-mediated antitumor responses, whereas CD4+ T cells merely provide some assistance to CD8+ T cells as the "helpers." In recent years, numerous studies support the notion that CD4+ T cells play an indispensable role in antitumor responses. Here, we summarize and discuss the current knowledge regarding the roles of CD4+ T cells in antitumor responses and immunotherapy, with a focus on the molecular and cellular mechanisms behind these observations. These new insights on CD4+ T cells may pave the way to further optimize cancer immunotherapy.

Immunological synapse formation between T regulatory cells and cancer-associated fibroblasts promotes tumour development

Cancer-associated fibroblasts (CAFs) have emerged as a dominant non-hematopoietic cell population in the tumour microenvironment, serving diverse functions in tumour progression. However, the mechanisms via which CAFs influence the anti-tumour immunity remain poorly understood. Here, using multiple tumour models and biopsies from cancer patients, we report that α-SMA+ CAFs can form immunological synapses with Foxp3+ regulatory T cells (Tregs) in tumours. Notably, α-SMA+ CAFs can phagocytose and process tumour antigens and exhibit a tolerogenic phenotype which instructs movement arrest, activation and proliferation in Tregs in an antigen-specific manner. Moreover, α-SMA+ CAFs display double-membrane structures resembling autophagosomes in their cytoplasm. Single-cell transcriptomic data showed an enrichment in autophagy and antigen processing/presentation pathways in α-SMA-expressing CAF clusters. Conditional knockout of Atg5 in α-SMA+ CAFs promoted inflammatory re-programming in CAFs, reduced Treg cell infiltration and attenuated tumour development. Overall, our findings reveal an immunosuppressive mechanism entailing the formation of synapses between α-SMA+ CAFs and Tregs in an autophagy-dependent manner.

A pan-cancer single-cell transcriptional analysis of antigen-presenting cancer-associated fibroblasts in the tumor microenvironment

Background

Cancer-associated fibroblasts (CAFs) are the primary stromal cells found in tumor microenvironment, and display high plasticity and heterogeneity. By using single-cell RNA-seq technology, researchers have identified various subpopulations of CAFs, particularly highlighting a recently identified subpopulation termed antigen-presenting CAFs (apCAFs), which are largely unknown.

Methods

We collected datasets from public databases for 9 different solid tumor types to analyze the role of apCAFs in the tumor microenvironment.

Results

Our data revealed that apCAFs, likely originating mainly from normal fibroblast, are commonly found in different solid tumor types and generally are associated with anti-tumor effects. apCAFs may be associated with the activation of CD4+ effector T cells and potentially promote the survival of CD4+ effector T cells through the expression of C1Q molecules. Moreover, apCAFs exhibited highly enrichment of transcription factors RUNX3 and IKZF1, along with increased glycolytic metabolism.

Conclusions

Taken together, these findings offer novel insights into a deeper understanding of apCAFs and the potential therapeutic implications for apCAFs targeted immunotherapy in cancer.

Treg-tissue cell interactions in repair and regeneration

Regulatory T (Treg) cells are classically known for their critical immunosuppressive functions that support peripheral tolerance. More recent work has demonstrated that Treg cells produce pro-repair mediators independent of their immunosuppressive function, a process that is critical to repair and regeneration in response to numerous tissue insults. These factors act on resident parenchymal and structural cells to initiate repair in a tissue-specific context. This review examines interactions between Treg cells and tissue-resident non-immune cells-in the context of tissue repair, fibrosis, and cancer-and discusses areas for future exploration.

Inflammatory Profiles Induced by Intranasal Immunization with Ricin Toxin-immune Complexes

The underlying contribution of immune complexes in modulating adaptive immunity in mucosal tissues remains poorly understood. In this report, we examined, in mice, the proinflammatory response elicited by intranasal delivery of the biothreat agent ricin toxin (RT) in association with two toxin-neutralizing mAbs, SylH3 and PB10. We previously demonstrated that ricin-immune complexes (RICs) induce the rapid onset of high-titer toxin-neutralizing Abs that persist for months. We now demonstrate that such responses are dependent on CD4+ T cell help, because treatment of mice with an anti-CD4 mAb abrogated the onset of RT-specific Abs following intranasal RICs exposure. To define the inflammatory environment associated with RIC exposure, we collected bronchoalveolar lavage fluid (BALF) and sera from mice 6, 12, and 18 h after they had received RT or RICs by the intranasal route. A 32-plex cytometric bead array revealed an inflammatory profile elicited by RT that was dominated by IL-6 (>1500-fold increase in BALF) and secondarily by KC (CXCL1), G-CSF, GM-CSF, and MCP-1. RICs induced inflammatory profiles in both BALF and serum response that were similar to RT, albeit at markedly reduced levels. These results demonstrate that RICs retain the capacity to induce local and systemic inflammatory cytokines/chemokines that, in turn, may influence Ag sampling and presentation in the lung mucosa and draining lymph nodes. A better understanding of the fate of immune complexes following intranasal delivery has implications for the development of mucosal vaccines for biothreats and emerging infectious diseases.

Targeting pathogenic fibroblast-like synoviocyte subsets in rheumatoid arthritis

Fibroblast-like synoviocytes (FLSs) play a central role in RA pathogenesis and are the main cellular component in the inflamed synovium of patients with rheumatoid arthritis (RA). FLSs are emerging as promising new therapeutic targets in RA. However, fibroblasts perform many essential functions that are required for sustaining tissue homeostasis. Direct targeting of general fibroblast markers on FLSs is challenging because fibroblasts in other tissues might be altered and side effects such as reduced wound healing or fibrosis can occur. To date, no FLS-specific targeted therapies have been applied in the clinical management of RA. With the help of high-throughput technologies such as scRNA-seq in recent years, several specific pathogenic FLS subsets in RA have been identified. Understanding the characteristics of these pathogenic FLS clusters and the mechanisms that drive their differentiation can provide new insights into the development of novel FLS-targeting strategies for RA. Here, we discuss the pathogenic FLS subsets in RA that have been elucidated in recent years and potential strategies for targeting pathogenic FLSs.

Integrated transcriptomic analysis systematically reveals the heterogeneity and molecular characterization of cancer-associated fibroblasts in osteosarcoma

BACKGROUND

Osteosarcoma (OS), with a peak incidence during the adolescent growth spurt, is correlated with poor prognosis for its high malignancy. The tumor microenvironment (TME) is highly complicated, with frequent interactions between tumor and stromal cells. The cancer-associated fibroblasts (CAFs) in the TME have been considered to actively involve in the progression, metastasis, and drug resistance of OS. This study aimed to characterize cellular heterogeneity and molecular characterization in CAFs subtypes and explore the potential targeting therapeutic strategies to improve the prognosis of OS patients.

METHODS

The single-cell atlas of human OS tumor lesions were constructed from the GEO database. Then significant marker genes and potential biological functions for each CAFs subtype were identified and explored using the Seurat R package. Next, by performing the survival analyses and constructing the risk scores for CAFs subtypes, we aimed to identify and characterize the prognostic values of specific marker genes and different CAFs subtypes. Furthermore, we explored the therapeutic targets and innovative drugs targeting different CAFs subtypes based on the GDSC database. Finally, prognoses related CAFs subtypes were further validated through immunohistochemistry (IHC) on clinical OS specimens.

RESULTS

Overall, nine main cell clusters and five subtypes of CAFs were identified. The differentially expressed marker genes for each CAFs clusters were then identified. Moreover, through Gene Ontology (GO) enrichment analysis, we defined the CAFs_2 (upregulated CXCL14 and C3), which was closely related to leukocyte migration and chemotaxis, as inflammatory CAFs (iCAFs). Likewise, we defined the CAFs_4 (upregulated CD74, HLA-DRA and HLA-DRB1), which was closely related to antigen process and presentation, as antigen-presenting CAFs (apCAFs). Furthermore, Kaplan-Meier analyses showed that CAFs_2 and CAFs_4 were correlated with poor clinical prognosis of OS patients. Meanwhile, therapeutic drugs targeting CAFs_2 and CAFs_4, such as 17-AAG/Docetaxel/Bleomycin and PHA-793887/NG-25/KIN001-102, were also explored, respectively. Finally, IHC assay confirmed the abundant CAFs_2 and CAFs_4 subtypes infiltration in the OS microenvironment compared with adjacent tissues.

CONCLUSION

Our study revealed the diversity, complexity, and heterogeneity of CAFs in OS, and complemented the single-cell atlas in OS TME.

Exploring the diversity of cancer-associated fibroblasts: insights into mechanisms of drug resistance

Introduction: Among the various stromal cell types within the tumor microenvironment, cancer-associated fibroblasts (CAFs) emerge as the predominant constituent, exhibiting a diverse array of oncogenic functions not intrinsic to normal fibroblasts. Their involvement spans across all stages of tumorigenesis, encompassing initiation, progression, and metastasis. Current understanding posits the coexistence of distinct subpopulations of CAFs within the tumor microenvironment across a spectrum of solid tumors, showcasing both pro- and antitumor activities. Recent advancements in single-cell transcriptomics have revolutionized our ability to meticulously dissect the heterogeneity inherent to CAF populations. Furthermore, accumulating evidence underscores the pivotal role of CAFs in conferring therapeutic resistance to tumors against various drug modalities. Consequently, efforts are underway to develop pharmacological agents specifically targeting CAFs. Methods: This review embarks on a comprehensive analysis, consolidating data from 36 independent single-cell RNA sequencing investigations spanning 17 distinct human malignant tumor types. Results: Our exploration centers on elucidating CAF population markers, discerning their prognostic relevance, delineating their functional contributions, and elucidating the underlying mechanisms orchestrating chemoresistance. Discussion: Finally, we deliberate on the therapeutic potential of harnessing CAFs as promising targets for intervention strategies in clinical oncology.

Single-Cell Analysis Identifies NOTCH3-Mediated Interactions between Stromal Cells That Promote Microenvironment Remodeling and Invasion in Lung Adenocarcinoma

Cancer immunotherapy has revolutionized the treatment of lung adenocarcinoma (LUAD); however, a significant proportion of patients do not respond. Recent transcriptomic studies to understand determinants of immunotherapy response have pinpointed stromal-mediated resistance mechanisms. To gain a better understanding of stromal biology at the cellular and molecular level in LUAD, we performed single-cell RNA sequencing of 256,379 cells, including 13,857 mesenchymal cells, from 9 treatment-naïve patients. Among the mesenchymal cell subsets, FAP+PDPN+ cancer-associated fibroblasts (CAF) and ACTA2+MCAM+ pericytes were enriched in tumors and differentiated from lung-resident fibroblasts. Imaging mass cytometry revealed that both subsets were topographically adjacent to the perivascular niche and had close spatial interactions with endothelial cells (EC). Modeling of ligand and receptor interactomes between mesenchymal and ECs identified that NOTCH signaling drives these cell-to-cell interactions in tumors, with pericytes and CAFs as the signal receivers and arterial and PLVAPhigh immature neovascular ECs as the signal senders. Either pharmacologically blocking NOTCH signaling or genetically depleting NOTCH3 levels in mesenchymal cells significantly reduced collagen production and suppressed cell invasion. Bulk RNA sequencing data demonstrated that NOTCH3 expression correlated with poor survival in stroma-rich patients and that a T cell-inflamed gene signature only predicted survival in patients with low NOTCH3. Collectively, this study provides valuable insights into the role of NOTCH3 in regulating tumor stroma biology, warranting further studies to elucidate the clinical implications of targeting NOTCH3 signaling.

SIGNIFICANCE

NOTCH3 signaling activates tumor-associated mesenchymal cells, increases collagen production, and augments cell invasion in lung adenocarcinoma, suggesting its critical role in remodeling tumor stroma.

Bioengineered Hydrogels Recapitulate Fibroblast Heterogeneity in Cancer

Recently mapped transcriptomic landscapes reveal the extent of heterogeneity in cancer-associated fibroblasts (CAFs) beyond previously established single-gene markers. Functional analyses of individual CAF subsets within the tumor microenvironment are critical to develop more accurate CAF-targeting therapeutic strategies. However, there is a lack of robust preclinical models that reflect this heterogeneity in vitro. In this study, single-cell RNA sequencing datasets acquired from head and neck squamous cell carcinoma tissues to predict microenvironmental and cellular features governing individual CAF subsets are leveraged. Some of these features are then incorporated into a tunable hyaluronan-based hydrogel system to culture patient-derived CAFs. Control over hydrogel degradability and integrin adhesiveness enabled derivation of the predominant myofibroblastic and inflammatory CAF subsets, as shown through changes in cell morphology and transcriptomic profiles. Last, using these hydrogel-cultured CAFs, microtubule dynamics are identified, but not actomyosin contractility, as a key mediator of CAF plasticity. The recapitulation of CAF heterogeneity in vitro using defined hydrogels presents unique opportunities for advancing the understanding of CAF biology and evaluation of CAF-targeting therapeutics.