Single-Cell Analysis Reveals Fibroblast Clusters Linked to Immunotherapy Resistance in Cancer

Modeling Stromal Cells Inside the Tumor Microenvironment of Ovarian Cancer: In Vitro Generation of Cancer-Associated Fibroblast-Like Cells and Their Impact in a 3D Model

The tumor microenvironment (TME) is the combination of cells and factors that promotes tumor progression, and cancer-associated fibroblasts (CAFs) are a key component within TME. CAF originates from various stromal cells and is activated by factors such as transforming growth factor-beta (TGF-β) secreted by tumor cells, favoring chemoresistance and metastasis. Recent publications have underlined plasticity and heterogeneity and their strong contribution to the reactive stroma within the TME. Our study aimed to replicate the TME's structure by creating a 3D in vitro model of ovarian cancer (OC). By incorporating diverse tumor and stromal cells, we simulated a physiologically relevant environment for studying CAF-like cell behavior within tumor spheroids in a context-dependent manner. CAF-like cells were generated by exposing human dermal fibroblasts to OC cell line conditioned media in the presence or absence of TGF-β. Herein, we found that different stimuli induce the generation of heterogeneous populations of CAF-like cells. Notably, we observed the ability of CAF-like cells to shape the intratumoral architecture and to contribute to functional changes in tumor cell behavior. This study highlights the importance of precise assessment of CAF for potential therapeutic interventions and further provides a reliable model for investigating novel therapeutic targets in OC.

Exosomal circRNAs: key modulators in breast cancer progression

Breast cancer (BC) poses significant challenges globally, necessitating a deeper understanding of its complexities. Exosomes are cell-specific secreted extracellular vesicles of interest, characterized by a lipid bilayer structure. Exosomes can carry a variety of bioactive components, including nucleic acids, lipids, amino acids, and small molecules, to mediate intercellular signaling. CircRNAs are a novel class of single-stranded RNA molecules, characterized by a closed-loop structure. CircRNAs mainly exert ceRNA functions to intricately modulate gene expression and signaling pathways in breast cancer, influencing tumor progression and therapeutic responses. The unique packaging of circRNAs within exosomes serves as novel genetic information transmitters, facilitating communication between BC cells and microenvironmental cells, thereby regulating critical aspects of BC progression, immune evasion, and drug resistance. Besides, exosomal circRNAs possess the capabilities of serving as diagnostic and therapeutic biomarkers of BC, due to their stability, specificity, and regulatory roles in tumorigenesis and metastasis. Therefore, this review aims to elucidate the novel roles and mechanisms of exosomal circRNAs in BC progression, as well as their potential for diagnosis and therapeutics. The ongoing investigations of exosomal circRNAs will potentially revolutionize treatment paradigms and improve patient outcomes of BC.

Fibroblast Activation Protein (FAP)+ cancer-associated fibroblasts induce macrophage M2-like polarization via the Fibronectin 1-Integrin α5β1 axis in breast cancer

Cancer-associated fibroblasts expressing fibroblast activation protein (FAP+ CAFs) are critical modulators of the breast cancer microenvironment, yet their immunoregulatory mechanisms remain poorly understood. Through integrated analysis of single-cell RNA sequencing data, clinical specimens, and in vivo and in vitro experiments, we identified FAP+ CAFs as the predominant stromal population associated with poor clinical outcomes and immunosuppressive features. Mechanistically, FAP+ CAFs secrete high levels of fibronectin 1 (FN1), which engages integrin α5β1 on macrophages to trigger FAK-AKT-STAT3 signaling, driving their polarization toward an immunosuppressive M2-like phenotype. Importantly, pharmacological disruption of FN1-integrin α5β1 signaling using Cilengitide effectively reprogrammed the tumor immune landscape and suppressed tumor growth in mice models. These findings establish FAP+ CAF-derived FN1 as a critical orchestrator of tumor immunosuppression and identify the FN1-integrin α5β1 axis as a promising therapeutic target in breast cancer.

Spatial mapping of gene signatures in H&E-stained images: a proof of concept for interpretable predictions using additive multiple instance learning

The relative abundance of cancer-associated fibroblast (CAF) subtypes influences a tumor's response to treatment, especially immunotherapy. However, the gene expression signatures associated with these CAF subtypes have yet to realize their potential as clinical biomarkers. Here, we describe an interpretable machine learning (ML) approach, additive multiple instance learning (aMIL), to predict bulk gene expression signatures from hematoxylin and eosin (H&E)-stained whole slide images (WSI), focusing on an immunosuppressive LRRC15+ CAF-enriched TGFβ-CAF signature. aMIL models accurately predicted TGFβ-CAF across various cancer types. Tissue regions contributing most highly to slide-level predictions of TGFβ-CAF were evaluated by ML models characterizing spatial distributions of diverse cell and tissue types, stromal subtypes, and nuclear morphology. In breast cancer, regions contributing most to TGFβ-CAF-high predictions ("excitatory") were localized to cancer stroma with high fibroblast density and mature collagen fibers. Regions contributing most to TGFβ-CAF-low predictions ("inhibitory") were localized to cancer epithelium and densely inflamed stroma. Fibroblast and lymphocyte nuclear morphology also differed between excitatory and inhibitory regions. Thus, aMIL enables a data-driven link between histologic features and transcription, offering biological interpretability beyond typical black-box models.

Snail1 as a key prognostic biomarker of cancer-associated fibroblasts in breast tumors

Accurate cancer diagnosis is crucial for selecting optimal treatments, yet current classification systems often include non-responders who receive ineffective therapies. Cancer-associated fibroblasts (CAFs) play a central role in tumor progression, and CAF biomarkers are increasingly recognized for their prognostic value. Recent studies have revealed significant heterogeneity within CAF populations, with distinct subtypes linked to different tumors and stages of disease. In this review, we summarize recent findings from patient samples and mouse models of breast cancer, focusing on gene signatures identified by single-cell RNA sequencing that define CAF subtypes and predict cancer prognosis. Additionally, we explore the genes and pathways regulated by Snail1, a transcription factor whose expression in breast and colon CAFs is associated with malignancy. Altogether these data emphasize the fibrotic and immunosuppressive roles of Snail1-expressing fibroblasts and unveil an undescribed streamlined Snail1-related gene signature in CAFs with prognostic potential in breast cancer and other solid tumors.

Combining spatial transcriptomics and ECM imaging in 3D for mapping cellular interactions in the tumor microenvironment

Tumors are complex ecosystems composed of malignant and non-malignant cells embedded in a dynamic extracellular matrix (ECM). In the tumor microenvironment, molecular phenotypes are controlled by cell-cell and ECM interactions in 3D cellular neighborhoods (CNs). While their inhibition can impede tumor progression, routine molecular tumor profiling fails to capture cellular interactions. Single-cell spatial transcriptomics (ST) maps receptor-ligand interactions but usually remains limited to 2D tissue sections and lacks ECM readouts. Here, we integrate 3D ST with ECM imaging in serial sections from one clinical lung carcinoma to systematically quantify molecular states, cell-cell interactions, and ECM remodeling in CN. Our integrative analysis pinpointed known immune escape and tumor invasion mechanisms, revealing several druggable drivers of tumor progression in the patient under study. This proof-of-principle study highlights the potential of in-depth CN profiling in routine clinical samples to inform microenvironment-directed therapies. A record of this paper's transparent peer review process is included in the supplemental information.

Fibroblast atlas: Shared and specific cell types across tissues

Understanding the heterogeneity of fibroblasts depends on decoding the complexity of cell subtypes, their origin, distribution, and interactions with other cells. Here, we integrated 249,156 fibroblasts from 73 studies across 10 tissues to present a single-cell atlas of fibroblasts. We provided a high-resolution classification of 18 fibroblast subtypes. In particular, we revealed a previously undescribed cell population, TSPAN8+ chromatin remodeling fibroblasts, characterized by high expression of genes with functions related to histone modification and chromatin remodeling. Moreover, TSPAN8+ chromatin remodeling fibroblasts were detectable in spatial transcriptome data and multiplexed immunofluorescence assays. Compared with other fibroblast subtypes, TSPAN8+ chromatin remodeling fibroblasts exhibited higher scores in cell differentiation and resident fibroblast, mainly interacting with endothelial cells and T cells through ligand VEGFA and receptor F2R, and their presence was associated with poor prognosis. Our analyses comprehensively defined the shared and specific characteristics of fibroblast subtypes across tissues and provided a user-friendly data portal, Fibroblast Atlas.

Spatially Resolved Tumor Ecosystems and Cell States in Gastric Adenocarcinoma Progression and Evolution

SIGNIFICANCE

Integration of spatial transcriptomic (GeoMx Digital Spatial Profiler) and single-cell RNA sequencing data from multiple gastric cancers identifies spatially resolved expression-based intratumoral heterogeneity, associated with distinct immune microenvironments. We uncovered two separate evolutionary trajectories associated with specific molecular subtypes, clinical prognoses, stromal neighborhoods, and genetic drivers. Tumor-stroma interfaces emerged as a unique state of tumor ecology.

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 dual role of CXCL9/SPP1 polarized tumor-associated macrophages in modulating anti-tumor immunity in hepatocellular carcinoma

Introduction

The main challenge for cancer therapy lies in immuno-suppressive tumor micro-environment. Reprogramming tumor-associated macrophages (TAMs) into an anti-tumor phenotype is a promising strategy.

Methods

A comprehensive analysis by combing multi-regional single-cell, bulk and spatial transcriptome profiling with radiomics characterization was conducted to dissect the heterogeneity of TAMs and resolve the landscape of the CXCL9:SPP1 (CS) macrophage polarity in HCC.

Results

TAMs were particularly increased in HCC. SPP1+ TAMs and CXCL9+ TAMs were identified as the dominant subtypes with different evolutionary trajectories. SPP1+ TAMs, located in the tumor core, co-localized with cancer-associated fibroblasts to promote tumor growth and further contributed to worse prognosis. In contrast, CXCL9+ TAMs, located in the peritumoral region, synergized with CD8+ T cells to create an immunostimulatory micro-environment. For the first time, we explored the applicability of CS polarity in HCC tumors and revealed several key transcription factors involved in shaping this polarity. Moreover, CS polarity could serve as a potential indicator of prognostic and micro-environmental status for HCC patients. Based on medical imaging data, we developed a radiomics tool, RCSP (Radiogenomics-based CXCL9/SPP1 Polarity), to assist in non-invasively predicting the CS polarity in HCC patients.

Conclusion

Our research sheds light on the regulatory roles of SPP1+ TAMs and CXCL9+ TAMs in the micro-environment and provides new therapeutic targets or insights for the reprogramming of targeted macrophages in HCC.

Exosome-Mediated Cellular Communication in the Tumor Microenvironment Imparts Drug Resistance in Breast Cancer

Globally, breast cancer (BC) is the leading cause of cancer-related death for women. BC is characterized by heterogeneity, aggressive behavior, and high metastatic potential. Chemotherapy, administered as monotherapy or adjuvant therapy, remains a cornerstone of treatment; however, acquired drug resistance is a significant clinical challenge. Deciphering mechanisms of drug resistance will be central to developing more efficient treatment options and improving patient outcomes. The current review examines the multifaceted nature of exosomes in conferring drug resistance in BC through complex communication networks within the tumor microenvironment. We further explore recent advances in understanding how exosomes contribute to resistance against established chemotherapeutic agents such as tamoxifen, paclitaxel, doxorubicin, platinum-based drugs, trastuzumab, and newer immunotherapies, such as immune checkpoint inhibitors. Moreover, we discuss existing systematic approaches to investigating the exosome-drug resistance relationship in BC. Finally, we explore promising therapeutic approaches to overcome exosome-dependent drug resistance in BC, highlighting potential avenues for improved treatment efficacy. Investigating the distinct functions and cargo of exosomes offers potential for developing innovative approaches to overcoming treatment resistance.

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.

Conserved spatial subtypes and cellular neighborhoods of cancer-associated fibroblasts revealed by single-cell spatial multi-omics

Cancer-associated fibroblasts (CAFs) are a multifaceted cell population essential for shaping the tumor microenvironment (TME) and influencing therapy responses. Characterizing the spatial organization and interactions of CAFs within complex tissue environments provides critical insights into tumor biology and immunobiology. In this study, through integrative analyses of over 14 million cells from 10 cancer types across 7 spatial transcriptomics and proteomics platforms, we discover, validate, and characterize four distinct spatial CAF subtypes. These subtypes are conserved across cancer types and independent of spatial omics platforms. Notably, they exhibit distinct spatial organizational patterns, neighboring cell compositions, interaction networks, and transcriptomic profiles. Their abundance and composition vary across tissues, shaping TME characteristics, such as levels, distribution, and state composition of tumor-infiltrating immune cells, tumor immune phenotypes, and patient survival. This study enriches our understanding of CAF spatial heterogeneity in cancer and paves the way for novel approaches to target and modulate CAFs.

Cancer‑associated fibroblasts: a pivotal regulator of tumor microenvironment in the context of radiotherapy

BACKGROUND

In the course of tumor treatment, radiation therapy (RT) not only kills cancer cells, but also induces complex biological effects in non-malignant cells around cancer cells. These biological effects such as angiogenesis, changes in stromal composition and immune cell infiltration remodel the tumor microenvironment (TME). As one of the major components of the TME, Cancer‑associated fibroblasts (CAFs) are not only involved in tumorigenesis, progression, recurrence, and metastasis but also regulate the tumor-associated immune microenvironment. CAFs and tumor cells or immune cells have complex intercellular communication in the context of tumor radiation.

MAIN CONTENT

Different cellular precursors, spatial location differences, absence of specific markers, and advances in single-cell sequencing technology have gradually made the abundant heterogeneity of CAFs well known. Due to unique radioresistance properties, CAFs can survive under high doses of ionizing radiation. However, radiation can induce phenotypic and functional changes in CAFs and further act on tumor cells and immune cells to promote or inhibit tumor progression. To date, the effect of RT on CAFs and the effect of irradiated CAFs on tumor progression and TME are still not well defined.

CONCLUSION

In this review, we review the origin, phenotypic, and functional heterogeneity of CAFs and describe the effects of RT on CAFs, focusing on the mutual crosstalk between CAFs and tumor or immune cells after radiation. We also discuss emerging strategies for targeted CAFs therapy.

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.

The fibroinflammatory response in cancer

Fibroinflammation refers to the highly integrated fibrogenic and inflammatory responses mediated by the concerted function of fibroblasts and innate immune cells in response to tissue perturbation. This process underlies the desmoplastic remodelling of the tumour microenvironment and thus plays an important role in tumour initiation, growth and metastasis. More specifically, fibroinflammation alters the biochemical and biomechanical signalling in malignant cells to promote their proliferation and survival and further supports an immunosuppressive microenvironment by polarizing the immune status of tumours. Additionally, the presence of fibroinflammation is often associated with therapeutic resistance. As such, there is increasing interest in targeting this process to normalize the tumour microenvironment and thus enhance the treatment of solid tumours. Herein, we review advances made in unravelling the complexity of cancer-associated fibroinflammation that can inform the rational design of therapies targeting this.

Combination therapy with Chicoric acid and PD-1/PD-L1 blockade improves the immunotherapy response in patient-derived ovarian cancer xenograft model

PURPOSE

Limited treatment options exist for refractory ovarian cancer (OC) due to its poor response to immune therapies. Therefore, there is an urgent need to develop new effective treatment strategies. Chicoric acid (CA) is reported to have immune-enhancing properties, but its efficacy in cancer treatment is not well understood. We hypothesize that CA might improve the efficacy of PD-1/PD-L1 blockade immunotherapy in refractory OC patients.

METHODS

Patient-derived xenograft (PDX) models were constructed from chemoresistant advanced high-grade serous ovarian cancer patients. These models were treated with CA, aPD-1/aPD-L1 antibodies, or a combination of both. Single-cell RNA sequencing was performed to analyze the cellular composition of the tumor microenvironment (TME), evaluate treatment efficacy, and explore therapeutic mechanisms. Variations in peripheral blood lymphocytes were analyzed via fluorescence-activated cell sorting. Immunohistochemistry confirmed the variations in tumor-infiltrating lymphocytes and tumor cells.

RESULTS

Immunocompetent peripheral blood mononuclear cell (PBMC)-PDX models were successfully constructed using malignant ascites fluid and PBMCs. After treatment, 158,734 cells from 15 samples were categorized into epithelial cells, T lymphocytes, myeloid cells, fibroblasts, and endothelial cells. CA enhanced the antitumor ability of immune cells against OC cells. Notably, CA stimulated the proliferation of CD45 + and CD3 + cells and promoted the migration of CD8 + and CD4 + T cells from peripheral blood to infiltrate the TME. Additionally, CA enhanced the response of OCs to aPD-L1/aPD-1 treatment, strengthened the interaction between tumor and nontumor cells, and identified APP/CD74 as a critical ligand‒receptor pair. CHI3L1 was also found to be a potential marker for predicting immunotherapy efficacy in OC.

CONCLUSION

This study demonstrated that combination therapy with CA and aPD-1/aPD-L1 might be a promising strategy for treating OC effectively.

New insights into cancer immune checkpoints landscape from single-cell RNA sequencing

Immune checkpoint blockade (ICB) therapy represents a pivotal advancement in tumor immunotherapy by restoring the cytotoxic lymphocytes' anti-tumor activity through the modulation of immune checkpoint functions. Nevertheless, many patients experience suboptimal therapeutic outcomes, likely due to the immunosuppressive tumor microenvironment, drug resistance, and other factors. Single-cell RNA sequencing has assisted to precisely investigate the immune infiltration patterns before and after ICB treatment, enabling a high-resolution depiction of previously unrecognized functional interaction among immune checkpoints. This review addresses the heterogeneity between tumor microenvironments that respond to or resist ICB therapy, highlighting critical factors underlying the variation in immunotherapy efficacy and elucidating treatment failure. Furthermore, a comprehensive examination is provided of how specific ICBs modulate immune and tumor cells to achieve anti-tumor effects and generate treatment resistance, alongside a summary of emerging immune checkpoints identified as promising targets for cancer immunotherapy through single-cell RNA sequencing applications.

Single-cell and spatial transcriptome profiling reveal CTHRC1+ fibroblasts promote EMT through WNT5A signaling in colorectal cancer

BACKGROUND

Cancer-associated fibroblasts (CAFs), known for facilitating the progression and metastasis of colorectal cancer (CRC), have become a promising therapeutic target. However, the significant heterogeneity of CAFs and their intricate crosstalk with tumor cells present substantial challenges in the development of precise and effective therapeutic strategies.

METHODS

Single-cell RNA sequencing (scRNA-seq) technology was used to identify various cell subtypes. Spatial transcriptomics (ST) was employed to map the spatial niches and colocalization patterns of these cell subtypes. Cell-cell interactions among these subtypes were analysed via CellChat and NicheNet software. Tumor cell invasion, migration, and proliferation were assessed through wound healing assays, transwell assays, colony formation assays, and xenograft mouse models.

RESULTS

We identified a significant spatial colocalization between CTHRC1+ CAFs and a distinct subtype of malignant epithelial cells, both residing within the EMT-active spatial niche. Our results demonstrate that CTHRC1+ CAFs, as a major source of WNT5A, promote epithelial-mesenchymal transition (EMT) and enhance tumor cell invasiveness by upregulating MSLN expression in adjacent malignant epithelial cells. This signaling axis contributes significantly to CRC progression and metastasis.

CONCLUSIONS

Targeting the CTHRC1+ CAF-WNT5A-MSLN signaling axis presents a promising therapeutic strategy for advanced CRC patients. Our study provides new insights into the role of CAFs in CRC progression and offers potential avenues for developing targeted therapies to disrupt this pathway.

The landscape of malignant transition: Unraveling cancer cell-of-origin and heterogeneous tissue microenvironment

Understanding disease progression and sophisticated tumor ecosystems is imperative for investigating tumorigenesis mechanisms and developing novel prevention strategies. Here, we dissected heterogeneous microenvironments during malignant transitions by leveraging data from 1396 samples spanning 13 major tissues. Within transitional stem-like subpopulations highly enriched in precancers and cancers, we identified 30 recurring cellular states strongly linked to malignancy, including hypoxia and epithelial senescence, revealing a high degree of plasticity in epithelial stem cells. By characterizing dynamics in stem-cell crosstalk with the microenvironment along the pseudotime axis, we found differential roles of ANXA1 at different stages of tumor development. In precancerous stages, reduced ANXA1 levels promoted monocyte differentiation toward M1 macrophages and inflammatory responses, whereas during malignant progression, upregulated ANXA1 fostered M2 macrophage polarization and cancer-associated fibroblast transformation by increasing TGF-β production. Our spatiotemporal analysis further provided insights into mechanisms responsible for immunosuppression and a potential target to control evolution of precancer and mitigate the risk for cancer development.

Comprehensive molecular portrait reveals genetic diversity and distinct molecular subtypes of small intestinal neuroendocrine tumors

Small intestinal neuroendocrine tumors (siNETs) are rare bowel tumors arising from malignant enteroendocrine cells, which normally regulate digestion throughout the intestine. Though infrequent, their incidence is rising through better diagnosis, fostering research into their origin and treatment. To date, siNETs are considered to be a single entity and are clinically treated as such. Here, by performing a multi-omics analysis of siNETs, we unveil four distinct molecular groups with strong clinical relevance and provide a resource to study their origin and clinical features. Transcriptomic, genetic and DNA methylation profiles identify two groups linked to distinct enteroendocrine differentiation patterns, another with a strong immune phenotype, and the last with mesenchymal properties. This latter subtype displays the worst prognosis and resistance to treatments in line with infiltration of cancer-associated fibroblasts. These data provide insights into the origin and diversity of these rare diseases, in the hope of improving clinical research into their management.

Targeting Cancer-Associated Fibroblasts: Eliminate or Reprogram?

Cancer-associated fibroblasts (CAFs) are key components of the tumor microenvironment (TME). Given their various roles in tumor progression and treatment resistance, CAFs are promising therapeutic targets in cancer. The elimination of tumor-promoting CAFs has been investigated in various animal models to determine whether it effectively suppresses tumor growth. Based on recent evidence, several simple strategies have been proposed to eliminate tumor-promoting CAFs and attenuate these features. In addition, attention has focused on the critical role that CAFs play in the immunosuppressive TME. Therefore, the functional reprogramming of CAFs in combination with immune checkpoint inhibitors has also been investigated as a possible therapeutic approach. However, although potential targets in CAFs have been widely characterized, the plasticity and heterogeneity of CAFs complicate the understanding of their properties and present difficulties for clinical application. Moreover, the identification of tumor-suppressive CAFs highlights the necessity for the development of therapeutic approaches that can distinguish and switch between tumor-promoting and tumor-suppressive CAFs in an appropriate manner. In this review, we introduce the origins and diversity of CAFs, their role in cancer, and current therapeutic strategies aimed at targeting CAFs, including ongoing clinical evaluations.

LATS1/2 inactivation in the mammary epithelium drives the evolution of a tumor-associated niche

Basal-like breast cancers exhibit distinct cellular heterogeneity that contributes to disease pathology. In this study we used a genetic mouse model of basal-like breast cancer driven by epithelial-specific inactivation of the Hippo pathway-regulating LATS1 and LATS2 kinases to elucidate epithelial-stromal interactions. We demonstrate that basal-like carcinoma initiation in this model is accompanied by the accumulation of distinct cancer-associated fibroblasts and macrophages and dramatic extracellular matrix remodeling, phenocopying the stromal diversity observed in human triple-negative breast tumors. Dysregulated epithelial-stromal signals were observed, including those mediated by TGF-β, PDGF, and CSF. Autonomous activation of the transcriptional effector TAZ was observed in LATS1/2-deleted cells along with non-autonomous activation within the evolving tumor niche. We further show that inhibition of the YAP/TAZ-associated TEAD family of transcription factors blocks the development of the carcinomas and associated microenvironment. These observations demonstrate that carcinomas resulting from Hippo pathway dysregulation in the mammary epithelium are sufficient to drive cellular events that promote a basal-like tumor-associated niche and suggest that targeting dysregulated YAP/TAZ-TEAD activity may offer a therapeutic opportunity for basal-like mammary tumors.

Integrated spatial multi-omics profiling of Fusobacterium nucleatum in breast cancer unveils its role in tumour microenvironment modulation and cancer progression

Tumour-associated microbiota are integral components of the tumour microenvironment (TME). However, previous studies on intratumoral microbiota primarily rely on bulk tissue analysis, which may obscure their spatial distribution and localized effects. In this study, we applied in situ spatial-profiling technology to investigate the spatial distribution of intratumoral microbiota in breast cancer and their interactions with the local TME. Using 5R 16S rRNA gene sequencing and RNAscope FISH/CISH on patients' tissue, we identified significant spatial heterogeneity in intratumoral microbiota, with Fusobacterium nucleatum (F. nucleatum) predominantly localized in tumour cell-rich areas. GeoMx digital spatial profiling (DSP) revealed that regions colonized by F. nucleatum exhibit significant influence on the expression of RNAs and proteins involved in proliferation, migration and invasion. In vitro studies indicated that co-culture with F. nucleatum significantly stimulates the proliferation and migration of breast cancer cells. Integrative spatial multi-omics and co-culture transcriptomic analyses highlighted the MAPK signalling pathways as key altered pathways. By intersecting these datasets, VEGFD and PAK1 emerged as critical upregulated proteins in F. nucleatum-positive regions, showing strong positive correlations with MAPK pathway proteins. Moreover, the upregulation of VEGFD and PAK1 by F. nucleatum was confirmed in co-culture experiments, and their knockdown significantly reduced F. nucleatum-induced proliferation and migration. In conclusion, intratumoral microbiota in breast cancer exhibit significant spatial heterogeneity, with F. nucleatum colonization markedly altering tumour cell protein expression to promote progression and migration. These findings provide novel perspectives on the role of microbiota in breast cancer, identify potential therapeutic targets, and lay the foundation for future cancer treatments. KEY POINTS: Intratumoral Fusobacterium nucleatum exhibits significant spatial heterogeneity within breast cancer tissues. F. nucleatum colonization alters the expression of key proteins involved in tumour progression and migration. The MAPK signalling pathway is a critical mediator of F. nucleatum-induced breast cancer cell proliferation and migration. VEGFD and PAK1 are potential therapeutic targets to mitigate F. nucleatum-induced tumour progression.

FAP upregulates PD-L1 expression in cancer-associated fibroblasts to exacerbate T cells dysfunction and suppress anti-tumor immunity

FAP-positive cancer-associated fibroblasts (CAFs), recognized as a critical subset of CAFs, have been implicated in fostering an immunosuppressive tumor microenvironment in various cancers. However, their potential mechanisms of immunosuppression, particularly in modulating T cells, remain elusive. In this study, multiple internal cohorts consisting of 328 patients as well as 5 external cohorts were integrated to delineate the association between unfavorable prognosis or therapeutic resistance and FAP+ CAFs in gastric cancer patients. Subsequently, using in vivo mice models and in vitro co-culture system, we found that elevated infiltration levels of FAP+ CAF exacerbated immunosuppression in the tumor microenvironment by facilitating CD8+ T cells dysfunction. Mechanistically, FAP impeded the degradation of STAT1 protein in CAFs, thereby sustaining PD-L1 transcription and fostering T cell exhaustion. Treatment with PD-L1 neutralizing antibodies effectively attenuated FAP-mediated immunosuppression, restoring anti-tumor immunity of T cells. Overall, our findings underscore the vital role of FAP+ CAFs in directly suppressing T cell-mediated anti-tumor immunity via PD-L1 upregulation, paving the way for the development of FAP-targeted therapies in clinical settings.

IFNγ and TNFα drive an inflammatory secretion profile in cancer-associated fibroblasts from human non-small cell lung cancer

Cancer-associated fibroblasts (CAFs) are the dominant nonmalignant component of the tumour microenvironment (TME). CAFs demonstrate a high level of inter- and intra-tumour heterogeneity in solid tumours, though the drivers of CAF subpopulations are not fully understood. Here, we demonstrate that non-small cell lung cancer (NSCLC) patient-derived CAFs upregulate the secretion of inflammatory cytokines (IL6, LIF, IL33, GM-CSF, IL1ra) and chemokines (CCL2, CCL3, CCL4, CCL20, CXCL8, CXCL9, CXCL10, CXCL11) in response to in vitro co-culture with anti-CD3/anti-CD28-stimulated peripheral blood mononuclear cells (PBMCs) via IFNγ and TNFα. Furthermore, T-cell-derived IFNγ inhibits CXCL12 secretion by CAFs in vitro. Our results highlight the ability of T-cell effector cytokines to modulate the CAF secretome in NSCLC.

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.

Collagen remodeling-mediated signaling pathways and their impact on tumor therapy

In addition to their traditional roles in maintaining tissue morphology and organ development, emerging evidence suggests that collagen (COL) remodeling-referring to dynamic changes in the quantity, stiffness, arrangements, cleavage states, and homo-/hetero-trimerization of COLs-serves as a key signaling mechanism that governs tumor growth and metastasis. COL receptors act as switches, linking various forms of COL remodeling to different cell types during cancer progression, including cancer cells, immune cells, and cancer-associated fibroblasts. In this review, we summarize recent findings on the signaling pathways mediated by COL arrangement, cleavage, and trimerization states (both homo- and hetero-), as well as the roles of the primary COL receptors-integrin, DDR1/2, LAIR-1/2, MRC2, and GPVI-in cancer progression. We also discuss the latest therapeutic strategies targeting COL fragments, cancer-associated fibroblasts, and COL receptors, including integrins, DDR1/2, and LAIR1/2. Understanding the pathways modulated by COL remodeling and COL receptors in various pathological contexts will pave the way for developing new precision therapies.

Tumor microenvironment and drug resistance in lung adenocarcinoma: molecular mechanisms, prognostic implications, and therapeutic strategies

The fight against lung adenocarcinoma (LUAD) is challenged by tumor microenvironment (TME)-mediated drug resistance, which limits effective treatment. This study examines the LUAD TME and identifies four distinct subtypes through multi-omics profiling: immune-rich, immune-exhausted, stromal-dominant, and TME-desert. Each subtype has unique molecular features, tumor diversity, and links to clinical outcomes. Immune-rich subtypes respond better to immune checkpoint inhibitors, while stromal-dominant and TME-desert subtypes show resistance to treatment and poor prognosis. Molecular analysis uncovers subtype-specific mutations, chromosomal instability, and altered signaling pathways, pointing to potential therapeutic targets. In silico drug screening identifies promising treatments for resistant subtypes. These findings, validated in independent cohorts, highlight the critical role of the TME in drug resistance and treatment response, providing insights for personalized treatment strategies in LUAD.

Spatially resolved transcriptomics reveal the determinants of primary resistance to immunotherapy in NSCLC with mature tertiary lymphoid structures

Effectiveness of immune checkpoint inhibitors (ICIs) in non-small cell lung cancer (NSCLC) has been linked to the presence of mature tertiary lymphoid structures (mTLSs) within the tumor microenvironment (TME). However, only a subset of mTLS-positive NSCLC derives benefit, thus highlighting the need to unravel ICI response determinants. The comprehensive analysis of ICI-treated patients with NSCLC (n = 509) from the Bergonié Institute Profiling (BIP) study (NCT02534649) reveals that the presence of mTLSs correlates with improved clinical outcomes, independently of programmed death ligand 1 (PD-L1) expression and genomic features. Employing spatial transcriptomics alongside multiplex immunofluorescence (mIF), we show that two distinct subsets of cancer-associated fibroblasts (CAFs) are essential factors in mediating primary resistance to ICIs in mTLS-positive NSCLC. These CAFs are associated with immune exclusion, CD8+ T cell exhaustion, and increased regulatory CD4+ T cell infiltration, underscoring an immunosuppressive TME. Our study highlights the pivotal role of specific CAF subsets in thwarting ICIs, proposing new therapeutic targets to enhance immunotherapy efficacy.

Use of a universal targeting CAR T cell to simultaneously kill cancer cells and cancer-associated fibroblasts

CAR T cells therapies have demonstrated success in treating hematologic malignancies, but have proven less effective in eradicating solid tumors. While suppressive immune cells may contribute to reduced CAR T cell efficacies in malignant masses, cancer-associated fibroblasts (CAFs) are also believed to facilitate tumor survival by secreting growth factors, immunosuppressive cytokines, and extracellular matrix components that inhibit drug and immune cell filtration and facilitate metastasis. In an effort to eliminate both CAFs and cancer cells simultaneously, we have employed a universal CAR T cell that can attack both cell types when supplemented with appropriate bispecific adapters. We show here that tumor regression is indeed enhanced when CAR T cells are directed to concurrently kill both cancer cells and CAFs. We further demonstrate that simultaneous targeting of both cell types enhances CAR T cell proliferation, activation, tumor infiltration, and tumor distribution relative to targeting only a single cell type. Because all of these benefits are achieved in both cold and hot tumors without significant toxicity, we conclude that use of a universal CAR T cell in combination with multiple bispecific adapters can provide a safe, potent, cost-effective, and scalable alternative to the treatment of solid tumors with conventional CAR T cells.

High prevalence of FAP+ cancer-associated fibroblasts predicts poor outcome in patients with high-grade serous ovarian cancer with high CD8 T-cell density

OBJECTIVE

Studies have implied that fibroblasts may act as regulators of immune cells in the tumor microenvironment (TME). We investigated the clinical relevance of fibroblast activation protein (FAP) positive stroma in high-grade serous ovarian cancer (HGSC) in relation to CD8+ lymphocyte's infiltration.

METHODS

In a discovery cohort (N = 113) of HGSC, expression of FAP and CD8 in the TME was analyzed with immunohistochemistry. Results were correlated with overall survival (OS) and progression-free survival (PFS). The findings were validated in an independent cohort of HGSC (N = 121) and in public available datasets.

RESULTS

High infiltration of CD8+ cells in the TME of HGSC was found to be associated with longer OS, as previously known. Increased expression of FAP was associated with shorter median PFS (11.4 vs. 18.6 months) in tumors with high density of CD8+ cells (HR 4.03, CI 95 % 1.38-11.72, p = 0.01). Similarly, in the validation cohort, high intensity of FAP in cases with high density of CD8+ cells was associated with shorter OS, 31.5 vs 76.9 months (HR 2.83; 95 % CI 1.17-6.86, p = 0.02). The results were consistent in multivariable analyses. The association between high FAP expression and poor outcome in high density CD8 HGSC was also confirmed in publicly available datasets.

CONCLUSIONS

The TME infiltration of FAP-positive fibroblasts is associated with poor prognosis in HGSC with high CD8+ cells density. Targeting the FAP+ subset of fibroblasts may unlock the local immune-activation in the TME thus enhance the positive prognostic effect of T-cells in ovarian cancer.

Single-cell RNA Sequencing Analysis Reveals Cancer-associated Fibroblast Signature for Prediction of Clinical Outcomes and Immunotherapy in Gastric Cancer

Gastric cancer (GC) is a significant worldwide health concern and is a leading cause of cancer-related mortality. Immunotherapy has arisen as a promising strategy to stimulate the patient's immune system in combating cancer cells. Nevertheless, the effectiveness of immunotherapy in individuals with gastric cancer (GC) is not yet optimal. Thus, it is crucial to discover biomarkers capable appof predicting the advantages of immunotherapy for tailored treatment. The tumor microenvironment (TME) and its constituents, including cancer-associated fibroblasts (CAFs), exert a substantial influence on immune responses and treatment outcomes. In this investigation, we utilized single-cell RNA sequencing to profile CAFs in GC and established a scoring method, referred to as the CAF score (CAFS), for the prediction of patient prognosis and response to immunotherapy. Through our analysis, we successfully identified distinct subgroups within CAFs based on CAF score (CAFS), namely CAFS-high and CAFS-low subgroups. Notably, we noted that individuals within the CAFS-high subgroup experienced a lessF favorable prognosis and displayed diminished responsiveness to immunotherapy in contrast to the CAFS low subgroup. Furthermore, we analyzed the mutation and immune characteristics of these subgroups, identifying differentially mutated genes and immune cell compositions. We established that CAFS could forecast treatment advantages in patients with gastric cancer, both for chemotherapy and immunotherapy. Its efficacy was additionally confirmed in contrast to other biomarkers, including Tumor Immune Dysfunction and Exclusion (TIDE) and Immunophenotypic Score (IPS). These findings emphasize the clinical relevance and potential utility of CAFS in guiding personalized treatment strategies for gastric cancer.

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.

LIM domain only 7: a novel driver of immune evasion through regulatory T cell differentiation and chemotaxis in pancreatic ductal adenocarcinoma

With advancements in genomics and immunology, immunotherapy has emerged as a revolutionary strategy for tumor treatment. However, pancreatic ductal adenocarcinoma (PDAC), an immunologically "cold" tumor, exhibits limited responsiveness to immunotherapy. This study aimed to address the urgent need to uncover PDAC's immune microenvironment heterogeneity and identify the molecular mechanisms driving immune evasion. Using single-cell RNA sequencing datasets and spatial proteomics, we discovered LIM domain only 7 (LMO7) in PDAC cells as a previously unrecognized driver of immune evasion through Treg cell enrichment. LMO7 was positively correlated with infiltrating regulatory T cells (Tregs) and dysfunctional CD8+ T cells. A series of in vitro and in vivo experiments demonstrated LMO7's significant role in promoting Treg cell differentiation and chemotaxis while inhibiting CD8+ T cells and natural killer cell cytotoxicity. Mechanistically, LMO7, through its LIM domain, directly bound and promoted the ubiquitination and degradation of Foxp1. Foxp1 negatively regulated transforming growth factor-beta (TGF-β) and C-C motif chemokine ligand 5 (CCL5) expression by binding to sites 2 and I/III, respectively. Elevated TGF-β and CCL5 levels contribute to Treg cell enrichment, inducing immune evasion in PDAC. Combined treatment with TGF-β/CCL5 antibodies, along with LMO7 inhibition, effectively reversed immune evasion in PDAC, activated the immune response, and prolonged mouse survival. Therefore, this study identified LMO7 as a novel facilitator in driving immune evasion by promoting Treg cell enrichment and inhibiting cytotoxic effector functions. Targeting the LMO7-Foxp1-TGF-β/CCL5 axis holds promise as a therapeutic strategy for PDAC. Graphical abstract revealing LMO7 as a novel facilitator in driving immune evasion by promoting Tregs differentiation and chemotaxis, inducing CD8+ T/natural killer cells inhibition.

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.

Tumor-associated-fibrosis and active collagen-CD44 axis characterize a poor-prognosis subtype of gastric cancer and contribute to tumor immunosuppression

BACKGROUND

Tumor-associated fibrosis modifies the tumor microenvironment (TME), hinders the infiltration and activity of cytotoxic immune cells, and is a critical pathological process leading to the ineffectiveness of tumor immunotherapy in gastric cancer (GC). However, the specific mechanisms and interventions are yet to be fully explored.

METHODS

Our study included 375 gastric cancer samples from TCGA, 1 single-cell RNA sequencing (scRNA-seq) dataset comprising of 15 gastric cancer samples from GEO, 19 cohorts of immunotherapy and 2 GWAS datasets. Consensus clustering identified a gastric cancer subtype characterized primarily by fibrosis, and various methods such as pseudotime analysis, CellChat analysis and Colocalization analysis were used to explore its mechanisms.

RESULTS

A subtype of gastric cancer was identified with poor prognosis, characterized by higher malignancy, drug resistance, and poor immune infiltration, associated with elevated expression of genes related with Extracellular matrix (ECM). Single-cell transcriptome analysis showed active Collagen-CD44 signaling axis between cancer-associated fibroblasts (CAFs) and immune cells in gastric cancer, with ECM-related genes upregulated during tumor progression. The expression of CD44 was significantly elevated in the subtype, associated with poor prognosis and tumor immune suppression in gastric cancer, potentially involved in the recruitment of immunosuppressive cells such as M2 macrophages and regulatory T cells (Tregs) and the upregulation of multiple immune checkpoints including PD-1/PD-L1.

CONCLUSION

Our study identified a new subtype of gastric cancer, revealing that fibrosis is a critical mechanism driving immune suppression in gastric cancer and emphasizing the central role of the Collagen-CD44 signaling axis. The Collagen-CD44 signaling axis has the potential to serve as a novel therapeutic target for gastric cancer by enhancing immune cell-mediated tumor suppression. By combining it with immune checkpoint inhibitors (ICIs), it may improve the efficacy of immunotherapy for gastric cancer and offer new hope for treatment.

The Immune-Genomics of Cholangiocarcinoma: A Biological Footprint to Develop Novel Immunotherapies

Cholangiocarcinoma (CCA) represents approximately 3% of all gastrointestinal cancers and is a highly heterogeneous and aggressive malignancy originating from the epithelial cells of the biliary tree. CCA is classified by anatomical location into intrahepatic (iCCA), extrahepatic (eCCA), gallbladder cancer (GBC), and ampullary cancers. Although considered a rare tumor, CCA incidence has risen globally, particularly due to the increased diagnosis of iCCA. Genomic and immune profiling studies have revealed significant heterogeneity within CCA, leading to the identification of molecular subtypes and actionable genetic alterations in 40-60% of cases, particularly in iCCA. Among these, FGFR2 rearrangements or fusions (7-15%) and IDH1 mutations (10-20%) are common in iCCA, while HER2 amplifications/overexpression are more frequent in eCCA and GBC. The tumor-immune microenvironment (TIME) of CCAs plays an active role in the pathogenesis and progression of the disease, creating a complex and plastic environment dominated by immune-suppressive populations. Among these, cancer-associated fibroblasts (CAFs) are a key component of the TIME and are associated with worse survival due to their role in maintaining a poorly immunogenic landscape through the deposition of stiff extracellular matrix and release of pro-tumor soluble factors. Improved understanding of CCA tumor biology has driven the development of novel treatments. Combination therapies of cisplatin and gemcitabine with immune checkpoint inhibitors (ICIs) have replaced the decade-long standard doublet chemotherapy, becoming the new standard of care in patients with advanced CCA. However, the survival improvements remain modest prompting research into more effective ways to target the TIME of CCAs. As key mechanisms of immune evasion in CCA are uncovered, novel immune molecules emerge as potential therapeutic targets. Current studies are exploring strategies targeting multiple immune checkpoints, angiogenesis, and tumor-specific antigens that contribute to immune escape. Additionally, the success of ICIs in advanced CCA has led to interest in their application in earlier stages of the disease, such as in adjuvant and neoadjuvant settings. This review offers a comprehensive overview of the immune biology of CCAs and examines how this knowledge has guided clinical drug development, with a focus on both approved and emergent treatment strategies.

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.

ANXA10 sensitizes microsatellite instability-high colorectal cancer to anti-PD-1 immunotherapy via assembly of HLA-DR dimers by regulating CD74

BACKGROUND

Microsatellite instability-high (MSI-H) metastatic colorectal cancer (CRC) patients are the dominant population in immune checkpoint blockade treatments, while more than half of them could not benefit from single-agent immunotherapy. We tried to identify the biomarker of MSI-H CRC and explore its role and mechanism in anti-PD-1 treatments. Tumor-specific MHC-II was linked to a better response to anti-PD-1 in MSI-H CRC and CD74 promoted assembly and transport of HLA-DR dimers.

METHODS

The characteristic gene was screened by data analysis of single-cell and bulk transcriptome sequencing from public datasets. MSI-H CRC cells co-cultured with peripheral blood mononuclear cells and syngeneic model in C57BL/6 mice were performed to detect the sensitivity to anti-PD-1 treatments respectively.

RESULTS

ANXA10 was identified as a characteristic gene of MSI-H CRC and its expression was obviously greater in MSI-H than MSS CRC. ANXA10 significantly sensitized MSI-H CRC to anti-PD-1 treatments in vitro and in vivo. Specifically, ANXA10 promoted HLA-DR dimers in and on the surface of MSI-H CRC by increasing CD74 expression. Besides, this work demonstrated that ANXA10 contributed to better clinical benefits with anti-PD-1 therapy in MSI-H CRC patients.

CONCLUSIONS

Our results provided a novel molecular marker ANXA10 to identify benefit population of MSI-H CRC for improving efficacy of anti-PD-1 and contributed to selection of treatment strategies.

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.

An integrated single-cell and spatial transcriptomic atlas of thyroid cancer progression identifies prognostic fibroblast subpopulations

Thyroid cancer progression from curable well-differentiated thyroid carcinoma to highly lethal anaplastic thyroid carcinoma is distinguished by tumor cell de-differentiation and recruitment of a robust stromal infiltrate. Combining an integrated thyroid cancer single-cell sequencing atlas with spatial transcriptomics and bulk RNA-sequencing, we define stromal cell subpopulations and tumor-stromal cross-talk occurring across the histologic and mutational spectrum of thyroid cancer. We identify distinct inflammatory and myofibroblastic cancer-associated fibroblast (iCAF and myCAF) populations and perivascular-like populations. The myCAF population is only found in malignant samples and is associated with tumor cell invasion, BRAF V600E mutation, lymph node metastasis, and disease progression. Tumor-adjacent myCAFs abut invasive tumor cells with a partial epithelial-to-mesenchymal phenotype. Tumor-distant iCAFs infiltrate inflammatory autoimmune thyroid lesions and anaplastic tumors. In summary, our study provides an integrated atlas of thyroid cancer fibroblast subtypes and spatial characterization at sites of tumor invasion and de-differentiation, defining the stromal reorganization central to disease progression.

Tumor microenvironment-responsive engineered hybrid nanomedicine for photodynamic-immunotherapy via multi-pronged amplification of reactive oxygen species

Reactive oxygen species (ROS) is promising in cancer therapy by accelerating tumor cell death, whose therapeutic efficacy, however, is greatly limited by the hypoxia in the tumor microenvironment (TME) and the antioxidant defense. Amplification of oxidative stress has been successfully employed for tumor therapy, but the interactions between cancer cells and the other factors of TME usually lead to inadequate tumor treatments. To tackle this issue, we develop a pH/redox dual-responsive nanomedicine based on the remodeling of cancer-associated fibroblasts (CAFs) for multi-pronged amplification of ROS (ZnPP@FQOS). It is demonstrated that ROS generated by ZnPP@FQOS is endogenously/exogenously multiply amplified owing to the CAFs remodeling and down-regulation of anti-oxidative stress in cancer cells, ultimately achieving the efficient photodynamic therapy in a female tumor-bearing mouse model. More importantly, ZnPP@FQOS is verified to enable the stimulation of enhanced immune responses and systemic immunity. This strategy remarkably potentiates the efficacy of photodynamic-immunotherapy, thus providing a promising enlightenment for tumor therapy.

Single cell and spatial analysis of immune-hot and immune-cold tumours identifies fibroblast subtypes associated with distinct immunological niches and positive immunotherapy response

Cancer-associated Fibroblasts (CAFs) have emerged as critical regulators of anti-tumour immunity, with both beneficial and detrimental properties that remain poorly characterised. To investigate this, we performed single-cell and spatial transcriptomic analysis, comparing head & neck squamous cell carcinoma (HNSCC) subgroups, which although heterogenous, can be considered broadly immune-hot and immune-cold (human papillomavirus [HPV]+ve and HPV-ve tumours respectively). This identified six fibroblast subpopulations, including two with immunomodulatory gene expression profiles (IL-11 + inflammatory [i]CAF and CCL19 + fibroblastic reticular cell [FRC]-like). IL-11 + iCAF were spatially associated with inflammatory monocytes and regulated in vitro through synergistic activation of canonical NF-κB signalling by IL-1β and TNF-α. FRC-like were enriched in immune-hot HPV+ve tumours, associated with CD4 + T-cells and B-cells in tertiary lymphoid structures and regulated through non-canonical NF-κB signalling via lymphotoxin. Pan-cancer analysis revealed several 'iCAF' subgroups present in both normal and cancer tissues; IL11 + iCAF were found in cancers from the gastrointestinal (GI) tract and transcriptomically distinct from iCAFs previously described in pancreatic and breast cancers with greater inflammatory properties; FRC-like fibroblasts were present at low frequencies in all tumour types, and were associated with significantly better survival in patients receiving checkpoint immunotherapy. This work clarifies and expands current literature on immunomodulatory CAFs, highlighting links with important immunological niches.

Multi-omic profiling highlights factors associated with resistance to immuno-chemotherapy in non-small-cell lung cancer

Although immune checkpoint blockade (ICB) therapies have shifted the treatment paradigm for non-small-cell lung cancer (NSCLC), many patients remain resistant. Here we characterize the tumor cell states and spatial cellular compositions of the NSCLC tumor microenvironment (TME) by analyzing single-cell transcriptomes of 232,080 cells and spatially resolved transcriptomes of tumors from 19 patients before and after ICB-chemotherapy. We find that tumor cells and secreted phosphoprotein 1-positive macrophages interact with collagen type XI alpha 1 chain-positive cancer-associated fibroblasts to stimulate the deposition and entanglement of collagen fibers at tumor boundaries, obstructing T cell infiltration and leading to poor prognosis. We also reveal distinct states of tertiary lymphoid structures (TLSs) in the TME. Activated TLSs are associated with improved prognosis, whereas a hypoxic microenvironment appears to suppress TLS development and is associated with poor prognosis. Our study provides novel insights into different cellular and molecular components corresponding to NSCLC ICB-chemotherapeutic responsiveness, which will benefit future individualized immuno-chemotherapy.

Convergent inducers and effectors of T cell paralysis in the tumour microenvironment

Tumorigenesis embodies the formation of a heterotypic tumour microenvironment (TME) that, among its many functions, enables the evasion of T cell-mediated immune responses. Remarkably, most TME cell types, including cancer cells, fibroblasts, myeloid cells, vascular endothelial cells and pericytes, can be stimulated to deploy immunoregulatory programmes. These programmes involve regulatory inducers (signals-in) and functional effectors (signals-out) that impair CD8+ and CD4+ T cell activity through cytokines, growth factors, immune checkpoints and metabolites. Some signals target specific cell types, whereas others, such as transforming growth factor-β (TGFβ) and prostaglandin E2 (PGE2), exert broad, pleiotropic effects; as signals-in, they trigger immunosuppressive programmes in most TME cell types, and as signals-out, they directly inhibit T cells and also modulate other cells to reinforce immunosuppression. This functional diversity and redundancy pose a challenge for therapeutic targeting of the immune-evasive TME. Fundamentally, the commonality of regulatory programmes aimed at abrogating T cell activity, along with paracrine signalling between cells of the TME, suggests that many normal cell types are hard-wired with latent functions that can be triggered to prevent inappropriate immune attack. This intrinsic capability is evidently co-opted throughout the TME, enabling tumours to evade immune destruction.

Identification of Small-Molecule Inhibitors Targeting Different Signaling Pathways in Cancer-Associated Fibroblast Reprogramming under Tumor-Stroma Interaction

Cancer-associated fibroblasts (CAFs) interact reciprocally with tumor cells through various signaling pathways in many cancer types, including cutaneous squamous cell carcinoma. Among normal fibroblast subtypes, papillary fibroblasts (PFs) and reticular fibroblasts (RFs) respond distinctly to tumor cell signaling, eventuating the differentiation of RFs rather than PFs into CAFs. The regulation of subtype differentiation in fibroblasts remains poorly explored. In this study, we assessed the differences between PFs, RFs, and CAFs and examined the effects of small-molecule inhibitors targeting the TGFβ, phosphoinositide 3-kinase/protein kinase B/mTOR, and NOTCH pathways on the tumor-promoting property of CAFs and CAF reprogramming in 2-dimensional and 3-dimensional cultures. Blocking TGFβ and phosphoinositide 3-kinase strongly deactivated and concurrently induced a PF phenotype in RFs and CAFs. Three-dimensional coculturing of a cutaneous squamous cell carcinoma cell line MET2 with RFs or CAFs led to enhanced tumor invasion, RF-CAF transition, and cytokine production, which were further repressed by blocking TGFβ and phosphoinositide 3-kinase/mTOR pathways but not NOTCH pathway. In conclusion, the study identified biomarkers for PFs, RFs, and CAFs and displayed different effects of blocking key signaling pathways in CAFs and tumor cell-CAF interplay. These findings prompted a CAF-to-PF therapeutic strategy and provided perspectives of using included inhibitors in CAF-based cancer therapy.

Tumor microenvironment and immunotherapy for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of breast cancer known for its high aggressiveness and poor prognosis. Conventional treatment of TNBC is challenging due to its heterogeneity and lack of clear targets. Recent advancements in immunotherapy have shown promise in treating TNBC, with immune checkpoint therapy playing a significant role in comprehensive treatment plans. The tumor microenvironment (TME), comprising immune cells, stromal cells, and various cytokines, plays a crucial role in TNBC progression and response to immunotherapy. The high presence of tumor-infiltrating lymphocytes and immune checkpoint proteins in TNBC indicates the potential of immunotherapeutic strategies. However, the complexity of the TME, while offering therapeutic targets, requires further exploration of its multiple roles in immunotherapy. In this review, we discuss the interaction mechanism between TME and TNBC immunotherapy based on the characteristics and composition of TME, and elaborate on and analyze the effect of TME on immunotherapy, the potential of TME as an immune target, and the ability of TME as a biomarker. Understanding these dynamics will offer new insights for enhancing therapeutic approaches and investigating stratification and prognostic markers for TNBC patients.

Mindin regulates fibroblast subpopulations through distinct Src family kinases during fibrogenesis

Fibrosis results from excessive extracellular matrix (ECM) deposition, which causes tissue stiffening and organ dysfunction. Activated fibroblasts, central to fibrosis, exhibit increased migration, proliferation, contraction, and ECM production. However, it remains unclear if the same fibroblast performs all of the processes that fall under the umbrella term of "activation." Owing to fibroblast heterogeneity in connective tissues, subpopulations with specific functions may operate under distinct regulatory controls. Using a transgenic mouse model of skin fibrosis, we found that Mindin (also known as spondin-2), secreted by Snail-transgenic keratinocytes, differentially regulates fibroblast subpopulations. Mindin promotes migration and inflammatory gene expression in SCA1+ dermal fibroblasts via Fyn kinase. In contrast, it enhances contractility and collagen production in papillary CD26+ fibroblasts through c-Src signaling. Moreover, in the context of the fibrotic microenvironment of the tumor stroma, we found that differential responses of resident fibroblast subpopulations to Mindin extend to the generation of functionally heterogeneous cancer-associated fibroblasts. This study identifies Mindin as a key orchestrator of dermal fibroblast heterogeneity, reshaping cellular dynamics and signaling diversity in the complex landscapes of skin fibrosis and cancer.