Identification of fibrocyte cluster in tumors reveals the role in antitumor immunity by PD-L1 blockade

Hypoxia-inducible factor-targeting therapy augmented the sensitivity to programmed death ligand-1 blockade by enhancing interferon-γ-induced chemokines in tumor cells

Immune checkpoint inhibitors (ICIs) targeting programmed death ligand-1 (PD-L1) provide clinical benefits for various advanced malignancies. However, the predictive factors that determine sensitivity to ICIs have not been fully elucidated. We focused on tumor-derived CXCL10/11 as a pivotal factor that determines the response to PD-L1 blockade by regulating T cell accumulation and tumor angiogenesis. We previously reported that CXCL10/11 was upregulated by interferon (IFN)-γ in ICI-sensitive tumor cells but not in ICI-resistant cells, including mouse Lewis lung carcinoma (LLC). In the present study, gene silencing of tumor-derived CXCL10/11 induced resistance to PD-L1 blockade in AB1-HA mesothelioma cell-bearing mice. To identify the mechanisms underlying ICI resistance, we performed a microarray analysis to compare the IFN-γ-inducible genes between ICI-sensitive AB1-HA and ICI-resistant LLC in vitro. A pathway analysis based on microarray data indicated that hypoxia-inducible factor (HIF) 1A is the key signal that inhibits CXCL10/11 expression. We revealed that the HIF1A inhibitors echinomycin (EC) and YC-1 upregulated CXCL10/11 genes induced by IFN-γ in tumor cells in vitro. In addition, combination therapy with PD-L1 blockade and EC demonstrated synergistic antitumor effects in LLC-bearing mice. Combination therapy enhanced tumor infiltration of CD8 T cells and suppressed tumor angiogenesis. The present study suggests that HIF1A signaling in tumor cells dominates ICI resistance via the downregulation of tumor-derived CXCL10/11.

Hepatic Growth Factor as a Potential Biomarker for Lung Adenocarcinoma: A Multimodal Study

(1) Background: Despite previous studies linking inflammatory cytokines to lung adenocarcinoma (LUAD), their causal mechanisms remain unclear. This study aims to explore the causal relationship between inflammatory cytokines and LUAD to fill this knowledge gap. (2) Methods: This study employs a comprehensive approach, integrating Mendelian randomization (MR) analysis, single-cell RNA sequencing (scRNA-seq), and transcriptomic sequencing (RNA-seq) data to investigate the relationship between inflammatory cytokines and LUAD. (3) Results: In forward MR analysis, elevated levels of hepatocyte growth factor (HGF), interleukin-1 receptor antagonist (IL-1RA), IL-5, monocyte chemoattractant protein-3, and monokine induced by interferon-γ were causally associated with an increased risk of LUAD. In reverse MR analysis, LUAD exhibited a positive causal relationship with the levels of regulated upon activation normal T cell expressed and secreted factor (RANTES) and stromal cell-derived factor-1α. The scRNA-seq data further identified specific cell populations that may influence LUAD onset and progression through the expression of particular inflammatory genes and intercellular communication. RNA-seq data analysis highlighted the role of the HGF gene in LUAD diagnosis, demonstrating its strong correlation with patient prognosis and immune cell infiltration within the tumor microenvironment. (4) Conclusions: The findings reveal a causal relationship between inflammatory cytokines and LUAD, with HGF emerging as a potential biomarker of significant clinical relevance. This study provides new insights into the molecular mechanisms underlying LUAD and lays the foundation for future therapeutic strategies.

Fibrocyte enrichment and myofibroblastic adaptation causes nucleus pulposus fibrosis and associates with disc degeneration severity

Fibrotic remodeling of nucleus pulposus (NP) leads to structural and mechanical anomalies of intervertebral discs that prone to degeneration, leading to low back pain incidence and disability. Emergence of fibroblastic cells in disc degeneration has been reported, yet their nature and origin remain elusive. In this study, we performed an integrative analysis of multiple single-cell RNA sequencing datasets to interrogate the cellular heterogeneity and fibroblast-like entities in degenerative human NP specimens. We found that disc degeneration severity is associated with an enrichment of fibrocyte phenotype, characterized by CD45 and collagen I dual positivity, and expression of myofibroblast marker α-smooth muscle actin. Refined clustering and classification distinguished the fibrocyte-like populations as subtypes in the NP cells - and immunocytes-clusters, expressing disc degeneration markers HTRA1 and ANGPTL4 and genes related to response to TGF-β. In injury-induced mouse disc degeneration model, fibrocytes were found recruited into the NP undergoing fibrosis and adopted a myofibroblast phenotype. Depleting the fibrocytes in CD11b-DTR mice in which myeloid-derived lineages were ablated by diphtheria toxin could markedly attenuate fibrous modeling and myofibroblast formation in the NP of the degenerative discs, and prevent disc height loss and histomorphological abnormalities. Marker analysis supports that disc degeneration progression is dependent on a function of CD45+COL1A1+ and αSMA+ cells. Our findings reveal that myeloid-derived fibrocytes play a pivotal role in NP fibrosis and may therefore be a target for modifying disc degeneration and promoting its repair.

PDGFRα inhibition reduces myofibroblast expansion in the fibrotic rim and enhances recovery after ischemic stroke

Ischemic stroke is a major cause of disability in adults. Early treatment with thrombolytics and/or thrombectomy can significantly improve outcomes; however, following these acute interventions, treatment is limited to rehabilitation therapies. Thus, identification of therapeutic strategies that can help restore brain function in the post-acute phase remains a major challenge. Here we report that genetic or pharmacologic inhibition of the PDGF-CC/PDGFRα pathway, which has previously been implicated in stroke pathology, significantly reduced myofibroblast expansion in the border of the fibrotic scar and improved outcome in a sensory-motor integration test after experimental ischemic stroke. This was supported by gene expression analyses of cerebrovascular fragments showing upregulation of profibrotic/proinflammatory genes, including genes of the TGF pathway, after ischemic stroke or intracerebroventricular injection of active PDGF-CC. Further, longitudinal intravital 2-photon imaging revealed that inhibition of PDGFRα dampened the biphasic pattern of stroke-induced vascular leakage and enhanced vascular perfusion in the ischemic lesion. Importantly, we found PDGFRα inhibition to be effective in enhancing functional recovery when initiated 24 hours after ischemic stroke. Our data implicate the PDGF-CC/PDGFRα pathway as a crucial mediator modulating post-stroke pathology and suggest a post-acute treatment opportunity for patients with ischemic stroke targeting myofibroblast expansion to foster long-term CNS repair.

Fibrocytes in tumor microenvironment: Identification of their fraction and novel therapeutic strategy

Fibrocytes were identified as bone marrow-derived myeloid cells that also have fibroblast-like phenotypes, such as ECM production and differentiation to myofibroblasts. Although fibrocytes are known to contribute to various types of tissue fibrosis, their functions in the tumor microenvironment are unclear. We focused on fibrocytes as pivotal regulators of tumor progression. Our previous studies have indicated that fibrocytes induce angiogenesis and cancer stem cell-like phenotypes by secreting various growth factors. In contrast, immune checkpoint inhibitor (ICI)-treated fibrocytes demonstrated antigen-presenting capacity and enhanced antitumor T cell proliferation. Taken together, these findings indicate that fibrocytes have multiple effects on tumor progression. However, the detailed phenotypes of fibrocytes have not been fully elucidated because the isolation of distinct fibrocyte clusters has not been achieved without culturing in ECM-coated conditions or intracellular staining of ECM. The development of single-cell analyses partially resolves these problems. Single-cell RNA sequences in CD45+ immune cells from tumor tissue identified ECM-expressing myeloid-like cells as distinct fibrocyte clusters. In addition, these findings enabled the isolation of tumor-infiltrating fibrocytes as CD45+CD34+ cells. These tumor-infiltrating fibrocytes demonstrated both antigen-presenting ability and differentiation into myofibroblast-like cancer-associated fibroblasts. Considering these functions of fibrocytes in tumor progression, molecular-targeting agents for the migration, activity, and differentiation of fibrocytes are promising therapeutic strategies. Furthermore, identification of specific cell surface markers and master regulators of fibrocytes will advance novel fibrocyte-targeting therapies. In this review, we discuss the multiple roles of tumor-infiltrating fibrocytes and novel cancer therapeutic strategies.

Collagen induction of immune cells in the mammary glands during pregnancy

The mammary glands are dynamic tissues affected by pregnancy-related hormones during the pregnancy-lactation cycle. Collagen production and its dynamics are essential to the remodeling of the mammary glands. Alterations of the mammary microenvironment and stromal cells during the pregnancy-lactation cycle are important for understanding the physiology of the mammary glands and the development of breast tumors. In this study, we performed an evaluation of collagen dynamics in the mammary fat pad during the pregnancy-lactation cycle. Reanalysis of single-cell RNA-sequencing (scRNA-Seq) data showed the ectopic collagen expression in the immune cells and cell-cell interactions for collagens with single-cell resolution. The scRNA-Seq data showed that type I and type III collagen were produced not only by stromal fibroblasts but also by lymphoid and myeloid cell types in the pregnancy phase. Furthermore, the total cell-cell interaction score for collagen interactions was dramatically increased in the pregnancy tissue. The data presented in this study provide evidence that immune cells contribute, at least in part, to mammary collagen dynamics. Our findings suggest that immune cells, including lymphoid and myeloid cells, might be supportive members of the extracellular matrix orchestration in the pregnancy-lactation cycle of the mammary glands.NEW & NOTEWORTHY Our study evaluated mammary gland collagen dynamics during the pregnancy-lactation cycle using single-cell RNA-sequencing data. We found ectopic collagen expression in immune cells and an increase in collagen interactions during pregnancy. Type I and type III collagen were produced by lymphoid, myeloid, and stromal fibroblast cells during pregnancy. These findings suggest that immune cells, including lymphoid and myeloid cells, play a crucial role in supporting the extracellular matrix in mammary glands during pregnancy-lactation cycles.

Alterations in the mammary gland and tumor microenvironment of formerly obese mice

BACKGROUND

Obesity is a risk factor for breast cancer, and women with obesity that develop breast cancer have a worsened prognosis. Within the mammary gland, obesity causes chronic, macrophage-driven inflammation and adipose tissue fibrosis. Weight loss is a recommended intervention to resolve obesity, but the impact of weight loss on the mammary gland microenvironment and in tumors has not been well identified.

METHODS

To examine the effects of weight loss following obesity, mice were fed a high-fat diet for 16 weeks to induce obesity, then switched to a low-fat diet for 6 weeks. We examined changes in immune cells, including fibrocytes, which are myeloid lineage cells that have attributes of both macrophages and myofibroblasts, and collagen deposition within the mammary glands of non-tumor-bearing mice and within the tumors of mice that were transplanted with estrogen receptor alpha positive TC2 tumor cells.

RESULTS

In formerly obese mice, we observed reduced numbers of crown-like structures and fibrocytes in mammary glands, while collagen deposition was not resolved with weight loss. Following transplant of TC2 tumor cells into the mammary glands of lean, obese, and formerly obese mice, diminished collagen deposition and cancer-associated fibroblasts were observed in tumors from formerly obese mice compared to obese mice. Within tumors of obese mice, increased myeloid-derived suppressor cells and diminished CD8+ T cells were identified, while the microenvironment of tumors of formerly obese mice were more similar to tumors from lean mice. When TC2 tumor cells were mixed with CD11b+CD34+ myeloid progenitor cells, which are the cells of origin for fibrocytes, and transplanted into mammary glands of lean and obese mice, collagen deposition within the tumors of both lean and obese was significantly greater than when tumor cells were mixed with CD11b+CD34- monocytes or total CD45+ immune cells.

CONCLUSIONS

Overall, these studies demonstrate that weight loss resolved some of the microenvironmental conditions within the mammary gland that may contribute to tumor progression. Additionally, fibrocytes may contribute to early collagen deposition in mammary tumors of obese mice leading to the growth of desmoplastic tumors.

Short-range interactions between fibrocytes and CD8+ T cells in COPD bronchial inflammatory response

Bronchi of chronic obstructive pulmonary disease (COPD) are the site of extensive cell infiltration, allowing persistent contact between resident cells and immune cells. Tissue fibrocytes interaction with CD8⁺ T cells and its consequences were investigated using a combination of in situ, in vitro experiments and mathematical modeling. We show that fibrocytes and CD8⁺ T cells are found in the vicinity of distal airways and that potential interactions are more frequent in tissues from COPD patients compared to those of control subjects. Increased proximity and clusterization between CD8⁺ T cells and fibrocytes are associated with altered lung function. Tissular CD8⁺ T cells from COPD patients promote fibrocyte chemotaxis via the CXCL8-CXCR1/2 axis. Live imaging shows that CD8⁺ T cells establish short-term interactions with fibrocytes, that trigger CD8⁺ T cell proliferation in a CD54- and CD86-dependent manner, pro-inflammatory cytokines production, CD8⁺ T cell cytotoxic activity against bronchial epithelial cells and fibrocyte immunomodulatory properties. We defined a computational model describing these intercellular interactions and calibrated the parameters based on our experimental measurements. We show the model's ability to reproduce histological ex vivo characteristics, and observe an important contribution of fibrocyte-mediated CD8⁺ T cell proliferation in COPD development. Using the model to test therapeutic scenarios, we predict a recovery time of several years, and the failure of targeting chemotaxis or interacting processes. Altogether, our study reveals that local interactions between fibrocytes and CD8⁺ T cells could jeopardize the balance between protective immunity and chronic inflammation in the bronchi of COPD patients.

Effects of altered glycolysis levels on CD8+ T cell activation and function

CD8+ T cells are an important component of the body's adaptive immune response. During viral or intracellular bacterial infections, CD8+ T cells are rapidly activated and differentiated to exert their immune function by producing cytokines. Alterations in the glycolysis of CD8+ T cells have an important effect on their activation and function, while glycolysis is important for CD8+ T cell functional failure and recovery. This paper summarizes the importance of CD8+ T cell glycolysis in the immune system. We discuss the link between glycolysis and CD8+ T cell activation, differentiation, and proliferation, and the effect of altered glycolysis on CD8+ T cell function. In addition, potential molecular targets to enhance and restore the immune function of CD8+ T cells by affecting glycolysis and the link between glycolysis and CD8+ T cell senescence are summarized. This review provides new insights into the relationship between glycolysis and CD8+ T cell function, and proposes novel strategies for immunotherapy by targeting glycolysis.

Alterations in the Mammary Gland and Tumor Microenvironment of Formerly Obese Mice

Obesity is a risk factor for breast cancer, and women with obesity that develop breast cancer have a worsened prognosis. Within the mammary gland, obesity causes chronic, macrophage-driven inflammation and adipose tissue fibrosis. To examine the impact of weight loss on the mammary microenvironment, mice were fed high-fat diet to induce obesity, then switched to a low-fat diet. In formerly obese mice, we observed reduced numbers of crown-like structures and fibrocytes in mammary glands, while collagen deposition was not resolved with weight loss. Following transplant of TC2 tumor cells into the mammary glands of lean, obese, and formerly obese mice, diminished collagen deposition and cancer-associated fibroblasts were observed in tumors from formerly obese mice compared to obese mice. When TC2 tumor cells were mixed with CD11b+CD34+ myeloid progenitor cells, collagen deposition within the tumors was significantly greater compared to when tumor cells were mixed with CD11b+CD34- monocytes, suggesting that fibrocytes contribute to early collagen deposition in mammary tumors of obese mice. Overall, these studies show that weight loss resolved some of the microenvironmental conditions within the mammary gland that may contribute to tumor progression.