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Abstract Background Cancer‐associated fibroblasts (CAFs) are a major stromal component of human breast cancers and often promote tumor proliferation, progression and malignancy. We previously established an experimental CAF (exp‐CAF) cell line equipped with a potent tumor‐promoting ability. It was generated through prolonged incubation of immortalized human mammary fibroblasts with human breast cancer cells in a tumor xenograft mouse model. Results Herein, we found that the exp‐CAFs highly express Runt‐related transcription factor 3 (RUNX3), while counterpart fibroblasts do not. In breast cancer patients, the proportion of RUNX3‐positive stromal fibroblast‐like cells tends to be higher in cancerous regions than in non‐cancerous regions. These findings suggest an association of RUNX3 with CAF characteristics in human breast cancers. To investigate the functional role of RUNX3 in CAFs, the exp‐CAFs with or without shRNA‐directed knockdown of RUNX3 were implanted with breast cancer cells subcutaneously in immunodeficient mice. Comparison of the resulting xenograft tumors revealed that tumor growth was significantly attenuated when RUNX3 expression was suppressed in the fibroblasts. Consistently, Ki‐67 and CD31 immunohistochemical staining of the tumor sections indicated reduction of cancer cell proliferation and microvessel formation in the tumors formed with the RUNX3‐suppressed exp‐CAFs. Conclusion These results suggest that increased RUNX3 expression could contribute to the tumor‐promoting ability of CAFs through mediating cancer cell growth and neoangiogenesis in human breast tumors.

Abstract Cancer-associated fibroblasts (CAFs), enriched in the tumor stroma, have received increasing attention because of their multifaceted effects on tumorigenesis, development, metastasis, and treatment resistance in malignancies. CAFs contributed to suppressive microenvironment via different mechanisms, while CAFs also exerted some antitumor effects. Therefore, CAFs have been considered promising therapeutic targets for their remarkable roles in malignant tumors. However, patients with malignancies failed to benefit from current CAFs-targeted drugs in many clinical trials, which suggests that further in-depth investigation into CAFs is necessary. Here, we summarize and outline the heterogeneity and plasticity of CAFs mainly by exploring their origin and activation, highlighting the regulation of CAFs in the tumor microenvironment during tumor evolution, as well as the critical roles performed by CAFs in tumor immunity. In addition, we summarize the current immunotherapies targeting CAFs, and conclude with a brief overview of some prospects for the future of CAFs research in the end. Video Abstract

Cancer-associated fibroblasts (CAFs) play critical roles in the tumor microenvironment and exert tumor-promoting or tumor-retarding effects on cancer development. Astragaloside IV has been suggested to rescue the pathological impact of CAFs in gastric cancer. This study aimed to investigate the potential mechanism of astragaloside IV in the regulation of CAF pathological functions in gastric cancer development. Homeobox A6 (HOXA6), and Zinc Finger and BTB Domain Containing 12 (ZBTB12) are highly expressed in gastric CAFs compared with normal fibroblasts (NFs) based on the GSE62740 dataset. We found that astragaloside IV-stimulated CAFs suppressed cell growth, migration, and invasiveness of gastric cancer cells. HOXA6 and ZBTB12 were downregulated after astragaloside IV treatment in CAFs. Further analysis revealed that HOXA6 or ZBTB12 knockdown in CAFs also exerted inhibitory effects on the malignant phenotypes of gastric cells. Additionally, HOXA6 or ZBTB12 overexpression in CAFs enhanced gastric cancer cell malignancy, which was reversed after astragaloside IV treatment. Moreover, based on the hTFtarget database, ZBTB12 is a target gene that may be transcriptionally regulated by HOXA6. The binding between HOXA6 and ZBTB12 promoter in 293T cells and CAFs was further confirmed. HOXA6 silencing also induced the downregulation of ZBTB12 mRNA and protein in CAFs. Astragaloside IV was demonstrated to regulate the expression of ZBTB12 by mediating the transcriptional activity of HOXA6. Our findings shed light on the therapeutic value of astragaloside IV for gastric cancer.

Abstract Aims This study aims to explore the role of exosomes from cancer-associated fibroblasts (CAFs) induced by PDGF-BB in promoting the malignancy of oral squamous cell carcinoma (OSCC) and provide new insight into the mechanism of OSCC progression and its treatment. Main methods Exosomes were extracted from human oral mucosa fibroblasts (hOMFs) and CAFs. Differentially expressed miRNAs of exosomes between hOMFs and CAFs were analysed using high-throughput sequencing and self-programmed R software. Cal-27, a human tongue squamous carcinoma cell line, was treated with exosomes. Differentially expressed miRNAs between clinical cancer tissues and adjacent tissues and between hOMF and CAF exosomes were verified by qRT‒PCR. The effect of miR-3529-3p on Cal-27 cells was clarified by overexpressing or knocking down miR-3529-3p in Cal-27 cells. Sample expression and differentially expressed miRNA expression were compared between cancer and paracarcinoma tissues. Key findings We found that exosomes from CAFs (CAF-Exos) were internalized by tongue squamous carcinoma cells and promoted their proliferation, migration, invasion, and antiapoptotic effects. MiR-3529-3p was a significant differentially expressed miRNA between CAF-Exos and exosomes from hOMFs (hOMF-Exos). The overexpression of miR-3529-3p promoted proliferation, migration, and invasion and inhibited apoptosis of Cal-27 cells. Significance This study explores the role of PDGF-BB-induced CAFs in promoting malignancy in OSCC. This study will provide new insight into the mechanism of OSCC progression and its treatment.

Abstract Glutamine fructose‐6‐phosphate aminotransferase 2 (GFPT2) is a rate‐limiting enzyme in hexosamine biosynthesis involved in the occurrence and progress of many cancers. What role it plays in gastric cancer (GC) is still unclear. In this study, transcriptome sequencing data from the Harbin Medical University (HMU)‐GC cohort and The Cancer Genome Atlas (TCGA) dataset were combined with the HMU‐TCGA training cohort to analyze the biological function and clinical significance of GFPT2. The correlation of GFPT2 with immune cells and stromal cells was analyzed in the GC immune microenvironment through transcriptome sequencing data and a public single‐cell sequencing database. In cell lines, GC tissues, and the tissue microarray, GFPT2 protein expression was confirmed by western blotting and immunohistochemistry. The mRNA of GFPT2 was highly expressed in the tumor (p

Abstract F18-fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) plays a crucial role in tumour diagnosis, staging, and therapy response evaluation of various cancer types and has been a standard imaging modality used in clinical oncology practice for many years. However, it has certain limitations in evaluating some particular gastrointestinal cancer types due to low FDG-avidity or interphering physiological background activity. Fibroblast activation protein (FAP), a protein of the tumour microenvironment, is overexpressed in a wide range of cancers which makes it an attractive target for both tumour imaging and therapy. Recently, FAP-targeted radiopharmaceuticals are widely used in clinical research and achieved great results in tumour imaging. Considering the limitations of FDG PET/CT and the lack of physiological FAP-targeted tracer uptake in liver and intestinal loops, gastrointestinal cancers are among the most promising indications of FAP-targeted imaging. Herein, we present a comprehensive review of FAP-targeted imaging in gastrointestinal cancers in order to clarify the current and potential future role of this class of molecules in gastrointestinal oncology.

Cancer‐associated fibroblasts (CAFs), a major component of the tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDAC), play an important role in tumorigenesis, metastasis, and chemoresistance. Tumor‐derived small extracellular vesicles (sEVs), which mediate cell‐to‐cell communication between cancer cells and fibroblasts, are also critical for cancer progression and metastasis. However, it remains unclear how PDAC cell‐derived sEVs activate fibroblasts, which contributes to tumor progression. Here, we report that ezrin (EZR) expression in PDAC cell‐derived sEVs (sEV‐EZR) can activate fibroblasts, resulting in increased migration ability and high expression of α‐SMA, PDGFRB, and high production of extracellular matrix in fibroblasts. Reciprocally, sEV‐EZR‐activated fibroblasts enhanced PDAC cell proliferation, invasion, and metastasis to the liver in animal models. Conversely, fibroblasts treated with PDAC cell‐derived sEVs with EZR knockdown resulted in the reduced metastatic ability of PDAC. Mechanistically, we demonstrated that PDAC cell‐derived sEV‐EZR increases the STAT3 and YAP‐1 signaling pathways to induce fibroblast activation, and the activated fibroblasts promote PDAC cell proliferation, invasion, and liver metastasis. Inhibition of the STAT3 and YAP‐1 signaling pathways by gene knockdown can abrogate sEV‐EZR‐induced effects. These findings suggest that targeting the interaction between PDAC cell‐derived sEV‐EZR and fibroblasts is a potential therapeutic strategy for PDAC.

Abstract Background The tumour microenvironment consists of a complex and dynamic milieu of cancer cells, including tumour-associated stromal cells (leukocytes, fibroblasts, vascular cells, etc.) and their extracellular products. During invasion and metastasis, cancer cells actively remodel the tumour microenvironment and alterations of microenvironment, particularly cancer-associated fibroblasts (CAFs), can promote tumour progression. However, the underlying mechanisms of the CAF formation and their metastasis-promoting functions remain unclear. Methods Primary liver fibroblasts and CAFs were isolated and characterized. CAFs in clinical samples were identified by immunohistochemical staining and the clinical significance of CAFs was also analysed in two independent cohorts. A transwell coculture system was used to confirm the role of HCC cells in CAF recruitment and activation. qRT-PCR, western blotting and ELISA were used to screen paracrine cytokines. The role and mechanism of Egfl7 in CAFs were explored via an in vitro coculture system and an in vivo mouse orthotopic transplantation model. Results We showed that CAFs in hepatocellular carcinoma (HCC) are characterized by the expression of α-SMA and that HCC cells can recruit liver fibroblasts (LFs) and activate them to promote their transformation into CAFs. High α-SMA expression, indicating high CAF infiltration, was correlated with malignant characteristics. It was also an independent risk factor for HCC survival and could predict a poor prognosis in HCC patients. Then, we demonstrated that EGF-like domain multiple 7 (Egfl7) was preferentially secreted by HCC cells, and exhibited high potential to recruit and activate LFs into the CAF phenotype. The ability of Egfl7 to modulate LFs relies upon increased phosphorylation of FAK and AKT via the receptor ανβ3 integrin. Strikingly, CAFs activated by paracrine Egfl7 could further remodel the tumour microenvironment by depositing fibrils and collagen and in turn facilitate HCC cell proliferation, invasion and metastasis. Conclusion Our data highlighted a novel role of Egfl7 in remodelling the tumour microenvironment: it recruits LFs and activates them to promote their transformation into CAFs via the ανβ3 integrin signaling pathway, which further promotes HCC progression and contributes to poor clinical outcomes in HCC patients. Video Abstract

Abstract Background Esophageal squamous cell carcinoma (ESCC), an aggressive gastrointestinal tumor, often has high early lymphatic metastatic potential. Cancer‐associated fibroblasts (CAFs) are primary components in tumor microenvironment (TME), and the impact of CAFs and its derived exosomes on lymphangiogenesis remains elusive. Materials and Methods CAFs and the microlymphatic vessel density (MLVD) in ESCC was examined. Exosomes were extracted from primary normal fibroblast (NFs) and CAFs. Subsequently, tumor‐associated lymphatic endothelial cells (TLECs) were treated with these exosomes, and the effect on their biological behavior was examined. miR‐100‐5p was selected as the target miRNA, and its effect on TLECs was examined. The target of miR‐100‐5p was predicted and confirmed. Subsequently, IGF1R, PI3K, AKT, and p‐AKT expression in TLECs and tumors treated with exosomes and miR‐100‐5p were examined. Results A large number of CAFs and microlymphatic vessels were present in ESCC, leading to a poor prognosis. CAF‐derived exosomes promoted proliferation, migration, invasion, and tube formation in TLECs. Further, they also enhanced lymphangiogenesis in ESCC xenografts. miR‐100‐5p levels were significantly lower in CAF‐derived exosomes than in NF‐derived exosomes. miR‐100‐5p inhibited proliferation, migration, invasion, and tube formation in TLECs. Further, miR‐100‐5p inhibited lymphangiogenesis in ESCC xenografts. Mechanistic studies revealed that this inhibition was mediated by the miR‐100‐5p‐induced inhibition of IGF1R/PI3K/AKT axis. Conclusion Taken together, our study demonstrates that CAF‐derived exosomes with decreased miR‐100‐5p levels exhibit pro‐lymphangiogenesis capacity, suggesting a possibility of targeting IGF1R/PI3K/AKT axis as a strategy to inhibit lymphatic metastasis in ESCC.

Tumor-associated macrophages (TAMs) and cancer-associated fibroblasts (CAFs) are known to play supportive roles in tumor development and progression, but their interactions in colorectal cancer (CRC) remain unclear. Here, we investigated the effects of colon-cancer-derived CAFs on TAM differentiation, migration, and tumor immunity, both in vitro and in vivo. When co-cultured with monocytes, CAFs attracted monocytes and induced their differentiation into M2 macrophages. Immunohistology of surgically resected human CRC specimens and orthotopically transplanted mouse tumors revealed a correlation between numbers of CAFs and numbers of M2 macrophages. In a mouse model of CRC orthotopic transplantation, treatment with an inhibitor of the colony-stimulating factor-1 receptor (PLX3397) depleted M2 macrophages and increased CD8-positive T cells infiltrating the tumor nest. While this treatment had a minor effect on tumor growth, combining PLX3397 with anti-PD-1 antibody significantly reduced tumor growth. RNA-seq following combination therapy showed activation of tumor immunity. In summary, CAFs are involved in the induction and mobilization of M2 macrophage differentiation in the CRC tumor immune microenvironment, and the combination of cancer immunotherapy and PLX3397 may represent a novel therapeutic option for CRC.

Ovarian cancer (OC) is one of the most lethal gynecologic cancers that is typically diagnosed at the very late stage of disease progression. Thus, there is an unmet need to develop diagnostic probes for early detection of OC. One approach may rely on RNA as a molecular biomarker. In this regard, FLJ22447 lncRNA is an RNA biomarker that is over-expressed in ovarian cancer (OC) and in cancer-associated fibroblasts (CAFs). CAFs appear early on in OC as they provide a metastatic niche for OC progression. FIT-PNAs (forced intercalation-peptide nucleic acids) are DNA analogs that are designed to fluoresce upon hybridization to their complementary RNA target sequence. In recent studies, we have shown that the introduction of cyclopentane PNAs into FIT-PNAs (cpFIT-PNA) results in superior RNA sensors. Herein, we report the design and synthesis of cpFIT-PNAs for the detection of this RNA biomarker in living OC cells (OVCAR8) and in CAFs. cpFIT-PNA was compared to FIT-PNA and the cell-penetrating peptide (CPP) of choice was either a simple one (four L-lysines) or a CPP with enhanced cellular uptake (CLIP6). The combination of CLIP6 with cpFIT-PNA resulted in a superior sensing of FLJ22447 lncRNA in OVCAR8 cells as well as in CAFs. Moreover, incubation of CLIP6-cpFIT-PNA in OVCAR8 cells leads to a significant decrease (ca. 60%) in FLJ22447 lncRNA levels and in cell viability, highlighting the potential theranostic use of such molecules.

A heterogenous population of inflammatory elements, other immune and nonimmune cells and cancer-associated fibroblasts (CAFs) are evident in solid malignancies where they coexist with the growing tumor mass. In highly desmoplastic malignancies, CAFs are the prominent mesenchymal cell type in the tumor microenvironment (TME), where their presence and abundance signal a poor prognosis. CAFs play a major role in the progression of various cancers by remodeling the supporting stroma into a dense, fibrotic matrix while secreting factors that promote the maintenance of cancer stem-like characteristics, tumor cell survival, aggressive growth and metastasis and reduced sensitivity to chemotherapeutics. Tumors with high stromal fibrotic signatures are more likely to be associated with drug resistance and eventual relapse. Identifying the molecular underpinnings for such multidirectional crosstalk among the various normal and neoplastic cell types in the TME may provide new targets and novel opportunities for therapeutic intervention. This review highlights recent concepts regarding the complexity of CAF biology in cholangiocarcinoma, a highly desmoplastic cancer. The discussion focuses on CAF heterogeneity, functionality in drug resistance, contributions to a progressively fibrotic tumor stroma, the involved signaling pathways and the participating genes.

The DSL-6A/C1 murine pancreatic ductal adenocarcinoma (PDAC) tumor model was established in Lewis rats and characterized through a comprehensive multiparametric analysis to compare it to other preclinical tumor models and explore potential diagnostic and therapeutical targets. DSL-6A/C1 tumors were histologically analyzed to elucidate PDAC features. The tumor microenvironment was studied for immune cell prevalence. Multiparametric MRI and PET imaging were utilized to characterize tumors, and 68Ga-FAPI-46-targeting cancer-associated fibroblasts (CAFs), were used to validate the histological findings. The histology confirmed typical PDAC characteristics, such as malformed pancreatic ductal malignant cells and CAFs. Distinct immune landscapes were identified, revealing an increased presence of CD8+ T cells and a decreased CD4+ T cell fraction within the tumor microenvironment. PET imaging with 68Ga-FAPI tracers exhibited strong tracer uptake in tumor tissues. The MRI parameters indicated increasing intralesional necrosis over time and elevated contrast media uptake in vital tumor areas. We have demonstrated that the DSL-6A/C1 tumor model, particularly due to its high tumorigenicity, tumor size, and 68Ga-FAPI-46 sensitivity, is a suitable alternative to established small animal models for many forms of preclinical analyses and therapeutic studies of PDAC.

Decorin (DCN), a member of the small leucine-rich proteoglycan gene family, is secreted from stromal fibroblasts with non-cell-autonomous anti-breast-cancer effects. Therefore, in the present study, we sought to elucidate the function of decorin in breast stromal fibroblasts (BSFs). We first showed DCN downregulation in active cancer-associated fibroblasts (CAFs) compared to their adjacent tumor counterpart fibroblasts at both the mRNA and protein levels. Interestingly, breast cancer cells and the recombinant IL-6 protein, both known to activate fibroblasts in vitro, downregulated DCN in BSFs. Moreover, specific DCN knockdown in breast fibroblasts modulated the expression/secretion of several CAF biomarkers and cancer-promoting proteins (α-SMA, FAP- α, SDF-1 and IL-6) and enhanced the invasion/proliferation abilities of these cells through activation of the STAT3/AUF1 signaling. Furthermore, DCN-deficient fibroblasts promoted the epithelial-to-mesenchymal transition and stemness processes in BC cells in a paracrine manner, which increased their resistance to cisplatin. These DCN-deficient fibroblasts also enhanced angiogenesis and orthotopic tumor growth in mice in a paracrine manner. On the other hand, ectopic expression of DCN in CAFs suppressed their active features and their paracrine pro-carcinogenic effects. Together, the present findings indicate that endogenous DCN suppresses the pro-carcinogenic and pro-metastatic effects of breast stromal fibroblasts.

Immune responses to cancer are highly variable, with mismatch repair-deficient (MMRd) tumors exhibiting more anti-tumor immunity than mismatch repair-proficient (MMRp) tumors. To understand the rules governing these varied responses, we transcriptionally profiled 371,223 cells from colorectal tumors and adjacent normal tissues of 28 MMRp and 34 MMRd individuals. Analysis of 88 cell subsets and their 204 associated gene expression programs revealed extensive transcriptional and spatial remodeling across tumors. To discover hubs of interacting malignant and immune cells, we identified expression programs in different cell types that co-varied across tumors from affected individuals and used spatial profiling to localize coordinated programs. We discovered a myeloid cell-attracting hub at the tumor-luminal interface associated with tissue damage and an MMRd-enriched immune hub within the tumor, with activated T cells together with malignant and myeloid cells expressing T cell-attracting chemokines. By identifying interacting cellular programs, we reveal the logic underlying spatially organized immune-malignant cell networks.

Lung adenocarcinoma, the most prevalent lung cancer subtype, is characterized by its high propensity to metastasize. Despite the importance of metastasis in lung cancer mortality, its underlying cellular and molecular mechanisms remain largely elusive. Here, we identified miR-200 miRNAs as potent suppressors for lung adenocarcinoma metastasis. miR-200 expression is specifically repressed in mouse metastatic lung adenocarcinomas, and miR-200 decrease strongly correlates with poor patient survival. Consistently, deletion of mir-200c/141 in the KrasLSL-G12D/+ ; Trp53flox/flox lung adenocarcinoma mouse model significantly promoted metastasis, generating a desmoplastic tumor stroma highly reminiscent of metastatic human lung cancer. miR-200 deficiency in lung cancer cells promotes the proliferation and activation of adjacent cancer-associated fibroblasts (CAFs), which in turn elevates the metastatic potential of cancer cells. miR-200 regulates the functional interaction between cancer cells and CAFs, at least in part, by targeting Notch ligand Jagged1 and Jagged2 in cancer cells and inducing Notch activation in adjacent CAFs. Hence, the interaction between cancer cells and CAFs constitutes an essential mechanism to promote metastatic potential.

Autophagy inhibitors are currently being evaluated in clinical trials for the treatment of diverse cancers, largely due to their ability to impede tumor cell survival and metabolic adaptation. More recently, there is growing interest in whether and how modulating autophagy in the host stroma influences tumorigenesis. Fibroblasts play prominent roles in cancer initiation and progression, including depositing type 1 collagen and other extracellular matrix (ECM) components, thereby stiffening the surrounding tissue to enhance tumor cell proliferation and survival, as well as secreting cytokines that modulate angiogenesis and the immune microenvironment. This constellation of phenotypes, pathologically termed desmoplasia, heralds poor prognosis and reduces patient survival. Using mouse mammary cancer models and syngeneic transplantation assays, we demonstrate that genetic ablation of stromal fibroblast autophagy significantly impedes fundamental elements of the stromal desmoplastic response, including collagen and proinflammatory cytokine secretion, extracellular matrix stiffening, and neoangiogenesis. As a result, autophagy in stromal fibroblasts is required for mammary tumor growth in vivo, even when the cancer cells themselves remain autophagy-competent . We propose the efficacy of autophagy inhibition is shaped by this ability of host stromal fibroblast autophagy to support tumor desmoplasia.

Objective To investigate the effect of lenvatinib on the autophagy and migration of cancer-associated fibroblasts (CAFs) in hepatocellular carcinoma (HCC) tissue. Methods Primary CAFs from HCC patients were isolated and cultured and were then treated with an equal volume of DMSO (DMSO group) or 46 nmol/L lenvatinib (lenvatinib group) for 72 h. Transcriptomic sequencing and the omics analysis of drug targets were performed for the two groups, and GO functional enrichment analysis and KEGG pathway enrichment analysis were performed for differentially expressed genes and peptides. Transmission electron microscopy was used to observe the effect of lenvatinib on autophagy of CAFs, and Transwell assay and wound hea-ling assay were used to observe the effect of lenvatinib on the migration ability of CAFs. Results The differentially expressed genes and peptides between the DMSO group and the lenvatinib group were mainly enriched in the functions and pathways such as cell migration and autophagy. Transmission electron microscopy showed that the lenvatinib group had a significantly higher number of autophagosomes than the DMSO group (t=5.376,P

Abstract Background Cancer-associated fibroblasts (CAFs) have significant tumor regulatory functions, and CAFs-derived exosomes (CAFs-Exo) released from CAFs play an important role in the progression of oral squamous cell carcinoma (OSCC). However, a lack of comprehensive molecular biological analysis leaves the regulatory mechanisms of CAFs-Exo in OSCC unclear. Methods We used platelet derived growth factor-BB (PDGF-BB) to induce the transformation of human oral mucosa fibroblast (hOMF) into CAFs, and extracted exosomes from the supernatant of CAFs and hOMF. We validated the effect of CAFs-Exo on tumor progression by exosomes co-culture with Cal-27 and tumor-forming in nude mice. The cellular and exosomal transcriptomes were sequenced, and immune regulatory genes were screened and validated using mRNA-miRNA interaction network analysis in combination with publicly available databases. Results The results showed that CAFs-Exo had a stronger ability to promote OSCC proliferation and was associated with immunosuppression. We discovered that the presence of immune-related genes in CAFs-Exo may regulate the expression of PIGR, CD81, UACA, and PTTG1IP in Cal-27 by analyzing CAFs-Exo sequencing data and publicly available TCGA data. This may account for the ability of CAFs-Exo to exert immunomodulation and promote OSCC proliferation. Conclusions CAFs-Exo was found to be involved in tumor immune regulation through hsa-miR-139-5p, ACTR2 and EIF6, while PIGR, CD81, UACA and PTTG1IP may be potentially effective targets for the treatment of OSCC in the future.

With the advancement of anticancer therapy, there is increasing interest in understanding the tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs) play a pivotal role in the TME and have been the focus of much research in recent years. CAFs play an active role in cancer progression through complex interactions with other cells in the TME, releasing regulatory factors, synthesizing and remodeling the extracellular matrix. However, research on the role of CAFs in renal cell carcinoma (RCC) is still in its nascent stages. Here, we describe the origins and subgroups of CAFs, the roles of CAFs in the development and progression of RCC, the impact of CAFs on RCC prognosis, and the potential of CAFs as treatment targets in RCC. By analyzing CAF subsets, biomarkers, and targeted therapies, we present the significance and contribution of CAFs in RCC research. Furthermore, we highlight the distinct contribution of CAFs in advanced RCC through horizontal comparison with other cancers. This paper provides a comprehensive perspective of recent and foundational studies on the role of CAFs in RCC and other types of cancers and new insights for further study of CAFs in RCC.

Abstract The identification of contributing factors leading to the development of Colorectal Cancer (CRC), as the third fatal malignancy, is crucial. Today, the tumor microenvironment has been shown to play a key role in CRC progression. Fibroblast-Activation Protein-α (FAP) is a type II transmembrane cell surface proteinase expressed on the surface of cancer-associated fibroblasts in tumor stroma. As an enzyme, FAP has di- and endoprolylpeptidase, endoprotease, and gelatinase/collagenase activities in the Tumor Microenvironment (TME). According to recent reports, FAP overexpression in CRC contributes to adverse clinical outcomes such as increased lymph node metastasis, tumor recurrence, and angiogenesis, as well as decreased overall survival. In this review, studies about the expression level of FAP and its associations with CRC patients' prognosis are reviewed. High expression levels of FAP and its association with clinicopathological factors have made as a potential target. In many studies, FAP has been evaluated as a therapeutic target and diagnostic factor into which the current review tries to provide a comprehensive insight. Video Abstract

Abstract Radiation therapy is recognized as an effective modality in the treatment of lung cancer, but radioresistance resulting from prolonged treatment reduces the chances of recovery. MicroRNAs (miRNAs) play a pivotal role in radiotherapy immunity. In this study, we aimed to investigate the mechanism by which miR‐196a‐5p affects radioresistance in lung cancer. The radioresistant lung cancer cell line A549R26–1 was established by radiation treatment. Cancer‐associated fibroblasts (CAFs) and normal fibroblasts (NFs) were observed by microscopy, and the expression levels of CAF‐specific marker proteins were detected by immunofluorescence. The shape of the exosomes was observed by electron microscopy. A CCK‐8 assay was used to detect cell viability, while clone formation assays were used to detect cell proliferative capacity. Flow cytometry was performed to investigate apoptosis. The binding of miR‐196a‐5p and NFKBIA was predicted and further verified by the dual luciferase reporter experiment. qRT–PCR and western blotting were used to detect gene mRNA and protein levels. We found that exosomes secreted by CAFs could enhance lung cancer cell radioresistance. Moreover, miR‐196a‐5p potentially bound to NFKBIA, promoting malignant phenotypes in radioresistant cells. Furthermore, exosomal miR‐196a‐5p derived from CAFs increased radiotherapy immunity in lung cancer. Exosomal miR‐196a‐5p derived from CAFs enhanced radioresistance in lung cancer cells by downregulating NFKBIA, providing a new potential target for the treatment of lung cancer.

Inflammatory response induces phenotypic modulation of fibroblasts into myofibroblasts. Although transforming growth factor-βs (TGF-βs) evoke such transition, the details of the mechanism are still unknown. Here, we report that a LIM domain protein, cysteine-and glycine-rich protein 2 (CSRP2 [CRP2]) plays a vital role in the functional expression profile in myofibroblasts and cancer-associated fibroblasts (CAFs). Knock-down of CRP2 severely inhibits the expression of smooth muscle cell (SMC) genes, cell motility, and CAF-mediated collective invasion of epidermoid carcinoma. We elucidate the following molecular bases: CRP2 directly binds to myocardin-related transcription factors (MRTF-A/B [MRTFs]) and serum response factor (SRF) and stabilizes the MRTF/SRF/CArG-box complex to activate SMC gene expression. Furthermore, a three-dimensional structural analysis of CRP2 identifies the amino acids required for the CRP2-MRTF-A interaction. Polar amino acids in the C-terminal half (serine-152, glutamate-154, serine-155, threonine-156, threonine-157, and threonine-159 in human CRP2) are responsible for direct binding to MRTF-A. On the other hand, hydrophobic amino acids outside the consensus sequence of the LIM domain (tryptophan-139, phenylalanine-144, leucine-153, and leucine-158 in human CRP2) play a role in stabilizing the unique structure of the LIM domain. Key words: CRP2, 3D structure, myocardin-related transcription factor, myofibroblast, cancer-associated fibroblasts

Abstract Background Breast cancer brain metastasis (BCBM) is a growing therapeutic challenge and clinical concern. Stromal cancer-associated fibroblasts (CAFs) are crucial factors in the modulation of tumorigeneses and metastases. Herein, we investigated the relationship between the expression of stromal CAF markers in metastatic sites, platelet-derived growth factor receptor-beta (PDGFR-β), and alpha-smooth muscle actin (α-SMA) and the clinical and prognostic variables in BCBM patients. Methods Immunohistochemistry (IHC) of the stromal expression of PDGFR-β and α-SMA was performed on 50 cases of surgically resected BCBM. The expression of the CAF markers was analyzed in the context of clinico-pathological characteristics. Results Expression of PDGFR-β and α-SMA was lower in the triple-negative (TN) subtype than in other molecular subtypes (p = 0.073 and p = 0.016, respectively). And their expressions were related to a specific pattern of CAF distribution (PDGFR-β, p = 0.009; α-SMA, p = 0.043) and BM solidity (p = 0.009 and p = 0.002, respectively). High PDGFR-β expression was significantly related to longer recurrence-free survival (RFS) (p = 0.011). TN molecular subtype and PDGFR-β expression were independent prognostic factors of recurrence-free survival (p = 0.029 and p = 0.030, respectively) and TN molecular subtype was an independent prognostic factor of overall survival (p

Abstract Cancer-associated fibroblasts (CAFs) are the most abundant stromal cells within the tumor microenvironment (TME). They extensively communicate with the other cells. Exosome-packed bioactive molecules derived from CAFs can reshape the TME by interacting with other cells and the extracellular matrix, which adds a new perspective for their clinical application in tumor targeted therapy. An in-depth understanding of the biological characteristics of CAF-derived exosomes (CDEs) is critical for depicting the detailed landscape of the TME and developing tailored therapeutic strategies for cancer treatment. In this review, we have summarized the functional roles of CAFs in the TME, particularly focusing on the extensive communication mediated by CDEs that contain biological molecules such as miRNAs, proteins, metabolites, and other components. In addition, we have also highlighted the prospects for diagnostic and therapeutic applications based on CDEs, which could guide the future development of exosome-targeted anti-tumor drugs.

Abstract Oral cancers are among the common head and neck malignancies. Different anticancer therapy modalities such as chemotherapy, immunotherapy, radiation therapy, and also targeted molecular therapy may be prescribed for targeting oral malignancies. Traditionally, it has been assumed that targeting malignant cells alone by anticancer modalities such as chemotherapy and radiotherapy suppresses tumor growth. In the last decade, a large number of experiments have confirmed the pivotal role of other cells and secreted molecules in the tumor microenvironment (TME) on tumor progression. Extracellular matrix and immunosuppressive cells such as tumor-associated macrophages, myeloid-derived suppressor cells (MDSCs), cancer-associated fibroblasts (CAFs), and regulatory T cells (Tregs) play key roles in the progression of tumors like oral cancers and resistance to therapy. On the other hand, infiltrated CD4 + and CD8 + T lymphocytes, and natural killer (NK) cells are key anti-tumor cells that suppress the proliferation of malignant cells. Modulation of extracellular matrix and immunosuppressive cells, and also stimulation of anticancer immunity have been suggested to treat oral malignancies more effectively. Furthermore, the administration of some adjuvants or combination therapy modalities may suppress oral malignancies more effectively. In this review, we discuss various interactions between oral cancer cells and TME. Furthermore, we also review the basic mechanisms within oral TME that may cause resistance to therapy. Potential targets and approaches for overcoming the resistance of oral cancers to various anticancer modalities will also be reviewed. The findings for targeting cells and potential therapeutic targets in clinical studies will also be reviewed.

Abstract The tumor microenvironment is one of the important drivers of tumor development. Cancer-associated fibroblasts (CAFs) are a major component of the tumor stroma and actively participate in tumor development, invasion, metastasis, drug resistance, and other biological behaviors. CAFs are a highly heterogeneous group of cells, a reflection of the diversity of their origin, biomarkers, and functions. The diversity of CAF origin determines the complexity of CAF biomarkers, and CAF subpopulations expressing different biomarkers may play contrasting roles in tumor progression. In this review, we provide an overview of these emerging CAF biomarkers and the biological functions that they suggest, which may give a better understanding of the relationship between CAFs and tumor cells and be of great significance for breakthroughs in precision targeted therapy for tumors. Video Abstract

During the last decade, immunotherapy has radically changed perspectives on anti-tumor treatments. However, solid tumor treatment by immunotherapy has not met expectations. Indeed, poor clinical response to treatment has highlighted the need to understand and avoid immunotherapy resistance. Cholangiocarcinoma (CCA) is the second cause of hepatic cancer-related deaths because of drug inefficacy and chemo-resistance in a majority of patients. Thus, intense research is ongoing to better understand the mechanisms involved in the chemo-resistance processes. The tumor microenvironment (TME) may be involved in tumor therapy resistance by limiting drug access. Indeed, cells such as cancer-associated fibroblasts (CAFs) alter TME by producing in excess an aberrant extracellular matrix (ECM). Interestingly, CAFs are the dominant stromal component in CCA that secrete large amounts of stiff ECM. Stiff ECM could contribute to immune exclusion by limiting anti-tumor T-cells drop-in. Herein, we summarize features, functions, and interactions among CAFs, tumor-associated ECM, and immune cells in TME. Moreover, we discuss the strategies targeting CAFs and the remodeling of the ECM to improve immunotherapy and drug therapies.

In clinical practice, we noticed that triple negative breast cancer (TNBC) patients had higher shear-wave elasticity (SWE) stiffness than non-TNBC patients and a higher α-SMA expression was found in TNBC tissues than the non-TNBC tissues. Moreover, SWE stiffness also shows a clear correlation to neoadjuvant response efficiency. To elaborate this phenomenon, TNBC cell membrane-modified polylactide acid-glycolic acid (PLGA) nanoparticle was fabricated to specifically deliver artesunate to regulate SWE stiffness through inhibiting CAFs functional status. As tested in MDA-MB-231 and E0771 orthotopic tumor models, CAFs functional status inhibited by 231M-ARS@PLGA nanoparticles (231M-AP NPs) had reduced the SWE stiffness as well as attenuated hypoxia of tumor as tumor soil loosening agent which amplified the antitumor effects of paclitaxel and PD1 inhibitor. Single-cell sequencing indicated that the two main CAFs (extracellular matrix and wound healing CAFs) that produces extracellular matrix could influence the tumor SWE stiffness as well as the antitumor effect of drugs. Further, biomimetic nanoparticles inhibited CAFs function could attenuate tumor hypoxia by increasing proportion of inflammatory blood vessels and oxygen transport capacity. Therefore, our finding is fundamental for understanding the role of CAFs on affecting SWE stiffness and drugs antitumor effects, which can be further implied in the potential clinical theranostic predicting in neoadjuvant therapy efficacy through non-invasive analyzing of SWE imaging.

Fibrotic tumors, such as pancreatic ductal adenocarcinoma (PDAC), are characterized for high desmoplastic reaction, which results in high intra-tumoral solid stress leading to the compression of blood vessels. These microarchitectural alterations cause loss of blood flow and poor intra-tumoral delivery of therapeutics. Currently, there is a lack of relevant in vitro models capable of replicating these mechanical characteristics and to test anti-desmoplastic compounds. Here, a multi-layered vascularized 3D PDAC model consisting of primary human pancreatic stellate cells (PSCs) embedded in collagen/fibrinogen (Col/Fib), mimicking tumor tissue within adjunct healthy tissue, is presented to study the fibrosis-induced compression of vasculature in PDAC. It is demonstrated how the mechanical and biological stimulation induce PSC activation, extracellular matrix production and eventually vessel compression. The clinical relevance is confirmed by correlating with patient transcriptomic data. Furthermore, the effects of gradual vessel compression on the fluid dynamics occurring within the channel is evaluated in silico. Finally, it is demonstrated how cancer-associated fibroblast (CAF)-modulatory therapeutics can inhibit the cell-mediated compression of blood vessels in PDAC in vitro, in silico and in vivo. It is envisioned that this 3D model is used to improve the understanding of mechanical characteristics in tumors and for evaluating novel anti-desmoplastic therapeutics.