Cancer-associated fibroblasts in gastrointestinal cancer

Cancer-associated fibroblasts-derived HAPLN1 promotes tumour invasion through extracellular matrix remodeling in gastric cancer

BACKGROUND

Cancer-associated fibroblasts (CAFs) are the most principal cells of depositing and remodeling extracellular matrix (ECM) within solid tumours. Both CAFs and ECM have been demonstrated to play critical roles in tumour development. However, the functional roles of CAFs-associated ECM or ECM remodeling in the pathogenesis of gastric cancer remain unclear.

METHODS

Bioinformatics analysis of the differentially expressed genes between CAFs and corresponding normal fibroblasts (NFs) in gastric cancer was performed. The clinical relevance of hyaluronan and proteoglycan link protein 1 (HAPLN1) was investigated using TCGA data and human gastric cancer specimens. Spheroid cell invasion assay and nude mouse xenograft model were introduced to assay cell invasion. Second harmonic generation (SHG) was used to image and analyze the changes of collagen fibers in ECM.

RESULTS

HAPLN1 was identified as the most significantly up-regulated gene in CAFs of gastric cancer, and higher HAPLN1 levels were associated with shorter overall survival. HAPLN1 was prominently produced by CAFs, and its levels were correlated positively with tumor T staging (P < 0.0001), lymph node metastasis (P = 0.0006) and TNM stage (P = 0.0063). Mechanically, gastric cancer cells activate fibroblasts to up-regulate HAPLN1 expression via activation of TGF-β1/Smad2/3 signaling, which in turn promotes tumour migration and invasion. Importantly, SHG assays with mouse xenograft models and human samples further demonstrated CAFs-derived HAPLN1 increased tumour invasiveness through ECM remodeling.

CONCLUSIONS

This study sheds light on the role of CAFs-derived HAPLN1 in the pathogenesis of gastric cancer, and provides insights for the development of novel strategies for prevention and treatment of gastric carcinoma.

Circulating Clusterin Levels and Cancer Risk: A Systematic Review and Meta-Analysis

Introduction

The previous reports on clusterin (CLU) levels in various types of cancer have been controversial and heterogeneous. The present meta-analysis has aimed to evaluate the association between soluble CLU levels and the risk of different human cancers based on observational studies.

Methods

A systematic literature review was conducted to determine the relevant eligible studies in English language from health-related electronic databases up to January 2021. Random effects models were used to calculate the summary standard mean difference (SMD) with 95% confidence intervals (CIs) to identify the correlation between CLU levels and cancer risk. The meta-regression, sensitivity, Galbraith, and subgroup analyses were performed to explore the source of between-study heterogeneity. Furthermore, the funnel plot and Egger’s linear regression tests were carried out to evaluate the risk of publication bias.

Results

According to 16 eligible articles, 3331 patients and 839 healthy controls were included in our meta-analysis. Overall, the CLU levels were significantly higher in various cancer cases compared to the healthy groups (SMD = 1.50, 95% CI = 0.47–2.53). Moreover, subgroup analysis based on types of cancer showed a significant correlation between CLU levels and the risk of digestive system cancers (SMD = 1.54, 95% CI = 0.91–2.18, P <0.001), especially in HCC (SMD = 1.89, 95% CI = 0.76–3.03, P = 0.001), and CRC (SMD = 1.63, 95% CI = 0.0–3.23, P = 0.048).

Conclusion

The present meta-analysis indicates a significant association of CLU levels with the risk of digestive system cancers such as hepatocellular carcinoma and colorectal cancer. Therefore, CLU can be monitored as a novel molecular biomarker for the prognosis and diagnosis of various types of cancers particularly in the digestive system.

The cancer-inhibitory effects of proliferating tumor-residing fibroblasts

Initiation, local progression, and metastasis of cancer are associated with specific morphological, molecular, and functional changes in the extracellular matrix and the fibroblasts within the tumor microenvironment (TME). In the early stages of tumor development, fibroblasts are an obstacle that cancer cells must surpass or nullify to progress. Thus, in early tumor progression, specific signaling from cancer cells activates bio-pathways, which abolish the innate anticancer properties of fibroblasts and convert a high proportion of them to tumor-promoting cancer-associated fibroblasts (CAFs). Following this initial event, a wide spectrum of gene expression changes gradually leads to the development of a stromal fibroblast population with complex heterogeneity, creating fibroblast subtypes with characteristic profiles, which may alternate between being tumor-promotive and tumor-suppressive, topologically and chronologically in the TME. These fibroblast subtypes form the tumor's histological landscape including areas of cancer growth, inflammation, angiogenesis, invasion fronts, proliferating and non-proliferating fibroblasts, cancer-cell apoptosis, fibroblast apoptosis, and necrosis. These features reflect general deregulation of tissue homeostasis within the TME. This review discusses fundamental and current knowledge that has established the existence of anticancer fibroblasts within the various interacting elements of the TME. It is proposed that the maintenance of fibroblast proliferation is an essential parameter for the activation of their anticancer capacity, similar to that by which normal fibroblasts would be activated in wound repair, thus maintaining tissue homeostasis. Encouragement of research in this direction may render new means of cancer therapy and a greater understanding of tumor progression.

Diabetes mellitus contribution to the remodeling of the tumor microenvironment in gastric cancer

Compelling pieces of evidence derived from both clinical and experimental research has demonstrated the crucial contribution of diabetes mellitus (DM) as a risk factor associated with increased cancer incidence and mortality in many human neoplasms, including gastric cancer (GC). DM is considered a systemic inflammatory disease and therefore, this inflammatory status may have profound effects on the tumor microenvironment (TME), particularly by driving many molecular mechanisms to generate a more aggressive TME. DM is an active driver in the modification of the behavior of many cell components of the TME as well as altering the mechanical properties of the extracellular matrix (ECM), leading to an increased ECM stiffening. Additionally, DM can alter many cellular signaling mechanisms and thus favoring tumor growth, invasion, and metastatic potential, as well as key elements in regulating cellular functions and cross-talks, such as the microRNAs network, the production, and cargo of exosomes, the metabolism of cell stroma and resistance to hypoxia. In the present review, we intend to highlight the mechanistic contributions of DM to the remodeling of TME in GC.

CD248+ Cancer-Associated Fibroblasts: A Novel Prognostic and Therapeutic Target for Renal Cell Carcinoma

BACKGROUND

The tumor microenvironment (TME) plays an important role in the progression of renal cell carcinoma (RCC). Cancer-associated fibroblasts (CAFs) are considered to constitute a major component of the TME and participate in various tumor-promoting molecular events. We have previously confirmed that CD248 represents a promising biomarker of CAFs, which may provide insight into CAF-based tumor-promoting effects. However, CAF-mediated tumor progression and the potential mechanism of CD248 remain largely unknown in RCC patients.

METHODS

Expression profiling and clinical data of RCC patients were obtained from The Cancer Genome Atlas (TCGA) database. An MCP-counter algorithm and Kaplan-Meier survival analysis were performed to explore the prognostic value of CAFs and CD248, respectively. A Pearson correlation coefficient test and Student's t-test were employed to evaluate the relationship between immunosuppressive TME and CD248 or CAFs. Immunohistochemistry and immunofluorescence staining were performed to confirm CD248 expression within CAFs. CD248-specific siRNA was used to investigate the potential function of CD248 in CAF tumor promotion. Differentially expressed genes (DEGs), weighted gene co-expression network analysis (WGCNA), and enrichment analysis were conducted to clarify the function of CD248+ CAFs in RCC progression and the associated regulatory mechanism.

RESULTS

CD248 overexpression and CAF infiltration could predict poor RCC prognosis, which may involve the immunosuppressive TME. CD248 may serve as a promising CAFs biomarker and be involved with the tumor-promoting effect of CAFs. Moreover, CD248+ CAF infiltration may contribute to RCC progression and an immunosuppressive TME through cell-extracellular matrix (ECM) interactions and metabolism regulation.

CONCLUSION

CD248+ CAFs participate in the regulation of RCC progression and immunosuppressive TME, which may represent a novel prognostic and therapeutic target for RCC.

Cancer associated-fibroblast-derived exosomes in cancer progression

To identify novel cancer therapies, the tumor microenvironment (TME) has received a lot of attention in recent years in particular with the advent of clinical successes achieved by targeting immune checkpoint inhibitors (ICIs). The TME consists of multiple cell types that are embedded in the extracellular matrix (ECM), including immune cells, endothelial cells and cancer associated fibroblasts (CAFs), which communicate with cancer cells and each other during tumor progression. CAFs are a dominant and heterogeneous cell type within the TME with a pivotal role in controlling cancer cell invasion and metastasis, immune evasion, angiogenesis and chemotherapy resistance. CAFs mediate their effects in part by remodeling the ECM and by secreting soluble factors and extracellular vesicles. Exosomes are a subtype of extracellular vesicles (EVs), which contain various biomolecules such as nucleic acids, lipids, and proteins. The biomolecules in exosomes can be transmitted from one to another cell, and thereby affect the behavior of the receiving cell. As exosomes are also present in circulation, their contents can also be explored as biomarkers for the diagnosis and prognosis of cancer patients. In this review, we concentrate on the role of CAFs-derived exosomes in the communication between CAFs and cancer cells and other cells of the TME. First, we introduce the multiple roles of CAFs in tumorigenesis. Thereafter, we discuss the ways CAFs communicate with cancer cells and interplay with other cells of the TME, and focus in particular on the role of exosomes. Then, we elaborate on the mechanisms by which CAFs-derived exosomes contribute to cancer progression, as well as and the clinical impact of exosomes. We conclude by discussing aspects of exosomes that deserve further investigation, including emerging insights into making treatment with immune checkpoint inhibitor blockade more efficient.

Cancer-Associated Fibroblasts Promote the Upregulation of PD-L1 Expression Through Akt Phosphorylation in Colorectal Cancer

Upregulation of immune checkpoint proteins is one of the main mechanisms for tumor immune escape. The expression of programmed death ligand-1 (PD-L1) in colorectal cancer (CRC) is higher than in normal colorectal epithelial tissue, and patients with higher PD-L1 expression have a poorer prognosis. Additionally, PD-L1 expression in CRC is affected by the tumor microenvironment (TME). As a major component of the TME, cancer-associated fibroblasts (CAFs) can act as immune regulators and generate an immunosuppressive tumor microenvironment. Therefore, we speculated that CAFs may be related to the upregulation of PD-L1 in CRC, which leads to tumor immune escape. We found that CAFs upregulate PD-L1 expression in CRC cells through AKT phosphorylation, thereby reducing the killing of CRC cells by peripheral blood mononuclear cells. The ratio of CAFs to CRC cells was positively correlated with AKT phosphorylation and the expression of PD-L1 in CRC in vitro. Consistent with the in vitro results, high CAF content and high expression of PD-L1 were negatively correlated with disease-free survival (DFS) of CRC patients. These results indicate that the upregulation of PD-L1 expression in CRC by CAFs through the activation of Akt is one of the molecular mechanisms of tumor immune escape. Thus, targeted anti-CAF therapy may help improve the efficacy of immunotherapy.

Chimeric Antigen Receptor T-Cell Therapy in Lung Cancer: Potential and Challenges

Chimeric antigen receptor T (CAR-T) cell therapy has exhibited a substantial clinical response in hematological malignancies, including B-cell leukemia, lymphoma, and multiple myeloma. Therefore, the feasibility of using CAR-T cells to treat solid tumors is actively evaluated. Currently, multiple basic research projects and clinical trials are being conducted to treat lung cancer with CAR-T cell therapy. Although numerous advances in CAR-T cell therapy have been made in hematological tumors, the technology still entails considerable challenges in treating lung cancer, such as on−target, of−tumor toxicity, paucity of tumor-specific antigen targets, T cell exhaustion in the tumor microenvironment, and low infiltration level of immune cells into solid tumor niches, which are even more complicated than their application in hematological tumors. Thus, progress in the scientific understanding of tumor immunology and improvements in the manufacture of cell products are advancing the clinical translation of these important cellular immunotherapies. This review focused on the latest research progress of CAR-T cell therapy in lung cancer treatment and for the first time, demonstrated the underlying challenges and future engineering strategies for the clinical application of CAR-T cell therapy against lung cancer.

Regulatory role of the transforming growth factor-β signaling pathway in the drug resistance of gastrointestinal cancers

Gastrointestinal (GI) cancer, including esophageal, gastric, and colorectal cancer, is one of the most prevalent types of malignant carcinoma and the leading cause of cancer-related deaths. Despite significant advances in therapeutic strategies for GI cancers in recent decades, drug resistance with various mechanisms remains the prevailing cause of therapy failure in GI cancers. Accumulating evidence has demonstrated that the transforming growth factor (TGF)-β signaling pathway has crucial, complex roles in many cellular functions related to drug resistance. This review summarizes current knowledge regarding the role of the TGF-β signaling pathway in the resistance of GI cancers to conventional chemotherapy, targeted therapy, immunotherapy, and traditional medicine. Various processes, including epithelial-mesenchymal transition, cancer stem cell development, tumor microenvironment alteration, and microRNA biogenesis, are proposed as the main mechanisms of TGF-β-mediated drug resistance in GI cancers. Several studies have already indicated the benefit of combining antitumor drugs with agents that suppress the TGF-β signaling pathway, but this approach needs to be verified in additional clinical studies. Moreover, the identification of potential biological markers that can be used to predict the response to TGF-β signaling pathway inhibitors during anticancer treatments will have important clinical implications in the future.

FSTL1 Secreted by Activated Fibroblasts Promotes Hepatocellular Carcinoma Metastasis and Stemness

The tumor microenvironment plays a critical role in maintaining the immature phenotype of tumor-initiating cells (TIC) to promote cancer. Hepatocellular carcinoma (HCC) is a unique disease in that it develops in the setting of fibrosis and cirrhosis. This pathologic state commonly shows an enrichment of stromal myofibroblasts, which constitute the bulk of the tumor microenvironment and contribute to disease progression. Follistatin-like 1 (FSTL1) has been widely reported as a proinflammatory mediator in different fibrosis-related and inflammatory diseases. Here we show FSTL1 expression to be closely correlated with activated fibroblasts and to be elevated in regenerative, fibrotic, and disease liver states in various mouse models. Consistently, FSTL1 lineage cells gave rise to myofibroblasts in a CCL₄-induced hepatic fibrosis mouse model. Clinically, high FSTL1 in fibroblast activation protein-positive (FAP⁺) fibroblasts were significantly correlated with more advanced tumors in patients with HCC. Although FSTL1 was expressed in primary fibroblasts derived from patients with HCC, it was barely detectable in HCC cell lines. Functional investigations revealed that treatment of HCC cells and patient-derived 3D organoids with recombinant FSTL1 or with conditioned medium collected from hepatic stellate cells or from cells overexpressing FSTL1 could promote HCC growth and metastasis. FSTL1 bound to TLR4 receptor, resulting in activation of AKT/mTOR/4EBP1 signaling. In a preclinical mouse model, blockade of FSTL1 mitigated HCC malignancy and metastasis, sensitized HCC tumors to sorafenib, prolonged survival, and eradicated the TIC subset. Collectively, these data suggest that FSTL1 may serve as an important novel diagnostic/prognostic biomarker and therapeutic target in HCC. SIGNIFICANCE: This study shows that FSTL1 secreted by activated fibroblasts in the liver microenvironment augments hepatocellular carcinoma malignancy, providing a potential new strategy to improve treatment of this aggressive disease.

Key promoters of tumor hallmarks

Evolution of tumor hallmarks is a result of accommodation of tumor cells with their nearby milieu called tumor microenvironment (TME). Accommodation or adaptive responses is highly important for a cell to survive, without which no cell is allowed to take any further steps in tumorigenesis. Metabolism of cancer cells is largely depended on stroma. Composition and plasticity of cells within the stroma is highly affected from inflammatory setting of TME. Hypoxia which is a common event in many solid cancers, is known as one of the key hallmarks of chronic inflammation and the master regulator of metastasis. Transforming growth factor (TGF)-β is produced in the chronic inflammatory and chronic hypoxic settings, and it is considered as a cardinal factor for induction of all tumor hallmarks. Aging, obesity and smoking are the main predisposing factors of cancer, acting mainly through modulation of TME.

The Novel Tumor Microenvironment-Related Prognostic Gene AIF1 May Influence Immune Infiltrates and is Correlated with TIGIT in Esophageal Cancer

BACKGROUND

Esophageal carcinoma (EC) is the sixth most common cause of cancer-related mortality worldwide. Studying the associations of the tumor microenvironment (TME) with pathology and prognosis would illustrate the underlying mechanism of prognostic prediction and provide novel targets for immunotherapy in the treatment of EC.

METHODS

Transcriptomic profiles of 159 EC patients were obtained from The Cancer Genome Atlas (TCGA) database. Stromal and immune scores were calculated using the ESTIMATE algorithm. Differentially expressed genes (DEGs) were identified by the optimal score cutoff. Functional enrichments were analyzed by DAVID, while prognostic genes were explored using the Kaplan-Meier method. Validation analysis was performed using immunohistochemistry in tissue microarrays containing samples from 145 EC patients. Multiplex immunofluorescence staining was performed to detect a panel of 6 immune markers, including T-cell immunoreceptor with Ig and ITIM domains (TIGIT), in 90 EC patients.

RESULTS

Immune scores significantly increased with increasing age, while stromal scores were dramatically elevated with increasing tumor stage. Fifteen TME-related DEGs including allograft inflammatory factor 1 (AIF1) were identified as prognostic factors of EC. Furthermore, the validation cohort indicated that AIF1 was negatively associated with the prognosis of esophageal squamous cell carcinoma patients. Subsequent analyses suggested that AIF1 may affect immune infiltrates, including T cells and natural-killer cells. Moreover, a correlation between AIF1 and TIGIT was identified.

CONCLUSIONS

These results indicate that the TME-related gene AIF1 is a promising predictor of prognosis and is related to immune infiltrates and TIGIT expression in EC. However, further mechanistic studies are needed.

The Oncogenic Role and Immune Infiltration for CARM1 Identified by Pancancer Analysis

Chromatin-modifying enzymes, especially protein arginine methyltransferases (PRMTs), have been identified as candidate targets for cancer. Cellular or animal-based evidence has suggested an association between coactivator-linked arginine methyltransferase 1 (CARM1) and cancer progression. However, the relationship between CARM1 and patient prognosis and immune infiltration in pancancer patients is unknown. On the basis of the GEO and TCGA databases, we first investigated the possible oncogenic functions of CARM1 in thirty-three tumor types. CARM1 expression was elevated in many types of tumors. In addition, there was a significant association between CARM1 expression and the survival rate of tumor patients. Uterine corpus endometrial carcinoma (UCES) samples had the highest CARM1 mutation frequency of all cancer types. In head and neck squamous cell carcinoma (HNSC) and lung squamous cell carcinoma (LUSC), CARM1 expression was associated with the level of CD8+ T cell infiltration, and cancer-associated fibroblast infiltration was also observed in other tumors including kidney renal papillary cell carcinoma (KIRC) and prostate adenocarcinoma (PRAD). CARM1 was involved in immune modulation and played an important role in the tumor microenvironment (TME). Furthermore, activities associated with RNA transport and its metabolism were included in the possible mechanisms of CARM1. Herein, our first pancancer research explores the oncogenic role of CARM1 in various tumors. CARM1 is associated with immune infiltrates and can be employed as a predictive biomarker in pancancer.

Non-immune Cell Components in the Gastrointestinal Tumor Microenvironment Influencing Tumor Immunotherapy

Interactions of genetic susceptibility factors, immune microenvironment, and microbial factors contribute to gastrointestinal tumorigenesis. The suppressive immune microenvironment reshaped by the tumors during gastrointestinal tumorigenesis directly contributes to T-cell depletion in tumor immunotherapy. Soluble factors secreted by tumor cells or stromal cells collectively shape the suppressive immune environment. Here, we reviewed the key factors in the gastrointestinal tumor microenvironment that influence tumor immunotherapy, focusing on the effects of fibroblasts, neuronal cells, soluble cytokines, exosomes, and the microbiome in tumor microenvironment. Research in this field has helped to identify more precise and effective biomarkers and therapeutic targets in the era of tumor immunotherapy.

Microcyst fluid promotes the migration and invasion of fibroblasts in the adventitial layer of alveolar echinococcosis

Alveolar echinococcosis (AE) caused by Echinococcus multilocularis (E. multilocularis), characterized by lesions composed of an aggregate of microcysts embedded in a granulomatous host's reaction. The periphery of parasite granulomas often additionally displays fibrotic reactions of varying intensity, in which E. multilocularis microenvironment fibroblasts (EMFs) laid down collagen. However, the regulation of EMFs by the infiltration of E. multilocularis microcyst fluid (MF) into granulomas remains poorly defined. This study aimed to investigate the effect of MF on migration and invasion of primary isolated EMFs cells. A mouse model of secondary infection with AE was established, and the model construction was evaluated by HE staining. EMFs were cultured in primary by tissue block adherency method. The isolated cells were identified by qPCR, immunofluorescence and Western blot. Then CCK-8 assay, cell migration/invasion assay and flow cytometry were performed to detect the effects of MF on the proliferation, migration, invasion and cell cycle of EMFs, respectively. The expressions of MMP2 and MMP9 at mRNA and protein levels in EMFs were detected by RT-qPCR and Western blot. The effect of PI3K-Akt signal transduction pathway on regulating the expression of MMPs expression was assessed by Western blot. As indicated from the results, EMFs were successfully isolated from the E. multilocularis microenvironment and identified as myofibroblasts. MF significantly facilitated the proliferation and cell cycle progression of EMFs. In addition, MF significantly improved the migration and invasion of EMFs. MF was further confirmed to up-regulate mRNA and protein expressions of MMP2 and MMP9 in EMFs, which was related to the activation of the PI3K-Akt signaling pathway. The present study demonstrates that MF can promote the migration and invasion of EMFs cells significantly, which might be via activating PI3K-Akt signaling pathway.

Engineered exosome-like nanovesicles suppress tumor growth by reprogramming tumor microenvironment and promoting tumor ferroptosis

Tumor vaccines that induce effective and sustained antitumor immunity are highly promising for cancer therapy. However, the antitumor potential of these vaccines is weakened due to the immunosuppressive characteristics of the tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs) are the most abundant stromal cells within the TME; they play an important role in tumor growth, metastasis, immunosuppression, and drug resistance. Fibroblast activation protein-α (FAP) is overexpressed in CAFs in more than 90% of human tumor tissues. Further, FAP⁺CAFs are an ideal interstitial target for the immunotherapy of solid tumors. Exosomes derived from tumor cells contain many tumor antigens, which can be used as the basis of tumor vaccines that elicit strong antitumor immunity. Almost all exosome-based cancer vaccines have been designed and developed for tumor parenchymal cells. Moreover, the exosome production is very low and the purification is very difficult, limiting their clinical application as tumor vaccines. In this study, we developed FAP gene-engineered tumor cell-derived exosome-like nanovesicles (eNVs-FAP) as a tumor vaccine that can be prepared easily and in large quantities. The eNVs-FAP vaccine inhibited tumor growth by inducing strong and specific cytotoxic T lymphocyte (CTL) immune responses against tumor cells and FAP⁺CAFs and reprogramming the immunosuppressive TME in the colon, melanoma, lung, and breast cancer models. Moreover, eNVs-FAP vaccine-activated cellular immune responses could promote tumor ferroptosis by releasing interferon-gamma (IFN-γ) from CTLs and depleting FAP⁺CAFs. Thus, eNVs-FAP is a candidate tumor vaccine targeting both the tumor parenchyma and the stroma. STATEMENT OF SIGNIFICANCE: Nanovaccines can activate immune cells and promote an antitumor immune response. In this study, we developed the fibroblast activation protein-α (FAP) gene-engineered tumor cell-derived exosome-like vesicle vaccines (eNVs-FAP). A large number of eNVs-FAP were obtained by continuously squeezing FAP gene-engineered tumor cells. eNVs-FAP showed excellent antitumor effects in a variety of tumor-bearing mouse models. The mechanistic analysis showed that eNVs-FAP promoted the maturation of dendritic cells (DCs), increased the infiltration of effector T cells into target tumor cells and FAP-positive cancer-associated fibroblasts (FAP⁺CAFs), and reduced the proportion of immunosuppressive cells, including M2-like tumor-associated macrophages (M2-TAMs), myeloid-derived suppressor cells (MDSCs), and regulatory T cells (Tregs), in the tumor microenvironment (TME). Moreover, the clearance of FAP⁺CAFs helped enhance interferon-gamma-induced tumor cell ferroptosis.

Cancer-associated fibroblasts impact the clinical outcome and treatment response in colorectal cancer via immune system modulation: a comprehensive genome-wide analysis

Background

Cancer-associated fibroblasts (CAFs) in the tumour microenvironment are associated with poor prognosis and chemoresistance in multiple solid tumours. However, there is a lack of universal measures of CAFs in colorectal cancer (CRC). The aim of this study was to assess the utility of a fibroblast-related gene signature (FRGS) for predicting patient outcomes and reveal its relevant mechanism.

Methods

The GSE39582 dataset, which includes 316 CRC patients who did not receive adjuvant chemotherapy was used as a discovery cohort to identify the prognostic fibroblast-related genes (FRGs). A total of 1352 CRC patients were divided into one training cohort (GSE39582, n = 461) and two validation cohorts (TCGA, n = 338; meta-validation, n = 553) for the construction of the FRGS and the verification of its prognostic value in stage II/III CRC patients. Functional annotation and analysis were performed to explore the underlying mechanism. The ability of the FRGS to predict immunotherapy response was further tested in a clear cell renal cell carcinoma (ccRCC) cohort.

Results

An 11-gene signature that had prognostic value for stage II/III CRC patients in both validation cohorts was developed (TCGA cohort: HR = 1.90, 95% CI 1.16–3.12, P < 0.01; meta-validation cohort: HR = 1.95, 95% CI 1.39–2.73, P < 0.001). A high level of CAFs was correlated with worse prognosis in CRC patients who did not receive adjuvant chemotherapy (HR = 3.63, 95% CI 2.24–5.88, P < 0.001). Importantly, patients in the low-risk group were found to be benefit from chemotherapy (P < 0.01), but not in the high CAF group (P > 0.05). Similar results were found in the TCGA cohort. Integrated with clinical characteristics, the FRGS was confirmed to be an independent prognostic factor in the multivariate analysis after adjustment for tumour TNM stage (GSE39582 cohort: HR = 3.19, 95% CI 1.88–5.41, P < 0.001; TCGA cohort: HR = 5.00, 95% CI 1.58–15.85, P = 0.007; meta-validation cohort: HR = 2.99, 95% CI 1.44–6.21, P = 0.003). Furthermore, the enrichment analysis found that the antitumour immune response was suppressed and the infiltration of CD4 T cells and M1 macrophages was depressed in the high CAF group. The FRGS was also found to have value in predicting for immunotherapy response in the ccRCC cohort.

Conclusions

The 11-gene FRGS had independent prognostic value for CRC patients, as well as utility in the prediction of benefit from chemotherapy. CAFs in the tumour microenvironment might have an impact on the prognosis of CRC patients via inhibiting immune response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-021-00402-3.

Metronomic Anti-Cancer Therapy: A Multimodal Therapy Governed by the Tumor Microenvironment

Simple Summary

Metronomic chemotherapy with different mechanisms of action against cancer cells and their microenvironment represents an exceptional holistic cancer treatment. Each type of tumor has its own characteristics, including each individual tumor in each patient. Understanding the complexity of the dynamic interactions that take place between tumor and stromal cells and the microenvironment in tumor progression and metastases, as well as the response of the host and the tumor itself to anticancer therapy, will allow therapeutic actions with long-lasting effects to be implemented using metronomic regimens. This study aims to highlight the complexity of cellular interactions in the tumor microenvironment and summarize some of the preclinical and clinical results that explain the multimodality of metronomic therapy, which, together with its low toxicity, supports an inhibitory effect on the primary tumor and metastases. We also highlight the possible use of nano-therapeutic agents as good partners for metronomic chemotherapy.

Abstract

The concept of cancer as a systemic disease, and the therapeutic implications of this, has gained special relevance. This concept encompasses the interactions between tumor and stromal cells and their microenvironment in the complex setting of primary tumors and metastases. These factors determine cellular co-evolution in time and space, contribute to tumor progression, and could counteract therapeutic effects. Additionally, cancer therapies can induce cellular and molecular responses in the tumor and host that allow them to escape therapy and promote tumor progression. In this study, we describe the vascular network, tumor-infiltrated immune cells, and cancer-associated fibroblasts as sources of heterogeneity and plasticity in the tumor microenvironment, and their influence on cancer progression. We also discuss tumor and host responses to the chemotherapy regimen, at the maximum tolerated dose, mainly targeting cancer cells, and a multimodal metronomic chemotherapy approach targeting both cancer cells and their microenvironment. In a combination therapy context, metronomic chemotherapy exhibits antimetastatic efficacy with low toxicity but is not exempt from resistance mechanisms. As such, a better understanding of the interactions between the components of the tumor microenvironment could improve the selection of drug combinations and schedules, as well as the use of nano-therapeutic agents against certain malignancies.

Roles of the Mesenchymal Stromal/Stem Cell Marker Meflin/Islr in Cancer Fibrosis

Fibroblasts synthesise the extracellular matrix (ECM) such as collagen and elastin, the excessive accumulation of which can lead to fibrosis and organ dysfunction under pathological conditions. Cancer-associated fibroblasts (CAFs) are major constituents of the tumour microenvironment (TME) that accompany the desmoplastic reaction responsible for anti-cancer treatment resistance. Thus, it is important to dissect the roles of CAFs in the TME to develop new therapeutic strategies for refractory cancers. Recent progress in the studies of CAF biology suggests that the functions of CAFs are complicated and that they are composed of functionally distinct populations, including cancer-promoting CAFs (pCAFs) and cancer-restraining CAFs (rCAFs). We recently identified a new cell surface marker for rCAFs in pancreatic and colon cancers, designated as Meflin (mesenchymal stromal cell- and fibroblast-expressing Linx paralogue)/Islr (immunoglobulin super family containing leucine-rich repeat). Based on the distribution of Meflin/Islr-positive cells, we also considered it a specific candidate marker for mesenchymal stroma/stem cells. Meflin/Islr-positive CAFs have been shown to suppress cancer progression by being involved in regulating collagen structures and BMP signalling in the TME. This review describes the function of Meflin/Islr in cancer fibrosis as well as in cardiac and lung fibrosis and its potential in the development of new cancer therapeutics.

Single-cell RNA sequencing reveals spatiotemporal heterogeneity and malignant progression in pancreatic neuroendocrine tumor

Aims: Using Single-cell RNA sequencing (scRNA-seq), we explored the spatiotemporal heterogeneity of pancreatic neuroendocrine tumors (pNETs) and the underlying mechanism for malignant progression.

Methods: scRNA-seq was conducted on three tumor tissues (two primary tissues from different sites, one liver metastatic lesion), one normal liver tissue, and peripheral blood mononuclear cells from one patient with a metastatic G2 pNET, followed by bioinformatics analysis and validation in a pNETs cohort.

Results: The transcriptome data of 24.544 cells were obtained. We identified subpopulations of functional heterogeneity within malignant cells, immune cells, and fibroblasts. There were intra- and inter-heterogeneities of cell subpopulations for malignant cells, macrophages, T cells, and fibroblasts among all tumor sites. Cell trajectory analysis revealed several hallmarks of carcinogenesis, including the hypoxia pathway, metabolism reprogramming, and aggressive proliferation, which were activated at different stages of tumor progression. Evolutionary analysis based on mitochondrial mutations defined two dominant clones with metastatic capacity. Finally, we developed a gene signature (PCSK1 and SMOC1) defining the metastatic potential of the tumor and its prognostic value was validated in a cohort of thirty G1/G2 patients underwent surgical resection.

Conclusions: Our scRNA-seq analysis revealed intra- and intertumor heterogeneities in cell populations, transcriptional states, and intercellular communications among primary and metastatic lesions of pNETs. The single-cell level characterization of the spatiotemporal dynamics of malignant cell progression provided new insights into the search for potential novel prognostic biomarkers of pNETs.

Crosstalk between cancer-associated fibroblasts and immune cells in the tumor microenvironment: new findings and future perspectives

Cancer-associated fibroblasts (CAFs), a stromal cell population with cell-of-origin, phenotypic and functional heterogeneity, are the most essential components of the tumor microenvironment (TME). Through multiple pathways, activated CAFs can promote tumor growth, angiogenesis, invasion and metastasis, along with extracellular matrix (ECM) remodeling and even chemoresistance. Numerous previous studies have confirmed the critical role of the interaction between CAFs and tumor cells in tumorigenesis and development. However, recently, the mutual effects of CAFs and the tumor immune microenvironment (TIME) have been identified as another key factor in promoting tumor progression. The TIME mainly consists of distinct immune cell populations in tumor islets and is highly associated with the antitumor immunological state in the TME. CAFs interact with tumor-infiltrating immune cells as well as other immune components within the TIME via the secretion of various cytokines, growth factors, chemokines, exosomes and other effector molecules, consequently shaping an immunosuppressive TME that enables cancer cells to evade surveillance of the immune system. In-depth studies of CAFs and immune microenvironment interactions, particularly the complicated mechanisms connecting CAFs with immune cells, might provide novel strategies for subsequent targeted immunotherapies. Herein, we shed light on recent advances regarding the direct and indirect crosstalk between CAFs and infiltrating immune cells and further summarize the possible immunoinhibitory mechanisms induced by CAFs in the TME. In addition, we present current related CAF-targeting immunotherapies and briefly describe some future perspectives on CAF research in the end.

Organ Specificity and Heterogeneity of Cancer-Associated Fibroblasts in Colorectal Cancer

Fibroblasts constitute a ubiquitous mesenchymal cell type and produce the extracellular matrix (ECM) of connective tissue, thereby providing the structural basis of various organs. Fibroblasts display differential transcriptional patterns unique to the organ of their origin and they can be activated by common stimuli such as transforming growth factor-β (TGF-β) and platelet-derived growth factor (PDGF) signaling. Cancer-associated fibroblasts (CAFs) reside in the cancer tissue and contribute to cancer progression by influencing cancer cell growth, invasion, angiogenesis and tumor immunity. CAFs impact on the tumor microenvironment by remodeling the ECM and secreting soluble factors such as chemokines and growth factors. Differential expression patterns of molecular markers suggest heterogeneous features of CAFs in terms of their function, pathogenic role and cellular origin. Recent studies elucidated the bimodal action of CAFs on cancer progression and suggest a subgroup of CAFs with tumor-suppressive effects. This review attempts to describe cellular features of colorectal CAFs with an emphasis on their heterogeneity and functional diversity.

New Frontiers in Cancer Imaging and Therapy Based on Radiolabeled Fibroblast Activation Protein Inhibitors: A Rational Review and Current Progress

Over the past decade, the tumor microenvironment (TME) has become a new paradigm of cancer diagnosis and therapy due to its unique biological features, mainly the interconnection between cancer and stromal cells. Within the TME, cancer-associated fibroblasts (CAFs) demonstrate as one of the most critical stromal cells that regulate tumor cell growth, progression, immunosuppression, and metastasis. CAFs are identified by various biomarkers that are expressed on their surfaces, such as fibroblast activation protein (FAP), which could be utilized as a useful target for diagnostic imaging and treatment. One of the advantages of targeting FAP-expressing CAFs is the absence of FAP expression in quiescent fibroblasts, leading to a controlled targetability of diagnostic and therapeutic compounds to the malignant tumor stromal area using radiolabeled FAP-based ligands. FAP-based radiopharmaceuticals have been investigated strenuously for the visualization of malignancies and delivery of theranostic radiopharmaceuticals to the TME. This review provides an overview of the state of the art in TME compositions, particularly CAFs and FAP, and their roles in cancer biology. Moreover, relevant reports on radiolabeled FAP inhibitors until the year 2021 are highlighted-as well as the current limitations, challenges, and requirements for those radiolabeled FAP inhibitors in clinical translation.

Comparing immunotherapies to other frequently used treatments of gastric cancer

Introduction: Although standard doublet chemotherapy represents the upfront gold standard to increase survival and improve quality of life of gastric cancer patients, overall improvements in long-term outcomes are modest and novel treatments are urgently needed. Among these, immunotherapy is an increasingly attractive option.Areas covered: A number of clinical trials have shown that checkpoint inhibitors may be of value, but many unclear issues remain controversial and should be promptly untangled. In our short review, we offer the current available data regarding immunotherapies in gastric cancers, discuss potential limits of the reported trials, compare outcomes of checkpoints inhibitor to those of standard chemotherapy or other novel treatments, and present basic principles of immune surveillance and immune escape that may be embraced in the near future with novel drug combinations.Expert opinion: Gastric cancer patients may benefit from immunotherapy, both given alone in advanced lines and upfront in combination with chemotherapy. We believe that appropriate patients' and tumor's selection are crucial issues to maximize its potential efficacy. In addition, we think that assay standardization, biomarker agreement, and translational studies will improve the benefit-to-risk ratio of these agents in the clinical practice.

Recent advances in active targeting of nanomaterials for anticancer drug delivery

One of the challenges in cancer chemotherapy is the low target to non-target ratio of therapeutic agents which incur severe adverse effect on the healthy tissues. In this regard, nanomaterials have tremendous potential for impacting cancer therapy by altering the toxicity profile of the drug. Some of the striking advantages provided by the nanocarriers mediated targeted drug delivery are relatively high build-up of drug concentration at the tumor site, improved drug content in the formulation and enhanced colloidal stability. Further, nanocarriers with tumor-specific moieties can be targeted to the cancer cell through cell surface receptors, tumor antigens and tumor vasculatures with high affinity and accuracy. Moreover, it overcomes the bottleneck of aimless drug biodistribution, undesired toxicity and heavy dosage of administration. This review discusses the recent developments in active targeting of nanomaterials for anticancer drug delivery through cancer cell surface targeting, organelle specific targeting and tumor microenvironment targeting strategies. Special emphasis has been given towards cancer cell surface and organelle specific targeting as delivery of anticancer drugs through these routes have made paradigm change in cancer management. Further, the current challenges and future prospects of nanocarriers mediated active drug targeting are also demonstrated.

Machine Learning for Future Subtyping of the Tumor Microenvironment of Gastro-Esophageal Adenocarcinomas

Tumor progression involves an intricate interplay between malignant cells and their surrounding tumor microenvironment (TME) at specific sites. The TME is dynamic and is composed of stromal, parenchymal, and immune cells, which mediate cancer progression and therapy resistance. Evidence from preclinical and clinical studies revealed that TME targeting and reprogramming can be a promising approach to achieve anti-tumor effects in several cancers, including in GEA. Thus, it is of great interest to use modern technology to understand the relevant components of programming the TME. Here, we discuss the approach of machine learning, which recently gained increasing interest recently because of its ability to measure tumor parameters at the cellular level, reveal global features of relevance, and generate prognostic models. In this review, we discuss the relevant stromal composition of the TME in GEAs and discuss how they could be integrated. We also review the current progress in the application of machine learning in different medical disciplines that are relevant for the management and study of GEA.

High temperature requirement A1 in cancer: biomarker and therapeutic target

As the life expectancy of the population increases worldwide, cancer is becoming a substantial public health problem. Considering its recurrence and mortality rates, most cancer cases are difficult to cure. In recent decades, a large number of studies have been carried out on different cancer types; unfortunately, tumor incidence and mortality have not been effectively improved. At present, early diagnostic biomarkers and accurate therapeutic strategies for cancer are lacking. High temperature requirement A1 (HtrA1) is a trypsin-fold serine protease that is also a chymotrypsin-like protease family member originally discovered in bacteria and later discovered in mammalian systems. HtrA1 gene expression is decreased in diverse cancers, and it may play a role as a tumor suppressor for promoting the death of tumor cells. This work aimed to examine the role of HtrA1 as a cell type-specific diagnostic biomarker or as an internal and external regulatory factor of diverse cancers. The findings of this study will facilitate the development of HtrA1 as a therapeutic target.

Fibroblasts Influence Metastatic Melanoma Cell Sensitivity to Combined BRAF and MEK Inhibition

Simple Summary

Preclinical 3D in vitro coculture models are known to be more complex systems than monolayer cell culture and mimic the physiological environment more closely. Three-dimensional dermal equivalents provide a relevant environment for cutaneous metastatic melanoma cells and are capable of modulating a cancer cell’s response to drugs. We showed that a combined targeted therapy (vemurafenib and cobimetinib) efficiently inhibits cell proliferation and induces apoptosis, especially in the 3D coculture model. A cancer-associated fibroblast population isolated from a cutaneous melanoma was also sensitive to the treatment but with no detectable induction of apoptosis. To better understand the complex crosstalk between melanoma cells and their microenvironment, we compared the influence of conditioned media obtained from healthy or cancer-associated fibroblasts on the response of metastatic melanomas to the drugs. Our data indicate that normal fibroblast supernatants potentialize the therapy’s efficiency, whereas cancer-associated fibroblast secretomes favor melanoma cell survival.

Abstract

The sensitivity of melanoma cells to targeted therapy compounds depends on the tumor microenvironment. Three-dimensional (3D) in vitro coculture systems better reflect the native structural architecture of tissues and are ideal for investigating cellular interactions modulating cell sensitivity to drugs. Metastatic melanoma (MM) cells (SK-MEL-28 BRAF V600E mutant and SK-MEL-2 BRAF wt) were cultured as a monolayer (2D) or cocultured on 3D dermal equivalents (with fibroblasts) and treated with a BRAFi (vemurafenib) combined with a MEK inhibitor (MEKi, cobimetinib). The drug combination efficiently inhibited 2D and 3D MM cell proliferation and survival regardless of their BRAF status. Two-dimensional and three-dimensional cancer-associated fibroblasts (CAFs), isolated from a cutaneous MM biopsy, were also sensitive to the targeted therapy. Conditioned media obtained from healthy dermal fibroblasts or CAFs modulated the MM cell’s response differently to the treatment: while supernatants from healthy fibroblasts potentialized the efficiency of drugs on MM, those from CAFs tended to increase cell survival. Our data indicate that the secretory profiles of fibroblasts influence MM sensitivity to the combined vemurafenib and cobimetinib treatment and highlight the need for 3D in vitro cocultures representing the complex crosstalk between melanoma and CAFs during preclinical studies of drugs.

Overexpression of Nicotinamide N-methyltransferase mainly covers stroma of colorectal cancer and correlates with unfavorable survival by its product 1-MNA

Background: Accumulating evidence indicates that Nicotinamide N-methyltransferase (NNMT) is abnormally expressed in tumor tissues of several cancers including colorectal cancer (CRC) and associated with cancer progression. However, the distribution characteristics and the clinical value of each part of NNMT expression in CRC are still not fully understood. The purpose of this study is to determine the distribution of NNMT expression and its association with survival in CRC. Methods: By using the cancer genome atlas (TCGA) and clinical proteomic tumor analysis consortium (CPTAC), we firstly analyzed the difference of gene and protein levels of NNMT between CRC and normal colorectal tissue. Then, NNMT protein expressions were detected in 18 intraepithelial neoplastic samples and 177 CRC tumor samples through immunohistochemistry in our study cohort. Furthermore, the relationship between NNMT expression and clinicopathological characteristics, overall survival (OS) and disease-free survival (DFS) of CRC patients were analyzed by Pearson χ2 test and log-rank test, respectively, in public datasets and our study cohort. Lastly, the function of NNMT and its product 1-methyl-nicotinamide (1-MNA) on migration and invasion in colorectal cancer cells was analyzed by wound healing assay and transwell assay. Results: We determined that higher NNMT expression in CRC tissues than normal tissues in both gene and protein level in TCGA and CPTAC datasets (all p < 0.05). In addition, the strong relationships of NNMT expression with stromal cells were found in the TCGA cohort. Fortunately, our cohort could validate that the expression of NNMT in tumor stroma cell was significantly higher than that in tumor cell (p < 0.0001), and both of them were significantly higher than that in adjacent normal tissue (ANT) (p < 0.0001 and p < 0.0001, respectively). Furthermore, the positive NNMT expression in tumor cell and stromal cell were associated with series of unfavorable clinical characteristics, including advanced TNM stage, lymph node metastasis, distant metastasis (all p < 0.05). Also, higher NNMT was associated with unfavorable survival both in our study and public datasets, including TCGA and two Gene Expression Omnibus (GEO) datasets (GSE33113 and GSE17538). Moreover, the functional experiments showed that stromal cells with high NNMT expression can secret 1-MAN to promote migration and invasion of CRC cells in vitro. Conclusions: In CRC, NNMT is overexpressed in tumor cells and stroma cells, and then mainly expressed in tumor stroma cells. Overexpression of NNMT in tumor cell and stroma cell both are associated with metastasis and unfavorable survival. Besides, stromal cells with high NNMT expression secrets 1-MAN to promote migration and invasion of CRC cells. Therefore, NNMT may be a potential prognostic indicator in CRC patients.

Lung-Resident Mesenchymal Stem Cell Fates within Lung Cancer

Simple Summary

Lung cancer remains the leading cause of cancer-related deaths worldwide. Herein, the heterogeneous tumor stroma decisively impacts on tumor progression, therapy resistance, and, thus, poor clinical outcome. Among the numerous non-epithelial cells constructing the complex environment of lung carcinomas, mesenchymal stem cells (MSC) gained attraction being stromal precursor cells that could be recruited and ‘educated’ by lung cancer cells to adopt a tumor-associated MSC phenotype, serve as source for activated fibroblasts and presumably for vascular mural cells finally reinforcing tumor progression. Lung-resident MSCs should be considered as ‘local MSCs in stand by’ ready to be arranged within the cancer stroma.

Abstract

Lung-resident mesenchymal stem cells (LR-MSCs) are non-hematopoietic multipotent stromal cells that predominately reside adventitial within lung blood vessels. Based on their self-renewal and differentiation properties, LR-MSCs turned out to be important regulators of normal lung homeostasis. LR-MSCs exert beneficial effects mainly by local secretion of various growth factors and cytokines that in turn foster pulmonary regeneration including suppression of inflammation. At the same time, MSCs derived from various tissues of origins represent the first choice of cells for cell-based therapeutic applications in clinical medicine. Particularly for various acute as well as chronic lung diseases, the therapeutic applications of exogenous MSCs were shown to mediate beneficial effects, hereby improving lung function and survival. In contrast, endogenous MSCs of normal lungs seem not to be sufficient for lung tissue protection or repair following a pathological trigger; LR-MSCs could even contribute to initiation and/or progression of lung diseases, particularly lung cancer because of their inherent tropism to migrate towards primary tumors and metastatic sites. However, the role of endogenous LR-MSCs to be multipotent tumor-associated (stromal) precursors remains to be unraveled. Here, we summarize the recent knowledge how ‘cancer-educated’ LR-MSCs impact on lung cancer with a focus on mesenchymal stem cell fates.

Hydrogel-based colorectal cancer organoid co-culture models

The lack of cancer-associated fibroblasts (CAFs) in patient-derived organoid (PDO) models is a major limitation as CAFs contribute to tumor progression and drug resistance. In the present study, we addressed this problem by establishing in vitro conditions that enable the co-culture of colorectal cancer (CRC) PDO with patient-derived CAFs. Considering that the CRC extracellular matrix is high in hyaluronan and collagen I, we hypothesized that hyaluronan-gelatin hydrogels may serve as a suitable alternative 3D matrix to traditionally used basement membrane extracts to support the co-culture of CRC PDO and CAFs. We report the development of in vitro models consisting of CRC PDO encapsulated within a well-defined three-dimensional (3D) hyaluronan-gelatin hydrogel and co-cultured with patient-derived CAFs. Through RNA- and whole -exome sequencing, we first show that these hydrogels are capable of maintaining key molecular characteristics of the original patient tumors in CRC PDO but not support the culture of CAFs. Further, based on our findings that CRC PDO culture medium poorly supports CAF viability, we developed a co-culture strategy that maintains the viability of both CRC PDO and CAFs. We found that even in the absence of growth factors conventionally used to support CRC PDO culture, CAFs were able to maintain the proliferation of the cultured CRC PDO in the hydrogels and restore distinct biological pathways absent in the PDO culture alone but present in patient tissues. Lastly, we demonstrate that these CRC PDO-CAFs co-culture models are suitable for evaluating standard-of-care drugs, making them potentially very useful for realizing personalized cancer medicine. STATEMENT OF SIGNIFICANCE: We report the development of an engineered tumor microenvironment consisting of colorectal cancer patient-derived organoids (CRC PDO) encapsulated within a well-defined three-dimensional (3D) hyaluronan-gelatin hydrogel and co-cultured with patient-derived cancer-associated fibroblasts (CAFs). Through sequential culture, we found that in the absence of growth factors added to the co-culture, CAFs were able to maintain the proliferation of the cultured CRC PDO in the hydrogels and restore distinct biological pathways absent in the PDO culture alone but present in patient tissues. Lastly, we demonstrate that these CRC PDO-CAFs models are suitable for evaluating standard-of-care drugs, making them potentially very useful for realizing personalized cancer medicine.

Role of Intra- and Extracellular Lipid Signals in Cancer Stemness and Potential Therapeutic Strategy

Accumulating evidence showed that cancer stem cells (CSCs) play significant roles in cancer initiation, resistance to therapy, recurrence and metastasis. Cancer stem cells possess the ability of self-renewal and can initiate tumor growth and avoid lethal factors through flexible metabolic reprogramming. Abnormal lipid metabolism has been reported to be involved in the cancer stemness and promote the development of cancer. Lipid metabolism includes lipid uptake, lipolysis, fatty acid oxidation, de novo lipogenesis, and lipid desaturation. Abnormal lipid metabolism leads to ferroptosis of CSCs. In this review, we comprehensively summarized the role of intra- and extracellular lipid signals in cancer stemness, and explored the feasibility of using lipid metabolism-related treatment strategies for future cancer.

Bufalin suppresses tumour microenvironment-mediated angiogenesis by inhibiting the STAT3 signalling pathway

BACKGROUND

Antiangiogenic therapy has increasingly become an important strategy for the treatment of colorectal cancer. Recent studies have shown that the tumour microenvironment (TME) promotes tumour angiogenesis. Bufalin is an active antitumour compound whose efficacy has been indicated by previous studies. However, there are very few studies on the antiangiogenic effects of bufalin.

METHODS

Herein, human umbilical vein endothelial cell (HUVEC) tube formation, migration and adhesion tests were used to assess angiogenesis in vitro. Western blotting and quantitative PCR were used to detect relevant protein levels and mRNA expression levels. A subcutaneous xenograft tumour model and a hepatic metastasis model were established in mice to investigate the influence of bufalin on angiogenesis mediated by the TME in vivo.

RESULTS

We found that angiogenesis mediated by cells in the TME was significantly inhibited in the presence of bufalin. The results demonstrated that the proangiogenic genes in HUVECs, such as VEGF, PDGFA, E-selectin and P-selectin, were downregulated by bufalin and that this downregulation was mediated by inhibition of the STAT3 pathway. Overexpression of STAT3 reversed the inhibitory effects of bufalin on angiogenesis. Furthermore, there was little reduction in angiogenesis when bufalin directly acted on the cells in the tumour microenvironment.

CONCLUSION

Our findings demonstrate that bufalin suppresses tumour microenvironment-mediated angiogenesis by inhibiting the STAT3 signalling pathway in vascular endothelial cells, revealing that bufalin may be used as a new antiangiogenic adjuvant therapy medicine to treat colorectal cancer.

NF-κB and Pancreatic Cancer; Chapter and Verse

Pancreatic Ductal Adenocarcinoma (PDAC) is one of the world's most lethal cancers. An increase in occurrence, coupled with, presently limited treatment options, necessitates the pursuit of new therapeutic approaches. Many human cancers, including PDAC are initiated by unresolved inflammation. The transcription factor NF-κB coordinates many signals that drive cellular activation and proliferation during immunity but also those involved in inflammation and autophagy which may instigate tumorigenesis. It is not surprising therefore, that activation of canonical and non-canonical NF-κB pathways is increasingly recognized as an important driver of pancreatic injury, progression to tumorigenesis and drug resistance. Paradoxically, NF-κB dysregulation has also been shown to inhibit pancreatic inflammation and pancreatic cancer, depending on the context. A pro-oncogenic or pro-suppressive role for individual components of the NF-κB pathway appears to be cell type, microenvironment and even stage dependent. This review provides an outline of NF-κB signaling, focusing on the role of the various NF-κB family members in the evolving inflammatory PDAC microenvironment. Finally, we discuss pharmacological control of NF-κB to curb inflammation, focussing on novel anti-cancer agents which reinstate the process of cancer cell death, the Smac mimetics and their pre-clinical and early clinical trials.

The Extracellular Matrix in Pancreatic Cancer: Description of a Complex Network and Promising Therapeutic Options

The stroma is a relevant player in driving and supporting the progression of pancreatic ductal adenocarcinoma (PDAC), and a large body of evidence highlights its role in hindering the efficacy of current therapies. In fact, the dense extracellular matrix (ECM) characterizing this tumor acts as a natural physical barrier, impairing drug penetration. Consequently, all of the approaches combining stroma-targeting and anticancer therapy constitute an appealing option for improving drug penetration. Several strategies have been adopted in order to target the PDAC stroma, such as the depletion of ECM components and the targeting of cancer-associated fibroblasts (CAFs), which are responsible for the increased matrix deposition in cancer. Additionally, the leaky and collapsing blood vessels characterizing the tumor might be normalized, thus restoring blood perfusion and allowing drug penetration. Even though many stroma-targeting strategies have reported disappointing results in clinical trials, the ECM offers a wide range of potential therapeutic targets that are now being investigated. The dense ECM might be bypassed by implementing nanoparticle-based systems or by using mesenchymal stem cells as drug carriers. The present review aims to provide an overview of the principal mechanisms involved in the ECM remodeling and of new promising therapeutic strategies for PDAC.

Cancer-associated fibroblasts: overview, progress, challenges, and directions

Tumors are one of the main causes of death in humans. The development of safe and effective methods for early diagnosis and treatment of tumors is a difficult problem that needs to be solved urgently. It is well established that the occurrence of tumors involves complex biological mechanisms, and the tumor microenvironment (TME) plays an important role in regulating the biological behavior of tumors. Cancer-associated fibroblasts (CAFs) are a group of activated fibroblasts with significant heterogeneity and plasticity in the tumor microenvironment. They secrete a variety of active factors to regulate tumor occurrence, development, metastasis, and therapeutic resistance. Although most studies suggest that CAFs have significant tumor-promoting functions, some evidence indicates that they may have certain tumor-suppressive functions in the early stage of tumors. Current research on CAFs continues to face many challenges, and the heterogeneity of their origin, phenotype, and function is a major difficulty and hot spot. To provide new perspectives for the research on CAFs and tumor diagnosis and treatment, this review summarizes the definition, origin, biomarkers, generation mechanism, functions, heterogeneity, plasticity, subpopulations, pre-metastasis niches (PMN), immune microenvironment, and targeted therapy of CAFs, describes the research progress and challenges, and proposes possible future research directions based on existing reports.

The current knowledge concerning solid cancer and therapy

Solid cancers comprise a large number of new cases and deaths from cancer each year globally. There are a number of strategies for addressing tumors raised from solid organs including surgery, chemotherapy, radiotherapy, targeted therapy, immunotherapy, combinational therapy, and stem cell and extracellular vesicle (EV) therapy. Surgery, radiotherapy, and chemotherapy are the dominant cures, but are not always effective, in which even in a localized tumor there is a possibility of tumor relapse after surgical resection. Over half of the cancer patients will receive radiotherapy as a part of their therapeutic schedule. Radiotherapy can cause an abscopal response for boosting the activity of the immune system outside the local field of radiation, but it may also cause an unwanted bystander effect, predisposing nonradiated cells into carcinogenesis. In the context of immunotherapy, immune checkpoint inhibition is known as the standard-of-care, but the major concern is in regard with cold cancers that show low responses to such therapy. Stem-cell therapy can be used to send prodrugs toward the tumor area; this strategy, however, has its own predicaments, such as unwanted attraction toward the other sites including healthy tissues and its instability. A substitute to such therapy and quite a novel strategy is to use EVs, by virtue of their stability and potential to cross biological barriers and long-term storage of contents. Combination therapy is the current focus. Despite advances in the field, there are still unmet concerns in the area of effective cancer therapy, raising challenges and opportunities for future investigations.

Tackling TAMs for Cancer Immunotherapy: It's Nano Time

The tumor microenvironment (TME) is a highly complex environment that surrounds tumors. Interactions between cancer cells/non-cancerous cells and cells/non-cell components in the TME support tumor initiation, development, and metastasis. Of the cell types in the TME, tumor-associated macrophages (TAMs) have gained attention owing to their crucial roles in supporting tumors and conferring therapy resistance. Recent developments in nanotechnology raise opportunities for the application of nano targeted drug-delivery systems (Nano-TDDS) in cancer therapy. We focus our discussion on current knowledge of TAMs, and describe recent examples of Nano-TDDS-based TAM modulation, highlighting strategies to overcome in vivo delivery barriers associated with the TME and their potential for clinical translation.

Current challenges in targeting tumor desmoplasia to improve the efficacy of immunotherapy

Desmoplasia is crucial for the development, progression and treatment of immune-resistant malignancies. and treatment of immune-resistant malignancies. Targeting desmoplasia-related metabolic pathways appears to be an interesting approach to expand our stock of disposable anti-tumor agents.CXCL12/CXCR4 axis inhibition reduces fibrosis, alleviates immunosuppression and significantly enhances the efficacy of PD-1 immunotherapy. CD40L substitute therapy may increase the activity of T-cells, downregulate CD40+, prolong patients' survival and prevent cancer progression. Although FAPα antagonists used in preclinical models did not lead to permanent cure, an alleviation of immune-resistance, modification of desmoplasia and a decrease in angiogenesis were observed. Targeting DDR2 may enhance the effect of anti-PD-1 treatment in multiple neoplasm cell lines and has the ability to overcome the adaptation to BRAF-targeted therapy in melanoma. Reprogramming desmoplasia could potentially cooperate not only with present treatment, but also other potential therapeutic targets. We present the most promising metabolic pathways related to desmoplasia and discuss the emerging strategies to improve the efficacy of immunotherapy.

A review on the role of CAFs and CAF-derived exosomes in progression and metastasis of digestive system cancers

Cancers evolve as a result of the accelerated proliferation of cancer cells in a complicated, enriched, and active microenvironment. Tumor microenvironment (TME) components are the master regulators of any step of cancer development. The tumor microenvironment is composed of many cellular and noncellular components that contribute to the evolution of cancer cells. Cancer-associated fibroblasts (CAFs) are activated fibroblasts in the TME that implicate in tumor progression and metastasis dissemination through secretion of oncogenic factors which are carried to the secondary metastatic sites through exosomes. In this review, we aimed to assess the role of CAF-derived exosomes in TME construction and pre-metastatic niche formation in different cancers of the digestive system in order to better understand some important mechanisms of metastasis and provide possible targets for clinical intervention. This review article is divided into two thematic parts explaining the general mechanisms of pre-metastatic niche formation and metastasis and the role of CAF-derived exosomes in different digestive system cancers including colorectal, gastric, esophageal, pancreatic, and liver cancers.

Cancer-associated fibroblast infiltration in gastric cancer: the discrepancy in subtypes pathways and immunosuppression

Background

General role of cancer-associated fibroblast (CAF) and its infiltration characteristics in gastric cancer remains to be unknown.

Methods

We estimate CAF infiltration in bulk tumor tissue with RNA-seq data and analyzed its relationship with gastric cancer subtype, survival and immune microenvironment.

Results

We revealed CAF intend to have higher infiltration in diffuse, genomically stable, and advanced gastric cancer. CAF is associated with immunosuppressive microenvironment. Wide transcriptomics alterations occur in high CAF infiltrated gastric cancer, PI3K/AKT, TGFB and Hedgehog pathway are remarkable in this procedure. We utilized receptor tyrosine kinases and TGFB pathway ligands to construct risk score system that can predict survival.

Conclusion

Thus, CAF is associated with aggressive phenotype of gastric cancer and risk score based on RTK and TGFB pathway ligands expression is a promising tool for assessment of gastric cancer survival.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03012-z.

The distinct roles of exosomes in tumor-stroma crosstalk within gastric tumor microenvironment

Gastric cancer (GC) development is a complex process displaying polytropic cell and molecular landscape within gastric tumor microenvironment (TME). Stromal cells in TME, including fibroblasts, endothelial cells, mesenchymal stem cells, and various immune cells, support tumor growth, metastasis, and recurrence, functioning as the soil for gastric tumorigenesis. Importantly, exosomes secreted by either stromal cells or tumor cells during tumor-stroma crosstalk perform as crucial transporter of agents including RNAs and proteins for cell-cell communication in GC pathogenesis. Therefore, given the distinct roles of exosomes secreted by various cell types in GC TME, increasing evidence has indicated that exosomes present as new biomarkers for GC diagnosis and prognosis and shed light on novel approaches for GC treatment.

The functional cross talk between cancer cells and cancer associated fibroblasts from a cancer mechanics perspective

The function of biological tissues in health and disease is regulated at cellular level and is highly influenced by the physical microenvironment, through the interaction of forces between cells and ECM, which are perceived through mechanosensing pathways. In cancer, both chemical and physical signaling cascades and their interactions are involved during cell-cell and cell-ECM communications to meet requirements of tumor growth. Among stroma cells, cancer associated fibroblasts (CAFs) play key role in tumor growth and pave the way for cancer cells to initiate metastasis and invasion to other tissues, and without recruitment of CAFs, the process of cancer invasion is dysfunctional. This is through an intense chemical and physical cross talks with tumor cells, and interactive remodeling of ECM. During such interaction CAFs apply traction forces and depending on the mechanical properties, deform ECM and in return receive physical signals from the micromechanical environment. Such interaction leads to ECM remodeling by manipulating ECM structure and its mechanical properties. The results are in form of deposition of extra fibers, stiffening, rearrangement and reorganization of fibrous structure, and degradation which are due to a complex secretion and expression of different markers triggered by mechanosensing of tumor cells, specially CAFs. Such events define cancer progress and invasion of cancer cells. A systemic knowledge of chemical and physical factors provides a holistic view of how cancer process and enhances the current treatment methods to provide more diversity among targets that involves tumor cells and ECM structure.

Tumour heterogeneity and evolutionary dynamics in colorectal cancer

Colorectal cancer (CRC) has a global burden of disease. Our current understanding of CRC has progressed from initial discoveries which focused on the stepwise accumulation of key driver mutations, as encapsulated in the Vogelstein model, to one in which marked heterogeneity leads to a complex interplay between clonal populations. Current evidence suggests that an initial explosion, or “Big Bang”, of genetic diversity is followed by a period of neutral dynamics. A thorough understanding of this interplay between clonal populations during neutral evolution gives insights into the roles in which driver genes may participate in the progress from normal colonic epithelium to adenoma and carcinoma. Recent advances have focused not only on genetics, transcriptomics, and proteomics but have also investigated the ecological and evolutionary processes which transform normal cells into cancer. This review first describes the role which driver mutations play in the Vogelstein model and subsequently demonstrates the evidence which supports a more complex model. This article also aims to underscore the significance of tumour heterogeneity and diverse clonal populations in cancer progression.

Colorectal Cancer Cell-Derived Small Extracellular Vesicles Educate Human Fibroblasts to Stimulate Migratory Capacity

Colorectal cancer (CRC) is in the top 10 cancers most prevalent worldwide, affecting equally men and women. Current research on tumor-derived extracellular vesicles (EVs) suggests that these small extracellular vesicles (sEVs) play an important role in mediating cell-to-cell communication and thus potentially affecting cancer progression via multiple pathways. In the present study, we hypothesized that sEVs derived from different CRC cell lines differ in their ability to reprogram normal human fibroblasts through a process called tumor education. The sEVs derived from CRC cell lines (HT29 and HCT116) were isolated by a combination of ultrafiltration and polymeric precipitation, followed by characterization based on morphology, size, and the presence or absence of EV and non-EV markers. It was observed that the HT29 cells displayed a higher concentration of sEVs compared with HCT116 cells. For the first time, we demonstrated that HT29-derived sEVs were positive for low-molecular-weight protein tyrosine phosphatase (Lmwptp). CRC cell-derived sEVs were uptake by human fibroblasts, stimulating migratory ability via Rho-Fak signaling in co-incubated human fibroblasts. Another important finding showed that HT29 cell-derived sEVs are much more efficient in activating human fibroblasts to cancer-associated fibroblasts (CAFs). Indeed, the sEVs produced by the HT29 cells that are less responsive to a cytotoxic agent display higher efficiency in educating normal human fibroblasts by providing them advantages such as activation and migratory ability. In other words, these sEVs have an influence on the CRC microenvironment, in part, due to fibroblasts reprogramming.

Metabolic reprogramming of cancer-associated fibroblasts and its effect on cancer cell reprogramming

Cancer cells are well-known for adapting their metabolism to maintain high proliferation rates and survive in unfavorable environments with low oxygen and nutritional deficiency. Metabolic reprogramming most commonly arises from the tumor microenvironment (TME). The events of metabolic pathways include the Warburg effect, shift in Krebs cycle metabolites, and increase rate of oxidative phosphorylation that provides the energy for the development and invasion of cancer cells. The TME and shift in tumor metabolism shows a close relationship through bidirectional signaling pathways between the stromal and tumor cells. Cancer-associated fibroblasts (CAFs) are the main type of stromal cells in the TME and consist of a heterogeneous and plastic population that play key roles in tumor growth and metastatic capacity. Emerging evidence suggests that CAFs act as major regulators in shaping tumor metabolism especially through the dysregulation of several metabolic pathways, including glucose, amino acid, and lipid metabolism. The arrangement of these metabolic switches is believed to shape distinct CAF behavior and change tumor cell behavior by the CAFs. The crosstalk between cancer cells and CAFs is associated with cell metabolic reprogramming that contributes to cancer cell growth, progression, and evasion from cancer therapies. But the mechanism and process of this interaction remain unclear. This review aimed to highlight the metabolic couplings between tumor cells and CAFs. We reviewed the recent literature supporting an important role of CAFs in the regulation of cancer cell metabolism, and the relevant pathways, which may serve as targets for therapeutic interventions.

Development and validation of a nomogram based on stromal score to predict progression-free survival of patients with papillary thyroid carcinoma

Background

Growing evidence has proved that stromal cells, as the critical component of tumor microenvironment (TME), are closely associated with tumor's progression. However, the model based on stromal score to predict progression‐free survival (PFS) in papillary thyroid carcinoma (PTC) has not been developed. The study aimed at exploring the relation between stromal score and prognosis, then establishing a nomogram to predict PFS of patients with PTC.

Method

We obtained the stromal score and clinicopathological characteristics of PTC patients from The Cancer Genome Atlas (TCGA) database. Cox regression analysis assisted in selecting prognosis‐related factors. A stromal score‐based nomogram was built and verified in the training and validation cohorts, respectively. The calibration curve, concordance index (C‐index), decision curve analysis (DCA) as well as receiver operating characteristic (ROC) curve assisted in measuring the performance exhibited by the nomogram.

Results

We divided 381 PTC patients into the training cohort (n = 269) and the validation cohort (n = 112) randomly. Compared with patients who had a low stromal score, patients with a high stromal score appeared with significantly better PFS [Hazard ratio (HR) and 95% confidence interval (CI): 0.294, 0.130–0.664]. The C‐index of the PFS nomogram was 0.764 (0.662–0.866) in the training cohort and 0.717 (0.603–0.831) in the validation cohort. The calibration curves for PFS prediction in the nomogram were remarkably consistent with the actual observation. DCA indicated superior performance of the nomogram to predict PFS than the American Joint Committee on Cancer (AJCC) Tumor Node Metastasis (TNM) staging system. The ROC curves showed the favorable sensitivity and specificity of the novel nomogram.

Conclusion

High stromal score was significantly associated with improved PFS in patients with PTC. The nomogram based on the stromal score and clinicopathological patterns yielded a reliable performance to predict the prognosis of PTC.

Cancer-Associated Fibroblast Heterogeneity: A Factor That Cannot Be Ignored in Immune Microenvironment Remodeling

Cancer-associated fibroblasts (CAFs) are important, highly heterogeneous components of the tumor extracellular matrix that have different origins and express a diverse set of biomarkers. Different subtypes of CAFs participate in the immune regulation of the tumor microenvironment (TME). In addition to their role in supporting stromal cells, CAFs have multiple immunosuppressive functions, via membrane and secretory patterns, against anti-tumor immunity. The inhibition of CAFs function and anti-TME therapy targeting CAFs provides new adjuvant means for immunotherapy. In this review, we outline the emerging understanding of CAFs with a particular emphasis on their origin and heterogeneity, different mechanisms of their regulation, as well as their direct or indirect effect on immune cells that leads to immunosuppression.