The origin of the myofibroblasts in breast cancer. Recapitulation of tumor environment in culture unravels diversity and implicates converted fibroblasts and recruited smooth muscle cells

The impact of tumor microenvironment: unraveling the role of physical cues in breast cancer progression

Metastasis accounts for the vast majority of breast cancer-related fatalities. Although the contribution of genetic and epigenetic modifications to breast cancer progression has been widely acknowledged, emerging evidence underscores the pivotal role of physical stimuli in driving breast cancer metastasis. In this review, we summarize the changes in the mechanics of the breast cancer microenvironment and describe the various forces that impact migrating and circulating tumor cells throughout the metastatic process. We also discuss the mechanosensing and mechanotransducing molecules responsible for promoting the malignant phenotype in breast cancer cells. Gaining a comprehensive understanding of the mechanobiology of breast cancer carries substantial potential to propel progress in prognosis, diagnosis, and patient treatment.

Exploring the multifaceted role of direct interaction between cancer cells and fibroblasts in cancer progression

The interaction between the tumor microenvironment (TME) and the cancer cells is a complex and mutually beneficial system that leads to rapid cancer cells proliferation, metastasis, and resistance to therapy. It is now recognized that cancer cells are not isolated, and tumor progression is governed among others, by many components of the TME. The reciprocal cross-talk between cancer cells and their microenvironment can be indirect through the secretion of extracellular matrix (ECM) proteins and paracrine signaling through exosomes, cytokines, and growth factors, or direct by cell-to-cell contact mediated by cell surface receptors and adhesion molecules. Among TME components, cancer-associated fibroblasts (CAFs) are of unique interest. As one of the most abundant components of the TME, CAFs play key roles in the reorganization of the extracellular matrix, facilitating metastasis and chemotherapy evasion. Both direct and indirect roles have been described for CAFs in modulating tumor progression. In this review, we focus on recent advances in understanding the role of direct contact between cancer cells and cancer-associated fibroblasts (CAFs) in driving tumor development and metastasis. We also summarize recent findings on the role of direct contact between cancer cells and CAFs in chemotherapy resistance.

Evidence of steady-state fibroblast subtypes in the normal human breast as cells-of-origin for perturbed-state fibroblasts in breast cancer

BACKGROUND

Human breast cancer most frequently originates within a well-defined anatomical structure referred to as the terminal duct lobular unit (TDLU). This structure is endowed with its very own lobular fibroblasts representing one out of two steady-state fibroblast subtypes-the other being interlobular fibroblasts. While cancer-associated fibroblasts (CAFs) are increasingly appreciated as covering a spectrum of perturbed states, we lack a coherent understanding of their relationship-if any-with the steady-state fibroblast subtypes. To address this, we here established two autologous CAF lines representing inflammatory CAFs (iCAFs) and myofibroblast CAFs (myCAFs) and compared them with already established interlobular- and lobular fibroblasts with respect to their origin and impact on tumor formation.

METHODS

Primary breast tumor-derived CAFs were transduced to express human telomerase reverse transcriptase (hTERT) and sorted into CD105low and CD105high populations using fluorescence-activated cell sorting (FACS). The two populations were tested for differentiation similarities to iCAF and myCAF states through transcriptome-wide RNA-Sequencing (RNA-Seq) including comparison to an available iCAF-myCAF cell state atlas. Inference of origin in interlobular and lobular fibroblasts relied on RNA-Seq profiles, immunocytochemistry and growth characteristics. Osteogenic differentiation and bone formation assays in culture and in vivo were employed to gauge for origin in bone marrow-derived mesenchymal stem cells (bMSCs). Functional characteristics were assessed with respect to contractility in culture and interaction with tumor cells in mouse xenografts. The cells' gene expression signatures were tested for association with clinical outcome of breast cancer patients using survival data from The Cancer Genome Atlas database.

RESULTS

We demonstrate that iCAFs have properties in common with interlobular fibroblasts while myCAFs and lobular fibroblasts are related. None of the CAFs qualify as bMSCs as revealed by lack of critical performance in bone formation assays. Functionally, myCAFs and lobular fibroblasts are almost equally tumor promoting as opposed to iCAFs and interlobular fibroblasts. A myCAF gene signature is found to associate with poor breast cancer-specific survival.

CONCLUSIONS

We propose that iCAFs and myCAFs originate in interlobular and lobular fibroblasts, respectively, and more importantly, that the tumor-promoting properties of lobular fibroblasts render the TDLU an epicenter for breast cancer evolution.

The Influence of Betulin Derivatives EB5 and ECH147 on the Expression of Selected TGFβ Superfamily Genes, TGFβ1, GDF15 and BMP2, in Renal Proximal Tubule Epithelial Cells

Betulin derivatives are proposed to serve as an alternative to the drugs already established in oncologic treatment. Drug-induced nephrotoxicity leading to acute kidney injury frequently accompanies cancer treatment, and thus there is a need to research the effects of betulin derivatives on renal cells. The objective of our study was to assess the influence of the betulin derivatives 28-propynylobetulin (EB5) and 29-diethoxyphosphoryl-28-propynylobetulin (ECH147) on the expression of TGFβ1, BMP2 and GDF15 in renal proximal tubule epithelial cells (RPTECs) cultured in vitro. The changes in mRNA expression and copy numbers were assessed using real-time reverse transcription quantitative polymerase chain reaction (RT-qPCR) and the standard curve method, respectively. An enzyme-linked immunosorbent assay (ELISA) was used to evaluate the effect of the betulin derivatives on the protein concentration in the culture media's supernatant. The assessment of the betulin derivatives' influence on gene expression demonstrated that the mRNA level and protein concentration did not always correlate with each other. Each of the tested compounds affected the mRNA expression. The RT-qPCR analyses showed that EB5 and ECH147 induced effects similar to those of betulin or cisplatin and resulted in a decrease in the mRNA copy number of all the analyzed genes. The ELISA demonstrated that EB5 and ECH147 elevated the protein concentration of TGFβ1 and GDF15, while the level of BMP2 decreased. The concentration of the derivatives used in the treatment was crucial, but the effects did not always exhibit a simple linear dose-dependent relationship. Betulin and its derivatives, EB5 and ECH147, influenced the gene expression of TGFβ1, BMP2 and GDF15 in the renal proximal tubule epithelial cells. The observed effects raise the question of whether treatment with these compounds could promote the development of renal fibrosis.

Microenvironmental regulation in tumor progression: Interactions between cancer-associated fibroblasts and immune cells

The tumor microenvironment (TME), the "soil" on which tumor cells grow, has an important role in regulating the proliferation and metastasis of tumor cells as well as their response to treatment. Cancer-associated fibroblasts (CAFs), as the most abundant stromal cells of the TME, can not only directly alter the immunosuppressive effect of the TME through their own metabolism, but also influence the aggregation and function of immune cells by secreting a large number of cytokines and chemokines, reducing the body's immune surveillance of tumor cells and making them more prone to immune escape. Our study provides a comprehensive review of fibroblast chemotaxis, malignant transformation, metabolic characteristics, and interactions with immune cells. In addition, the current small molecule drugs targeting CAFs have been summarized, including both natural small molecules and targeted drugs for current clinical therapeutic applications. A complete review of the role of fibroblasts in TME from an immune perspective is presented, which has important implications in improving the efficiency of immunotherapy by targeting fibroblasts.

The role of cancer-associated fibroblasts in breast cancer metastasis

Breast cancer deaths are primarily caused by metastasis. There are several treatment options that can be used to treat breast cancer. There are, however, a limited number of treatments that can either prevent or inhibit the spread of breast tumor metastases. Thus, novel therapeutic strategies are needed. Studies have increasingly focused on the importance of the tumor microenvironment (TME) in metastasis of breast cancer. As the most abundant cells in the TME, cancer-associated fibroblasts (CAFs) play important roles in cancer pathogenesis. They can remodel the structure of the extracellular matrix (ECM) and engage in crosstalk with cancer cells or other stroma cells by secreting growth factors, cytokines, and chemokines, as well as components of the ECM, which assist the tumor cells to invade through the TME and cause distant metastasis. Clinically, CAFs not only foster the initiation, growth, angiogenesis, invasion, and metastasis of breast cancer but also serve as biomarkers for diagnosis, therapy, and prediction of prognosis. In this review, we summarize the biological characteristics and subtypes of CAFs and their functions in breast cancer metastasis, focusing on their important roles in the diagnosis, prognosis, and treatment of breast cancer. Recent studies suggest that CAFs are vital partners of breast cancer cells that assist metastasis and may represent ideal targets for prevention and treatment of breast cancer metastasis.

Crosstalk between colorectal cancer cells and cancer-associated fibroblasts in the tumor microenvironment mediated by exosomal noncoding RNAs

Colorectal cancer (CRC) is a common malignant tumor of the digestive system, and its morbidity rates are increasing worldwide. Cancer-associated fibroblasts (CAFs), as part of the tumor microenvironment (TME), are not only closely linked to normal fibroblasts, but also can secrete a variety of substances (including exosomes) to participate in the regulation of the TME. Exosomes can play a key role in intercellular communication by delivering intracellular signaling substances (e.g., proteins, nucleic acids, non-coding RNAs), and an increasing number of studies have shown that non-coding RNAs of exosomal origin from CAFs are not only closely associated with the formation of the CRC microenvironment, but also increase the ability of CRC to grow in metastasis, mediate tumor immunosuppression, and are involved in the mechanism of drug resistance in CRC patients receiving. It is also involved in the mechanism of drug resistance after radiotherapy in CRC patients. In this paper, we review the current status and progress of research on CAFs-derived exosomal non-coding RNAs in CRC.

Fibroblasts in cancer: Unity in heterogeneity

Tumor cells do not exist in isolation in vivo, and carcinogenesis depends on the surrounding tumor microenvironment (TME), composed of a myriad of cell types and biophysical and biochemical components. Fibroblasts are integral in maintaining tissue homeostasis. However, even before a tumor develops, pro-tumorigenic fibroblasts in close proximity can provide the fertile 'soil' to the cancer 'seed' and are known as cancer-associated fibroblasts (CAFs). In response to intrinsic and extrinsic stressors, CAFs reorganize the TME enabling metastasis, therapeutic resistance, dormancy and reactivation by secreting cellular and acellular factors. In this review, we summarize the recent discoveries on CAF-mediated cancer progression with a particular focus on fibroblast heterogeneity and plasticity.

In Vivo Detection of Circulating Cancer-Associated Fibroblasts in Breast Tumor Mouse Xenograft: Impact of Tumor Stroma and Chemotherapy

Cancer-associated fibroblasts (CAFs) are important drivers in the tumor microenvironment and facilitate the growth and survival of tumor cells, as well as metastasis formation. They may travel together with tumor cells to support their survival and aid in the formation of a metastatic niche. In this study, we aimed to study circulating CAFs (cCAFs) and circulating tumor cells (CTCs) in a preclinical breast tumor model in mice in order to understand the effect of chemotherapy on cCAFs and CTC formation. Tumors with MDA-MB-231 human breast tumor cells with/without primary human mammary fibroblasts (representing CAFs) were coinjected in SCID mice to develop tumors. We found that the tumors with CAFs grew faster than tumors without CAFs. To study the effect of the stroma on CTCs and cCAFs, we isolated cells using microsieve filtration technology and established ITGA5 as a new cCAF biomarker, which showed good agreement with the CAF markers FAP and α-SMA. We found that ITGA5+ cCAFs shed in the blood of mice bearing stroma-rich coinjection-based tumors, while there was no difference in CTC formation. Although treatment with liposomal doxorubicin reduced tumor growth, it increased the numbers of both cCAFs and CTCs in blood. Moreover, cCAFs and CTCs were found to form clusters in the chemotherapy-treated mice. Altogether, these findings indicate that the tumor stroma supports tumor growth and the formation of cCAFs. Furthermore, chemotherapy may exacerbate the formation of cCAFs and CTCs, which may eventually support the formation of a metastasis niche in breast cancer.

CD26-negative and CD26-positive tissue-resident fibroblasts contribute to functionally distinct CAF subpopulations in breast cancer

Cancer-associated fibroblasts (CAFs) are abundantly present in the microenvironment of virtually all tumors and strongly impact tumor progression. Despite increasing insight into their function and heterogeneity, little is known regarding the origin of CAFs. Understanding the origin of CAF heterogeneity is needed to develop successful CAF-based targeted therapies. Through various transplantation studies in mice, we show that CAFs in both invasive lobular breast cancer and triple-negative breast cancer originate from mammary tissue-resident normal fibroblasts (NFs). Single-cell transcriptomics, in vivo and in vitro studies reveal the transition of CD26+ and CD26- NF populations into inflammatory CAFs (iCAFs) and myofibroblastic CAFs (myCAFs), respectively. Functional co-culture experiments show that CD26+ NFs transition into pro-tumorigenic iCAFs which recruit myeloid cells in a CXCL12-dependent manner and enhance tumor cell invasion via matrix-metalloproteinase (MMP) activity. Together, our data suggest that CD26+ and CD26- NFs transform into distinct CAF subpopulations in mouse models of breast cancer.

Revisiting laminin and extracellular matrix remodeling in metastatic squamous cell carcinoma: What have we learned after more than four decades of research?

Patients with squamous cell carcinoma (SCC) have significantly lower survival upon the development of distant metastases. The extracellular matrix (ECM) is a consistent yet dynamic influence on the metastatic capacity of SCCs. The ECM encompasses a milieu of structural proteins, signaling molecules, and enzymes. Just over 40 years ago, the fibrous ECM glycoprotein laminin was identified. Roughly four decades of research have revealed a pivotal role of laminins in metastasis. However, trends in ECM alterations in some cancers have been applied broadly to all metastatic diseases, despite evidence that these characteristics vary by tumor type. We will summarize how laminins influence the SCC metastatic process exclusively. Enhanced laminin protein deposition occurs at the invasive edge of SCC tumors, which correlates with elevated levels of laminin-binding β1 integrins on SCC cells, increased MMP-3 presence, worse prognosis, and lymphatic dissemination. Although these findings are significant, gaps in knowledge of the formation of a premetastatic niche, the processes of intra- and extravasation, and the contributions of the ECM to SCC metastatic cell dormancy persist. Bridging these gaps requires novel in vitro systems and animal models that reproduce tumor-stromal interactions and spontaneous metastasis seen in the clinic. These advances will allow accurate assessment of laminins to predict responders to transforming growth factor-β inhibitors and immunotherapy, as well as potential combinatorial therapies with the standard of care. Such clinical interventions may drastically improve quality of life and patient survival by explicitly targeting SCC metastasis.

Bioinformatic and Experimental Analyses Reveal That KIF4A Is a Biomarker of Therapeutic Sensitivity and Predicts Prognosis in Cervical Cancer Patients

OBJECTIVE

This study aims to investigate the expression, prognostic value, and function of kinesin superfamily 4A (KIF4A) in cervical cancer.

METHODS

Cervical cancer cell lines (Hela and SiHa) and TCGA data were used for experimental and bioinformatic analyses. Overall survival (OS) and progression free survival (PFS) were compared between patients with high or low KIF4A expression. Copy number variation (CNV) and somatic mutations of patients were visualized and GISTIC 2.0 was used to identify significantly altered sites. The function of KIF4A was also explored based on transcriptome analysis and validated by experimental methods. Chemotherapeutic and immunotherapeutic benefits were inferred using multiple reference databases and algorithms.

RESULTS

Patients with high KIF4A expression had better OS and PFS. KIF4A could inhibit proliferation and migration and induce G₁ arrest of cervical cancer cells. Higher CNV load was observed in patients with low KIF4A expression, while the group with low KIF4A expression displayed more significantly altered sites. A total of 13 genes were found to mutate more in the low KIF4A expression group, including NOTCH1 and PUM1. The analysis revealed that low KIF4A expression may indicate an immune escape phenotype, and patients in this group may benefit more from immunotherapy. With respect to chemotherapy, cisplatin and gemcitabine may respond better in patients with high KIF4A expression, while 5-fluorouracil etc. may be responded better in patients with low KIF4A expression CONCLUSION: KIF4A is a tumor suppressor gene in cervical cancer, and it can be used as a prognostic and therapeutic biomarker in cervical cancer.

Cellular Plasticity and Heterotypic Interactions during Breast Morphogenesis and Cancer Initiation

Simple Summary

This review aims to discuss the structure, function and dynamics of the breast gland and how changes to the function of the breast’s cells can lead to different types of cancer.

Abstract

The human breast gland is a unique organ as most of its development occurs postnatally between menarche and menopause, a period ranging from 30 to 40 years. During this period, the monthly menstruation cycle drives the mammary gland through phases of cell proliferation, differentiation, and apoptosis, facilitated via a closely choreographed interaction between the epithelial cells and the surrounding stroma preparing the gland for pregnancy. If pregnancy occurs, maximal differentiation is reached to prepare for lactation. After lactation, the mammary gland involutes to a pre-pregnant state. These cycles of proliferation, differentiation, and involution necessitate the presence of epithelial stem cells that give rise to progenitor cells which differentiate further into the luminal and myoepithelial lineages that constitute the epithelial compartment and are responsible for the branching structure of the gland. Maintaining homeostasis and the stem cell niche depends strongly on signaling between the stem and progenitor cells and the surrounding stroma. Breast cancer is a slowly progressing disease whose initiation can take decades to progress into an invasive form. Accumulating evidence indicates that stem cells and/or progenitor cells at different stages, rather than terminally differentiated cells are the main cells of origin for most breast cancer subgroups. Stem cells and cancer cells share several similarities such as increased survival and cellular plasticity which is reflected in their ability to switch fate by receiving intrinsic and extrinsic signals. In this review, we discuss the concept of cellular plasticity in normal breast morphogenesis and cancer, and how the stromal environment plays a vital role in cancer initiation and progression.

Cancer-associated fibroblasts in breast cancer: Challenges and opportunities

The tumor microenvironment is proposed to contribute substantially to the progression of cancers, including breast cancer. Cancer-associated fibroblasts (CAFs) are the most abundant components of the tumor microenvironment. Studies have revealed that CAFs in breast cancer originate from several types of cells and promote breast cancer malignancy by secreting factors, generating exosomes, releasing nutrients, reshaping the extracellular matrix, and suppressing the function of immune cells. CAFs are also becoming therapeutic targets for breast cancer due to their specific distribution in tumors and their unique biomarkers. Agents interrupting the effect of CAFs on surrounding cells have been developed and applied in clinical trials. Here, we reviewed studies examining the heterogeneity of CAFs in breast cancer and expression patterns of CAF markers in different subtypes of breast cancer. We hope that summarizing CAF-related studies from a historical perspective will help to accelerate the development of CAF-targeted therapeutic strategies for breast cancer.

Origin, activation and heterogeneity of fibroblasts associated with pancreas and breast cancers

Pancreas and breast cancers both contain abundant stromal components within the tumor tissues. A prominent cell type within the stroma is cancer-associated fibroblasts (CAFs). CAFs play critical and complex roles establishing the tumor microenvironment to either promote or prevent tumor progression. Recently, complex genetic models and single cell-based techniques have provided emerging insights on the precise functions and cellular heterogeneity of CAFs. The transformation of normal fibroblasts into CAFs is a key event during tumor initiation and progression. Such coordination between tumor cells and fibroblasts plays an important role in cancer development. Reprograming fibroblasts is currently being explored for therapeutic benefits. In this review, we will discuss recent literature shedding light on the tissues of origin, activation mechanisms, and heterogeneity of CAFs comparing pancreas and breast cancers.

Cancer-associated fibroblasts and their role in tumor progression

The stromal elements of a malignant tumor can promote cancer progression and metastasis. The structure of the tumor stroma includes connective tissue elements, blood vessels, nerves, and extracellular matrix (ECM). Some of the cellular elements of the tumor stroma are cancer-associated fibroblasts (CAFs). The origin and function of CAFs have been actively studied over the past thirty years. CAFs produce collagen, the main scaffold protein of the extracellular matrix. Collagen in the tumor stroma stimulates fibrosis, enhances the rigidity of tumor tissue, and disrupts the transmission of proliferation and differentiation signaling pathways. CAFs control tumor angiogenesis, cell motility, tumor immunogenic properties, and the development of resistance to chemo- and immunotherapy. As a result of metabolic adaptation of rapidly growing tumor tissue to the nutrients and oxygen deprivation, the main type of energy production in cells changes from oxidative phosphorylation to anaerobic glycolysis. These changes lead to sequential molecular alterations, including the induction of specified transcriptional factors that result in the CAFs activation. The molecular phenotype of activated CAFs is similar to fibroblasts activated during inflammation. In activated CAFs, alpha-smooth muscle actin (α-SMA) is synthetized de novo and various proteases and fibronectin are produced. Since CAFs are found in all types of carcinomas, these cells are potential targets for the development of new approaches for anticancer therapy. Some CAFs originate from resident fibroblasts of the organs invaded by the tumor, while others originate from epithelial tumor cells, which are undergoing an epithelial-mesenchymal transition (EMT). To date, many molecular and metabolic inducers of the EMT have been discovered including the transforming growth factor-beta (TGF-β), hypoxia, and inflammation. This review classifies modern concepts of molecular markers of CAFs, their functional features, and discusses the stages of epithelial-mesenchymal transition, and the potential of CAFs as a target for antitumor therapy.

Regulation of Tumor Invasion by the Physical Microenvironment: Lessons from Breast and Brain Cancer

The success of anticancer therapies is often limited by heterogeneity within and between tumors. While much attention has been devoted to understanding the intrinsic molecular diversity of tumor cells, the surrounding tissue microenvironment is also highly complex and coevolves with tumor cells to drive clinical outcomes. Here, we propose that diverse types of solid tumors share common physical motifs that change in time and space, serving as universal regulators of malignancy. We use breast cancer and glioblastoma as instructive examples and highlight how invasion in both diseases is driven by the appropriation of structural guidance cues, contact-dependent heterotypic interactions with stromal cells, and elevated interstitial fluid pressure and flow. We discuss how engineering strategies show increasing value for measuring and modeling these physical properties for mechanistic studies. Moreover, engineered systems offer great promise for developing and testing novel therapies that improve patient prognosis by normalizing the physical tumor microenvironment. Expected final online publication date for the Annual Review of Biomedical Engineering, Volume 24 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Fibroblast heterogeneity in prostate carcinogenesis

Our understanding of stromal components, specifically cancer-associated fibroblasts (CAF), in prostate cancer (PCa), has evolved from considering these cells as inert bystanders to acknowledging their significance as players in prostate tumorigenesis. CAF are multifaceted-they promote cancer cell growth, migration and remodel the tumor microenvironment. Although targeting CAF could be a promising strategy for PCa treatment, they incorporate a high but undefined degree of intrinsic cellular heterogeneity. The interaction between CAF subpopulations, with the normal and tumor epithelium and with other cell types is not yet characterized. Defining these interactions and the critical signaling nodes that support tumorigenesis will enable the development of novel strategies to control prostate cancer progression. Here we will discuss the origins, molecular and functional heterogeneity of CAF in PCa. We highlight the challenges associated with delineating CAF heterogeneity and discuss potential areas of research that would assist in expanding our knowledge of CAF and their role in PCa tumorigenesis.

Cancer-associated fibroblasts and the tumor microenvironment in non-small cell lung cancer

INTRODUCTION

Non-small cell lung cancer (NSCLC) has a markedly poor prognosis as it progresses, and the prognosis is still unsatisfactory even with modern treatments. Cancer is composed of not only cancer cells, but also stroma consisting of various cell types. Cancer-associated fibroblasts (CAFs) are a major component of the stroma and the associated tumor microenvironment (TME). Particularly, CAFs are a critical component in elucidating the biological mechanisms of cancer progression and new therapeutic targets. This article outlines the TME formed by CAFs in NSCLC.

AREAS COVERED

Focusing on the TME in NSCLC, we discuss the mechanisms by which CAFs are involved in cancer progression, drug resistance, and the development of therapies targeting CAFs.

EXPERT OPINION

In the TME, CAFs profoundly contribute to tumor progression by interacting with cancer cells through direct contact or paracrine cytokine signaling. CAFs also interact with various other stromal components to establish a tumor-promoting immunosuppressive microenvironment and remodel the extracellular matrix. Furthermore, these effects are closely associated with drug resistance. Further elucidation of the stromal microenvironment, including CAFs, could prove to be crucial in the treatment of NSCLC.

Activated Pancreatic Stellate Cells Enhance the Warburg Effect to Cause the Malignant Development in Chronic Pancreatitis

Chronic pancreatitis (CP) is a precancerous condition associated with pancreatic ductal adenocarcinoma (PDAC), but its evolutionary mechanism is unclear. Pancreatic stellate cells (PSCs) are closely related to the occurrence and development of CP and PDAC, but it is not clear whether PSCs play a key role in this “inflammation-cancer transition”. Our research found that co-culture with activated PSCs promoted the proliferation, migration and invasion of normal pancreatic duct epithelial cells and pancreatic cancer cells. At the same time, activated PSCs had a significant effect on the expression of the glycolysis markers (pyruvate kinase M2, lactate dehydrogenase A, glucose transporter 1, hexokinase-II and monocarboxylate transporter 4; PKM2, LDHA, GLUT1, HK2 and MCT4) in normal pancreatic duct epithelial cells and pancreatic cancer cells and increased lactic acid production and glucose consumption in these two cells. In vivo experiments showed that the expression of the glycolysis markers in pancreatic duct epithelial cells and the marker protein (α-SMA) of activated PSCs in the pancreatic duct peripancreatic interstitium were higher in pancreatic cancer tissues and chronic pancreatitis tissues than in normal pancreatic tissues in both animals and humans. In addition, analysis of human tissue specimens showed that there is a correlation between the expression of glycolysis markers and α-SMA. These findings indicate that activated PSCs play an important role in the development and progression of chronic pancreatitis into pancreatic cancer by regulating and promoting aerobic glycolysis. Our research provides a new theoretical basis for further understanding the mechanism of CP malignancy and the selection of targets for reversing CP malignancy.

Engineering stromal heterogeneity in cancer

Based on our exponentially increasing knowledge of stromal heterogeneity from advances in single-cell technologies, the notion that stromal cell types exist as a spectrum of unique subpopulations that have specific functions and spatial distributions in the tumor microenvironment has significant impact on tumor modeling for drug development and personalized drug testing. In this Review, we discuss the importance of incorporating stromal heterogeneity and tumor architecture, and propose an overall approach to guide the reconstruction of stromal heterogeneity in vitro for tumor modeling. These next-generation tumor models may support the development of more precise drugs targeting specific stromal cell subpopulations, as well as enable improved recapitulation of patient tumors in vitro for personalized drug testing.

COL11A1 activates cancer-associated fibroblasts by modulating TGF-β3 through the NF-κB/IGFBP2 axis in ovarian cancer cells

Ovarian cancer has a unique tumor microenvironment (TME) that enables cancer-associated fibroblasts (CAFs) to interact with cellular and matrix constituents and influence tumor development and migration into the peritoneal cavity. Collagen type XI alpha 1 (COL11A1) is overexpressed in CAFs; therefore this study examines its role during CAF activation in epithelial ovarian cancer (EOC). Coculturing human ovarian fibroblasts (HOFs) with high COL11A1-expressing EOC cells or exposure to the conditioned medium of these cells prompted the expression of COL11A1 and CAF phenotypes. Conversely, coculturing HOFs with low COL11A1-expressing EOC cells or COL11A1-knockdown abrogated COL11A1 overexpression and secretion, in addition to CAF activation. Increased p-SP1 expression attributed to COL11A1-mediated extracellular signal-regulated kinase activation (ERK) induced p65 translocation into the nucleus and augmented its binding to the insulin-like growth factor binding protein 2 (IGFBP2) promoter, ultimately inducing TGF-β3 activation. The CAF-cancer cell crosstalk triggered interleukin-6 release, which in turn promoted EOC cell proliferation and invasiveness. These in vitro results were confirmed by in vivo findings in a mouse model, showing that COL11A1 overexpression in EOC cells promoted tumor formation and CAF activation, which was inhibited by TGF-β3 antibody. Human tumors with high TGF-β3 levels showed elevated expression of COL11A1 and IGFBP2, which was associated with poor survival. Our findings suggest the possibility that anti-TGF-β3 treatment strategy may be effective in targeting CAFs in COL11A1-positive ovarian tumors.

Cancer-Associated Fibroblasts in the Breast Tumor Microenvironment

Years of investigation have shed light on a theory in which breast tumor epithelial cells are under the effect of the stromal microenvironment. This review aims to discuss recent findings concerning the phenotypic and functional characteristics of cancer associated fibroblasts (CAFs) and their involvement in tumor evolution, as well as their potential implications for anti-cancer therapy. In this manuscript, we reviewed that CAFs play a fundamental role in initiation, growth, invasion, and metastasis of breast cancer, and also serve as biomarkers in the clinical diagnosis, therapy, and prognosis of this disease.

Adipose-derived mesenchymal stem cells differentiate into heterogeneous cancer-associated fibroblasts in a stroma-rich xenograft model

Cancer-associated fibroblasts (CAFs) are the key components of the densely proliferated stroma in pancreatic ductal adenocarcinoma (PDAC) and contribute to tumor progression and drug resistance. CAFs comprise heterogeneous subpopulations playing unique and vital roles. However, the commonly used mouse models have not been able to fully reproduce the histological and functional characteristics of clinical human CAF. Here, we generated a human cell-derived stroma-rich CDX (Sr-CDX) model, to reproduce the clinical tumor microenvironment. By co-transplanting human adipose-derived mesenchymal stem cells (AD-MSCs) and a human PDAC cell line (Capan-1) into mice, the Sr-CDX model recapitulated the characteristics of clinical pancreatic cancer, such as accelerated tumor growth, abundant stromal proliferation, chemoresistance, and dense stroma formed from the heterogeneous CAFs. Global RNA sequencing, single-cell based RNA sequencing, and histological analysis of CAFs in the Sr-CDX model revealed that the CAFs of the Sr-CDX mice were derived from the transplanted AD-MSCs and composed of heterogeneous subpopulations of CAF, including known and unknown subtypes. These lines of evidences suggest that our new tumor-bearing mouse model has the potential to address an open question in CAF research, that is the mechanism of CAF differentiation.

Adipose-derived mesenchymal stem cells differentiate into pancreatic cancer-associated fibroblasts in vitro

Cancer-associated fibroblasts (CAFs) are key components of the dense, proliferating stroma observed in pancreatic ductal adenocarcinoma (PDAC), and CAF subpopulations drive tumor heterogeneity and play a major role in PDAC progression and drug resistance. CAFs consist of heterogenous subpopulations such as myoblastic CAF (myCAF) and inflammatory CAF (iCAF), and each has distinct essential roles. However, it is not clear how CAF subpopulations are formed in PDAC. Adipose-derived MSCs (AD-MSCs), which possess a high multilineage potential and self-renewal capacity, are reported to be one of the in vivo CAF sources. Here, we aimed to investigate whether AD-MSCs can act as precursors for CAFs in vitro. We recorded morphological features and collected omics data from two in vitro co-culture models for recapitulating clinical PDAC. Additionally, we tested the advantages of the co-culture model in terms of accurately modeling morphology and CAF heterogeneity. We showed that AD-MSCs differentiate into two distinct CAF subpopulations: Direct contact co-culture with PDAC cell line Capan-1 induced differentiation into myCAFs and iCAFs, while indirect co-culture induced differentiation into only iCAFs. Using these co-culture systems, we also identified novel CAF markers that may be helpful for elucidating the mechanisms of CAFs in the tumor microenvironment (TME). In conclusion, AD-MSCs can differentiate into distinct CAF subtypes depending on the different co-culture conditions in vitro, and the identification of potential CAF markers may aid in future investigations of the mechanisms underlying the role of CAFs in the TME.

Cancer-Associated Fibroblasts: Understanding Their Heterogeneity

Simple Summary

Cancer-associated fibroblasts (CAFs) play an important contributory role in the microenvironment of tumors. They originate from different cells, have multiple pro-and anti-tumorigenic functions in tumors and their presence is variable among cancer types. Recently, there has been evidence that CAFs represent a highly heterogeneous group of cells that can now be characterized and identified at the single cell level. This review article summarizes our recent understanding of the highly heterogeneous nature of the origin, phenotype and function of CAFs and how such understanding will lead to a more precise approach to target or use CAFs and their precursor cells in the treatment of cancer.

Abstract

The tumor microenvironment (TME) plays a critical role in tumor progression. Among its multiple components are cancer-associated fibroblasts (CAFs) that are the main suppliers of extracellular matrix molecules and important contributors to inflammation. As a source of growth factors, cytokines, chemokines and other regulatory molecules, they participate in cancer progression, metastasis, angiogenesis, immune cell reprogramming and therapeutic resistance. Nevertheless, their role is not fully understood, and is sometimes controversial due to their heterogeneity. CAFs are heterogeneous in their origin, phenotype, function and presence within tumors. As a result, strategies to target CAFs in cancer therapy have been hampered by the difficulties in better defining the various populations of CAFs and by the lack of clear recognition of their specific function in cancer progression. This review discusses how a greater understanding of the heterogeneous nature of CAFs could lead to better approaches aimed at their use or at their targeting in the treatment of cancer.

Cancer-Associated Fibroblasts: Epigenetic Regulation and Therapeutic Intervention in Breast Cancer

Breast cancer is the leading cause of cancer-related mortality in women worldwide. Cancer-associated fibroblasts (CAFs) are a heterogeneous population of cells in the solid tumour microenvironment. These cells are positively linked to breast cancer progression. Breast CAFs can be categorised into distinct subtypes according to their roles in breast carcinogenesis. Epigenetic modifications change gene expression patterns as a consequence of altered chromatin configuration and DNA accessibility to transcriptional machinery, without affecting the primary structure of DNA. Epigenetic dysregulation in breast CAFs may enhance breast cancer cell survival and ultimately lead to therapeutic resistance. A growing body of evidence has described epigenetic modulators that target histones, DNA, and miRNA as a promising approach to treat cancer. This review aims to summarise the current findings on the mechanisms involved in the epigenetic regulation in breast CAFs and discusses the potential therapeutic strategies via targeting these factors.

Fibroblasts direct differentiation of human breast epithelial progenitors

BACKGROUND

Breast cancer arises within specific regions in the human breast referred to as the terminal duct lobular units (TDLUs). These are relatively dynamic structures characterized by sex hormone driven cyclic epithelial turnover. TDLUs consist of unique parenchymal entities embedded within a fibroblast-rich lobular stroma. Here, we established and characterized a new human breast lobular fibroblast cell line against its interlobular counterpart with a view to assessing the role of region-specific stromal cues in the control of TDLU dynamics.

METHODS

Primary lobular and interlobular fibroblasts were transduced to express human telomerase reverse transcriptase (hTERT). Differentiation of the established cell lines along lobular and interlobular pathways was determined by immunocytochemical staining and genome-wide RNA sequencing. Their functional properties were further characterized by analysis of mesenchymal stem cell (MSC) differentiation repertoire in culture and in vivo. The cells' physiological relevance for parenchymal differentiation was examined in heterotypic co-culture with fluorescence-activated cell sorting (FACS)-purified normal breast primary luminal or myoepithelial progenitors. The co-cultures were immunostained for quantitative assessment of epithelial branching morphogenesis, polarization, growth, and luminal epithelial maturation. In extension, myoepithelial progenitors were tested for luminal differentiation capacity in culture and in mouse xenografts. To unravel the significance of transforming growth factor-beta (TGF-β)-mediated crosstalk in TDLU-like morphogenesis and differentiation, fibroblasts were incubated with the TGF-β signaling inhibitor, SB431542, prior to heterotypic co-culture with luminal cells.

RESULTS

hTERT immortalized fibroblast cell lines retained critical phenotypic traits in culture and linked to primary fibroblasts. Cell culture assays and transplantation to mice showed that the origin of fibroblasts determines TDLU-like and ductal-like differentiation of epithelial progenitors. Whereas lobular fibroblasts supported a high level of branching morphogenesis by luminal cells, interlobular fibroblasts supported ductal-like myoepithelial characteristics. TDLU-like morphogenesis, at least in part, relied on intact TGF-β signaling.

CONCLUSIONS

The significance of the most prominent cell type in normal breast stroma, the fibroblast, in directing epithelial differentiation is largely unknown. Through establishment of lobular and interlobular fibroblast cell lines, we here demonstrate that epithelial progenitors are submitted to stromal cues for site-specific differentiation. Our findings lend credence to considering stromal subtleties of crucial importance in the development of normal breast and, in turn, breast cancer.

Interleukin-36 Cytokine/Receptor Signaling: A New Target for Tissue Fibrosis

Tissue fibrosis is a major unresolved medical problem, which impairs the function of various systems. The molecular mechanisms involved are poorly understood, which hinders the development of effective therapeutic strategies. Emerging evidence from recent studies indicates that interleukin 36 (IL-36) and the corresponding receptor (IL-36R), a newly-characterized cytokine/receptor signaling complex involved in immune-inflammation, play an important role in the pathogenesis of fibrosis in multiple tissues. This review focuses on recent experimental findings, which implicate IL-36R and its associated cytokines in different forms of organ fibrosis. Specifically, it outlines the molecular basis and biological function of IL-36R in normal cells and sums up the pathological role in the development of fibrosis in the lung, kidney, heart, intestine, and pancreas. We also summarize the new progress in the IL-36/IL-36R-related mechanisms involved in tissue fibrosis and enclose the potential of IL-36R inhibition as a therapeutic strategy to combat pro-fibrotic pathologies. Given its high association with disease, gaining new insight into the immuno-mechanisms that contribute to tissue fibrosis could have a significant impact on human health.

Review of cancer-associated fibroblasts and their microenvironment in post-chemotherapy recurrence

Cancer tissue comprises not only cancer cells, but also several types of non-cancerous cells, such as cancer-associated fibroblasts. These fibroblasts directly and/or indirectly communicate with the cancer cells and other types of stromal cells, to create a specific tumor microenvironment. Cytotoxic chemotherapy plays a central role in treating cancer; however, tumor re-progression (recurrence) is a significant problem for cancer patients. Cytotoxic anticancer drugs act on fibroblasts as well as cancer cells and, after chemotherapy, all surviving cells are in contact with one another in the local environment. Therefore, an understanding of the molecular interactions between surviving cancer cells and fibroblasts is necessary to prevent tumor re-progression and to sustain the effect of cytotoxic agents. After chemotherapy, the number of fibroblasts may increase, some of which are identifiable as tumor-promoting. In this review, we discuss the significance of cancer-associated fibroblasts in tumor re-progression after chemotherapy, and the potential value of targeting them to enhance clinical outcomes.

Stromal cell diversity associated with immune evasion in human triple-negative breast cancer

The tumour stroma regulates nearly all stages of carcinogenesis. Stromal heterogeneity in human triple-negative breast cancers (TNBCs) remains poorly understood, limiting the development of stromal-targeted therapies. Single-cell RNA sequencing of five TNBCs revealed two cancer-associated fibroblast (CAF) and two perivascular-like (PVL) subpopulations. CAFs clustered into two states: the first with features of myofibroblasts and the second characterised by high expression of growth factors and immunomodulatory molecules. PVL cells clustered into two states consistent with a differentiated and immature phenotype. We showed that these stromal states have distinct morphologies, spatial relationships and functional properties in regulating the extracellular matrix. Using cell signalling predictions, we provide evidence that stromal-immune crosstalk acts via a diverse array of immunoregulatory molecules. Importantly, the investigation of gene signatures from inflammatory-CAFs and differentiated-PVL cells in independent TNBC patient cohorts revealed strong associations with cytotoxic T-cell dysfunction and exclusion, respectively. Such insights present promising candidates to further investigate for new therapeutic strategies in the treatment of TNBCs.

Influence of Fibroblasts on Mammary Gland Development, Breast Cancer Microenvironment Remodeling, and Cancer Cell Dissemination

The stromal microenvironment regulates mammary gland development and tumorigenesis. In normal mammary glands, the stromal microenvironment encompasses the ducts and contains fibroblasts, the main regulators of branching morphogenesis. Understanding the way fibroblast signaling pathways regulate mammary gland development may offer insights into the mechanisms of breast cancer (BC) biology. In fact, the unregulated mammary fibroblast signaling pathways, associated with alterations in extracellular matrix (ECM) remodeling and branching morphogenesis, drive breast cancer microenvironment (BCM) remodeling and cancer growth. The BCM comprises a very heterogeneous tissue containing non-cancer stromal cells, namely, breast cancer-associated fibroblasts (BCAFs), which represent most of the tumor mass. Moreover, the different components of the BCM highly interact with cancer cells, thereby generating a tightly intertwined network. In particular, BC cells activate recruited normal fibroblasts in BCAFs, which, in turn, promote BCM remodeling and metastasis. Thus, comparing the roles of normal fibroblasts and BCAFs in the physiological and metastatic processes, could provide a deeper understanding of the signaling pathways regulating BC dissemination. Here, we review the latest literature describing the structure of the mammary gland and the BCM and summarize the influence of epithelial-mesenchymal transition (EpMT) and autophagy in BC dissemination. Finally, we discuss the roles of fibroblasts and BCAFs in mammary gland development and BCM remodeling, respectively.

Oroxylin A suppresses ACTN1 expression to inactivate cancer-associated fibroblasts and restrain breast cancer metastasis

Tumor initiation and progression are not only ascribed to the behavior of cancer cells, but also profoundly influenced by the tumor microenvironment. Inside, cancer-associated fibroblasts (CAFs) have become key factors to accelerate growth and metastasis for the abundance in most solid tumors. Our group previously reported that Oroxylin A (OA), a flavone from Scutellaria Baicalensis Georgi, possess the ability to suppress growth and invasion of several tumor cells. However, the regulatory effect of OA on stromal microenvironment is poorly understood. In this study, breast cancer-induced fibroblasts and primary breast CAFs from MMTV-PyMT mice were used to evaluate the influence of OA on the activation of fibroblasts. Results showed that OA could decrease the expression of α-SMA, fibronectin, vimentin and matrix metalloproteinases (MMPs). Thus, OA-deactivated CAFs did not further promote the proliferation and invasion in breast cancer cells. In vivo experiments, OA could also impede tumor metastasis through exhausting progressive CAFs. Mechanically, OA could specifically bind ACTN1 and significantly inhibit its expression to prevent CAF activation. As a consequence, OA could decrease the phosphorylation of FAK and STAT3, and reduce the secretion of CCL2 in CAFs. Altogether, OA could remodel stromal microenvironment and it is a potential therapeutic agent in breast cancer.

Shaping Up the Tumor Microenvironment With Cellular Fibronectin

Normal tissue homeostasis and architecture restrain tumor growth. Thus, for a tumor to develop and spread, malignant cells must overcome growth-repressive inputs from surrounding tissue and escape immune surveillance mechanisms that curb cancer progression. This is achieved by promoting the conversion of a physiological microenvironment to a pro-tumoral state and it requires a constant dialog between malignant cells and ostensibly normal cells of adjacent tissue. Pro-tumoral reprogramming of the stroma is accompanied by an upregulation of certain extracellular matrix (ECM) proteins and their cognate receptors. Fibronectin (FN) is one such component of the tumor matrisome. This large multidomain glycoprotein dimer expressed over a wide range of human cancers is assembled by cell-driven forces into a fibrillar array that provides an obligate scaffold for the deposition of other matrix proteins and binding sites for functionalization by soluble factors in the tumor microenvironment. Encoded by a single gene, FN regulates the proliferation, motile behavior and fate of multiple cell types, largely through mechanisms that involve integrin-mediated signaling. These processes are coordinated by distinct isoforms of FN, collectively known as cellular FN (as opposed to circulating plasma FN) that arise through alternative splicing of the FN1 gene. Cellular FN isoforms differ in their solubility, receptor binding ability and spatiotemporal expression, and functions that have yet to be fully defined. FN induction at tumor sites constitutes an important step in the acquisition of biological capabilities required for several cancer hallmarks such as sustaining proliferative signaling, promoting angiogenesis, facilitating invasion and metastasis, modulating growth suppressor activity and regulating anti-tumoral immunity. In this review, we will first provide an overview of ECM reprogramming through tumor-stroma crosstalk, then focus on the role of cellular FN in tumor progression with respect to these hallmarks. Last, we will discuss the impact of dysregulated ECM on clinical efficacy of classical (radio-/chemo-) therapies and emerging treatments that target immune checkpoints and explore how our expanding knowledge of the tumor ECM and the central role of FN can be leveraged for therapeutic benefit.

Effect of naive and cancer-educated fibroblasts on colon cancer cell circadian growth rhythm

Opportunistic modification of the tumour microenvironment by cancer cells enhances tumour expansion and consequently eliminates tumour suppressor components. We studied the effect of fibroblasts on the circadian rhythm of growth and protein expression in colon cancer HCT116 cells and found diminished oscillation in the proliferation of HCT116 cells co-cultured with naive fibroblasts, compared with those co-cultured with tumour-associated fibroblasts (TAFs) or those cultured alone, suggesting that TAFs may have lost or gained factors that regulate circadian phenotypes. Based on the fibroblast paracrine factor analysis, we tested IL6, which diminished HCT116 cell growth oscillation, inhibited early phase cell proliferation, increased early phase expression of the differentiation markers CEA and CDX2, and decreased early phase ERK5 phosphorylation. In conclusion, our data demonstrate how the cancer education of naive fibroblasts influences the circadian parameters of neighbouring cancer cells and highlights a putative role for IL6 as a novel candidate for preoperative treatments.

Three-dimensional models of breast cancer-fibroblasts interactions

IMPACT STATEMENT

Tumor stroma plays an important role in progression of cancers to a fatal metastatic disease. Modern treatment strategies are considering targeting tumor stroma to improve outcomes for cancer patients. A current challenge to develop stroma-targeting therapeutics is the lack of preclinical physiologic tumor models. Animal models widely used in cancer research lack human stroma and are not amenable to screening of chemical compounds for cancer drug discovery. In this review, we outline in vitro three-dimensional tumor models that we have developed to study the interactions among cancer cells and stromal cells. We describe development of the tumor models in a modular fashion, from a spheroid model to a sophisticated organotypic model, and discuss the importance of using correct physiologic models to recapitulate tumor-stromal signaling. These biomimetic tumor models will facilitate understanding of tumor-stromal signaling biology and provide a scalable approach for testing and discovery of cancer drugs.

Desmoplasia and Biophysics in Pancreatic Ductal Adenocarcinoma: Can We Learn From Breast Cancer?

Pancreatic ductal adenocarcinoma (PDAC) treatments have historically focused on targeting tumor cells directly. However, in pancreatic masses, the stroma encasing the malignant epithelial cells constitutes up to 80% to 90% of the tumor bulk. This extracellular matrix, which was previously neglected when designing cancer therapies, is now considered fundamental for tumor progression and drug delivery. Desmoplastic tissue is extensively cross-linked, resulting in tremendous tensile strength. This key pathological feature is procarcinogenic, linking PDAC and breast cancer (BC). Physical forces exerted onto cellular surfaces are detected intracellularly and transduced via biochemical messengers in a process called mechanotransduction. Mechanotransduction and tensional homeostasis are linked, with an integral role in influencing tumor growth, metastasis, and interactions with the immune system. It is essential to enhance our knowledge of these integral elements of parenchymal tumors. We aim to review the topic, with a special emphasis on desmoplastic processes and their importance in pancreatic and BC development and treatments, mindful that innovative diagnostic and therapeutic strategies cannot focus on biochemical pathways alone. We then focus on common therapeutic targets identified in both PDAC and BC models and/or patients, aiming to understand these treatments and draw similarities between the two tumors.

Toll-Like Receptors Signaling in the Tumor Microenvironment

The involvement of inflammation in cancer progression is well-established. The immune system can play both tumor-promoting and -suppressive roles, and efforts to harness the immune system to help fight tumor growth are at the forefront of research. Of particular importance is the inflammatory profile at the site of the tumor, with respect to both the leukocyte population numbers, the phenotype of these cells, as well as the contribution of the tumor cells themselves. In this regard, the pro-inflammatory effects of pattern recognition receptor expression and activation in the tumor microenvironment have emerged as a relevant issue both for therapy and to understand tumor development.Pattern recognition receptors (PRRs) were originally recognized as components of immune cells, particularly innate immune cells, as detectors of pathogens. PRR signaling in immune cells activates them, inducing robust antimicrobial responses. In particular, toll-like receptors (TLRs) constitute a family of membrane-bound PRRs which can recognize pathogen-associated molecular patterns (PAMPs) carried by bacteria, virus, and fungi. In addition, PRRs can recognize products generated by stressed cells or damaged tissues, namely damage-associated molecular patterns or DAMPS. Taking into account the role of the immune system in fighting tumors together with the presence of immune cells in the microenvironment of different types of tumors, strategies to activate immune cells via PRR ligands have been envisioned as an anticancer therapeutic approach.In the last decades, it has been determined that PRRs are present and functional on nonimmune cells and that their activation in these cells contributes to the inflammation in the tumor microenvironment. Both tumor-promoting and antitumor effects have been observed when tumor cell PRRs are activated. This argues against nonspecific activation of PRR ligands in the tumor microenvironment as a therapeutic approach. Therefore, the use of PRR ligands for anticancer therapy might benefit from strategies that specifically deliver these ligands to immune cells, thus avoiding tumor cells in some settings. This review focuses on these aspects of TLR signaling in the tumor microenvironment.

Molecular pathways regulated by areca nut in the etiopathogenesis of oral submucous fibrosis

Many oral mucosal lesions are due to substance abuse, such as tobacco and areca nut, amongst others. There is considerable evidence that oral lesions/disorders such as some leukoplakias, most erythroplakias, and submucous fibrosis have malignant potential, with a conversion rate of 5%-10% over a 10-year period. There have been several reports on possible biomarkers that predict malignant conversion of the oral lesions associated with these disorders. Management of these is mostly surgical removal of the lesion followed by observation, and in some cases treatment by antioxidants and anti-inflammatory agents. Oral submucous fibrosis is due to excessive deposition of extracellular matrix in the connective tissue plus, particularly, collagens. The deposition of collagen leads to stiffness of the affected regions and results in difficulty in mouth opening. Areca nut chewing is proposed as the most probable etiological factor in the manifestation of oral submucous fibrosis. Several studies suggest involvement of proinflammatory cytokines, dysregulated by areca nut, in the development of the disease. Amongst these, transforming growth factor-β is in the forefront, which is also shown to be involved in fibrosis of other organs. This review addresses the molecular mechanisms involved in oral submucous fibrosis development and provides a model for the regulation of transforming growth factor-β by areca nut. It provides an exemplar of the role of modern molecular techniques in the study of oral disease.

Crosstalk between cancer-associated fibroblasts and immune cells in cancer

Multiple studies have shown that cancer‐associated fibroblasts (CAFs) play an important role in tumour progression, including carcinogenesis, invasion, metastasis and the chemoresistance of cancer cells. Immune cells, including macrophages, natural killer cells, dendritic cells and T cells, play a dual role in the tumour microenvironment. Although increasing research has focused on studying interactions between distinct cells in the tumour microenvironment, the complex relationships between CAFs and immune cells remain unclear and need further study. Here, we summarize our current understanding of crosstalk between CAFs and immune cells, which may help clarify their diagnostic and therapeutic value in tumour progression.

Cancer-associated fibroblasts: how do they contribute to metastasis?

Cancer-associated fibroblasts (CAFs) are activated fibroblasts in the tumor microenvironment. They are one of the most prominent cell types in the stroma and produce large amounts of extracellular matrix molecules, chemokines, cytokines and growth factors. Importantly, CAFs promote cancer progression and metastasis by multiple pathways. This, together with their genetic stability, makes them an interesting target for cancer therapy. However, CAF heterogeneity and limited knowledge about the function of the different CAF subpopulations in vivo, are currently major obstacles for identifying specific molecular targets that are of value for cancer treatment. In this review, we discuss recent major findings on CAF development and their metastasis-promoting functions, as well as open questions to be addressed in order to establish successful cancer therapies targeting CAFs.

Giulio Gabbiani and the discovery of myofibroblasts

Myofibroblasts, specialized fibroblasts expressing the protein alpha-smooth muscle actin, are instrumental in wound contraction during normal wound healing. Tissue shortening is then stabilized by the synthesis of extracellular matrix, collagen in particular. Alpha-smooth muscle actin within myofibroblasts becomes organized in filamentous bundles, called stress fibers, that allow the retractile movement producing wound contraction. During hypertrophic scarring, skin deformations depend on the inappropriate action of these stress fibers that for unknown reasons persist even after the epithelialization of the wound. This historical review article is dedicated to the reconstruction of the discovery of this cell by the Italian scientist Giulio Gabbiani.

Contribution of p62/SQSTM1 to PDGF-BB-induced myofibroblast-like phenotypic transition in vascular smooth muscle cells lacking Smpd1 gene

Accumulating evidence indicates a critical role of autophagy in regulating vascular smooth muscle cell (SMC) homeostasis in atherogenesis. However, little is known about the modulatory role of autophagy in PDGF-BB-induced SMC transition towards the synthetic phenotype and extracellular matrix remodeling. We recently demonstrated that acid sphingomyelinase (ASM, encoded by Smpd1 gene) controls autophagy maturation in coronary arterial SMCs. Here, we demonstrate that PDGF-BB stimulation causes a myofibroblast-like non-canonical synthetic phenotype transition in Smpd1^−/− SMCs. These non-canonical phenotypic changes induced by PDGF-BB in Smpd1^−/− SMCs were characterized by increased expression of fibroblast-specific protein (FSP-1), massive deposition of collagen type I, decreased cell size, elevated inflammatory status with enhanced cytokine release and adhesion molecule expression. Mechanistically, PDGF-BB induces prolonged Akt activation that causes decreased autophagosome biogenesis and thereby exaggerates p62/SQSTM1 accumulation in Smpd1^−/− SMCs. More importantly, Akt inhibition or p62/SQSTM1 gene silencing attenuates PDGF-BB-induced phenotypic changes in Smpd1^−/− SMCs. This first demonstration of a p62/SQSTM1-dependent myofibroblast-like phenotypic transition in Smpd1^−/− SMCs suggests that ASM-mediated autophagy pathway contributes to maintaining the arterial smooth muscle homeostasis in situation of vascular remodeling during atherosclerosis.

Using deep convolutional neural networks to identify and classify tumor-associated stroma in diagnostic breast biopsies

The breast stromal microenvironment is a pivotal factor in breast cancer development, growth and metastases. Although pathologists often detect morphologic changes in stroma by light microscopy, visual classification of such changes is subjective and non-quantitative, limiting its diagnostic utility. To gain insights into stromal changes associated with breast cancer, we applied automated machine learning techniques to digital images of 2387 hematoxylin and eosin stained tissue sections of benign and malignant image-guided breast biopsies performed to investigate mammographic abnormalities among 882 patients, ages 40-65 years, that were enrolled in the Breast Radiology Evaluation and Study of Tissues (BREAST) Stamp Project. Using deep convolutional neural networks, we trained an algorithm to discriminate between stroma surrounding invasive cancer and stroma from benign biopsies. In test sets (928 whole-slide images from 330 patients), this algorithm could distinguish biopsies diagnosed as invasive cancer from benign biopsies solely based on the stromal characteristics (area under the receiver operator characteristics curve = 0.962). Furthermore, without being trained specifically using ductal carcinoma in situ as an outcome, the algorithm detected tumor-associated stroma in greater amounts and at larger distances from grade 3 versus grade 1 ductal carcinoma in situ. Collectively, these results suggest that algorithms based on deep convolutional neural networks that evaluate only stroma may prove useful to classify breast biopsies and aid in understanding and evaluating the biology of breast lesions.

Effects of 3-Tetrazolyl Methyl-3-Hydroxy-Oxindole Hybrid (THOH) on Cell Proliferation, Apoptosis, and G2/M Cell Cycle Arrest Occurs by Targeting Platelet-Derived Growth Factor D (PDGF-D) and the MEK/ERK Signaling Pathway in Human Lung Cell Lines SK-LU-1, A549, and A-427

Background

The aim of this study was to evaluate the effects of 3-tetrazolyl methyl-3-hydroxy-oxindole hybrid (THOH) on cell proliferation, apoptosis, and the cell cycle in human lung cancer cell lines SK-LU-1, A549, and A-427, and the normal lung fibroblast cell line, MRC-5, in vitro.

Material/Methods

Human lung adenocarcinoma cells SK-LU-1, A549, and A-427, and the normal lung fibroblast cells, MRC-5 were cultured and treated with increasing concentrations of 10 mM of a stock solution of THOH in dimethyl sulfoxide (DMSO). An MTT cell proliferation assay was used. Cell apoptosis and the cell cycle were studied using fluorescence-activated cell sorting (FACs) with fluorescein isothiocyanate (FITC), Annexin-V, propidium iodide (PI), and nuclear staining with 4′,6-diamidino-2-phenylindole (DAPI). DNA damage was measured using the comet (single-cell gel electrophoresis) assay. Cell migration was evaluated using a wound healing assay, and Western blotting was used to measure protein expression levels.

Results

Treatment of SK-LU-1 cells with THOH inhibited cell migration. Treatment of lung cancer cells, SK-LU-1, A549, and A-427, with THOH inhibited cell proliferation, with the most marked inhibition found in the SK-LU-1 lung cancer cells (IC₅₀, 12 μM). Treatment of lung cancer cells, SK-LU-1, A549, and A-427, with THOH increased cell apoptosis, resulted in G2/M cell cycle arrest, and inhibited both the platelet-derived growth factor D (PDGF-D) and MEK/ERK signaling pathways.

Conclusions

Treatment of adenocarcinoma cells, SK-LU-1, A549, and A-427, with THOH inhibited cell proliferation, apoptosis, and resulted in G2/M cell cycle arrest by targeting PDGF-D and the MEK/ERK signaling pathway.

Endoglin Expression on Cancer-Associated Fibroblasts Regulates Invasion and Stimulates Colorectal Cancer Metastasis

PURPOSE

Cancer-associated fibroblasts (CAF) are a major component of the colorectal cancer tumor microenvironment. CAFs play an important role in tumor progression and metastasis, partly through TGF-β signaling pathway. We investigated whether the TGF-β family coreceptor endoglin is involved in CAF-mediated invasion and metastasis.

EXPERIMENTAL DESIGN

CAF-specific endoglin expression was studied in colorectal cancer resection specimens using IHC and related to metastases-free survival. Endoglin-mediated invasion was assessed in vitro by transwell invasion, using primary colorectal cancer-derived CAFs. Effects of CAF-specific endoglin expression on tumor cell invasion were investigated in a colorectal cancer zebrafish model, whereas liver metastases were assessed in a mouse model.

RESULTS

CAFs specifically at invasive borders of colorectal cancer express endoglin and increased expression intensity correlated with increased disease stage. Endoglin-expressing CAFs were also detected in lymph node and liver metastases, suggesting a role in colorectal cancer metastasis formation. In stage II colorectal cancer, CAF-specific endoglin expression at invasive borders correlated with poor metastasis-free survival. In vitro experiments revealed that endoglin is indispensable for bone morphogenetic protein (BMP)-9-induced signaling and CAF survival. Targeting endoglin using the neutralizing antibody TRC105 inhibited CAF invasion in vitro. In zebrafish, endoglin-expressing fibroblasts enhanced colorectal tumor cell infiltration into the liver and decreased survival. Finally, CAF-specific endoglin targeting with TRC105 decreased metastatic spread of colorectal cancer cells to the mouse liver.

CONCLUSIONS

Endoglin-expressing CAFs contribute to colorectal cancer progression and metastasis. TRC105 treatment inhibits CAF invasion and tumor metastasis, indicating an additional target beyond the angiogenic endothelium, possibly contributing to beneficial effects reported during clinical evaluations.See related commentary by Becker and LeBleu, p. 6110.

Organotypic three-dimensional assays based on human leiomyoma-derived matrices

Alongside cancer cells, tumours exhibit a complex stroma containing a repertoire of cells, matrix molecules and soluble factors that actively crosstalk between each other. Recognition of this multifaceted concept of the tumour microenvironment (TME) calls for authentic TME mimetics to study cancer in vitro. Traditionally, tumourigenesis has been investigated in non-human, three-dimensional rat type I collagen containing organotypic discs or by means of mouse sarcoma-derived gel, such as Matrigel^®. However, the molecular compositions of these simplified assays do not properly simulate human TME. Here, we review the main properties and benefits of using human leiomyoma discs and their matrix Myogel for in vitro assays. Myoma discs are practical for investigating the invasion of cancer cells, as are cocultures of cancer and stromal cells in a stiff, hypoxic TME mimetic. Myoma discs contain soluble factors and matrix molecules commonly present in neoplastic stroma. In Transwell, IncuCyte, spheroid and sandwich assays, cancer cells move faster and form larger colonies in Myogel than in Matrigel^®. Additionally, Myogel can replace Matrigel^® in hanging-drop and tube-formation assays. Myogel also suits three-dimensional drug testing and extracellular vesicle interactions. To conclude, we describe the application of our myoma-derived matrices in 3D in vitro cancer assays.

This article is part of the discussion meeting issue ‘Extracellular vesicles and the tumour microenvironment’.

Modeling triple-negative breast cancer heterogeneity: Effects of stromal macrophages, fibroblasts and tumor vasculature

A hallmark of breast tumors is its spatial heterogeneity that includes its distribution of cancer stem cells and progenitor cells, but also heterogeneity in the tumor microenvironment. In this study we focus on the contributions of stromal cells, specifically macrophages, fibroblasts, and endothelial cells on tumor progression. We develop a computational model of triple-negative breast cancer based on our previous work and expand it to include macrophage infiltration, fibroblasts, and angiogenesis. In vitro studies have shown that the secretomes of tumor-educated macrophages and fibroblasts increase both the migration and proliferation rates of triple-negative breast cancer cells. In vivo studies also demonstrated that blocking signaling of selected secreted factors inhibits tumor growth and metastasis in mouse xenograft models. We investigate the influences of increased migration and proliferation rates on tumor growth, the effect of the presence on fibroblasts or macrophages on growth and morphology, and the contributions of macrophage infiltration on tumor growth. We find that while the presence of macrophages increases overall tumor growth, the increase in macrophage infiltration does not substantially increase tumor growth and can even stifle tumor growth at excessive rates.

Role of Stromal Paracrine Signals in Proliferative Diseases of the Aging Human Prostate

Androgens are essential for the development, differentiation, growth, and function of the prostate through epithelial–stromal interactions. However, androgen concentrations in the hypertrophic human prostate decrease significantly with age, suggesting an inverse correlation between androgen levels and proliferative diseases of the aging prostate. In elderly males, age- and/or androgen-related stromal remodeling is spontaneously induced, i.e., increased fibroblast and myofibroblast numbers, but decreased smooth muscle cell numbers in the prostatic stroma. These fibroblasts produce not only growth factors, cytokines, and extracellular matrix proteins, but also microRNAs as stromal paracrine signals that stimulate prostate epithelial cell proliferation. Surgical or chemical castration is the standard systemic therapy for patients with advanced prostate cancer. Androgen deprivation therapy induces temporary remission, but the majority of patients eventually progress to castration-resistant prostate cancer, which is associated with a high mortality rate. Androgen deprivation therapy-induced stromal remodeling may be involved in the development and progression of castration-resistant prostate cancer. In the tumor microenvironment, activated fibroblasts stimulating prostate cancer cell proliferation are called carcinoma-associated fibroblasts. In this review, we summarize the role of stromal paracrine signals in proliferative diseases of the aging human prostate and discuss the potential clinical applications of carcinoma-associated fibroblast-derived exosomal microRNAs as promising biomarkers.

TGFβ1-induced expression of caldesmon mediates epithelial-mesenchymal transition

Epithelial-mesenchymal transition (EMT) is an important process that mediates organ development and wound healing, and in pathological contexts, it can contribute to the progression of fibrosis and cancer. During EMT, cells exhibit marked changes in cytoskeletal organization and increased expression of a variety of actin associated proteins. Here, we sought to determine the role of caldesmon in mediating EMT in response to transforming growth factor (TGF)-β1. We find that the expression level and phosphorylation state of caldesmon increase as a function of time following induction of EMT by TGFβ1 and these changes in caldesmon correlate with increased focal adhesion number and size and increased cell contractility. Knockdown and forced expression of caldesmon in epithelial cells reveals that caldesmon expression plays an important role in regulating the expression of the myofibroblast marker alpha smooth muscle actin. Results from these studies provide insight into the role of cytoskeletal associated proteins in the regulation of EMT and may suggest ways to target the cell cytoskeleton for regulating EMT processes.