Loss of TGF-beta type II receptor in fibroblasts promotes mammary carcinoma growth and invasion through upregulation of TGF-alpha-, MSP- and HGF-mediated signaling networks

Volumetric analysis of the terminal ductal lobular unit architecture and cell phenotypes in the human breast

The major lactiferous ducts of the human breast branch out and end at terminal ductal lobular units (TDLUs). Despite their functional and clinical importance, the three-dimensional (3D) architecture of TDLUs has remained undetermined. Our quantitative and volumetric imaging of healthy human breast tissue demonstrates that highly branched TDLUs, which exhibit increased proliferation, are uncommon in the resting tissue regardless of donor age, parity, or hormonal contraception. Overall, TDLUs have a consistent shape and branch parameters, and they contain a main subtree that dominates in bifurcation events and exhibits a more duct-like keratin expression pattern. Simulation of TDLU branching morphogenesis in three dimensions suggests that evolutionarily conserved mechanisms regulate mammary gland branching in humans and mice despite their anatomical differences. In all, our data provide structural insight into 3D anatomy and branching of the human breast and exemplify the power of volumetric imaging in gaining a deeper understanding of breast biology.

Emerging Role of Fibroblasts in Vitiligo: A Formerly Underestimated Rising Star

Vitiligo is a disfiguring depigmentation disorder characterized by loss of melanocytes. Although numerous studies have been conducted on the pathogenesis of vitiligo, the underlying mechanisms remain unclear. Although most studies have focused on melanocytes and keratinocytes, growing evidence suggests the involvement of dermal fibroblasts, residing deeper in the skin. This review aims to elucidate the role of fibroblasts in both the physiological regulation of skin pigmentation and their pathological contribution to depigmentation, with the goal of shedding light on the involvement of fibroblasts in vitiligo. The topics covered in this review include alterations in the secretome, premature senescence, autophagy dysfunction, abnormal extracellular matrix, autoimmunity, and metabolic changes.

TGF-β signaling in health, disease, and therapeutics

Transforming growth factor (TGF)-β is a multifunctional cytokine expressed by almost every tissue and cell type. The signal transduction of TGF-β can stimulate diverse cellular responses and is particularly critical to embryonic development, wound healing, tissue homeostasis, and immune homeostasis in health. The dysfunction of TGF-β can play key roles in many diseases, and numerous targeted therapies have been developed to rectify its pathogenic activity. In the past decades, a large number of studies on TGF-β signaling have been carried out, covering a broad spectrum of topics in health, disease, and therapeutics. Thus, a comprehensive overview of TGF-β signaling is required for a general picture of the studies in this field. In this review, we retrace the research history of TGF-β and introduce the molecular mechanisms regarding its biosynthesis, activation, and signal transduction. We also provide deep insights into the functions of TGF-β signaling in physiological conditions as well as in pathological processes. TGF-β-targeting therapies which have brought fresh hope to the treatment of relevant diseases are highlighted. Through the summary of previous knowledge and recent updates, this review aims to provide a systematic understanding of TGF-β signaling and to attract more attention and interest to this research area.

Transcriptome analysis reveals differences in cell cycle, growth and migration related genes that distinguish fibroblasts derived from pre-invasive and invasive breast cancer

Background/Introduction

As the most common form of pre-invasive breast cancer, ductal carcinoma in situ (DCIS) affects over 50,000 women in the US annually. Despite standardized treatment involving lumpectomy and radiation therapy, up to 25% of patients with DCIS experience disease recurrence often with invasive ductal carcinoma (IDC), indicating that a subset of patients may be under-treated. As most DCIS cases will not progress to invasion, many patients may experience over-treatment. By understanding the underlying processes associated with DCIS to IDC progression, we can identify new biomarkers to determine which DCIS cases may become invasive and improve treatment for patients. Accumulation of fibroblasts in IDC is associated with disease progression and reduced survival. While fibroblasts have been detected in DCIS, little is understood about their role in DCIS progression.

Goals

We sought to determine 1) whether DCIS fibroblasts were similar or distinct from normal and IDC fibroblasts at the transcriptome level, and 2) the contributions of DCIS fibroblasts to breast cancer progression.

Methods

Fibroblasts underwent transcriptome profiling and pathway analysis. Significant DCIS fibroblast-associated genes were further analyzed in existing breast cancer mRNA databases and through tissue array immunostaining. Using the sub-renal capsule graft model, fibroblasts from normal breast, DCIS and IDC tissues were co-transplanted with DCIS.com breast cancer cells.

Results

Through transcriptome profiling, we found that DCIS fibroblasts were characterized by unique alterations in cell cycle and motility related genes such as PKMYT1, TGF-α, SFRP1 and SFRP2, which predicted increased cell growth and invasion by Ingenuity Pathway Analysis. Immunostaining analysis revealed corresponding increases in expression of stromal derived PKMYT1, TGF-α and corresponding decreases in expression of SFRP1 and SFRP2 in DCIS and IDC tissues. Grafting studies in mice revealed that DCIS fibroblasts enhanced breast cancer growth and invasion associated with arginase-1+ cell recruitment.

Conclusion

DCIS fibroblasts are phenotypically distinct from normal breast and IDC fibroblasts, and play an important role in breast cancer growth, invasion, and recruitment of myeloid cells. These studies provide novel insight into the role of DCIS fibroblasts in breast cancer progression and identify some key biomarkers associated with DCIS progression to IDC, with important clinical implications.

Epithelial-intrinsic defects in TGFβR signaling drive local allergic inflammation manifesting as eosinophilic esophagitis

Allergic diseases are a global health challenge. Individuals harboring loss-of-function variants in transforming growth factor-β receptor (TGFβR) genes have an increased prevalence of allergic disorders, including eosinophilic esophagitis. Allergic diseases typically localize to mucosal barriers, implicating epithelial dysfunction as a cardinal feature of allergic disease. Here, we describe an essential role for TGFβ in the control of tissue-specific immune homeostasis that provides mechanistic insight into these clinical associations. Mice expressing a TGFβR1 loss-of-function variant identified in atopic patients spontaneously develop disease that clinically, immunologically, histologically, and transcriptionally recapitulates eosinophilic esophagitis. In vivo and in vitro, TGFβR1 variant-expressing epithelial cells are hyperproliferative, fail to differentiate properly, and overexpress innate proinflammatory mediators, which persist in the absence of lymphocytes or external allergens. Together, our results support the concept that TGFβ plays a fundamental, nonredundant, epithelial cell-intrinsic role in controlling tissue-specific allergic inflammation that is independent of its role in adaptive immunity.

Resistance of MMTV-NeuT/ATTAC mice to anti-PD-1 immune checkpoint therapy is associated with macrophage infiltration and Wnt pathway expression

One of the central challenges for cancer therapy is the identification of factors in the tumor microenvironment that increase tumor progression and immune tolerance. In breast cancer, fibrosis is a histopathologic criterion for invasive cancer and poor survival that results from inflammatory factors and remodeling of the extracellular matrix to produce an immune tolerant microenvironment. To determine whether tolerance is associated with the immune checkpoint, Programmed Cell Death 1 (PD-1), NeuT/ATTAC mice, a conditional model of mammary fibrosis that we recently developed, were administered a murine-specific anti-PD-1 mAb related to pembrolizumab, and drug response was monitored by tumor development, imaging mass cytometry, immunohistochemistry and tumor gene expression by RNAseq. Tumor progression in NeuT/ATTAC mice was unaffected by weekly injection of anti-PD-1 over four months. Insensitivity to anti-PD-1 was associated with several processes, including increased tumor-associated macrophages (TAM), epithelial to mesenchymal transition (EMT), fibroblast proliferation, an enhanced extracellular matrix and the Wnt signaling pathway, including increased expression of Fzd5, Wnt5a, Vimentin, Mmp3, Col2a1 and Tgfβ1. These results suggest potential therapeutic avenues that may enhance PD-1 immune checkpoint sensitivity, including the use of tumor microenvironment targeted agents and Wnt pathway inhibitors.

Transforming Growth Factor-Beta Orchestrates Tumour and Bystander Cells in B-Cell Non-Hodgkin Lymphoma

Transforming growth factor-beta (TGFB) is a critical regulator of normal haematopoiesis. Dysregulation of the TGFB pathway is associated with numerous haematological malignancies including myelofibrosis, acute myeloid leukaemia, and lymphoid disorders. TGFB has classically been seen as a negative regulator of proliferation in haematopoiesis whilst stimulating differentiation and apoptosis, as required to maintain homeostasis. Tumours frequently develop intrinsic resistant mechanisms to homeostatic TGFB signalling to antagonise its tumour-suppressive functions. Furthermore, elevated levels of TGFB enhance pathogenesis through modulation of the immune system and tumour microenvironment. Here, we review recent advances in the understanding of TGFB signalling in B-cell malignancies with a focus on the tumour microenvironment. Malignant B-cells harbour subtype-specific alterations in TGFB signalling elements including downregulation of surface receptors, modulation of SMAD signalling proteins, as well as genetic and epigenetic aberrations. Microenvironmental TGFB generates a protumoural niche reprogramming stromal, natural killer (NK), and T-cells. Increasingly, evidence points to complex bi-directional cross-talk between cells of the microenvironment and malignant B-cells. A greater understanding of intercellular communication and the context-specific nature of TGFB signalling may provide further insight into disease pathogenesis and future therapeutic strategies.

Cancer Immunoediting: Elimination, Equilibrium, and Immune Escape in Solid Tumors

Emphasizing the dynamic processes between cancer and host immune system, the initially discovered concept of cancer immunosurveillance has been replaced by the current concept of cancer immunoediting consisting of three phases: elimination, equilibrium, and escape. Solid tumors composed of both cancer and host stromal cells are an example how the three phases of cancer immunoediting functionally evolve and how tumor shaped by the host immune system gets finally resistant phenotype. The elimination, equilibrium, and escape have been described in this chapter in details, including the role of immune surveillance, cancer dormancy, disruption of the antigen-presenting machinery, tumor-infiltrating immune cells, resistance to apoptosis, as well as the function of tumor stroma, microvesicles, exosomes, and inflammation.

Insights into Melanoma Fibroblast Populations and Therapeutic Strategy Perspectives: Friends or Foes?

Cutaneous melanoma (CM) is an aggressive and highly metastatic solid tumor associated with drug resistance. Before 2011, despite therapies based on cytokines or molecules inhibiting DNA synthesis, metastatic melanoma led to patient death within 18 months from diagnosis. However, recent studies on bidirectional interactions between melanoma cells and tumor microenvironment (TME) have had a significant impact on the development of new therapeutic strategies represented by targeted therapy and immunotherapy. In particular, the heterogeneous stromal fibroblast populations, including fibroblasts, fibroblast aggregates, myofibroblasts, and melanoma associated fibroblasts (MAFs), represent the most abundant cell population of TME and regulate cancer growth differently. Therefore, in this perspective article, we have highlighted the different impacts of fibroblast populations on cancer development and growth. In particular, we focused on the role of MAFs in sustaining melanoma cell survival, proliferation, migration and invasion, drug resistance, and immunoregulation. The important role of constitutively activated MAFs in promoting CM growth and immunoediting makes this cell type a promising target for cancer therapy.

Animal and Human Models of Tissue Repair and Fibrosis: An Introduction

Reductionist cell culture systems are not only convenient but essential to understand molecular mechanisms of myofibroblast activation and action in carefully controlled conditions. However, tissue myofibroblasts do not act in isolation and the complexity of tissue repair and fibrosis in humans cannot be captured even by the most elaborate culture models. Over the past five decades, numerous animal models have been developed to study different aspects of myofibroblast biology and interactions with other cells and extracellular matrix. The underlying principles can be broadly classified into: (1) organ injury by trauma such as prototypical full thickness skin wounds or burns; (2) mechanical challenges, such as pressure overload of the heart by ligature of the aorta or the pulmonary vein; (3) toxic injury, such as administration of bleomycin to lungs and carbon tetrachloride to the liver; (4) organ infection with viruses, bacteria, and parasites, such as nematode infections of liver; (5) cytokine and inflammatory models, including local delivery or viral overexpression of active transforming growth factor beta; (6) "lifestyle" and metabolic models such as high-fat diet; and (7) various genetic models. We will briefly summarize the most widely used mouse models used to study myofibroblasts in tissue repair and fibrosis as well as genetic tools for manipulating myofibroblast repair functions in vivo.

Adenosine/TGFβ axis in regulation of mammary fibroblast functions

Cancer associated fibroblasts (CAF) play a key role in cancer progression and metastasis. Diminished TGFβ response on CAF correlates with poor outcome and recurrence in cancer patients. Mechanisms behind lost TGFβ signaling on CAF are poorly understood, but, utilizing MMTV-PyMT mouse model, we have previously demonstrated that in tumor microenvironment myeloid cells, producing adenosine, contribute to downregulated TGFβ signaling on CAFs. In the current work, we performed serial in vitro studies to investigate the role of adenosine/TGFβ axis in mouse mammary fibroblast functions, i.e., proliferation, protein expression, migration, and contractility. We found that adenosine analog NECA diminished TGFβ-induced CCL5 and MMP9 expression. Additionally, we discovered that NECA completely inhibited effect of TGFβ to upregulate αSMA, key protein of cytoskeletal rearrangements, necessary for migration and contractility of fibroblasts. Our results show that TGFβ increases contractility of mouse mammary fibroblasts and human fibroblast cell lines, and NECA attenuates theses effects. Using pharmacological approach and genetically modified animals, we determined that NECA effects on TGFβ pathway occur via A_2A/A_2B adenosine receptor—AC—PKA dependent manner. Using isolated CD11b⁺ cells from tumor tissue of CD73-KO and CD39-KO animals in co-culture experiments with ATP and AMP, we confirmed that myeloid cells can affect functions of mammary fibroblasts through adenosine signaling. Our data suggest a novel mechanism of interaction between adenosine and TGFβ signaling pathways that can impact phenotype of fibroblasts in a tumor microenvironment.

Influence of Tumor Microenvironment and Fibroblast Population Plasticity on Melanoma Growth, Therapy Resistance and Immunoescape

Cutaneous melanoma (CM) tissue represents a network constituted by cancer cells and tumor microenvironment (TME). A key feature of CM is the high structural and cellular plasticity of TME, allowing its evolution with disease and adaptation to cancer cell and environmental alterations. In particular, during melanoma development and progression each component of TME by interacting with each other and with cancer cells is subjected to dramatic structural and cellular modifications. These alterations affect extracellular matrix (ECM) remodelling, phenotypic profile of stromal cells, cancer growth and therapeutic response. The stromal fibroblast populations of the TME include normal fibroblasts and melanoma-associated fibroblasts (MAFs) that are highly abundant and flexible cell types interacting with melanoma and stromal cells and differently influencing CM outcomes. The shift from the normal microenvironment to TME and from normal fibroblasts to MAFs deeply sustains CM growth. Hence, in this article we review the features of the normal microenvironment and TME and describe the phenotypic plasticity of normal dermal fibroblasts and MAFs, highlighting their roles in normal skin homeostasis and TME regulation. Moreover, we discuss the influence of MAFs and their secretory profiles on TME remodelling, melanoma progression, targeted therapy resistance and immunosurveillance, highlighting the cellular interactions, the signalling pathways and molecules involved in these processes.

Mapping the Metabolic Networks of Tumor Cells and Cancer-Associated Fibroblasts

Metabolism is considered to be the core of all cellular activity. Thus, extensive studies of metabolic processes are ongoing in various fields of biology, including cancer research. Cancer cells are known to adapt their metabolism to sustain high proliferation rates and survive in unfavorable environments with low oxygen and nutrient concentrations. Hence, targeting cancer cell metabolism is a promising therapeutic strategy in cancer research. However, cancers consist not only of genetically altered tumor cells but are interwoven with endothelial cells, immune cells and fibroblasts, which together with the extracellular matrix (ECM) constitute the tumor microenvironment (TME). Cancer-associated fibroblasts (CAFs), which are linked to poor prognosis in different cancer types, are one important component of the TME. CAFs play a significant role in reprogramming the metabolic landscape of tumor cells, but how, and in what manner, this interaction takes place remains rather unclear. This review aims to highlight the metabolic landscape of tumor cells and CAFs, including their recently identified subtypes, in different tumor types. In addition, we discuss various in vitro and in vivo metabolic techniques as well as different in silico computational tools that can be used to identify and characterize CAF-tumor cell interactions. Finally, we provide our view on how mapping the complex metabolic networks of stromal-tumor metabolism will help in finding novel metabolic targets for cancer treatment.

Organoid-based ex vivo reconstitution of Kras-driven pancreatic ductal carcinogenesis

The organoid culture technique has been recently applied to modeling carcinogenesis in several organs. To further explore its potential and gain novel insights into tumorigenesis, we here investigated whether pancreatic ductal adenocarcinoma (PDA) could be generated as subcutaneous tumors in immunocompromised nude mice, by genetic engineering of normal organoids. As expected, acute induction of KrasG12Din vitro occasionally led to development of tiny nodules compatible with early lesions known as pancreatic intraepithelial neoplasia (PanIN). KrasG12D-expressing cells were enriched after inoculation in the subcutis, yet proved rather declined during culture, suggesting that its advantage might depend on surrounding environments. Depletion of growth factors or concurrent Trp53 deletion resulted in its robust enrichment, invariably leading to development of PanIN or large high-grade adenocarcinoma, respectively, consistent with in vivo mouse studies for the same genotype. Progression from PanIN was also recapitulated by subsequent knockdown of common tumor suppressors, whereas the impact of Tgfbr2 deletion was only partially recapitulated, illustrating genotype-dependent requirement of the pancreatic niche for tumorigenesis. Intriguingly, analysis of tumor-derived organoids revealed that KrasG12D-expressing cells with spontaneous deletion of wild-type Kras were positively selected and exhibited an aging-related mutation signature in nude mice, mirroring the pathogenesis of human PDA, and that the sphere-forming potential and orthotopic tumorigenicity in syngenic mice were significantly augmented. These observations highlighted the relevance of the subcutis of nude mice in promoting PDA development despite its ectopic nature. Taken together, pancreatic carcinogenesis could be considerably recapitulated with organoids, which would probably serve as a novel disease model.

Expression of Podoplanin in Mammary Cancers in Female Dogs

BACKGROUND/AIM

Mammary neoplasms are very common tumours in female dogs. Cancer-associated fibroblasts (CAFs) play an important role in the oncogenesis process. One of the useful proteins used in the diagnostics of CAFs cells is podoplanin (PDPN). The aim of our study was to assess the expression of PDPN in mammary cancer in female dogs.

MATERIALS AND METHODS

Our study cohort included 61 cancers and 21 adenomas of the mammary tumour in bitches. Expression of podoplanin, Ki-67 and HER2 was determined using the Immunohistochemical (IHC) method. PDPN expression at the mRNA level was determined using real-time PCR.

RESULTS

Expression of PDPN in CAFs was observed in 22.9% of cases of mammary cancers in bitches, with no PDPN expression in adenomas. A positive correlation was found between the expression of PDPN in CAFs and the grade of histological malignancy and expression of Ki-67.

CONCLUSION

PDPN plays a significant role during the process of carcinogenesis of mammary tumours in female dogs.

Myeloid Cell-Derived TGFβ Signaling Regulates ECM Deposition in Mammary Carcinoma via Adenosine-Dependent Mechanisms

TGFβ plays a crucial role in the tumor microenvironment by regulating cell-cell and cell-stroma interactions. We previously demonstrated that TGFβ signaling on myeloid cells regulates expression of CD73, a key enzyme for production of adenosine, a protumorigenic metabolite implicated in regulation of tumor cell behaviors, immune response, and angiogenesis. Here, using an MMTV-PyMT mouse mammary tumor model, we discovered that deletion of TGFβ signaling on myeloid cells (PyMT/TGFβRII^LysM) affects extracellular matrix (ECM) formation in tumor tissue, specifically increasing collagen and decreasing fibronectin deposition. These changes were associated with mitigated tumor growth and reduced metastases. Reduced TGFβ signaling on fibroblasts was associated with their proximity to CD73⁺ myeloid cells in tumor tissue. Consistent with these findings, adenosine significantly downregulated TGFβ signaling on fibroblasts, an effect regulated by A_2A and A_2B adenosine receptors. METABRIC dataset analysis revealed that patients with triple-negative breast cancer and basal type harbored a similar signature of adenosine and ECM profiles; high expression of A_2B adenosine receptors correlated with decreased expression of Col1 and was associated with poor outcome. Taken together, our studies reveal a new role for TGFβ signaling on myeloid cells in tumorigenesis. This discovered cross-talk between TGFβ/CD73 on myeloid cells and TGFβ signaling on fibroblasts can contribute to ECM remodeling and protumorigenic actions of cancer-associated fibroblasts. SIGNIFICANCE: TGFβ signaling on fibroblasts is decreased in breast cancer, correlates with poor prognosis, and appears to be driven by adenosine that accelerates tumor progression and metastasis via ECM remodeling.

The prognostic importance of VEGF-A, PDGF-BB and c-MET in patients with metastatic colorectal cancer

INTRODUCTION

We aimed to assess the effect of VEGF-A, PDGF-BB, and c-Met expression levels on survival in patients with metastatic colorectal cancer receiving bevacizumab therapies.

PATIENTS AND METHODS

A total of 105 patients diagnosed with metastatic colorectal cancer between the years 2006 and 2016 were included in the research retrospectively.

RESULTS

The progression-free survival (PFS) durations of patients with high expression levels of VEGF-A and with low expression levels of VEGF-A were 11 months and 10 months (p = 0.44), respectively. The PFS durations of patients with high PDGF-BB expression and low PDGF-BB expression were 12 months and 10 months (p = 0.16), respectively, while the PFS durations of patients with high and low c-Met expression were 8 months and 13 months (p = 0.005), respectively. Metastatic overall survival was 27 months and 18 months (p = 0.05) in patients with high and low VEGF-A expression levels, respectively, 31 months and 21 months (p = 0.16) in patients with high and low PDGF-BB expression levels, respectively, and 21 months and 26 months (p = 0.11) in patients with high and low c-Met expression levels, respectively.

CONCLUSION

The results of this research revealed a high c-Met expression relationship with worse PFS and low VEGF-A expression associated with poor metastatic overall survival in patients with metastatic colorectal cancer receiving bevacizumab therapies.

Heterogeneity of human prostate carcinoma-associated fibroblasts implicates a role for subpopulations in myeloid cell recruitment

BACKGROUND

Carcinoma-associated fibroblasts (CAF) are a heterogeneous group of cells within the tumor microenvironment (TME) that can promote tumorigenesis in the prostate. By understanding the mechanism(s) by which CAF contributes to tumor growth, new therapeutic targets for the management of this disease may be identified. These studies determined whether unique sub-populations of human prostate CAF can be identified and functionally characterized.

METHODS

Single-cell RNA-seq of primary human prostate CAF followed by unsupervised clustering was utilized to generate cell clusters based on differentially expressed (DE) gene profiles. Potential communication between CAF and immune cells was analyzed using in vivo tissue recombination by combining CAF or normal prostate fibroblasts (NPF) with non-tumorigenic, initiated prostate epithelial BPH-1 cells. Resultant grafts were assessed for inflammatory cell recruitment.

RESULTS

Clustering of 3321 CAF allows for visualization of six subpopulations, demonstrating heterogeneity within CAF. Sub-renal capsule recombination assays show that the presence of CAF significantly increases myeloid cell recruitment to resultant tumors. This is supported by significantly increased expression of chemotactic chemokines CCL2 and CXCL12 in large clusters compared to other subpopulations. Bayesian analysis topologies also support differential communication signals between chemokine-related genes of individual clusters. Migration of THP-1 monocyte cells in vitro is stimulated in the presence of CAF conditioned medium (CM) compared with NPF CM. Further in vitro analyses suggest that CAF-derived chemokine CCL2 may be responsible for CAF-stimulated migration of THP-1 cells, since neutralization of this chemokine abrogates migration capacity.

CONCLUSIONS

CAF clustering based on DE gene expression supports the concept that clusters have unique functions within the TME, including a role in immune/inflammatory cell recruitment. These data suggest that CCL2 produced by CAF may be involved in the recruitment of inflammatory cells, but may also directly regulate the growth of the tumor. Further studies aimed at characterizing the subpopulation(s) of CAF which promote immune cell recruitment to the TME and/or stimulate prostate cancer growth and progression will be pursued.

Epigenetic changes in fibroblasts drive cancer metabolism and differentiation

Genomic changes that drive cancer initiation and progression contribute to the co-evolution of the adjacent stroma. The nature of the stromal reprogramming involves differential DNA methylation patterns and levels that change in response to the tumor and systemic therapeutic intervention. Epigenetic reprogramming in carcinoma-associated fibroblasts are robust biomarkers for cancer progression and have a transcriptional impact that support cancer epithelial progression in a paracrine manner. For prostate cancer, promoter hypermethylation and silencing of the RasGAP, RASAL3 that resulted in the activation of Ras signaling in carcinoma-associated fibroblasts. Stromal Ras activity initiated a process of macropinocytosis that provided prostate cancer epithelia with abundant glutamine for metabolic conversion to fuel its proliferation and a signal to transdifferentiate into a neuroendocrine phenotype. This epigenetic oncogenic metabolic/signaling axis seemed to be further potentiated by androgen receptor signaling antagonists and contributed to therapeutic resistance. Intervention of stromal signaling may complement conventional therapies targeting the cancer cell.

Current status and future prospects of transforming growth factor-β as a potential prognostic and therapeutic target in the treatment of breast cancer

The transforming growth factor-β (TGF-β) signaling pathway is one of the important pathways involved in the cancer cell proliferation, invasion, migration, angiogenesis, apoptosis, as well as in metastasis by agitation or invasion of metastasis-related factors, including matrix metalloproteinase (MMP), epithelial-to-mesenchymal transition (EMT), tumor microenvironment (TME), cancer stem cells (CSCs), and cell adhesion molecules (CAMs). These data suggest its potential value as a therapeutic object in the treatment of malignancies including breast cancer. Several pharmacological approaches have been established to suppress TGF-β pathway; such as vaccines, small molecular inhibitors, antisense oligonucleotides, and monoclonal antibodies. Some of these are now approved by the US Food and Drug Administration for targeting the TGF-β signaling pathway. This study attempts to summarize the current data about the functions of TGF-β in cancer cells, and their probable application in the cancer therapy with a specific emphasis on recent preclinical and clinical research in the treatment of breast cancer and its prognostic value.

Cancer-Associated Fibroblasts Enhance Survival and Progression of the Aggressive Pancreatic Tumor Via FGF-2 and CXCL8

Pancreatic ductal adenocarcinoma remains one of the most challenging human cancers. Desmoplasia is predominant in this disease exhibiting a strong stromal reaction with an abundance of the cancer-associated fibroblasts (CAFs). We aimed in this study to investigate the reciprocal interaction between the tumor cells and the CAFs and its effect on tumor cells survival. We hypothesized that the survival of pancreatic cancer cell with aggressive phenotype is modulated by the Interactions between malignant pancreatic tumor cells and surrounding CAFs. To examine this, we utilized co-culture methods where tumor cells with different malignant potentials, HPAF (low) HPAF-CD11 (moderate/high) co-cultured with CAFs. CAFs-conditioned media increased the growth of HPAF-CD11 but not HPAF cells and increased CXCL8 levels highly in HPAF-CD11 and slightly in HPAF. The growth stimulatory effect and elevated CXCL8 level caused by CAFs-conditioned media were diminished by neutralizing the fibroblast growth factor-2 (FGF-2). In addition, conditioned media of HPAF-CD11 increased CAFs cell number whereas that of HPAF did not, and these effects were suppressed by neutralizing CXCL8. Furthermore, data from gene expression microarray study exhibited different expression profiles between HPAF and HPAF-CD11 when co-culture with CAFs. A significant increase in CXCL8 and FGF-2 expression was observed with HPAF-CD11/CAFs co-culture and to a lower extent with HPAF/CAFs co-culture. Together, these data demonstrate a paracrine bi-directional interaction between pancreatic tumor cells and the CAFs through CXCL8 and FGF-2 that helps the tumor growth. Future in-depth study of these pathways will assist in obtaining diagnostic and therapeutic tools for pancreatic ductal adenocarcinoma.

CXCL1 Derived from Mammary Fibroblasts Promotes Progression of Mammary Lesions to Invasive Carcinoma through CXCR2 Dependent Mechanisms

With improved screening methods, the numbers of abnormal breast lesions diagnosed in women have been increasing over time. However, it remains unclear whether these breast lesions will develop into invasive cancers. To more effectively predict the outcome of breast lesions and determine a more appropriate course of treatment, it is important to understand the underlying mechanisms that regulate progression of non-invasive lesions to invasive breast cancers. A hallmark of invasive breast cancers is the accumulation of fibroblasts. Fibroblast proliferation and activation in the mammary gland is in part regulated by the Transforming Growth Factor beta1 pathway (TGF-β). In animal models, TGF-β suppression of CCL2 and CXCL1 chemokine expression is associated with metastatic progression of mammary carcinomas. Here, we show that transgenic overexpression of the Polyoma middle T viral antigen in the mouse mammary gland of C57BL/6 mice results in slow growing non-invasive lesions that progress to invasive carcinomas in a stage dependent manner. Invasive carcinomas are associated with accumulation of fibroblasts that show decreased TGF-β expression and high levels of CXCL1, but not CCL2. Using co-transplant models, we show that decreased TGF-β signaling in fibroblasts contribute to mammary carcinoma progression through enhancement of CXCL1/CXCR2 dependent mechanisms. Using cell culture models, we show that CXCL1 mediated mammary carcinoma cell invasion through NF-κB, AKT, Stat3 and p42/44MAPK dependent mechanisms. These studies provide novel mechanistic insight into the progression of pre-invasive lesions and identify new stromal biomarkers, with important prognostic implications.

Stromal epigenetic alterations drive metabolic and neuroendocrine prostate cancer reprogramming

Prostate cancer is an androgen-dependent disease subject to interactions between the tumor epithelium and its microenvironment. Here, we found that epigenetic changes in prostatic cancer-associated fibroblasts (CAF) initiated a cascade of stromal-epithelial interactions. This facilitated lethal prostate cancer growth and development of resistance to androgen signaling deprivation therapy (ADT). We identified a Ras inhibitor, RASAL3, as epigenetically silenced in human prostatic CAF, leading to oncogenic Ras activity driving macropinocytosis-mediated glutamine synthesis. Interestingly, ADT further promoted RASAL3 epigenetic silencing and glutamine secretion by prostatic fibroblasts. In an orthotopic xenograft model, subsequent inhibition of macropinocytosis and glutamine transport resulted in antitumor effects. Stromal glutamine served as a source of energy through anaplerosis and as a mediator of neuroendocrine differentiation for prostate adenocarcinoma. Antagonizing the uptake of glutamine restored sensitivity to ADT in a castration-resistant xenograft model. In validating these findings, we found that prostate cancer patients on ADT with therapeutic resistance had elevated blood glutamine levels compared with those with therapeutically responsive disease (odds ratio = 7.451, P = 0.02). Identification of epigenetic regulation of Ras activity in prostatic CAF revealed RASAL3 as a sensor for metabolic and neuroendocrine reprogramming in prostate cancer patients failing ADT.

Stromal Fibroblasts Mediate Anti-PD-1 Resistance via MMP-9 and Dictate TGFβ Inhibitor Sequencing in Melanoma

Although anti-PD-1 therapy has improved clinical outcomes for select patients with advanced cancer, many patients exhibit either primary or adaptive resistance to checkpoint inhibitor immunotherapy. The role of the tumor stroma in the development of these mechanisms of resistance to checkpoint inhibitors remains unclear. We demonstrated that pharmacologic inhibition of the TGFβ signaling pathway synergistically enhanced the efficacy of anti-CTLA-4 immunotherapy but failed to augment anti-PD-1/PD-L1 responses in an autochthonous model of BRAF^V600E melanoma. Additional mechanistic studies revealed that TGFβ pathway inhibition promoted the proliferative expansion of stromal fibroblasts, thereby facilitating MMP-9-dependent cleavage of PD-L1 surface expression, leading to anti-PD-1 resistance in this model. Further work demonstrated that melanomas escaping anti-PD-1 therapy exhibited a mesenchymal phenotype associated with enhanced TGFβ signaling activity. Delayed TGFβ inhibitor therapy, following anti-PD-1 escape, better served to control further disease progression and was superior to a continuous combination of anti-PD-1 and TGFβ inhibition. This work illustrates that formulating immunotherapy combination regimens to enhance the efficacy of checkpoint blockade requires an in-depth understanding of the impact of these agents on the tumor microenvironment. These data indicated that stromal fibroblast MMP-9 may desensitize tumors to anti-PD-1 and suggests that TGFβ inhibition may generate greater immunologic efficacy when administered following the development of acquired anti-PD-1 resistance.See related Spotlight on p. 1444.

Genetic Modifiers of the Breast Tumor Microenvironment

Multiple nonmalignant cell types in the tumor microenvironment (TME) impact breast cancer risk, metastasis, and response to therapy, yet most heritable mechanisms that influence TME cell function and breast cancer outcomes are largely unknown. Breast cancer risk is ∼30% heritable and >170 genetic loci have been associated with breast cancer traits. However, the majority of candidate genes have poorly defined mechanistic roles in breast cancer biology. Research indicates that breast cancer risk modifiers directly impact cancer cells, yet it is equally plausible that some modifier alleles impact the nonmalignant TME. The objective of this review is to examine the list of current breast cancer candidate genes that may modify breast cancer risk and outcome through the TME.

Salinomycin nanoparticles interfere with tumor cell growth and the tumor microenvironment in an orthotopic model of pancreatic cancer

AIMS

Recently, salinomycin (SAL) has been reported to inhibit proliferation and induce apoptosis in various tumors. The aim of this study was to deliver SAL to orthotopic model of pancreatic cancer by the aid of poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs).

METHODS

The NPs were physico-chemically characterized and evaluated for cytotoxicity on luciferase-transduced AsPC-1 cells in vitro as well as implanted orthotopically into the pancreas of nude mice.

RESULTS

SAL (3.5 mg/kg every other day) blocked tumor growth by 52% compared to the control group after 3 weeks of therapy. Western blotting of tumor protein extracts indicated that SAL treatment leads to up-regulation of E-cadherin, β-catenin, and transforming growth factor beta receptor (TGFβR) expressions in AsPC-1 orthotopic tumor. Noteworthy, immunofluorescence staining of adjacent tumor sections showed that treatment with SAL NPs cause significant apoptosis in the tumor cells rather than the stroma. Further investigations also revealed that TGFβR2 over-expression was induced in stroma cells after treatment with SAL NPs.

CONCLUSION

These results highlight SAL-loaded PLGA NPs as a promising system for pancreatic cancer treatment, while the mechanistic questions need to be subsequently tested.

Thrombospondin immune regulation and the kidney

Most therapeutic attempts to prevent the progression of kidney diseases have been based on interventions to inhibit the production of transforming growth factor-β (TGF-β). Thrombospondins (TSPs) play an important role in activating TGF-β. In the healthy kidney, two TSPs are expressed, TSP1 and TSP2, which exert contrasting effects. While TSP1 is a major activator of TGF-β in renal cells and exerts pro-inflammatory effects both in vitro and in vivo, TSP2 lacks the ability for TGF-β activation but regulates matrix remodeling and inflammation in experimental kidney disease. The effects of TSPs in the kidney have been mostly investigated by using the murine model of unilateral ureteral obstruction. In this model, TSP1 expression is increased along with the development of interstitial fibrosis and TGF-β. Relief of the obstruction gradually improves renal function and decreases the expression in TSP1 and TGF-β1. Several inhibitors of TSP1 prevented progressive interstitial fibrosis in murine models of ureteral obstruction, suggesting that control of latent TGF-β activation by inhibiting TSP1 might represent a novel potential target for preventing renal interstitial fibrosis. However, further studies are needed to assess whether TSP1-mediated TGF-β activation can be safely used in humans. In fact, TSPs normally act to suppress tumors in vivo. Moreover, TGF-β can exert a pivotal function in the immune system, as it may induce the production of regulatory T cells and suppress B cell responses. Knowledge of the molecular mechanisms involved in TGF-β regulation may help in finding effective treatments of tissue fibrosis, cancer and autoimmune disease.

Cancer-associated fibroblasts in tumor microenvironment - Accomplices in tumor malignancy

There is much cellular heterogeneity in the tumor microenvironment. The tumor epithelia and stromal cells co-evolve, and this reciprocal relationship dictates almost every step of cancer development and progression. Despite this, many anticancer therapies are designed around druggable features of tumor epithelia, ignoring the supportive role of stromal cells. Cancer-associated fibroblasts (CAFs) are the dominant cell type within the reactive stroma of many tumor types. Numerous previous studies have highlighted a pro-tumorigenic role for CAFs via secretion of various growth factors, cytokines, chemokines, and the degradation of extracellular matrix. Recent works showed that CAFs secrete H₂O₂ to effect stromal-mediated field cancerization, transform primary epithelial cells, and aggravate cancer cell aggressiveness, in addition to inflammatory and mitogenic factors. Molecular characterization of CAFs also underscores the importance of Notch and specific nuclear receptor signaling in the activation of CAFs. This review consolidates recent findings of CAFs and highlights areas for future investigations.

Chemokine Signaling Facilitates Early-Stage Breast Cancer Survival and Invasion through Fibroblast-Dependent Mechanisms

Ductal carcinoma in situ (DCIS) is the most common form of breast cancer, with 50,000 cases diagnosed every year in the United States. Overtreatment and undertreatment remain significant clinical challenges in patient care. Identifying key mechanisms associated with DCIS progression could uncover new biomarkers to better predict patient prognosis and improve guided treatment. Chemokines are small soluble molecules that regulate cellular homing through molecular gradients. CCL2-mediated recruitment of CCR2⁺ macrophages are a well-established mechanism for metastatic progression. Although the CCL2/CCR2 pathway is a therapeutic target of interest, little is known about the role of CCR2 expression in breast cancer. Here, using a mammary intraductal injection (MIND) model to mimic DCIS formation, the role of CCR2 was explored in minimally invasive SUM225 and highly invasive DCIS.com breast cancer cells. CCR2 overexpression increased SUM225 breast cancer survival and invasion associated with accumulation of CCL2 expressing fibroblasts. CCR2-deficient DCIS.com breast cancer cells formed fewer invasive lesions with fewer CCL2⁺ fibroblasts. Cografting CCL2-deficient fibroblasts with DCIS.com breast cancer cells in the subrenal capsule model inhibited tumor invasion and survival associated with decreased expression of aldehyde dehydrogenase (ALDH1), a proinvasive factor, and decreased expression of HTRA2, a proapoptotic serine protease. Through data mining analysis, high expression of CCR2 and ALDH1 and low HTRA2 expression were correlated with poor prognosis of breast cancer patients.Implications: This study demonstrates that CCR2 overexpression in breast cancer drives early-stage breast cancer progression through stromal-dependent expression of CCL2 with important insight into prognosis and treatment of DCIS. Mol Cancer Res; 16(2); 296-308. ©2017 AACR.

Dichotomous roles of TGF-β in human cancer

Transforming growth factor-β (TGF-β) mediates numerous biological processes, including embryonic development and the maintenance of cellular homeostasis in a context-dependent manner. Consistent with its central role in maintaining cellular homeostasis, inhibition of TGF-β signaling results in disruption of normal homeostatic processes and subsequent carcinogenesis, defining the TGF-β signaling pathway as a tumor suppressor. However, once carcinogenesis is initiated, the TGF-β signaling pathway promotes cancer progression. This dichotomous function of the TGF-β signaling pathway is mediated through altering effects on both the cancer cells, by inducing apoptosis and inhibiting proliferation, and the tumor microenvironment, by promoting angiogenesis and inhibiting immunosurveillance. Current studies support inhibition of TGF-β signaling either alone, or in conjunction with anti-angiogenic therapy or immunotherapy as a promising strategy for the treatment of human cancers.

Stromal PDGFR-α Activation Enhances Matrix Stiffness, Impedes Mammary Ductal Development, and Accelerates Tumor Growth

The extracellular matrix (ECM) is critical for mammary ductal development and differentiation, but how mammary fibroblasts regulate ECM remodeling remains to be elucidated. Herein, we used a mouse genetic model to activate platelet derived growth factor receptor-alpha (PDGFRα) specifically in the stroma. Hyperactivation of PDGFRα in the mammary stroma severely hindered pubertal mammary ductal morphogenesis, but did not interrupt the lobuloalveolar differentiation program. Increased stromal PDGFRα signaling induced mammary fat pad fibrosis with a corresponding increase in interstitial hyaluronic acid (HA) and collagen deposition. Mammary fibroblasts with PDGFRα hyperactivation also decreased hydraulic permeability of a collagen substrate in an in vitro microfluidic device assay, which was mitigated by inhibition of either PDGFRα or HA. Fibrosis seen in this model significantly increased the overall stiffness of the mammary gland as measured by atomic force microscopy. Further, mammary tumor cells injected orthotopically in the fat pads of mice with stromal activation of PDGFRα grew larger tumors compared to controls. Taken together, our data establish that aberrant stromal PDGFRα signaling disrupts ECM homeostasis during mammary gland development, resulting in increased mammary stiffness and increased potential for tumor growth.

MYC Mediates Large Oncosome-Induced Fibroblast Reprogramming in Prostate Cancer

Communication between cancer cells and the tumor microenvironment results in the modulation of complex signaling networks that facilitate tumor progression. Here, we describe a new mechanism of intercellular communication originating from large oncosomes (LO), which are cancer cell-derived, atypically large (1-10 μm) extracellular vesicles (EV). We demonstrate that, in the context of prostate cancer, LO harbor sustained AKT1 kinase activity, nominating them as active signaling platforms. Active AKT1 was detected in circulating EV from the plasma of metastatic prostate cancer patients and was LO specific. LO internalization induced reprogramming of human normal prostate fibroblasts as reflected by high levels of α-SMA, IL6, and MMP9. In turn, LO-reprogrammed normal prostate fibroblasts stimulated endothelial tube formation in vitro and promoted tumor growth in mice. Activation of stromal MYC was critical for this reprogramming and for the sustained cellular responses elicited by LO, both in vitro and in vivo in an AKT1-dependent manner. Inhibition of LO internalization prevented activation of MYC and impaired the tumor-supporting properties of fibroblasts. Overall, our data show that prostate cancer-derived LO powerfully promote establishment of a tumor-supportive environment by inducing a novel reprogramming of the stroma. This mechanism offers potential alternative options for patient treatment. Cancer Res; 77(9); 2306-17. ©2017 AACR.

Aberrant low expression of p85α in stromal fibroblasts promotes breast cancer cell metastasis through exosome-mediated paracrine Wnt10b

P85α, which acts as a tumour suppressor, is frequently found to be downregulated in various human cancers. However, the role of p85α in the tumour microenvironment is unknown. Here, we report that aberrantly low expression of p85α in breast cancer stroma is clinically relevant to breast cancer disease progression. Stromal fibroblasts can acquire the hallmarks of cancer-associated fibroblasts (CAFs) as a result of the loss of p85α expression. Paracrine Wnt10b from p85α-deficient fibroblasts can promote cancer progression via epithelial-to-mesenchymal transition (EMT) induced by the canonical Wnt pathway. Moreover, exosomes have a key role in paracrine Wnt10b transport from fibroblasts to breast cancer epithelial cells. Our results reveal that p85α expression in stromal fibroblasts haves a crucial role in regulating breast cancer tumourigenesis and progression by modifying stromal–epithelial crosstalk and remodelling the tumour microenvironment. Therefore, p85α can function as a tumour suppressor and represent a new candidate for diagnosis, prognosis and targeted therapy.

Epithelial and non-epithelial Ptch1 play opposing roles to regulate proliferation and morphogenesis of the mouse mammary gland

Patched 1 (Ptch1) has epithelial, stromal and systemic roles in murine mammary gland organogenesis, yet specific functions remain undefined. Cre-recombinase-mediated Ptch1 ablation in mammary epithelium increased proliferation and branching, but did not phenocopy transgenic expression of activated smoothened (SmoM2). The epithelium showed no evidence of canonical hedgehog signaling, and hyperproliferation was not blocked by smoothened (SMO) inhibition, suggesting a non-canonical function of PTCH1. Consistent with this possibility, nuclear localization of cyclin B1 was increased. In non-epithelial cells, heterozygous Fsp-Cre-mediated Ptch1 ablation increased proliferation and branching, with dysplastic terminal end buds (TEB) and ducts. By contrast, homozygous Ptch1 ablation decreased proliferation and branching, producing stunted ducts filled with luminal cells showing altered ovarian hormone receptor expression. Whole-gland transplantation into wild-type hosts or estrogen/progesterone treatment rescued outgrowth and hormone receptor expression, but not the histological changes. Bone marrow transplantation failed to rescue outgrowth. Ducts of Fsp-Cre;Ptch1^fl/fl mice were similar to Fsp-Cre;SmoM2 ducts, but Fsp-Cre;SmoM2 outgrowths were not stunted, suggesting that the histology might be mediated by Smo in the local stroma, with systemic Ptch1 required for ductal outgrowth and proper hormone receptor expression in the mammary epithelium.

Summary: Systemic and tissue-specific depletion of patched 1 in epithelial and stromal compartments of the mammary gland defines functions in ductal patterning, proliferation and gene expression.

Mammary Gland Involution Provides a Unique Model to Study the TGF-β Cancer Paradox

Transforming Growth Factor-β (TGF-β) signaling in cancer has been termed the “TGF-β paradox”, acting as both a tumor suppresser and promoter. The complexity of TGF-β signaling within the tumor is context dependent, and greatly impacted by cellular crosstalk between TGF-β responsive cells in the microenvironment including adjacent epithelial, endothelial, mesenchymal, and hematopoietic cells. Here we utilize normal, weaning-induced mammary gland involution as a tissue microenvironment model to study the complexity of TGF-β function. This article reviews facets of mammary gland involution that are TGF-β regulated, namely mammary epithelial cell death, immune activation, and extracellular matrix remodeling. We outline how distinct cellular responses and crosstalk between cell types during physiologically normal mammary gland involution contribute to simultaneous tumor suppressive and promotional microenvironments. We also highlight alternatives to direct TGF-β blocking anti-cancer therapies with an emphasis on eliciting concerted microenvironmental-mediated tumor suppression.

Targeting TGF-β Signaling in Cancer

The transforming growth factor (TGF)-β signaling pathway is deregulated in many diseases, including cancer. In healthy cells and early-stage cancer cells, this pathway has tumor-suppressor functions, including cell-cycle arrest and apoptosis. However, its activation in late-stage cancer can promote tumorigenesis, including metastasis and chemoresistance. The dual function and pleiotropic nature of TGF-β signaling make it a challenging target and imply the need for careful therapeutic dosing of TGF-β drugs and patient selection. We review here the rationale for targeting TGF-β signaling in cancer and summarize the clinical status of pharmacological inhibitors. We discuss the direct effects of TGF-β signaling blockade on tumor and stromal cells, as well as biomarkers that can predict the efficacy of TGF-β inhibitors in cancer patients.

SHARPIN regulates collagen architecture and ductal outgrowth in the developing mouse mammary gland

SHARPIN is a widely expressed multifunctional protein implicated in cancer, inflammation, linear ubiquitination and integrin activity inhibition; however, its contribution to epithelial homeostasis remains poorly understood. Here, we examined the role of SHARPIN in mammary gland development, a process strongly regulated by epithelial-stromal interactions. Mice lacking SHARPIN expression in all cells (Sharpin^cpdm), and mice with a stromal (S100a4-Cre) deletion of Sharpin, have reduced mammary ductal outgrowth during puberty. In contrast, Sharpin^cpdm mammary epithelial cells transplanted in vivo into wild-type stroma, fully repopulate the mammary gland fat pad, undergo unperturbed ductal outgrowth and terminal differentiation. Thus, SHARPIN is required in mammary gland stroma during development. Accordingly, stroma adjacent to invading mammary ducts of Sharpin^cpdm mice displayed reduced collagen arrangement and extracellular matrix (ECM) stiffness. Moreover, Sharpin^cpdm mammary gland stromal fibroblasts demonstrated defects in collagen fibre assembly, collagen contraction and degradation in vitro Together, these data imply that SHARPIN regulates the normal invasive mammary gland branching morphogenesis in an epithelial cell extrinsic manner by controlling the organisation of the stromal ECM.

TβRIII Expression in Human Breast Cancer Stroma and the Role of Soluble TβRIII in Breast Cancer Associated Fibroblasts

The TGF-β pathway plays a major role in tumor progression through regulation of epithelial and stromal cell signaling. Dysfunction of the pathway can lead to carcinoma progression and metastasis. To gain insight into the stromal role of the TGF-β pathway in breast cancer, we performed laser capture microdissection (LCM) from breast cancer patients and reduction mammoplasty patients. Microdissected tumor stroma and normal breast stroma were examined for gene expression. Expression of the TGF-β type III receptor (TGFBR3) was greatly decreased in the tumor stroma compared to control healthy breast tissue. These results demonstrated a 44-fold decrease in TGFBR3 mRNA in tumor stroma in comparison to control tissue. We investigated publicly available databases, and have identified that TGFBR3 mRNA levels are decreased in tumor stroma. We next investigated fibroblast cell lines derived from cancerous and normal breast tissue and found that in addition to mRNA levels, TβRIII protein levels were significantly reduced. Having previously identified that cancer-associated fibroblasts secrete greater levels of tumor promoting cytokines, we investigated the consequences of soluble-TβRIII (sTβRIII) on fibroblasts. Fibroblast conditioned medium was analyzed for 102 human secreted cytokines and distinct changes in response to sTβRIII were observed. Next, we used the fibroblast-conditioned medium to stimulate human monocyte cell line THP-1. These results indicate a distinct transcriptional response depending on sTβRIII treatment and whether it was derived from normal or cancerous breast tissue. We conclude that the effect of TβRIII has distinct roles not only in cancer-associated fibroblasts but that sTβRIII has distinct paracrine functions in the tumor microenvironment.

Genetic tools for identifying and manipulating fibroblasts in the mouse

The use of mouse genetic tools to track and manipulate fibroblasts has provided invaluable in vivo information regarding the activities of these cells. Recently, many new mouse strains have been described for the specific purpose of studying fibroblast behavior. Colorimetric reporter mice and lines expressing Cre are available for the study of fibroblasts in the organs prone to fibrosis, including heart, kidney, liver, lung, and skeletal muscle. In this review we summarize the current state of the models that have been used to define tissue resident fibroblast populations. While these complex genetic reagents provide unique insights into the process of fibrosis, they also require a thorough understanding of the caveats and limitations. Here, we discuss the specificity and efficiency of the available genetic models and briefly describe how they have been used to document the mechanisms of fibrosis.

The biology and function of fibroblasts in cancer

Among all cells, fibroblasts could be considered the cockroaches of the human body. They survive severe stress that is usually lethal to all other cells, and they are the only normal cell type that can be live-cultured from post-mortem and decaying tissue. Their resilient adaptation may reside in their intrinsic survival programmes and cellular plasticity. Cancer is associated with fibroblasts at all stages of disease progression, including metastasis, and they are a considerable component of the general host response to tissue damage caused by cancer cells. Cancer-associated fibroblasts (CAFs) become synthetic machines that produce many different tumour components. CAFs have a role in creating extracellular matrix (ECM) structure and metabolic and immune reprogramming of the tumour microenvironment with an impact on adaptive resistance to chemotherapy. The pleiotropic actions of CAFs on tumour cells are probably reflective of them being a heterogeneous and plastic population with context-dependent influence on cancer.

The biology and function of fibroblasts in cancer

Among all cells, fibroblasts could be considered the cockroaches of the human body. They survive severe stress that is usually lethal to all other cells, and they are the only normal cell type that can be live-cultured from post-mortem and decaying tissue. Their resilient adaptation may reside in their intrinsic survival programmes and cellular plasticity. Cancer is associated with fibroblasts at all stages of disease progression, including metastasis, and they are a considerable component of the general host response to tissue damage caused by cancer cells. Cancer-associated fibroblasts (CAFs) become synthetic machines that produce many different tumour components. CAFs have a role in creating extracellular matrix (ECM) structure and metabolic and immune reprogramming of the tumour microenvironment with an impact on adaptive resistance to chemotherapy. The pleiotropic actions of CAFs on tumour cells are probably reflective of them being a heterogeneous and plastic population with context-dependent influence on cancer.

Targeted gene silencing of CCL2 inhibits triple negative breast cancer progression by blocking cancer stem cell renewal and M2 macrophage recruitment

Triple negative breast cancers are an aggressive subtype of breast cancer, characterized by the lack of estrogen receptor, progesterone receptor and Her2 expression. Triple negative breast cancers are non-responsive to conventional anti-hormonal and Her2 targeted therapies, making it necessary to identify new molecular targets for therapy. The chemokine CCL2 is overexpressed in invasive breast cancers, and regulates breast cancer progression through multiple mechanisms. With few approaches to target CCL2 activity, its value as a therapeutic target is unclear. In these studies, we developed a novel gene silencing approach that involves complexing siRNAs to TAT cell penetrating peptides (Ca-TAT) through non-covalent calcium cross-linking. Ca-TAT/siRNA complexes penetrated 3D collagen cultures of breast cancer cells and inhibited CCL2 expression more effectively than conventional antibody neutralization. Ca-TAT/siRNA complexes targeting CCL2 were delivered to mice bearing MDA-MB-231 breast tumor xenografts. In vivo CCL2 gene silencing inhibited primary tumor growth and metastasis, associated with a reduction in cancer stem cell renewal and recruitment of M2 macrophages. These studies are the first to demonstrate that targeting CCL2 expression in vivo may be a viable therapeutic approach to treating triple negative breast cancer.

Fibroblast-Mediated Collagen Remodeling Within the Tumor Microenvironment Facilitates Progression of Thyroid Cancers Driven by BrafV600E and Pten Loss

Contributions of the tumor microenvironment (TME) to progression in thyroid cancer are largely unexplored and may illuminate a basis for understanding rarer aggressive cases of this disease. In this study, we investigated the relationship between the TME and thyroid cancer progression in a mouse model where thyroid-specific expression of oncogenic BRAF and loss of Pten (Braf(V600E)/Pten(-/-)/TPO-Cre) leads to papillary thyroid cancers (PTC) that rapidly progress to poorly differentiated thyroid cancer (PDTC). We found that fibroblasts were recruited to the TME of Braf(V600E)/Pten(-/-)/TPO-Cre thyroid tumors. Conditioned media from cell lines established from these tumors, but not tumors driven by mutant H-ras, induced fibroblast migration and proliferation in vitro Notably, the extracellular matrix of Braf(V600E)/Pten(-/-)/TPO-Cre tumors was enriched with stromal-derived fibrillar collagen, compared with wild-type or Hras-driven tumors. Further, type I collagen enhanced the motility of Braf(V600E)/Pten(-/-)/TPO-Cre tumor cells in vitro In clinical specimens, we found COL1A1 and LOX to be upregulated in PTC and expressed at highest levels in PDTC and anaplastic thyroid cancer. Additionally, increased expression levels of COL1A1 and LOX were associated with decreased survival in thyroid cancer patients. Overall, our results identified fibroblast recruitment and remodeling of the extracellular matrix as pivotal features of the TME in promoting thyroid cancer progression, illuminating candidate therapeutic targets and biomarkers in advanced forms of this malignancy. Cancer Res; 76(7); 1804-13. ©2016 AACR.

Ménétrier's Disease: Its Mimickers and Pathogenesis

Ménétrier’s disease is a rare protein-losing hypertrophic gastropathy. Histologically, it can be mistaken for other disorders showing hypertrophic gastropathy. The pathogenesis of Ménétrier’s disease is not fully understood; however, it appears that the epidermal growth factor receptor (EGFR) ligand, transforming growth factor alpha, contributes to the pathogenesis of this disorder. In this review, we will discuss disease entities that can mimic Ménétrier’s disease and the role of EGFR signaling in Ménétrier’s disease.

Myeloid-specific TGF-β signaling in bone promotes basic-FGF and breast cancer bone metastasis

Breast cancer (BCa) bone metastases cause osteolytic bone lesions, which result from the interactions of metastatic BCa cells with osteoclasts and osteoblasts. Osteoclasts differentiate from myeloid lineage cells. To understand the cell-specific role of transforming growth factor beta (TGF-β) in the myeloid lineage, in BCa bone metastases, MDA-MB-231 BCa cells were intra-tibially or intra-cardially injected into LysM(Cre)/Tgfbr2(floxE2/floxE2) knockout (LysM(Cre)/Tgfbr2 KO) or Tgfbr2(floxE2/floxE2) mice. Metastatic bone lesion development was compared by analysis of both lesion number and area. We found that LysM(Cre)/Tgfbr2 knockout significantly decreased MDA-MB-231 bone lesion development in both the cardiac and tibial injection models. LysM(Cre)/Tgfbr2 knockout inhibited the tumor cell proliferation, angiogenesis and osteoclastogenesis of the metastatic bones. Cytokine array analysis showed that basic fibroblast growth factor (bFGF) was downregulated in MDA-MB-231-injected tibiae from the LysM(Cre)/Tgfbr2 KO group, and intravenous injection of the recombinant bFGF to LysM(Cre)/Tgfbr2 KO mice rescued the inhibited metastatic bone lesion development. The mechanism by which bFGF rescued the bone lesion development was by promotion of tumor cell proliferation through the downstream mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERK)-cFos pathway after binding to the FGF receptor 1 (FGFR1). Consistent with animal studies, we found that in human BCa bone metastatic tissues, TGF-β type II receptor (TβRII) and p-Smad2 were expressed in osteoclasts and tumor cells, and were correlated with the expression of FGFR1. Our studies suggest that myeloid-specific TGF-β signaling-mediated bFGF in the bone promotes BCa bone metastasis.

The Cancer Cell Oxygen Sensor PHD2 Promotes Metastasis via Activation of Cancer-Associated Fibroblasts

Several questions about the role of the oxygen sensor prolyl-hydroxylase 2 (PHD2) in cancer have not been addressed. First, the role of PHD2 in metastasis has not been studied in a spontaneous tumor model. Here, we show that global PHD2 haplodeficiency reduced metastasis without affecting tumor growth. Second, it is unknown whether PHD2 regulates cancer by affecting cancer-associated fibroblasts (CAFs). We show that PHD2 haplodeficiency reduced metastasis via two mechanisms: (1) by decreasing CAF activation, matrix production, and contraction by CAFs, an effect that surprisingly relied on PHD2 deletion in cancer cells, but not in CAFs; and (2) by improving tumor vessel normalization. Third, the effect of concomitant PHD2 inhibition in malignant and stromal cells (mimicking PHD2 inhibitor treatment) is unknown. We show that global PHD2 haplodeficiency, induced not only before but also after tumor onset, impaired metastasis. These findings warrant investigation of PHD2's therapeutic potential.

TGF-β Negatively Regulates CXCL1 Chemokine Expression in Mammary Fibroblasts through Enhancement of Smad2/3 and Suppression of HGF/c-Met Signaling Mechanisms

Fibroblasts are major cellular components of the breast cancer stroma, and influence the growth, survival and invasion of epithelial cells. Compared to normal tissue fibroblasts, carcinoma associated fibroblasts (CAFs) show increased expression of numerous soluble factors including growth factors and cytokines. However, the mechanisms regulating expression of these factors remain poorly understood. Recent studies have shown that breast CAFs overexpress the chemokine CXCL1, a key regulator of tumor invasion and chemo-resistance. Increased expression of CXCL1 in CAFs correlated with poor patient prognosis, and was associated with decreased expression of TGF-β signaling components. The goal of these studies was to understand the role of TGF-β in regulating CXCL1 expression in CAFs, using cell culture and biochemical approaches. We found that TGF-β treatment decreased CXCL1 expression in CAFs, through Smad2/3 dependent mechanisms. Chromatin immunoprecipitation and site-directed mutagenesis assays revealed two new binding sites in the CXCL1 promoter important for Smad2/3 modulation of CXCL1 expression. Smad2/3 proteins also negatively regulated expression of Hepatocyte Growth Factor (HGF), which was found to positively regulate CXCL1 expression in CAFs through c-Met receptor dependent mechanisms. HGF/c-Met signaling in CAFs was required for activity of NF-κB, a transcriptional activator of CXCL1 expression. These studies indicate that TGF-β negatively regulates CXCL1 expression in CAFs through Smad2/3 binding to the promoter, and through suppression of HGF/c-Met autocrine signaling. These studies reveal novel insight into how TGF-β and HGF, key tumor promoting factors modulate CXCL1 chemokine expression in CAFs.

Plasma macrophage-stimulating protein and hepatocyte growth factor levels are associated with prostate cancer progression

Hepatocyte growth factor (HGF) is a well-known multifunctional growth factor, and evidence has accumulated indicating that the HGF/MET (HGF receptor) signaling axis is involved in the progression of cancer. Macrophage-stimulating protein (MSP) is also known as a growth factor which activates not only macrophages but also cancer cells and osteoclasts through the activation of the specific Receptor d'origine nantais (RON). Pro-HGF and pro-MSP lack biological activity and, therefore, require proteolytic activation for conversion to an active two-chain form by HGF activator (HGFA). Although, there are several studies on HGF/MET signaling with castration-resistant prostate cancer (CRPC) and bone metastasis, reports on plasma protein are rare. In addition, the MSP/RON signaling axis in PC is not well understood. Here, we analyzed associations between PC progression and plasma HGF and MSP levels. We tested plasma samples from 58 patients with PC: 36 with castration-resistant (CR) PC and 22 with pretreatment for PC as control. We used enzyme-linked immunosorbent assay (ELISA) kit to determine plasma levels of HGF, MSP and HGFA, and examined correlations with clinicopathological characteristics such as Gleason grade and bone metastasis. PCR was used to evaluate HGF and MSP-related molecules in PC cell lines. Plasma levels of HGF, MSP and HGFA in the CRPC group were higher than in the control group (HGF: P < 0.001; MSP: P = 0.008; HGFA: P < 0.001). HGF and MSP levels were significantly correlated (P = 0.003). In the CRPC group, plasma HGF and MSP levels and Gleason score were not correlated; however, high plasma MSP level correlated with bone metastasis. (P = 0.016). In cell lines, PC3 expressed significantly more HGF, MET and RON than did LNCaP (P < 0.001), and both cell lines expressed MSP. Plasma concentrations of HGF, MSP and HGFA are significantly elevated in patients with CRPC. Also, as plasma MSP levels are significantly associated with bone metastasis in CRPC patients, MSP may be a candidate for serum marker of bone metastasis. Our results show the importance of the HGF/MET and MSP/RON signaling systems in CRPC.