Understanding the role of stromal fibroblasts in cancer progression

The major cellular components of tumor microenvironment, referred to as the cancer stroma, are composed of cancer-associated fibroblasts that support tumor epithelial growth, invasion and therapeutic resistance. Thus when we speak of developing therapies that address tumor heterogeneity it is not only a matter of different mutations within the tumor epithelia. While individual mutations in the stromal compartment are controversial, the heterogeneity in fibroblastic population in a single tumor is not up for debate. Cooperative interaction among heterotypic fibroblasts and tumor cells contribute to cancer progression. Therefore to tackle solid tumors, we need to understand its complex microenvironment. Here we review some seminal developments in the field of tumor microenvironment, mainly focusing on cancer-associated fibroblast.     

Understanding the role of stromal fibroblasts in cancer progression

The major cellular components of tumor microenvironment, referred to as the cancer stroma, are composed of cancer-associated fibroblasts that support tumor epithelial growth, invasion and therapeutic resistance. Thus when we speak of developing therapies that address tumor heterogeneity it is not only a matter of different mutations within the tumor epithelia. While individual mutations in the stromal compartment are controversial, the heterogeneity in fibroblastic population in a single tumor is not up for debate. Cooperative interaction among heterotypic fibroblasts and tumor cells contribute to cancer progression. Therefore to tackle solid tumors, we need to understand its complex microenvironment. Here we review some seminal developments in the field of tumor microenvironment, mainly focusing on cancer-associated fibroblast.     

Role of cancer-associated fibroblasts in breast cancer development and prognosis

Since Paget's "Seed and Soil" hypothesis in 1889 on cancer growth and metastasis, several studies on various solid tumors have confirmed the active role of the tumor milieu on the onset, growth and spread of neoplastic cells. Fibroblasts constitute the major components of the tumor microenvironment (stroma), and are therefore the most studied cell type. Therefore, a large amount of data has emerged showing the cancer-promoting function of these cells through paracrine effects that escort tumor cells through all the carcinogenesis steps. This involves many signaling proteins that transmit the message in both directions, allowing cooperative crosstalk between cancer cells and their stroma. This prompted several researchers to investigate the potential use of the molecular and cellular features of active stromal fibroblasts to generate specific tools for prevention, prognosis and treatment of cancer. Herein, I review the cellular and molecular features of active cancer-associated fibroblasts and their origin. Additionally, I summarize our current understanding of the procarcinogenic actions of these cells and their potential prognostic value for breast cancer patients.     

Tumor immune microenvironment: sanctuary of tumor and target for immunotherapy

The tumor immune microenvironment (TIME) is the cellular environment in which tumors exist. This includes: surrounding blood vessels, immune cells, fibroblasts, bone marrow-derived inflammatory cells, lymphocytes, signaling molecules, immune checkpoint proteins and the extracellular matrix (ECM). The TIME plays a critical role in cancer progression and regulation. Tumors can influence the microenvironment by releasing extracellular signals, promoting tumor angiogenesis and inducing peripheral immune tolerance, while the immune cells in the microenvironment can affect the growth and evolution of cancerous cells. The molecules and cells in the TIME influence disease outcome by altering the balance of suppressive versus cytotoxic responses in the vicinity of the tumor. Having a better understanding of the tumor immune microenvironment will pave the way for identifying new targets for immunotherapies that promote cancer elimination.     

TGF-β对肿瘤微环境中免疫监视及细胞外基质的调控作用

转化生长因子β(transforming growth factorβ,TGF-β)是一种多功能的细胞因子,能够调控细胞增殖、分化、黏附、迁移及凋亡等行为,在胚胎发育过程和成体组织稳态维持中发挥重要的作用。而在许多疾病状态下,特别是在癌症中,TGF-β不仅能够影响肿瘤细胞的增殖与转移,其对于肿瘤微环境的调控与塑造也受到越来越多的关注。肿瘤微环境是指肿瘤在发生和发展过程中所处的内环境,由肿瘤细胞本身、相邻正常组织中的间质细胞,以及这些细胞所释放的众多细胞因子等共同组成。肿瘤微环境是肿瘤发展的重要机制,也是肿瘤临床治疗领域亟待探索的关键问题。TGF-β是调节肿瘤微环境组成和功能的主要参与者之一。在本综述中,将着重讨论TGF-β对于肿瘤微环境中的免疫监视机制及肿瘤细胞外基质的主要影响。即TGF-β对于构成先天性和获得性抗肿瘤免疫应答的各种类群的免疫细胞具有广泛的调控作用,从而削弱宿主的肿瘤免疫监视功能。同时,TGF-β通过促进肿瘤相关成纤维细胞的产生,以及肿瘤细胞外基质的纤维化,有助于肿瘤的恶变和转移。此外,还介绍了通过阻断肿瘤微环境中TGF-β信号通路进行肿瘤治疗的主要策略及独特优势。而未来进一步解析TGF-β信号在肿瘤微环境中的复杂调控作用,并建立有效的靶向干预方法对于开发高效的抗肿瘤药物具有重要的意义。     

Vessel abnormalization: another hallmark of cancer? Molecular mechanisms and therapeutic implications

As a result of excessive production of angiogenic molecules, tumor vessels become abnormal in structure and function. By impairing oxygen delivery, abnormal vessels fuel a vicious cycle of non-productive angiogenesis, which creates a hostile microenvironment from where tumor cells escape through leaky vessels and which renders tumors less responsive to chemoradiation. While anti-angiogenic strategies focused on inhibiting new vessel growth and destroying pre-existing vessels, clinical studies showed modest anti-tumor effects. For many solid tumors, anti-VEGF treatment offers greater clinical benefit when combined with chemotherapy. This is partly due to a normalization of the tumor vasculature, which improves cytotoxic drug delivery and efficacy and offers unprecedented opportunities for anti-cancer treatment. Here, we overview key novel molecular players that induce vessel normalization.     

黏着斑激酶与肿瘤微环境

黏着斑激酶（focal adhesion kinase, FAK）是一种胞质非受体酪氨酸激酶。FAK和肿瘤密切相关,在多种癌细胞中高表达,促进癌细胞的发生、生长、存活、增殖、粘附、转移和侵袭以及血管生成等过程。肿瘤微环境包括肿瘤细胞、周围血管、免疫细胞、纤维母细胞、内皮细胞、信号分子和细胞外基质,它对癌症的发展和恶化具有重要作用。肿瘤细胞可以通过分泌细胞外信号影响微环境,使其有利于肿瘤生存和发展|肿瘤微环境中的基质细胞能通过产生趋化因子、基质降解酶和生长因子促进肿瘤侵袭和转移。本文综述肿瘤微环境在癌症发生发展过程中的作用及FAK在肿瘤微环境中的调控作用,为肿瘤疾病的治疗提供新思路。     

Regulation of invadopodia by the tumor microenvironment

The tumor microenvironment consists of stromal cells, extracellular matrix (ECM), and signaling molecules that communicate with cancer cells. As tumors grow and develop, the tumor microenvironment changes. In addition, the tumor microenvironment is not only influenced by signals from tumor cells, but also stromal components contribute to tumor progression and metastasis by affecting cancer cell function. One of the mechanisms that cancer cells use to invade and metastasize is mediated by actin-rich, proteolytic structures called invadopodia. Here, we discuss how signals from the tumor environment, including growth factors, hypoxia, pH, metabolism, and stromal cell interactions, affect the formation and function of invadopodia to regulate cancer cell invasion and metastasis. Understanding how the tumor microenvironment affects invadopodia biology could aid in the development of effective therapeutics to target cancer cell invasion and metastasis.     

Regulation of invadopodia by the tumor microenvironment

The tumor microenvironment consists of stromal cells, extracellular matrix (ECM), and signaling molecules that communicate with cancer cells. As tumors grow and develop, the tumor microenvironment changes. In addition, the tumor microenvironment is not only influenced by signals from tumor cells, but also stromal components contribute to tumor progression and metastasis by affecting cancer cell function. One of the mechanisms that cancer cells use to invade and metastasize is mediated by actin-rich, proteolytic structures called invadopodia. Here, we discuss how signals from the tumor environment, including growth factors, hypoxia, pH, metabolism, and stromal cell interactions, affect the formation and function of invadopodia to regulate cancer cell invasion and metastasis. Understanding how the tumor microenvironment affects invadopodia biology could aid in the development of effective therapeutics to target cancer cell invasion and metastasis.     

Components of the hepatocellular carcinoma microenvironment and their role in tumor progression

This review summarizes recently published data on the mechanisms of tumor cell interaction with the tumor microenvironment. Tumor stroma influences the processes of hepatocarcinogenesis, epithelial-to-mesenchymal transition, invasion, and metastasis. The tumor microenvironment includes both cellular and noncellular components. Main cellular components of hepatocellular carcinoma (HCC) stroma are tumor-associated fibroblasts, hepatic stellate cells, immune cells, and endothelial cells that produce extracellular components of tumor microenvironment such as extracellular matrix, various proteins, proteolytic enzymes, growth factors, and cytokines. The noncellular components of the stroma modulate signaling pathways in tumor cells and stimulate invasion and metastasis. The tumor microenvironment composition and organization can serve as prognostic factors in HCC pathogenesis. Current approaches in HCC targeted therapy are aimed at creating efficient strategies for interrupting tumor interactions with the stroma. Recent data on the composition and role of the microenvironment in HCC pathogenesis, as well as new developments in antitumor drug design are discussed.     

Three-dimensional Cell Culture Model for Measuring the Effects of Interstitial Fluid Flow on Tumor Cell Invasion

The growth and progression of most solid tumors depend on the initial transformation of the cancer cells and their response to stroma-associated signaling in the tumor microenvironment ¹. Previously, research on the tumor microenvironment has focused primarily on tumor-stromal interactions ^1-2. However, the tumor microenvironment also includes a variety of biophysical forces, whose effects remain poorly understood. These forces are biomechanical consequences of tumor growth that lead to changes in gene expression, cell division, differentiation and invasion³. Matrix density ⁴, stiffness ^5-6, and structure ^6-7, interstitial fluid pressure ⁸, and interstitial fluid flow ⁸ are all altered during cancer progression.Interstitial fluid flow in particular is higher in tumors compared to normal tissues ^8-10. The estimated interstitial fluid flow velocities were measured and found to be in the range of 0.1-3 μm s^-1, depending on tumor size and differentiation ^{9, 11}. This is due to elevated interstitial fluid pressure caused by tumor-induced angiogenesis and increased vascular permeability ¹². Interstitial fluid flow has been shown to increase invasion of cancer cells ^13-14, vascular fibroblasts and smooth muscle cells ¹⁵. This invasion may be due to autologous chemotactic gradients created around cells in 3-D ¹⁶ or increased matrix metalloproteinase (MMP) expression ¹⁵, chemokine secretion and cell adhesion molecule expression ¹⁷. However, the mechanism by which cells sense fluid flow is not well understood. In addition to altering tumor cell behavior, interstitial fluid flow modulates the activity of other cells in the tumor microenvironment. It is associated with (a) driving differentiation of fibroblasts into tumor-promoting myofibroblasts ¹⁸, (b) transporting of antigens and other soluble factors to lymph nodes ¹⁹, and (c) modulating lymphatic endothelial cell morphogenesis ²⁰.The technique presented here imposes interstitial fluid flow on cells in vitro and quantifies its effects on invasion (Figure 1). This method has been published in multiple studies to measure the effects of fluid flow on stromal and cancer cell invasion ^{13-15, 17}. By changing the matrix composition, cell type, and cell concentration, this method can be applied to other diseases and physiological systems to study the effects of interstitial flow on cellular processes such as invasion, differentiation, proliferation, and gene expression.     

Transient Tumor-Fibroblast Interactions Increase Tumor Cell Malignancy by a TGF-β Mediated Mechanism in a Mouse Xenograft Model of Breast Cancer

Carcinoma are complex societies of mutually interacting cells in which there is a progressive failure of normal homeostatic mechanisms, causing the parenchymal component to expand inappropriately and ultimately to disseminate to distant sites. When a cancer cell metastasizes, it first will be exposed to cancer associated fibroblasts in the immediate tumor microenvironment and then to normal fibroblasts as it traverses the underlying connective tissue towards the bloodstream. The interaction of tumor cells with stromal fibroblasts influences tumor biology by mechanisms that are not yet fully understood. Here, we report a role for normal stroma fibroblasts in the progression of invasive tumors to metastatic tumors. Using a coculture system of human metastatic breast cancer cells (MCF10CA1a) and normal murine dermal fibroblasts, we found that medium conditioned by cocultures of the two cell types (CoCM) increased migration and scattering of MCF10CA1a cells in vitro, whereas medium conditioned by homotypic cultures had little effect. Transient treatment of MCF10CA1a cells with CoCM in vitro accelerated tumor growth at orthotopic sites in vivo, and resulted in an expanded pattern of metastatic engraftment. The effects of CoCM on MCF10CA1a cells were dependent on small amounts of active TGF-β1 secreted by fibroblasts under the influence of the tumor cells, and required intact ALK5-, p38-, and JNK signaling in the tumor cells. In conclusion, these results demonstrate that transient interactions between tumor cells and normal fibroblasts can modify the acellular component of the local microenvironment such that it induces long-lasting increases in tumorigenicity and alters the metastatic pattern of the cancer cells in vivo. TGF-β appears to be a key player in this process, providing further rationale for the development of anti-cancer therapeutics that target the TGF-β pathway.     

Ex Vivo Treatment Response of Primary Tumors and/or Associated Metastases for Preclinical and Clinical Development of Therapeutics

The molecular analysis of established cancer cell lines has been the mainstay of cancer research for the past several decades. Cell culture provides both direct and rapid analysis of therapeutic sensitivity and resistance. However, recent evidence suggests that therapeutic response is not exclusive to the inherent molecular composition of cancer cells but rather is greatly influenced by the tumor cell microenvironment, a feature that cannot be recapitulated by traditional culturing methods. Even implementation of tumor xenografts, though providing a wealth of information on drug delivery/efficacy, cannot capture the tumor cell/microenvironment crosstalk (i.e., soluble factors) that occurs within human tumors and greatly impacts tumor response. To this extent, we have developed an ex vivo (fresh tissue sectioning) technique which allows for the direct assessment of treatment response for preclinical and clinical therapeutics development. This technique maintains tissue integrity and cellular architecture within the tumor cell/microenvironment context throughout treatment response providing a more precise means to assess drug efficacy.     

P-Selectin-Mediated Adhesion between Platelets and Tumor Cells Promotes Intestinal Tumorigenesis in ApcMin/+ Mice

Studies have indicated that platelets play an important role in tumorigenesis, and an abundance of platelets accumulate in the ovarian tumor microenvironment outside the vasculature. However, whether cancer cells recruit platelets within intestinal tumors and how they signal adherent platelets to enter intestinal tumor tissues remain unknown. Here, we unexpectedly found that large numbers of platelets were deposited within human colorectal tumor specimens using immunohistochemical staining, and these platelets were fully associated with tumor development. We further report the robust adhesion of platelet aggregates to tumor cells within intestinal tumors, which occurs via a mechanism that is dependent on P-selectin (CD62P), a cell adhesion molecule that is abundantly expressed on activated platelets. Using spontaneous intestinal tumor mouse models, we determined that the genetic deletion of P-selectin suppressed intestinal tumor growth, which was rescued by the infusion of wild-type platelets but not P-selectin^-/- platelets. Mechanistically, platelet adhesion to tumor cells induced the secretion of vascular endothelial growth factor (VEGF) to promote angiogenesis and accelerate intestinal tumor cell proliferation. Our results indicate that the adherence of platelets to tumor cells could promote tumor growth and metastasis. By targeting this platelet-tumor cell interaction, recombinant soluble P-selectin may have therapeutic value for the treatment of intestinal tumors.     

3D Bioprinted cancer models: Revolutionizing personalized cancer therapy

After cardiovascular disease, cancer is the leading cause of death worldwide with devastating health and economic consequences, particularly in developing countries. Inter-patient variations in anti-cancer drug responses further limit the success of therapeutic interventions. Therefore, personalized medicines approach is key for this patient group involving molecular and genetic screening and appropriate stratification of patients to treatment regimen that they will respond to. However, the knowledge related to adequate risk stratification methods identifying patients who will respond to specific anti-cancer agents is still lacking in many cancer types. Recent advancements in three-dimensional (3D) bioprinting technology, have been extensively used to generate representative bioengineered tumor in vitro models, which recapitulate the human tumor tissues and microenvironment for high-throughput drug screening. Bioprinting process involves the precise deposition of multiple layers of different cell types in combination with biomaterials capable of generating 3D bioengineered tissues based on a computer-aided design. Bioprinted cancer models containing patient-derived cancer and stromal cells together with genetic material, extracellular matrix proteins and growth factors, represent a promising approach for personalized cancer therapy screening. Both natural and synthetic biopolymers have been utilized to support the proliferation of cells and biological material within the personalized tumor models/implants. These models can provide a physiologically pertinent cell–cell and cell–matrix interactions by mimicking the 3D heterogeneity of real tumors. Here, we reviewed the potential applications of 3D bioprinted tumor constructs as personalized in vitro models in anticancer drug screening and in the establishment of precision treatment regimens.     

The effects of CA IX catalysis products within tumor microenvironment

Solid tumors are composed of both cancer cells and various types of accessory cells, mainly fibroblasts, that collectively compose the so called tumor-microenvironment. Cancer-associated fibroblasts have been described to actively participate in cancer progression by establishing a cytokine-mediated as well as metabolic crosstalk with cancer cells. In the present paper we show that activated human fibroblasts are able to boost tumor cells proliferation and that this effect is greatly dependent on stromal carbonic anhydrase IX (CA IX) activity. In fact fibroblasts show a strong upregulation of CA IX expression upon activation by cancer cells, while CA IX products, protons and bicarbonate, exert differential effects on cancer cells proliferation. While acidification of extracellular pH, a typical condition of rapidly growing solid tumors, is detrimental for tumor cells proliferation, bicarbonate, through its organication, supplies cancer cells with intermediates useful to sustain their high proliferation rate. Here we propose a new kind of fibroblasts/tumor cells crosstalk within tumor microenvironment, mediated by stromal CA IX products, aimed to favor cancer cells growth, opening new perspectives on CA IX role in tumor microenvironment.     

拟素化酶和去拟素化酶在肺癌发生发展中的作用

蛋白质拟素化是一种类似于泛素化的翻译后修饰，由NEDD8活化酶E1 (NAE)、NEDD8耦联酶E2 (UBE2M或UBE2F)和NEDD8连接酶E3三种酶催化组成的级联反应。Cullin家族蛋白是拟素化修饰的生理性底物，Cullin的拟素化修饰激活Cullin-RING连接酶（CRLs）,CRLs是最大一类E3泛素连接酶家族，介导了其中约20%蛋白质的泛素化降解来调节许多生物过程，包括细胞周期调控、DNA损伤修复、细胞生长、代谢、存活、自噬、迁移和免疫逃逸等。去拟素化过程则是通过特异性的去拟素化酶将拟素分子NEDD8从底物蛋白上水解并移除，释放至细胞中以维持拟素化的动态平衡。NEDD8和拟素化修饰的催化酶在多种癌症中高表达或活性上调，导致CRLs的过度激活，催化许多抑癌蛋白质的降解，从而促进肺癌细胞的增殖与存活以及肺肿瘤的发生发展。蛋白质拟素化修饰已被证实是有希望的癌症靶点。同样地，多种去拟素化酶在肺癌中高表达，其改变也与多种恶性肿瘤的发生发展密切相关，亦是潜在的肿瘤治疗重要靶点。本综述主要聚焦于拟素化及去拟素化通路在肺癌细胞中表达水平的改变，如何调节肺癌细胞的生长、存活和肺癌微环境...     

The tumor microenvironment: a critical determinant of neoplastic evolution

Evolution of neoplastic cells has generally been regarded as a cumulative intrinsic process resulting in altered cell characteristics enabling enhanced growth properties, evasion of apoptotic signals, unlimited replicative potential and gain of properties enabling the ability to thrive in ectopic tissues and in some cases, ability to metastasize. Recently however, the role of the neoplastic microenvironment has become appreciated largely due to the realization that tumors are not merely masses of neoplastic cells, but instead, are complex tissues composed of both a non-cellular (matrix proteins) and a cellular 'diploid' component (tumor-associated fibroblasts, capillary-associated cells and inflammatory cells), in addition to the ever-evolving neoplastic cells. With these realizations, it has become evident that early and persistent inflammatory responses observed in or around many solid tumors, play important roles in establishing an environment suitable for neoplastic progression by providing diverse factors that alter tissue homeostasis. Using cutaneous melanoma and squamous cell carcinoma as tumor models, we review the current literature focussing on inflammatory and tumor-associated fibroblast responses as critical mediators of neoplastic progression for these malignancies.     

Niche-Dependent Gene Expression Profile of Intratumoral Heterogeneous Ovarian Cancer Stem Cell Populations

Intratumoral heterogeneity challenges existing paradigms for anti-cancer therapy. We have previously demonstrated that the human embryonic stem cells (hESC)-derived cellular microenvironment in immunocompromised mice, enables functional distinction of heterogeneous tumor cells, including cells which do not grow into a tumor in a conventional direct tumor xenograft platform. We have identified and characterized six cancer cell subpopulations each clonally expanded from a single cell, derived from human ovarian clear cell carcinoma of a single tumor, to demonstrate striking intratumoral phenotypic heterogeneity that is dynamically dependent on the tumor growth microenvironment. These cancer cell subpopulations, characterized as cancer stem cell subpopulations, faithfully recapitulate the full spectrum of histological phenotypic heterogeneity known for human ovarian clear cell carcinoma. Each of the six subpopulations displays a different level of morphologic and tumorigenic differentiation wherein growth in the hESC-derived microenvironment favors growth of CD44+/aldehyde dehydrogenase positive pockets of self-renewing cells that sustain tumor growth through a process of tumorigenic differentiation into CD44-/aldehyde dehydrogenase negative derivatives. Strikingly, these derivative cells display microenvironment-dependent plasticity with the capacity to restore self-renewal markers and CD44 expression. In the current study, we delineate the distinct gene expression and epigenetic profiles of two such subpopulations, representing extremes of phenotypic heterogeneity in terms of niche-dependent self-renewal and tumorigenic differentiation. By combining Gene Set Enrichment, Gene Ontology and Pathway-focused array analyses with methylation status, we propose a suite of robust differences in tumor self-renewal and differentiation pathways that underlie the striking intratumoral phenotypic heterogeneity which characterize this and other solid tumor malignancies.