Tumor angiogenesis activity in cells grown in tissue culture.

Normal, viral transformed and tumor-derived cells grown in tissue culture and representing different species were tested for their ability to produce an extracellular tumor angiogenesis factor (TAF). TAF was assayed by measuring the host-mediated vascular response of the chorioallantoic membrane to TAF preparations. All of the viral transformed and tumor-derived cells tested, including SVT2, SVW126, Welker 256 rat carcinoma, B-16 mouse melanoma, human glioblastoma, and human meningioma cells, produced TAF. The potency of the TAF preparations, as measured by the number of cells needed to induce a positive vascular response on the chorioallantoic membrane, varied from cell line to cell line. The most potent cells tested were the glioblastoma and maningioma brain tumor cells. Since these brain tumors are found to be the most highly vascularized tumors in vivo, it was concluded that a correlation exists between the vascularity of a tumor in vivo and the potency of TAF in vitro. There was no detectable angiogenesis activity induced by density-inhibited BALB/c primary mouse embryo or early-passage human skin fibroblasts, even when relatively large numbers of cells were used to make a sample. However, density-inhibited BALB/c 3T3 aan W138 human embryonic lung fibroblasts, two cell lines widely regarded as demonstrating "normal" growth behavior in culture, produced TAF. From these and other observations, it was suggested that BALB/c 3T3 and W138 are not fully "normal" cells. Furthermore, it was suggested that the production of TAF is an early event in the cell transformation process that precedes the loss of density inhibition of growth in vitro.     

The role of the microenvironment and intercellular cross-talk in tumor angiogenesis

The expression of angiogenic factors in tumors is controlled by intrinsic factors in the tumor and by the host microenvironment. Endothelial cells within particular tumor microenvironments interact not only with tumor cells but also with immune cells, fibroblasts, pericytes, and the extracellular matrix (ECM). The relationship and cross-talk among these cells determine gene expression, phenotypic distinction, and ultimately whether endothelial cells survive, proliferate, or undergo apoptosis. The diversity of angiogenic factor expression in tumors at different sites, combined with the fact that endothelial cells in different organs and tumors are phenotypically distinct, constitutes a formidable challenge for the development of effective anti-angiogenic therapies.     

肿瘤相关成纤维细胞与肿瘤细胞的相互作用

肿瘤相关成纤维细胞（TAF）对肿瘤发生、生长、血管形成、浸润与转移有重要作用。TAF细胞通过产生旁分泌因子,影响上皮细胞转化,在肿瘤——宿主界面微环境形成中发挥重要作用。本文对TAF细胞的起源,TAF细胞形态及生物学特征及TAF细胞调节信号通路与肿瘤细胞的相互作用的研究现状作一综述。     

基质金属蛋白酶与肿瘤微环境的关系

基质金属蛋白酶(MMP)及其抑制剂组织金属蛋白酶抑制剂(TIMP)对细胞外基质(ECM)的变化共同调节肿瘤微环境.MMP可控制肿瘤演进过程中多种蛋白酶的表达.成纤维细胞、炎症细胞和上皮细胞等宿主细胞中MMP的变化与肿瘤形成呈正或负相关.     

Modifying the soil to affect the seed: role of stromal-derived matrix metalloproteinases in cancer progression

In the 1980's, as the importance of matrix metalloproteinases (MMPs) in cancer progression was discovered, it was recognized that in most tumors these proteases were abundantly and sometimes exclusively expressed not by tumor cells, but by normal host-derived cells like fibroblasts, vascular endothelial cells, myofibroblasts, pericytes or inflammatory cells that contribute to the tumor microenvironment. Later experiments in mice deficient in specific MMPs revealed that host-derived MMPs play a critical role not only in tumor cell invasion, but also in carcinogenesis, angiogenesis, vasculogenesis and metastasis. Tumor cells secrete many factors, cytokines and chemokines that directly or indirectly increase the expression of these MMPs in the tumor microenvironment where they exert extracellular matrix (ECM) degrading and sheddase activities. The knowledge of the complex role that stromal-derived MMPs play in the interaction between tumor cells and stromal cells should allow us to consider specific windows in cancer treatment when MMP inhibition could have a valuable therapeutic effect.     

The role of stromal fibroblasts in lung carcinogenesis: A target for chemoprevention?

The tumour microenvironment plays an essential role in the development and spread of cancers. Tumour cells interact with the surrounding extracellular matrix (ECM), embedded within which, are a variety of non‐cancer cells including cells of the vasculature, immune system and fibroblasts. The essential role of fibroblasts in the cultivation and maintenance of an environment in which tumour cells are able to maintain their aggressive phenotypic traits is becoming increasingly well documented. Cancer‐associated fibroblasts are able to secrete a vast array of ECM‐modulating factors, meaning that they have potential for a functional role in every step of the carcinogenic process. In particular, they are likely to have a role in early tumour‐initiating inflammatory events, and so may provide a potential target for chemopreventive intervention. This review summarises the known interactions between lung tumour cells and surrounding reactive fibroblasts, highlighting the need to further investigate cancer‐associated fibroblasts as therapeutic targets in lung cancer chemoprevention strategies.     

Relationship of tumor leucocytic infiltration to host defense mechanisms and prognosis

Summary The interface between the tumor and the host is often the site of leucocytic infiltration. We will examine the dea that the infiltrating leucocytes of human and experimental tumors are components of the host ammunological defense against the tumor, and that the presence of the infiltrate is a marker of favorable prognosis. Leucocytes could infiltrate tumors because of an active immune response, either nonspecific or specifically directed to tumor-associated antigens. Leucocyte influx may also occur because of chemotactic factors secreted by the tumor cells. Some tumors release factors which enhance vascular permeability and permit improved access by leucocytes to the tumor focus. The consequences of leucocytic infiltration include tumor cell cytolysis, cytostasis, or stimulation of proliferation. The present state of our knowledge of the interactions between tumor cells and infiltrating leucocytes precludes broad generalization of mechanisms. Further study will probably reveal that the mechanisms are diverse, and that there are some systems in which immune interactions occur at this interface and others in which they do not.     

Understanding tumor-stroma interplays for targeted therapies by armed mesenchymal stromal progenitors: the Mesenkillers

A tumor represents a complex structure containing malignant cells strictly coupled with a large variety of surrounding cells constituting the tumor stroma (TS). In recent years, the importance of TS for cancer initiation, development, local invasion and metastases has become increasingly clear allowing the identification of TS as one of the possible ways to indirectly target tumors. Inside the heterogeneous stromal cell population, tumor associated fibroblasts (TAF) play a crucial role providing both functional and supportive environments. During both tumor and stroma development, several findings suggest that TAF could be recruited from different sources such as locally derived host fibroblasts, via epithelial/endothelial mesenchymal transitions or from circulating pools of fibroblasts deriving form mesenchymal progenitors, namely mesenchymal stem/stromal cells (MSC). These insights prompted scientists to identify multimodal approaches to target TS by biomolecules, monoclonal antibodies, and more recently via cell based strategies. These latter strategies appear extremely promising, although still associated with debated and unclear findings. This review discusses crosstalk between cancers and their stroma, dissecting specific tumor types, such as sarcoma, pancreatic and breast carcinoma, where stroma plays distinct paradigmatic roles. The recognition of these distinct stromal functions may help in planning effective and safer approaches aimed either to eradicate or to substitute TS by novel compounds and/or MSC having specific killing activities.     

Predicting prognosis and therapeutic response from interactions between lymphocytes and tumor cells

As epithelial tumors grow from single cells to a malignant mass of invasive tissue, they must exploit the innate inflammatory response, while evading the adaptive immune system. Prognosis of solid tumors has historically focused on macroscopic features such as size, grade, and mitotic index. It is now clear that prognosis assessment must also consider the stromal and immune cells that surround and infiltrate the tumor. Tumors promote growth, angiogenesis, and tissue remodeling by subverting the normal functions of macrophages and other cells of the innate immune system that inhabit their microenvironment. Simultaneously, tumor cells escape from and inactivate the adaptive immune system by exploiting the mechanisms preventing damaging auto‐immune responses in cytotoxic T cells. The presence of CD8+ T cells within epithelial tumors is now a well‐supported marker of better prognosis in many tumor types. However, this benefit is counterbalanced by immune regulatory cell populations that promote tumor escape from immune surveillance and metastasis. Therapeutic approaches that kill tumor cells selectively by re‐activating immune checkpoints are becoming an established therapeutic option, but it is not yet clear how to identify which patients will benefit from this treatment modality. Evidence is accumulating that identifying the presence of T cell‐activating neoantigens, produced by mutated proteins in tumors, will play an important role in checkpoint inhibitor prognosis. This review provides an overview of the evidence that lymphocytic infiltration of tumors has prognostic value in many epithelial tumor types and is linked to the success of chemical and immune checkpoint therapeutic strategies.     

Immunotherapy targeting fibroblast activation protein inhibits tumor growth and increases survival in a murine colon cancer model

Murine studies have shown that immunological targeting of fibroblast activation protein (FAP) can elicit protective immunity in the absence of significant pathology. Fibroblast activation protein is a product overexpressed by tumor‐associated fibroblasts (TAF) and is the predominant component of the stoma in most types of cancer. Tumor‐associated fibroblasts differ from normal adult tissue fibroblasts, and instead resemble transient fetal and wound healing‐associated fibroblasts. Tumor‐associated fibroblasts are critical regulators of tumorigenesis, but differ from tumor cells by being more genetically stable. Therefore, in comparison to tumor cells, TAF may represent more viable therapeutic targets for cancer immunotherapy. To specifically target TAF, we constructed a DNA vaccine directed against FAP. This vaccine significantly suppressed primary tumor and pulmonary metastases primarily through CD8⁺ T‐cell‐mediated killing in tumor‐bearing mice. Most importantly, tumor‐bearing mice vaccinated against FAP exhibited a 1.5‐fold increase in lifespan and no significant pathology. These results suggest that FAP, a product preferentially expressed by TAF, could function as an effective tumor rejection antigen. (Cancer Sci 2010; 101: 2325–2332)     

A role for glial cell derived neurotrophic factor induced expression by inflammatory cytokines and RET/GFR alpha 1 receptor up-regulation in breast cancer

By screening a tissue microarray of invasive breast tumors, we have shown that the receptor tyrosine kinase RET (REarranged during Transfection) and its coreceptor GFR alpha 1 (GDNF receptor family alpha-1) are overexpressed in a subset of estrogen receptor-positive tumors. Germ line-activating oncogenic mutations in RET allow this receptor to signal independently of GFR alpha 1 and its ligand glial cell-derived neurotrophic factor (GDNF) to promote a spectrum of endocrine neoplasias. However, it is not known whether tumor progression can also be driven by receptor overexpression and whether expression of GDNF, as has been suggested for other neurotrophic factors, is regulated in response to the inflammatory microenvironment surrounding many epithelial cancers. Here, we show that GDNF stimulation of RET(+)/GFR alpha 1(+) MCF7 breast cancer cells in vitro enhanced cell proliferation and survival, and promoted cell scattering. Moreover, in tumor xenografts, GDNF expression was found to be up-regulated on the infiltrating endogenous fibroblasts and to a lesser extent by the tumor cells themselves. Finally, the inflammatory cytokines tumor necrosis factor-alpha and interleukin-1 beta, which are involved in tumor promotion and development, were found to act synergistically to up-regulate GDNF expression in both fibroblasts and tumor cells. These data indicate that GDNF can act as an important component of the inflammatory response in breast cancers and that its effects are mediated by both paracrine and autocrine stimulation of tumor cells via signaling through the RET and GFR alpha 1 receptors.     

Local and distant recurrences in rectal cancer patients are predicted by the nonspecific immune response; specific immune response has only a systemic effect - a histopathological and immunohistochemical study

Background  

Invasion and metastasis is a complex process governed by the interaction of genetically altered tumor cells and the immunological and inflammatory host reponse. Specific T-cells directed against tumor cells and the nonspecific inflammatory reaction due to tissue damage, cooperate against invasive tumor cells in order to prevent recurrences. Data concerning involvement of individual cell types are readily available but little is known about the coordinate interactions between both forms of immune response.     

Tumor stroma derived biomarkers in cancer

In recent years the importance of the tumor stroma for the development, promotion and invasion of cancer is becoming increasingly clear. Besides a malignantly transformed cancer cell, tumors also contains many other cell types, including endothelial cells, fibroblasts and cells of the immune system. These cells together with the cancer cells produce the sum extracellular matrix (ECM) of the tumor. The ECM and the non-malignant cells of the tumor are defined as the “tumor stroma”. Just as the malignant cell itself can be the source of substances that can be used as biomarkers of cancer, the tumor stroma contains factors that potentially can be used as biomarkers when treating patients with cancer. In this review we will discuss the role of the tumor stroma as a source of new cancer biomarkers. This concept highlights a novel view of cancer and treats them as organized organs. Additionally, this further stresses the importance of including factors related to the tumor stroma into the diagnostic and therapeutic equation of cancer.     

CD90+ stromal cells are the major source of IL‐6, which supports cancer stem‐like cells and inflammation in colorectal cancer

IL‐6 is a pleiotropic cytokine increased in CRC and known to directly promote tumor growth. Colonic myofibroblasts/fibroblasts (CMFs or stromal cells) are CD90⁺ innate immune cells representing up to 30% of normal colonic mucosal lamina propria cells. They are expanded in CRC tumor stroma, where they also known as a cancer associated fibroblasts (CAFs). Cells of mesenchymal origin, such as normal myofibroblasts/fibroblasts, are known to secrete IL‐6; however, their contribution to the increase in IL‐6 in CRC and to tumor‐promoting inflammation is not well defined. Using in situ, ex vivo and coculture analyses we have demonstrated that the number of IL‐6 producing CMFs is increased in CRC (C‐CMFs) and they represent the major source of IL‐6 in T2‐T3 CRC tumors. Activity/expression of stem cell markers‐aldehyde dehydrogenase and LGR5‐ was significantly up‐regulated in colon cancer cells (SW480, Caco‐2 or HT29) cultured in the presence of conditioned medium from tumor isolated C‐CMFs in an IL‐6 dependent manner. C‐CMF and its derived condition medium, but not normal CMF isolated from syngeneic normal colons, induced differentiation of tumor promoting inflammatory T helper 17 cells (Th17) cell responses in an IL‐6 dependent manner. Our study suggests that CD90⁺ fibroblasts/myofibroblasts may be the major source of IL‐6 in T2‐T3 CRC tumors, which supports the stemness of tumor cells and induces an immune adaptive inflammatory response (a.k.a. Th17) favoring tumor growth. Taken together our data supports the notion that IL‐6 producing CAFs (a.k.a. C‐CMFs) may provide a useful target for treating or preventing CRCs.     

Role of exosomes in the immune microenvironment of ovarian cancer

Exosomes are excretory vesicles that can deliver a variety of bioactive cargo molecules to the extracellular environment. Accumulating evidence demonstrates exosome participation in intercellular communication, immune response, inflammatory response and they even play an essential role in affecting the tumor immune microenvironment. The role of exosomes in the immune microenvironment of ovarian cancer is mainly divided into suppression and stimulation. On one hand exosomes can stimulate the innate and adaptive immune systems by activating dendritic cells (DCs), natural killer cells and T cells, allowing these immune cells exert an antitumorigenic effect. On the other hand, ovarian cancer-derived exosomes initiate cross-talk with immunosuppressive effector cells, which subsequently cause immune evasion; one of the hallmarks of cancer. Exosomes induce the polarization of macrophages in M2 phenotype and induce apoptosis of lymphocytes and DCs. Exosomes further activate additional immunosuppressive effector cells (myeloid-derived suppressor cells and regulatory T cells) that induce fibroblasts to differentiate into cancer-associated fibroblasts. Exosomes also induce the tumorigenicity of mesenchymal stem cells to exert additional immune suppression. Furthermore, besides mediating the intercellular communication, exosomes carry microRNAs (miRNAs), proteins and lipids to the tumor microenvironment, which collectively promotes ovarian cancer cells to proliferate, invade and tumors to metastasize. Studying proteins, lipids and miRNAs carried by exosomes could potentially be used as an early diagnostic marker of ovarian cancer for designing treatment strategies.     

Cancer associated fibroblasts: the dark side of the coin

Valid experimental evidence has recently shown that progression of malignant tumors does not depend exclusively on cell-autonomous properties of the cancer cells, but is also deeply influenced by tumor stroma reactivity and undergoes a strict microenvironmental control. Beside structural environmental components as extracellular matrix (ECM) or hypoxia, stromal cells as macrophages, endothelial cells, and cancer-associated fibroblasts (CAFs) play a definite role in cancer progression. This review summarizes our current knowledge on the role of CAFs in tumor progression towards an aggressive phenotype, with particular emphasis on invasiveness, stemness, and preparation of metastatic niche. The controversial origins of CAFs as well as the therapeutical implications of targeting CAFs for anticancer therapy are discussed.     

Cytotoxic T cells - stroma interactions

The tumor microenvironment is a complex system playing an important role in tumor development and progression. Besides tumor cells, the tumor microenvironment harbours a variety of host-derived cells, such as endothelial cells, fibroblasts, innate and adaptive immune cells, as well as extracellular matrix (ECM) fibers, cytokines, and other mediators. This review discusses the potential role of hypoxia and endothelial cells within tumor microenvironment and emphasizes their interaction with antigen specific killer cells.     

The tumor microenvironment and its role in promoting tumor growth

The tumor microenvironment is created by the tumor and dominated by tumor-induced interactions. Although various immune effector cells are recruited to the tumor site, their anti-tumor functions are downregulated, largely in response to tumor-derived signals. Infiltrates of inflammatory cells present in human tumors are chronic in nature and are enriched in regulatory T cells (T(reg)) as well as myeloid suppressor cells (MSC). Immune cells in the tumor microenvironment not only fail to exercise antitumor effector functions, but they are co-opted to promote tumor growth. Sustained activation of the NF-kappaB pathway in the tumor milieu represents one mechanism that appears to favor tumor survival and drive abortive activation of immune cells. The result is tumor escape from the host immune system. Tumor escape is accomplished through the activation of one or several molecular mechanisms that lead to inhibition of immune cell functions or to apoptosis of anti-tumor effector cells. The ability to block tumor escape depends on a better understanding of cellular and molecular pathways operating in the tumor microenvironment. Novel therapeutic strategies that emerge are designed to change the pro-tumor microenvironment to one favoring acute responses and potent anti-tumor activity.     

Targeting HER-2/neu for active-specific immunotherapy in a mouse model of spontaneous breast cancer.

The identification of tumor-associated antigens has led to increased interest in vaccination strategies to treat and/or prevent cancer. This study examined the feasibility of active-specific immunotherapy against the breast-tumor antigen HER-2/neu using a HER-2/neu transgenic (rNeu-TG) mouse model. rNeu-TG mice develop spontaneous breast tumors after pregnancy, indicating that they fail to mount an effective immune response against rNeu. Allogeneic fibroblasts expressing HER-2/neu were used as a cell-based vaccine. Vaccination induced a rNeu-specific anti-tumor immune response that prevented tumor formation of transplanted breast-tumor cells, and also protected mice from spontaneous tumor formation. Both T-cell-mediated and humoral immune responses were detectable in vaccinated mice. Vaccination also protected tumor-bearing mice from a challenge with cell suspensions isolated from spontaneous tumors, indicating that rNeu-TG mice are not tolerant to rNeu, even after spontaneous tumor formation. However, established spontaneous tumors themselves were never affected. This observation correlated with T-cell infiltrations in the injected but not in the established spontaneous tumor. Thus, allogeneic fibroblasts are efficient vaccine vectors to prime a specific immune response against an over-expressed tumor antigen. Moreover, our results suggest striking differences in the immunological requirements for the rejection of an established vs. a transplanted tumor.     

Brain Tumor Immunotherapy: An Immunologist's Perspective

Key concepts in brain tumor immunotherapy are reviewed. "Immunotherapy" can refer to a fully-developed, tumor-specific immune response, or to its individual cellular or molecular mediators. The immune response is initiated most efficiently in organized lymphoid tissue. After initiation, antigen-specific T lymphocytes (T cells) survey the tissues – including the brain. If the T cells re-encounter their antigen at a tumor site, they can be triggered to carry out their effector functions. T cells can attack tumor in many ways, directly and indirectly, through cell-cell contact, secreted factors, and attraction and activation of other cells, endogenous or blood-borne. Recent work expands the list of candidate tumor antigens: they are not limited to cell surface proteins and need not be absolutely tumor-specific. Once identified, tumor antigens can be targeted immunologically, or in novel ways. The immune response is under complex regulatory control. Most current work aims to enhance initiation of the response (for example, with tumor vaccines), rather than enhancing the effector phase at the tumor site. The effector phase includes a rich, interactive set of cells and mediators; some that are not usually stressed are of particular interest against tumor in the brain. Within the brain, immune regulation varies from site to site, and local neurochemicals (such as substance P or glutamate) can contribute to local control. Given the complexity of a tumor, the brain, and the immune response, animal models are essential, but more emphasis should be given to their limitations and to step-by-step analysis, rather than animal "cures".