Proteoglycans: Master modulators of paracrine fibroblast–carcinoma cell interactions

Reciprocal interactions between tumor and stromal cells govern carcinoma growth and progression. Signaling functions between these cell types in the tumor microenvironment are largely carried out by secreted growth factors and cytokines. This review discusses how proteoglycans, which are abundantly present in normal and neoplastic tissues, modulate paracrine growth factor signaling events. General principles of proteoglycan involvement in paracrine signaling include stromal induction, core protein processing by proteases and growth factor binding via proteoglycan glycosaminoglycan chains or core protein domains.     

Growth of normal and neoplastic rat pleural mesothelial cells in the presence of conditioned medium from neoplastic mesothelial cells

Several transformed cells have been demonstrated to secrete growth factors. We studied the effect of conditioned medium from neoplastic rat pleural mesothelial cells on normal and neoplastic mesothelial cell growth. The results showed that the concentrated conditioned medium stimulated neoplastic mesothelial cell growth but inhibited reversibly normal mesothelial cell growth.     

Neoplastic progression of rat tracheal epithelial cells is associated with a reduction in the number of growth factors required for clonal proliferation in culture

Summary Factors regulating the proliferation of normal, preneoplastic, and neoplastic rat tracheal epithelial (RTE) cells were investigated to identify changes taking place during the progression of RTE cells to neoplasia. Normal RTE cells exhibit clonal proliferation in a serum-free medium containing pituitary extract, serum albumin, cholera toxin, epidermal growth factor, hydrocortisone, and insulin. All combinations of these six factors were examined for their abilities to support clonal proliferation of normal, preneoplastic, and neoplastic RTE cells. In general, preneoplastic RTE cells required fewer factors for proliferation than normal RTE cells, and neoplastic cells required fewer factors than preneoplastic cells. A common pattern of reductions has been identified in the growth factors required for the clonal proliferation of preneoplastic vs. normal RTE cells and for neoplastic vs. preneoplastic and normal RTE cells. Normal RTE cells exhibit clonal proliferation in a serum-free medium supplemented with a minimum of six factors: bovine serum albumin, bovine pituitary extract, cholera toxin, epidermal growth factor, hydrocortisone, and insulin. Preneoplastic RTE cells exhibit clonal proliferation in a serum-free medium supplemented with four factors: bovine serum albumin, bovine pituitary extract, hydrocortisone, and insulin. Finally, neoplastic RTE cells exhibit clonal proliferation in a serum-free medium supplemented with two factors: bovine serum albumin and bovine pituitary extract. These results suggest that the progression of RTE cells to neoplasia is associated with a series of changes in regulatory pathways that control cell proliferation.     

Apoptosis in the liver and its role in hepatocarcinogenesis

Apoptosis seems to be the predominant type of active cell death in the liver (type I), while in other tissues cells may die via biochemically and morphologically different pathways (type II, type III). Active cell death is under the control of growth factors and death signals. In the liver, endogenous factors, such as transforming growth factor 1 (TGF-1), activin A, CD95 ligand, and tumor necrosis factor (TNF) may be involved in induction of apoptosis. Release and action of these death factors seems to be triggered by exogenous signals such as withdrawal of hepato-mitogens, food restriction, etc.During stages of hepatocarcinogenesis, not only DNA synthesis but also apoptosis gradually increase from normal to preneoplastic to adenoma and carcinoma tissue. Also, in human carcinomas, birth and death rates of cells are several times higher than in surrounding liver. (Pre)neoplastic liver cells are more susceptible than normal hepatocytes to stimulation of cell replication and of cell death. Consequently, tumor promoters may act as survival factors, i.e., inhibit apoptosis preferentially in preneoplastic and even in malignant liver cells, thereby stimulating selective growth of (pre)neoplastic lesions. On the other hand, regimens favoring apoptosis and lowering cell replication may result in selective elimination of (pre)neoplastic cell clones from the liver. Finally, we have studied the first stage of carcinogenesis, namely the appearance of putatively initiated cells after a single dose of the genotoxic carcinogen N-nitrosomorpholine (NNM). Most of these cells were found to be eliminated by apoptosis, suggesting that initiation, at the organ level, can be reversed at least partially by preferential elimination of initiated cells. These events may be regulated by autocrine or paracrine actions of survival factors.     

Involvement of hepatocyte growth factor on hepatocarcinogenesis induced by peroxisome proliferators

Hepatocyte growth factor (HGF) has been known to enhance the growth of normal hepatocytes, but also to inhibit the growth of neoplastic cells. This article examines the involvement of HGF in the hepatocarcinogenesis caused by peroxisome proliferators (PPs). Up to 78 wk after male F-344 rats were orally given (4-chloro-6-[2,3-xylidino]-2-pyrimidinylthio) acetic acid (Wy-14,643), the hepatocarcinomas and (pre)neoplastic nodules in the livers were observed. At that time, the content of HGF and the expression of HGF mRNA in the liver tumors were significantly decreased. These changes were observed also in the liver of rats treated with other PPs, such as dehydroepiandrosterone and di(2-ethylhexyl)phthalate, but were not observed in tumors induced by genotoxic carcinogens (diethylnitrosamine-phenobarbital). In in vivo experiments, the formation of preneoplastic lesions and the tumors caused by Wy-14,643 administration were markedly suppressed by iv-injection of HGF in a dose-dependent manner. In the colony assay using (pre)neoplastic cells from livers of Wy-14,643-treated rats, HGF inhibited the colony formation of (pre)neoplastic cells in a dose-dependent manner. These findings may indicate that decreases in hepatic HGF levels are common and specific events induced by PPs, but not by genotoxic carcinogens, and that those changes play an important role in the promotion of neoplastic or preneoplastic cell growth induced by PPs.     

Cell shape and increased free cytosolic calcium [Ca2+]i induced by growth factors

Growth factors stimulate DNA synthesis of neoplastic cells but not of non-neoplastic cells in suspension cultures. Similarly, growth ceases in dense monolayers of non-neoplastic cells, while crowded neoplastic cells continue to grow. The mechanism of these important phenotypic changes is unknown; the block in growth stimulation could occur in early events of signal transduction at the plasma membrane or in a late step in the final steps of gene activation and induction of DNA synthesis. One particular early intracellular event, [Ca2+]i increases, is in fact necessary for the induction of DNA synthesis in attached non-neoplastic Balb/c 3T3 cells stimulated by platelet-derived growth factor (PDGF). We therefore used digital image analysis of intracellular Fura-2 fluorescence to determine whether PDGF can stimulate [Ca2+]i transients in suspension or in dense monolayer cultures of Balb/c 3T3 cells. In dense cells (greater than 8 x 10(4) cells/cm2) the basal [Ca2+]i and [Ca2+]i response to PDGF stimulation were both lower than those in sparser, more spread cells. PDGF also did not release internal stores of Ca2+ or produce Ca2+ influx in completely suspended cells. Remarkably, attachment alone, with minimal cell spreading, was enough to reinitiate the entire early signalling mechanism stimulated by PDGF. Thus, a block in PDGF-induced [Ca2+]i increases may contribute to the inability of PDGF to stimulate DNA synthesis in suspended non-neoplastic cells. This early block in signal transduction must be abrogated in neoplastic cells growing in suspension and dense monolayer cultures.     

Interaction of serum and cell spreading affects the growth of neoplastic and non-neoplastic fibroblasts

Both growth factor availability and cell-to-cell contact have been mechanisms used to explain cell growth regulation at high cell density. Recently Folkman and colleagues have shown that changes in cell shape, rather than cell-to-cell contact, can regulate the growth of fibroblasts. However, in those studies the relation between serum and shape regulation of growth was not studied, nor were neoplastic and non-neoplastic cells compared. In this report we have studied these aspects by varying cell spreading and serum concentration independently for 2 non-neoplastic and 3 neoplastic cell lines. Cell spreading (projected cell area) was controlled by decreasing the adhesiveness of tissue culture plastic plates with poly (hydroxyethyl methacrylate) [poly (HEMA)]. Cell growth was measured as the increase in cell number/day. We have found that more spreading increased net growth of both neoplastic and non-neoplastic cells, while less spreading (toward rounded configuration) depressed growth. There were also quantitative differences between neoplastic and non-neoplastic cells. Neoplastic cells continued to grow under conditions of cell rounding, which completely prevented the growth of their non-neoplastic counterparts. Some neoplastic cells also tended to show little or no increase in net cell number for serum concentrations above 10% as cells became more spread; in contrast, all non-neoplastic cells grew more with increasing concentrations of serum as they became well spread. Thus, in normal cells, it appears that the sensitivity of cells to humoral factors is governed by cell spreading. This interaction between serum and cell shape is less prominent in some neoplastic cells.     

Transforming growth factors and the regulation of cell proliferation

The number of different growth regulatory molecules which have been isolated and characterized is continuing to increase. As more information is obtained, it has become apparent that the cooperative actions of many factors with distinct activities is necessary for appropriate proliferative responses. An interplay of both growth stimulatory and growth inhibitory factors is essential for normal growth. Of crucial importance, therefore, is the appropriate regulation of growth factors. Unregulated expression, synthesis, posttranslational processing or activation of either positive or negative growth signals may contribute to neoplastic transformation (Fig. 3). Altered responses to normally positive or negative signals by transformed cells have been demonstrated by several investigators [64, 79, 84]. While altered growth factor responses in transformed cells are well documented, the mechanisms responsible for the loss of growth control are poorly understood and are likely to be both complex and numerous. Continued efforts to dissect and comprehend fully growth factor action on normal cells will be necessary before an understanding of neoplastic transformation can be achieved.     

<Emphasis Type="Italic">Drosophila</Emphasis> as an emerging model to study metastasis

Metastasis is the primary cause of human cancer-related deaths. Two recent studies describe a system for testing how multiple genetic events synergize to promote neoplastic growth and metastasis in Drosophila, paving the way for systematic approaches to understanding metastasis using the powerful tools of Drosophila genetics.     

皮肤成纤维细胞永生化的研究进展

正常体细胞的生命周期都是有限的 ,经过一定数目的分裂后 ,会进入增殖抑制状态。永生化细胞是近年来生物科学探索较多的领域之一。因为它不仅能为细胞生物学的研究提供性状稳定的研究对象 ,还为人类实现器官再生开辟了新方向。所以皮肤成纤维细胞的永生化对于皮肤疾病以及皮肤组织工程的研究都具有非常深远的意义。就皮肤成纤维细胞的永生化的研究作一阐述 ,并讨论其应用前景和可能面临的问题     

Epithelial-mesenchymal interconversions in normal ovarian surface epithelium and ovarian carcinomas: an exception to the norm

Cancer that arises from the ovarian surface epithelium (OSE) accounts for approximately 90% of human ovarian cancer, and is the fourth leading cause of cancer-related deaths among women in developed countries. The pathophysiology of epithelial ovarian cancer is still unclear because of the poor understanding of the complex nature of its development and the unusual mechanism(s) of disease progression. Recent studies have reported epithelial-mesenchymal transition (EMT) in cultured OSE and ovarian cancer cell lines in response to various stimuli, but our understanding of the importance of these observations for normal ovarian physiology and cancer progression is not well established. This review highlights the current literature on EMT-associated events in normal OSE and ovarian cancer cell lines, and discusses its implication for normal ovarian function as well as acquisition of neoplastic phenotypes. The pathological changes in OSE in response to EMT during neoplastic transformation and the contribution of hormones, growth factors, and cytokines that initiate and drive EMT to sustain normal ovarian function, as well as cancer development and progression are also discussed. Finally, emphasis is placed on the clinical implications of EMT and potential therapeutic opportunities that may arise from these observations have been proposed.     

Human Oncogenic Viruses: Old Facts and New Hypotheses

Molecular Biology - Numerous studies on the nature of neoplastic growth have demonstrated that oncogenic viruses may be one of the factors causing cancer. According to various estimates,...     

Scatter factor-dependent branching morphogenesis: structural and histological features

Branching morphogenesis is a multi-step process that controls the formation of polarised tubules starting from hollow cysts. Its execution entails a series of rate-limiting events which include reversible disruption of cell polarity, dismantling of intercellular contacts, acquisition of a motile phenotype, stimulation of cell proliferation, and final re-establishment of cell polarity for creation of the definitive structures. Branching morphogenesis takes place physiologically during development, accounting for the establishment of organs endowed with a ramified architecture such as glands, the respiratory tract and the vasculartree. In cancer, aberrant implementation of branching morphogenesis leads to deregulated proliferation, protection from apoptosis and enhanced migratory/invasive properties, which together exacerbate the aggressive features of neoplastic cells. Under both physiological and pathological conditions, branching morphogenesis is mainly accomplished by a family of growth factors known as scatter factors. In this review, we will summarise the current knowledge on the biological and functional roles of scatter factors during branching morphogenesis, with a special emphasis on the phenotypic (structural and histological) consequences of scatter factor activity in different tissues.     

Induction of unstable mutations in Drosophila melanogaster by microinjections of DNA from oncogene viruses into the embryonic polar plasm. Part IV. Malignantization of tissues of mutant larvae

We have demonstrated that larval tissues of mutant stocks induced by injections of oncogene virus DNA (Sa7 and RSV) show the neoplastic mode of growth after transplantation into the body cavity of wild-type flies. Neoplasms tested were shown to be ordinary benign insect neoplasms, and at the same time they show the dominant mode of heredity typical of the neoplasms of vertebrates. Genetic factors responsible for the neoplastic growth are localised in the 3rd chromosome in the stocks obtained after injections of the adenoviral Sa7 DNA, and in the 2nd and 3rd chromosomes in the mutant stocks induced by the retroviral DNA.     

Pathways connecting inflammation and cancer

Chronic and persistent inflammation contributes to cancer development and can predispose to carcinogenesis. Infection-driven inflammations are involved in the pathogenesis of approximately 15-20% of human tumors. However, even tumors that are not epidemiologically linked to pathogens are characterized by the presence of an inflammatory component in their microenvironment. Hallmarks of cancer-associated inflammation include the presence of infiltrating leukocytes, cytokines, chemokines, growth factors, lipid messengers, and matrix-degrading enzymes. Schematically, two interrelated pathways link inflammation and cancer: (1) genetic events leading to neoplastic transformation promote the construction of an inflammatory milieu; (2) tumor-infiltrating leukocytes, in particular macrophages, are prime regulators of cancer inflammation. Thus, an intrinsic pathway of inflammation (driven in tumor cells), as well as an extrinsic pathway (in tumor-infiltrating leukocytes) have been described and both contribute to tumor progression.     

Free-Radical Processes in Multistage Carcinogenesis

Rodent and human cells in culture, transformed in vitro by radiation or chemicals into malignant cells, afford us the opportunity to probe into early and late events in the neoplastic process at a cellular and molecular level. Transformation can be regarded as an abnormal expression of cellular genes. The initiating agents disrupt the integrity of the genetic apparatus altering DNA in ways that result in the activation of cellular transforming genes (oncogenes) during some stage of the neoplastic process. Events associated with initiation and promotion may overlap to some degree, but in order for them to occur, cellular permissive conditions prevail. Permissive and potentiating factors include free radicals, and thyroid hormone. and inadequate antioxidants. Protective factors which suppress the carcinogenic process include enzymatic and dietary antioxidants. These are constituitive under normal circumstances and can be induced under conditions of oxidative stress produced by a wide range of carcinogens.     

Identification of estrogen-inducible growth factors (estromedins) for rat and human mammary tumor cells in culture

Summary The role of polypeptide growth factors (estromedins) as mediators of estrogen-responsive mammary tumor growth is studied in this report. Three possible new mechanisms were investigated that include endocrine, autocrine, and paracrine related growth factors. The first hypothesis being tested is whether estrogens interact with target tissues and cause the biosynthesis and secretion of polypeptide growth factors, which then act as mitogens for normal and neoplastic mammary tissues. Data presented suggest that this mechanism involves estrogen interaction with uterus, kidney, and pituitary gland causing production of growth factors, which then enter the general circulation and promote growth of distant target tissues. This is an endocrine type mechanism. Another type of estromedin control (autocrine control) may be exerted in an autostimulatory way in which the target tissue produces the polypeptide factors for its own growth in response to estrogen stimulation. A variation of the autocrine mechanism may be a paracrine mechanism in which some cells of an estrogen-responsive normal or neoplastic tissue produce growth factors that act on adjacent or neighboring cells. From the data available, all three possible types of growth factors could be functioning synergistically to yield the final result of continuous estrogen responsive tumor growth in vivo. Presented in the symposium on Plant and Animal Physiology in Vitro at the 33rd Annual Meeting of the Tissue Culture Association, San Diego, California, June 6–10, 1982. This work was supported by American Cancer Society Grant BC-255; D. A. S. is the recipient of an American Cancer Society Faculty Research Award, FRA-212. D. D. is supported by a Rosalie B. Hite predoctoral fellowship from the Rosalie B. Hite Foundation, Houston, Texas. This symposium was supported in part by the following organizations: Bellco Glass, Inc., California Branch of the Tissue Culture Association, Collaborative Research, Hana Media, Hybridtech, K C Biological, Inc., and Millipore Corporation.