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Molecular/cell engineering approach to autocrine ligand control of cell function.

Tissue engineering, along with other modern cell- and tissue-based health care technologies, depends on successful regulation of cell function by molecular means, including pharmacological agents, materials, and genetics. This regulation is generally mediated by cell receptor/ligand interactions providing primary targets for molecular intervention. While regulatory ligands may often be exogenous in nature, in the categories of endocrine and paracrine hormone systems, they are being increasingly appreciated as crucial in local control of cell and tissue function. Improvements in design of health care technologies involving autocrine ligand interactions with cell receptors should benefit from increased qualitative and quantitative understanding of the kinetic and transport processes governing these interactions. In this symposium paper we offer a concise overview of our recent efforts combining molecular cell biology and engineering approaches to increase the understanding of how molecular and cellular parameters may be manipulated for improved control of cell and tissue function regulated by autocrine ligands.

Animals↗

Autocrine-paracrine inhibition of growth hormone and prolactin production by GH3 cell-conditioned medium.

In previous work we have shown that perifused GH3 cells exhibit spontaneously accelerating growth hormone (GH) and prolactin (PRL) secretory rates. This behavior contrasts with GH and PRL secretion rates that are decreasing or stable over the same 3-d period in static cell culture. We now report that GH3 cells maintained in serum-supplemented medium produce an autocrine-paracrine factor(s) which inhibits GH secretion in plate culture; PRL release is frequently reduced as well. The inhibitory effect of conditioned medium on GH secretion was concentration dependent, whereas PRL release was stimulated at low and inhibited at high concentrations over the same range. Extensive dialysis of conditioned medium using membranes with a molecular weight cut-off of 12,000-14,000 did not remove GH inhibition but produced a retentate that stimulated PRL secretion. Heat-inactivation of conditioned medium did not abolish inhibition of GH release but did remove the PRL-stimulatory effect. IGF-I added to fresh culture medium did not reproduce the GH-inhibitory effects of conditioned medium. We conclude that GH3 cell secretory behavior in perifusion and plate culture systems may be partially explained by the production of an autocrine-paracrine factor: its accumulation in plate culture inhibits GH and PRL secretion whereas its removal, by perifusing medium, allows GH and PRL secretion to accelerate.

Animals↗

Transferrin is an autocrine growth factor secreted by Reuber H-35 cells in serum-free culture.

We have previously reported that Reuber H-35 rat hepatoma cells secrete an autocrine growth-stimulating activity in serum-free culture. To characterize this activity, conditioned serum-free medium from dense H-35 donor cultures was collected in the absence and presence of [35S]methionine. A 1:4 dilution of conditioned medium into fresh serum-free medium resulted in an increase in mean H-35 cell numbers per assay dish from 1.59 +/- 0.12 X 10(5) to 3.35 +/- 0.34 X 10(5) after 44 h of incubation. Control, unconditioned medium, resulted in significantly (P less than 0.05) less growth (2.14 +/- 0.41 X 10(5) cells per dish). Trypsin digestion eliminated the growth-promoting effect of conditioned medium but had no effect on unconditioned medium. Dialysis did not diminish the growth-promoting activity of conditioned medium. The immunoprecipitate of [35S]methionine-containing conditioned medium with antisera against rat serum transferrin contained a dominant radioactive doublet of molecular weight equal to purified rat serum transferrin. A rat transferrin radioimmunoassay was devised and used to quantitate that 29.1 +/- 1.2 ng of transferrin was secreted per 10(6) cells per hour in serum-free culture. Addition of antitransferrin antibody resulted in a significant (P less than 0.025) decrease in H-35 cell growth after 48 h. Thus, a portion of the autocrine growth-promoting activity secreted by H-35 cells into serum-free culture is due to transferrin.

Animals↗

Autocrine factor-independent growth of mammalian fibroblasts established in fully synthetic medium: no v-onc requirement in establishment.

In a previous study Chinese hamster fibroblasts carrying a partially deleted v-src were established in a synthetic medium lacking macromolecular supplements and shown to possess a particular serum-free phenotype hereafter designated sf. In cloning efficiency assays, sf, unlike wild-type, fibroblasts required a threshold cell density to grow from single cells, suggesting autocrine stimulation. In the present study a conditioned medium harvested from sf cells was added to the same sf cells, and the resulting cloning density was found to markedly diminish rather than increase. Sf cells were found to be unable to grow at cloning density because of trypsin damage: sf cells seeded into trypsin inhibitor-containing medium cloned with no requirement for threshold cells and were therefore independent of autocrine secretion from neighboring cells. Their cloning efficiency reached 7.7%; this value could not be improved by subcloning the sf culture, and it diminished when selenium was not added to the assay medium. To determine whether v-src is involved in the sf phenotype, five clones of the parental Chinese hamster fibroblast line not infected with Rous sarcoma virus were explanted into serum-free cultures with no macromolecular additives as in the case of v-src-containing cells. Each clone gave rise to an sf cell line growing indefinitely in synthetic medium like the v-src-containing sf cells, showing that the v-src gene is not required either for the establishment or maintenance of the sf phenotype.

Animals↗

Acquisition of in vitro growth autonomy during B16 melanoma malignant progression is associated with autocrine stimulation by transferrin and fibronectin.

Four mouse B16 melanoma subclones representing distinct stages in the benign-to-malignant progression of that tumor (G3.15, G3.5, G3.12, and G3.26), and three phenotype conversion variants with enhanced malignancy (G3.15*, G3.5*, and G3.12*), were comparatively examined for exogenous mitogen and growth factor requirements and for responsiveness to exogenous and endogenous growth modulators in monolayer culture. Growth behavior in serum-free medium with or without mitogen or growth factor supplements, and in supplemented quiescent serum-containing medium, confirmed previous indications that the G3.5 and G3.15* phenotypes were identical, as were the G3.26 and G3.12* phenotypes. However, G3.12 differed from the closest conversion equivalent, G3.5*, and probably represents an aberrant phenotype within this sequence. There was a direct relationship between degree of malignancy (G3.15-->G3.5-->G3.5*-->G3.26), growth capacity in serum-free medium, and responsiveness to transferrin. Only G3.5*, G3.26, and G3.12* cells were growth-autonomous in serum-free medium and also highly responsive to mitogens. The polypeptide growth factors epidermal growth factor, platelet-derived growth factor, basic fibroblast growth factor, transforming growth factor-alpha, and insulinlike growth factor-1 and -2 were generally stimulatory in quiescent medium, but the degree of growth promotion was unrelated to malignancy level. Transforming growth factor-beta 1 was inhibitory to the more benign populations (G3.15, G3.5, and G3.15*) but stimulated proliferation of other cells. All populations produced autocrine fibronectin, and G3.12, G3.5*, G3.26, and G3.12* cells also produced autocrine transferrin. Only G3.12 cells failed to utilize both of those factors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Autocrine growth of human B lymphocytes: maintained response to autostimulatory factors is the special feature of immortalization by Epstein-Barr virus--a hypothesis.

The autocrine growth profile of human B lymphocytes transformed with Epstein-Barr virus (EBV) was found to comprise three distinct components: a B-cell growth factor (BCGF); an interleukin-1 (IL-1)-like activity; an activity requiring cell-to-cell contact for its action. Observations on the inhibition of the EBV-carrying Daudi lymphoma line by alpha-interferon indicated that loss of response to these autostimulatory factors was underlying growth cessation. Furthermore, a putative receptor for BCGF was found to be down-regulated on B cells stimulated with non-transforming mitogens but constitutively expressed following EBV-transformation. Taken together with recent evidence that normal B cells produce autostimulatory factors, these findings suggest that the special feature of autocrine growth by EBV-immortalized cells is a maintenance of what should normally be a transient phenotype, possibly through deregulation of receptor expression. This hypothesis is discussed.

B-Lymphocytes↗

Monocyte-derived dendritic cells that capture dead tumor cells secrete IL-12 and TNF-alpha through IL-12/TNF-alpha/NF-kappaB autocrine loop.

This study focused on the question of how monocyte-derived dendritic cells (Mo-DCs) that capture dead tumor cells (Mo-DCs-Tum) secrete interleukin 12 (IL-12) and tumor necrosis factor alpha (TNF-alpha). Mo-DCs-Tum showed higher secretions of IL-12 and TNF-alpha than were shown by Mo-DCs. Enhanced nuclear factor-kappa B (NF-kappaB) activation was also induced in Mo-DCs-Tum within 6 h. The NF-kappaB inhibitor, pyrrolidine dithiocarbamate (PDTC), suppressed both IL-12 and TNF-alpha secretions from Mo-DCs-Tum. Administration of recombinant TNF-alpha or IL-12 enhanced IL-12 or TNF-alpha secretion respectively in Mo-DCs-Tum. Addition of anti-TNF-alpha or anti-IL-12 neutralizing antibody decreased NF-kappaB activation and IL-12 or TNF-alpha secretion in Mo-DCs-Tum. These results suggest that TNF-alpha or IL-12 secretion induces NF-kappaB activation, and it stimulates further TNF-alpha and IL-12 secretions, i.e., an IL-12/TNF-alpha/NF-kappaB autocrine loop, in Mo-DCs-Tum. Thus, Mo-DCs-Tum secrete a large amount of IL-12 and TNF-alpha through accelerated NF-kappaB activation induced by the IL-12/TNF-alpha/NF-kappaB autocrine loop.

Apoptosis↗

Effect of interleukin-8 on production of tumor-associated substances and autocrine growth of human liver and pancreatic cancer cells.

We have previously reported that human liver cancer cell lines produce interleukin-8 (IL-8) at high levels. Those tumor cells appeared to express two kinds of IL-8 receptor on their surface. In order to analyze the role of IL-8 on the biological characteristics of those tumor cells, we suppressed IL-8 production from human liver (HuH-7 and HuCC-T1) and pancreatic cancer cell lines (HuP-T4) by treatment with IL-8 antisense oligonucleotides. Suppression of IL-8 production resulted not only in inhibition of cell growth, but also in an increase in the concentrations of some tumor-associated substances such as carbohydrate antigen 19-9 (CA19-9) in the medium. These data indicate that IL-8 produced by human liver and pancreatic tumors may act as an autocrine growth factor and may control the production of some tumor-associated substances. Furthermore, surface expression of sialyl-Lewis(a), which is a ligand for ELAM-1 on human umbilical vein endothelial cells (HUVEC), HuCC-T1 and HuP-T4 cells was decreased and the attachment of these tumor cells to HUVEC was inhibited by treatment with IL-8 antisense oligonucleotide. Since the soluble form of CA19-9 (sialyl-Lewis(a)) was shown to inhibit the tumor cell binding to HUVEC, the decrease in release of CA19-9 into the medium and increase in the expression of sialyl-Lewis(a) on the cell surface may suggest that IL-8 production from the tumor cells enhances metastatic potential by augmenting the binding activity of the tumor cells to HUVEC. These data demonstrate that a cytokine produced by tumor cells may function as an autocrine growth factor and affect tumor cell dissemination.

Antigens, CD↗

Establishment and characterization of an epithelioid sarcoma cell line with an autocrine response to interleukin-6.

A novel epithelioid sarcoma (ES) cell line, designated as ES-OMC-MN, was established from a 44-year-old woman with recurrence and metastasis of ES. The cells were spindle-shaped or polygonal and were positive for cytokeratin and vimentin on immunohistochemical staining. Electron microscopy revealed desmosome-like structures between the cells. These characteristics were also noted in the original tumor. Southern blot analysis of HindIII digests showed an additional 8.0 kb band and an 8.8 kb band in DNA from the cultured cells and the original tumor as well as the peripheral blood cells of the patient, while only an 8.8 kb band was observed in control human placental DNA. There were no point mutations of N-ras codons 12, 13, and 61, suggesting that the abnormality of N-ras was not due to mutation but to polymorphism. Interleukin-6 (IL-6) was secreted into the culture medium at high levels. Recombinant IL-6 augmented the proliferation of these cells, while cell growth was inhibited by incubation with an anti-IL-6 antibody. The cells also expressed surface IL-6 receptors, indicating that IL-6 acted on this cell line in an autocrine manner. IL-6 and IL-6 receptors were also found in the original tumor. These results demonstrate that ES-OMC-MN cells retained all the morphological and biochemical characteristics of the original tumor and suggest that an autocrine effect of IL-6 may be involved in the development of ES.

Adult↗

Farnesyltransferase inhibitor FTI-277 prevents autocrine growth stimulation of neuroblastoma by BDNF.

PURPOSE: Autocrine growth stimulation by IGF-II and BDNF is frequently observed in neuroblastoma. The signals of the receptors of these growth factors are transduced to the nucleus via the Ras-MAP-kinase pathway where they induce proliferation. Inactivation of Ras-proteins by farnesyltransferase inhibitors such as FTI-277 disrupts growth stimulation of ras-transformed cells. We investigated whether FTI-277 is also active against tumor cells with constitutively activated growth factor receptors but lacking ras-mutations. METHOD: We analyzed eight different neuroblastoma cell lines for the expression of BDNF and its receptor trkB. Two of these cell lines with a complete autocrine BDNF loop were treated with FTI-277, and the effects of Ras-inactivation on the signal transduction of BDNF were analyzed. RESULTS: Treatment of neuroblastoma cells with 10 microM FTI-277 for 4 days reduced the amount of membrane-bound Ras-protein to almost 50%. Activation of MAP-kinase, induction of N-myc expression, and proliferation were clearly reduced in the treated cells. In addition, we observed some cytotoxic effects of FTI-277 accompanied by morphological changes of the neuroblastoma cells and a delayed induction of apoptosis. CONCLUSION: Farnesyltransferase inhibitors are active against neuroblastoma cells but the mechanism of action is not limited to inactivation of Ras. Further investigations on the targets of FTI-277 are recommended.

Alkyl and Aryl Transferases↗

Evidence for autocrine growth stimulation of cultured colon tumor cells by a gastrin/cholecystokinin-like peptide.

The peptide gastrin has been shown to have growth stimulatory effects on normal as well as malignant gastrointestinal tissue. In this study, we have examined the possibility of autocrine growth-stimulation of cultured colon tumor cells by a gastrin-like peptide. The gastrin/CCK receptor antagonist dibutyryl cGMP inhibited the proliferation of two human colon carcinoma cell lines HCT 116 (EC50 = 1.3 mM) and CBS (EC50 = 2.5 mM) in a dose-dependent manner. Marked morphological changes were observed in HCT 116 cells after treatment with 1 mM dibutyryl cGMP. In receptor binding assays, dibutyryl cGMP competed with 125I-labeled gastrin for binding to HCT 116 cells (IC50 = 1.8 mM). Another derivative of cyclic GMP, 8-Bromo cGMP used as control due to its considerably weaker affinity for the gastrin/CCK receptor, did not compete with radiolabeled gastrin for binding to HCT 116 cells and had no effect on the morphology or proliferation in monolayer cultures of HCT 116 or CBS cells at concentrations up to 10 mM. Antigastrin/CCK antisera was also found to have dose-dependent cytostatic effects on HCT 116 and CBS cells adapted to growth in serum-free medium. The antiproliferative effect of the gastrin/CCK receptor antagonist and antigastrin/CCK antibodies suggested that a gastrin-like peptide secreted by these cells may promote growth. Radioimmunoassay of the conditioned medium of these two cell lines indicated the presence of a gastrin-like peptide (10-50 pg/10(6) cells/72 h). Northern analysis using an oligonucleotide DNA probe complementary to the nucleotide sequence coding the dodecapeptide carboxyl terminal of human gastrin showed three transcripts (0.7, 3.3, and 3.7 kb) that hybridized with the probe. These data provide, for the first time, evidence for an autocrine growth stimulatory role of a gastrin/CCK-like peptide in cultured colon tumor cells.

Blotting, Northern↗

N-linked oligosaccharide processing and autocrine stimulation of tumor cell proliferation.

Somatic mutations which impair complex-type N-linked oligosaccharide processing and chemical inhibitors of processing have been shown to reduce metastatic potential in several experimental tumor models. In this report, we demonstrate that glycosylation mutants of the metastatic MDAY-D2 tumor cell line with either truncated glycans lacking sialic acid and galactose or a mutant with less branched N-linked oligosaccharides grow more slowly in serum-free medium (SFM) than do MDAY-D2 cells. In medium containing fetal calf serum, growth rates of the cell lines were similar. A revertant of the former mutation showed a return to a more rapid growth rate in SFM. The N-linked processing inhibitor swainsonine also reduced cell growth rate in SFM but not in serum-containing medium. One of five randomly selected clones of the MDAY-D2 tumor cell line showed a slower growth rate in SFM and also showed decreased expression of branched N-linked oligosaccharides. These observations suggest that in MDAY-D2 cells, optimal factor-independent stimulation is dependent upon expression of branched complex-type N-linked oligosaccharides. The growth rate of MDAY-D2 cells in SFM was dependent on the initial seeding density of the cultures, and medium conditioned by the cells accelerated the growth of low-density cultures, suggesting that the cells respond to an autocrine factor. Culture supernatants conditioned by mutant and wild-type cells had similar levels of growth-stimulating activity. However, both mutants and swainsonine-treated cells were less responsive to this growth-stimulating activity. The growth rates of the MDAY-D2 tumor cell lines in vivo as subcutaneous tumors correlated with their relative growth rates in SFM in vitro. The results suggest that branched complex-type N-linked oligosaccharides commonly expressed in malignant cells are required for optimal autocrine-dependent growth in vitro and may be a significant factor in tumor progression in vivo.

Alkaloids↗

Autocrine regulation of bovine retinal capillary endothelial cell (BREC) proliferation by BREC-derived basic fibroblast growth factor.

Fibroblast growth factors (FGFs) are mitogenic for bovine retinal capillary endothelial cells (BREC) seeded at a low density. Seeding BREC cells at a high density greatly reduces their requirement for basic FGF (bFGF) in order to proliferate actively. We show here that monolayers of BREC cells synthesize and release into the culture medium a growth factor, which on the basis of biological activity, heparin affinity, immuno-cross reactivity with anti-bFGF antibodies and mRNA analysis, has been identified as basic fibroblast growth factor. These data indicate that BREC cells are able to synthesize and release bFGF, which can act as a promoting-growth factor for these cells by a para- and/or autocrine mechanism. We suggest thus, that this para- and/or autocrine mechanism involving bFGF may play a key role in preretinal neovascularization, particularly in diabetic patients presenting a proliferative retinopathy.

Animals↗

Interruption of a transforming growth factor alpha autocrine loop in Caco-2 cells by antisense oligodeoxynucleotides.

BACKGROUND & AIMS: We have previously shown that Caco-2 cell proliferation is driven by basolateral membrane epidermal growth factor receptors. The aim of this study was to investigate whether autocrine production of transforming growth factor alpha (TGF-alpha) activates these receptors and stimulates proliferation using antisense oligodeoxynucleotides. METHODS: Caco-2 cells grown on microporous membranes or Jurkat cells were exposed to conventional or 5' cholesterol-modified oligodeoxynucleotides synthesized with random, antisense, or missense base sequences. Indices of proliferation were measured, including [3H]thymidine or [3H]uridine uptake for studies of short-term stimulation and the methylthiotetrazole assay as an index of cell number increase over longer periods. Secretion of TGF-alpha by cells was detected using a soft agar bioassay. RESULTS: Incubation with antisense oligodeoxynucleotides inhibited TGF-alpha secretion compared with controls. Random and missense oligodeoxynucleotides had no effect on proliferation. The TGF-alpha antisense oligodeoxynucleotides markedly inhibited proliferation, an effect that was abolished by adding TGF-alpha to the medium. Oligonucleotides had no effect on Jurkat cells, a lymphocytic cell line lacking epidermal growth factor receptors. Cholesterol-modified oligodeoxynucleotides were more effective and specific than unmodified oligodeoxynucleotides. CONCLUSIONS: Caco-2 cell proliferation is driven by autocrine stimulation of epidermal growth factor receptors by TGF-alpha. This mechanism may be effectively inhibited by antisense oligodeoxynucleotides, particularly those modified by the 5' attachment of cholesterol.

Base Sequence↗

[Endocrine, paracrine and autocrine mechanisms of aromatase activity].

The endocrine, paracrine and autocrine mechanisms involved in aromatase activity. Development of a single follicle during the menstrual cycle is under control of hormones stimulating follicular maturation, ovulation and luteogenesis. Several factors intervene locally to avoid other follicles developing at the same time as the dominant follicle. These other follicles remain quiescent or go on to atresia. Atresia results from the action of several endocrine, paracrine and autocrine mechanisms which synergistically inhibit aromatase activity. The subsequent lack of estrogens reduces granulosa cell multiplication.

Aromatase↗

Production of soluble autocrine inhibitory factors by human glioma cell lines.

Gliomas in vitro exhibit density-limited growth upon the attainment of confluency, an effect usually attributed to cell-cell contact inhibition. Since gliomas have been demonstrated to secrete an array of soluble factors which can enhance tumor growth, we undertook this study to ascertain whether production of soluble factors by the tumor may also inhibit growth in an autocrine manner, and whether production of such factors is associated with the growth phase of the glioma. We observed that cell-conditioned medium (supernatants) from non-confluent glioma cultures induced growth, while confluent culture supernatants produced pronounced growth suppression. These latter supernatants enhanced proliferation of non-transformed astrocytes. Supernatants derived from all stages of confluency produced inhibition of lymphocyte proliferation. To characterize these factors, dialyzed supernatant was tested and found to continue to produce lymphocyte suppression but no glioma growth limitation. Growth of tumors in indomethacin or in acetylsalicylic acid to abolish prostanoid synthesis abrogated the inhibitory influence on glioma growth but only partially reversed the lymphocyte suppressive capacity. These studies suggest that gliomas do produce a growth phase dependent autocrine inhibitory factor(s), and that the production of these small molecular weight factors is at least partially under control of the cyclooxygenase pathway.

Adult↗

The effect of mycoplasma on the autocrine stimulation of human small cell lung cancer in vitro by bombesin and beta-endorphin.

The tumor stem cell clonogenic assay was utilized to investigate the autocrine growth response of small cell lung cancer (SCLC) to bombesin (BN) and beta-endorphin (beta-E). Mycoplasma contamination was detected in the human SCLC cell line NCl-H345 by a nucleic acid hybridization assay which detects mycoplasma ribosomal RNA. Clonogenic assays of mycoplasma (+) cells were compared to assays of the same cell line following treatment for mycoplasma. Concentrations of beta-E ranging from 0.1nM to 25nM or BN (0.1nM-100nM) were added to cells, media and agarose and applied to prepared base layers. Following incubation for 12-14 days at 37 degrees C, the degree of clonal growth stimulation was determined by colony counts greater than or equal to 42 mu. The non-infected cell population grew in the presence of 25nM BN up to 69% over control growth. The infected cells, however, did not grow more than 27% above control. In the presence of 10nM beta-E, colony counts of non-infected cells exceeded the control values by up to 187% whereas the mycoplasma (+) colonies did not grow more than 20% over the control values. These results indicate a marked reduction in the response of SCLC cell lines to the peptides BN and beta-E when infected with mycoplasma. Since infecting mycoplasma typically adhere to cellular membranes, these adherent mycoplasma may interfere with membrane receptors or alter signal transduction, thus, inhibiting the development of the autocrine response.

Bombesin↗

Autocrine regulation of erythropoietin gene expression in human hepatocellular carcinoma cells.

We have previously reported that a marked increase in erythropoietin (Epo) production can be demonstrated in Hep3B cell cultures in response to hypoxia (1). In order to determine whether this increase involves an autocrine mechanism, we have investigated the effects of purified human recombinant Epo (rHuEpo) on Epo production. Purified rHuEpo (5-80 mU/ml) produced a significant increase above control levels of Epo in Hep3B cell cultures under normoxic (20% O2) conditions. Hypoxic (1% o2) incubation of Hep3B cells with rHuEpo caused an increase over control levels of EpomRNA. Hep3B cells also expressed Epo receptor (Epo-R) transcripts. Binding studies [125I]Epo revealed that Hep3B cells contain a single class of binding site (kd=2.9 nmol/L and Bmax=1760 sites/cell). Antierythropoietin receptor monoclonal antibody inhibited the rHuEpo induced elevation in medium levels of Epo and blocked [125I]-Epo binding to Hep3B cell membranes. These results demonstrate that the expression of EpomRNA may be controlled, at least in part, by an autocrine mechanism.

Aerobiosis↗