Biological analyses of the effects of TiO2 and PEG-b-PLA nanoparticles on three-dimensional spheroid-based tumor

The aim of our study was to monitor the antiproliferative/ cytotoxic and genotoxic effects of both, poly(ethylene glycol)-block-poly(lactic acid) (PEG-b-PLA) and titanium dioxide (TiO2) nanoparticles on the tumor (HT-29, MCF-7, U118MG) and healthy (HEK-293T) cell lines during 2D cultivation and during cultivation in the spheroid form (3D cultivation). Cells or spheroids were cultivated with nanoparticles (0.01, 0.1, 1, 10, 50, and 100 ?g/ml) for 72 hours. The cytotoxic effect was determined by the MTT test and the genotoxic effect by the comet assay. We found that 2D cultivation of tumor cell lines with PEG-b-PLA and TiO2 nanoparticles had an anti-proliferative effect on human colon cancer cell line HT-29, human breast cancer cell line MCF-7, human glioma cell line U-118MG during 72h cultivation, but not on control/healthy HEK-293T cells. At the concentrations used, the tested nanoparticles caused no cytotoxic effect on tumor cell lines. Nanoparticles PEG-b-PLA induced significant damage to DNA in HT-29 and MCF-7 cells, while TiO2 nanoparticles in MCF-7 and U-118MG cells. Only PEG-b-PLA nanoparticles caused cytotoxic (IC50 = 7 mikrog/ml) and genotoxic effects on the healthy cell line HEK-293T after 72h cultivation. The cells which were cultivated in spheroid forms were more sensitive to both types of nanoparticles. After 72h cultivation, we observed the cytotoxic effect on both, the tumor and healthy cell lines.

Dynamics of cachexia-associated inflammatory changes in the brain accompanying intra-abdominal fibrosarcoma growth in Wistar rats

Accumulated data indicate that inflammation affecting brain structures participates in the development of cancer-related cachexia. However, the mechanisms responsible for the induction and progression of cancer-related neuroinflammation are still not fully understood. Therefore, we studied the time-course of neuroinflammation in selected brain structures and cachexia development in tumor-bearing rats. After tumor cells inoculation, specifically on the 7th, 14th, 21st, and 28th day of tumor growth, we assessed the presence of cancer-associated cachexia in rats. Changes in gene expression of inflammatory factors were studied in selected regions of the hypothalamus, brain stem, and circumventricular organs. We showed that the initial stages of cancer growth (7th and 14th day after tumor cells inoculation), are not associated with cachexia, or increased expression of inflammatory molecules in the brain. Even when we did not detect cachexia in tumor-bearing rats by the 21st day of the experiment, the inflammatory brain reaction had already started, as we found elevated levels of interleukin 1 beta, interleukin 6, tumor necrosis factor alpha, and glial fibrillary acidic protein mRNA levels in the nucleus of the solitary tract. Furthermore, we found increased interleukin 1 beta expression in the locus coeruleus and higher allograft inflammatory factor 1 expression in the vascular organ of lamina terminalis. Ultimately, the most pronounced manifestations of tumor growth were present on the 28th day post-inoculation of tumor cells. In these animals, we detected cancer-related cachexia and significant increases in interleukin 1 beta expression in all brain areas studied. We also observed significantly decreased expression of the glial cell activation markers allograft inflammatory factor 1 and glial fibrillary acidic protein in most brain areas of cachectic rats. In addition, we showed increased expression of cluster of differentiation 163 and cyclooxygenase 2 mRNA in the hypothalamic paraventricular nucleus, A1/C1 neurons, and area postrema of cachectic rats. Our data indicate that cancer-related cachexia is associated with complex neuroinflammatory changes in the brain. These changes can be found in both hypothalamic as well as extrahypothalamic structures, while their extent and character depend on the stage of tumor growth.

DNA Methylation Mediates EMT Gene Expression in Human Pancreatic Ductal Adenocarcinoma Cell Lines

Due to abundant stroma and extracellular matrix, accompanied by lack of vascularization, pancreatic ductal adenocarcinoma (PDAC) is characterized by severe hypoxia. Epigenetic regulation is likely one of the mechanisms driving hypoxia-induced epithelial-to-mesenchymal transition (EMT), responsible for PDAC aggressiveness and dismal prognosis. To verify the role of DNA methylation in this process, we assessed gene expression and DNA methylation changes in four PDAC cell lines. BxPC-3, MIA PaCa-2, PANC-1, and SU.86.86 cells were exposed to conditioned media containing cytokines and inflammatory molecules in normoxic and hypoxic (1% O2) conditions for 2 and 6 days. Cancer Inflammation and Immunity Crosstalk and Human Epithelial to Mesenchymal Transition RT² Profiler PCR Arrays were used to identify top deregulated inflammatory and EMT-related genes. Their mRNA expression and DNA methylation were quantified by qRT-PCR and pyrosequencing. BxPC-3 and SU.86.86 cell lines were the most sensitive to hypoxia and inflammation. Although the methylation of gene promoters correlated with gene expression negatively, it was not significantly influenced by experimental conditions. However, DNA methyltransferase inhibitor decitabine efficiently decreased DNA methylation up to 53% and reactivated all silenced genes. These results confirm the role of DNA methylation in EMT-related gene regulation and uncover possible new targets involved in PDAC progression.

Changes in gene expression in brain structures related to visceral sensation, autonomic functions, food intake, and cognition in melanoma-bearing mice

The brain exerts complex effects on the initiation and progression of cancer in the body. However, the influence of cancer localized in peripheral tissues on the brain has been only partially described. Therefore, we investigated gene expression in brain structures that participate in transmitting viscerosensory signals, regulating autonomic functions and food intake, as well as cognition in C57Bl/6J mice with B16-F10 melanoma. In addition, we investigated the relationship between peripheral inflammation and neuroinflammation. We found increased neuronal activity in the nucleus of the solitary tract of tumor-bearing mice, whereas neuronal activity in the A1/C1 catecholaminergic cell group, parabrachial nucleus, lateral hypothalamic area, ventromedial nucleus of the hypothalamus, paraventricular nucleus of the hypothalamus, and hippocampus was decreased. In the majority of investigated brain structures, we found increased gene expression of IL-1β, whereas gene expression of IL-6 and NF-κB was reduced or unchanged compared with controls. Melanoma-bearing mice also showed increased gene expression of tyrosine hydroxylase in the A1/C1 catecholaminergic cell group, nucleus of the solitary tract, and locus coeruleus, as well as reduced mRNA levels of hypocretin neuropeptide precursor protein in the lateral hypothalamic area, and proopiomelanocortin in the arcuate nucleus. In addition, we found reduced mRNA levels of Bcl-2, brain-derived neurotrophic factor, and doublecortin in the hippocampus. Our data indicate that skin melanoma induces complex changes in the brain, and these changes are most probably caused by cancer-related signals mediated by pro-inflammatory cytokines.

Sympathectomy reduces tumor weight and affects expression of tumor-related genes in melanoma tissue in the mouse

Accumulated evidence indicates that sympathetic nerves may potentiate tumor growth, including melanoma. To elucidate possible mechanisms for this effect, we performed chemical sympathectomy by intraperitoneal (i.p.) injection of the neurotoxin 6-hydroxydopamine hydrobromide (100 mg/kg of body weight); in nine adult male C57BL/6J mice; nine control mice received i.p. vehicle (VEH). Seven days later, all mice were injected subcutaneously with 3 × 10(3) B16-F10 melanoma cells. Mice were euthanized 20 d after injection of melanoma cells, for measurement of tumor weight and expression of genes related to sympathetic signaling, apoptosis, hypoxia and angiogenesis in tumor tissue. To assess potential involvement of the hypothalamo-pituitary-adrenocortical axis in the effect of sympathectomy on melanoma growth, concentrations of plasma corticosterone and level of glucocorticoid receptor mRNA in tumor tissue were determined. We found that sympathectomy significantly attenuated melanoma growth (tumor weight 0.29 ± 0.16 g versus 1.02 ± 0.30 g in controls; p < 0.05). In tumor tissue from sympathectomized mice, we found significantly increased gene expression (measured by real-time PCR), relative to VEH-injected controls, of tyrosine hydroxylase, neuropeptide Y and glucocorticoid receptor (all p < 0.05), and alpha1, beta1 and beta3 adrenergic receptors (all p < 0.025), and factors related to apoptosis (Bcl-2 and caspase-3; p < 0.05) and hypoxia (hypoxia inducible factor 1 alpha) (p = 0.005). Plasma corticosterone concentrations were significantly elevated (p < 0.05) in these mice. Our findings indicate that sympathectomy induces complex changes in the tumor microenvironment reducing melanoma growth. Such complex changes should be considered in the prediction of responses of cancer patients to interventions affecting sympathetic signaling in tumor tissue and its environment.

Hypericin fluorescence kinetics in the presence of low density lipoproteins: study on quail CAM assay for topical delivery

There has been increasing interest in fluorescence-based imaging techniques in clinical practice, with the aim to detect and visualize the tumour configuration and the border with healthy tissue. Strong photodynamic activity of hypericin (Hyp) can be improved by various molecular transport systems (e.g. LDL). Our aim was to examine pharmacokinetics of Hyp in the presence of LDL particles on ex ovo chorioallantoic membrane (CAM) of Japanese quail with implanted TE1 tumour spheroids (human squamocellular carcinoma). Spheroids were implanted on CAM surface on embryonal day 7 and after 24 hours formulations of free Hyp and Hyp:LDL 100:1 and 200:1 were topically applied. All experimental formulations in the fluorescent image very well visualized the tumour spheroid position, with gradual increase of fluorescence intensity in 6-h observation period. LDL transportation system exhibited clear superiority in fluorescence pharmacokinetics than free Hyp formulation by increasing tumour-normal difference. Our experimental results confirm that Hyp and Hyp:LDL complex is potent fluorophore for photodynamic diagnosis of squamocellular carcinoma.

Ambiguous effect of signals transmitted by the vagus nerve on fibrosarcoma incidence and survival of tumor-bearing rats

While the parasympathetic nervous system appears to be involved in the regulation of tumor progression, its exact role is still unclear. Therefore, using a rat BP6-TU2 fibrosarcoma tumor model, we investigated the effect of (1) reduction of vagal activity produced by subdiaphragmatic vagotomy; and (2) enhancement of vagal activity produced by continuous delivery of electric impulses to the cervical part of the vagus nerve on tumor development and survival of tumor-bearing rats. We also evaluated the expression of cholinergic receptors within in vitro cultivated BP6-TU2 cells. Interestingly, we found that both, vagal stimulation and subdiaphragmatic vagotomy slightly reduced tumor incidence. However, survival of tumor-bearing rats was not affected by any of the experimental approaches. Additionally, we detected mRNA expression of the α1, α2, α5, α7, and α10 subunits of nicotinic receptors and the M1, M3, M4, and M5 subtypes of muscarinic receptors within in vitro cultivated BP6-TU2 cells. Our data indicate that the role of the vagus nerve in modulation of fibrosarcoma development is ambiguous and uncertain and requires further investigation.

Chemical sympathectomy suppresses fibrosarcoma development and improves survival of tumor-bearing rats

Both experimental and clinical data indicate that the sympathetic nervous system may affect the development of certain tumors. To test this, in the present study we combined in vivo and in vitro approaches to study the effect of the sympathetic nervous system on proliferation of BP6-TU2 fibrosarcoma cells. First, we investigated the effect of 6-hydroxydopamine-induced sympathectomy on tumor development and survival of tumor-bearing rats. One week after chemical sympathectomy, we injected the BP6-TU2 fibrosarcoma cells intraperitoneally into male Wistar rats. The sympathectomy significantly reduced the incidence of intraperitoneal tumors and resulted in significantly improved survival of tumor-bearing rats compared to those with intact sympathetic innervation. Using immunohistochemical methods, we found neuron-specific enolase immunopositive structures within fibrosarcoma tissue, indicating innervation of tumors. Finally, an in vitro study showed elevated proliferation of BP6-TU2 fibrosarcoma cells in response to adding norepinephrine to the culture medium. Our findings indicate that sympathetic nerves directly potentiate the proliferation of BP6-TU2 fibrosarcoma cells in rats.

Leukemic cells modulate induction of COX-2 in human stromal fibroblasts

The interaction of cancer cells with surrounding normal tissue cells is of utmost importance for their survival and tumor progression. For these purposes the cancer cells exploit normal tissue responses associated with inflammation and tissue repair. In the immediate tumor microenvironment one of the early stromal markers is cyclooxygenase-2 (COX-2). In this study we evaluated the effect of leukemia cell lines on nemosis-induced COX-2 expression in stromal fibroblasts. We found that THP-1 cells were the most potent leukemic cells (IC50=746) to suppress COX-2 expression. The U-937 cell line exhibited similar suppressive potency (IC50=921), whereas the KG-1 cell line (IC50=3519) was the least potent to affect COX-2 expression in the stromal cells. Our study shows that human leukemic cells can actively participate in modulation of stromal inflammation via inhibition of COX-2 expression. In a co-culture model of leukemia cell lines and stromal fibroblasts, our data suggest that the tumor-stromal interactions are complexly regulated, and the straightforward association of COX-2 expression with tumor progression may require re-evaluation since some tumor cells, e.g. from hematologic malignancies, may differentially modulate inflammation and COX-2 expression.

Paracrine factors from fibroblast aggregates in a fibrin-matrix carrier enhance keratinocyte viability and migration

Efficient re-epithelialization of skin lesions is dependent on paracrine support from connective tissue fibroblasts. In deep skin defects, the supporting growth factor incentive is lacking. Current methods of keratinocyte transplantation with compromised attachment, spread, and cell proliferation warrant improvement and refinement. We describe here how human keratinocytes can be stimulated by matrix-embedded factors from a novel process of fibroblast activation: nemosis. Interestingly, the unique set of mediators released in this process also plays a key role in normal wound healing. To develop a system for targeted delivery of nemosis-derived paracrine effectors, herein designated as Finectra, we combined them with fibrin to establish a controlled-release gel. Keratinocytes seeded to cover this active matrix showed better adherence, outgrowth, and viability than did cells on control matrix. The matrix incorporating Finectra supported viability of both primary keratinocytes and green fluorescent protein (GFP)-labeled HaCaT cells, as evaluated by MTT assay and persistence of GFP-fluorescence. The fibrin-Finectra matrix promoted migration of keratinocytes to cover a larger area on the matrix, suggesting better wound coverage on transplantation. An inhibitor of EGFR/c-Met receptor tyrosine kinases abolished keratinocyte responses to fibrin-Finectra matrix. This matrix can thus deliver biologically relevant synergistic stimuli to keratinocytes and hasten re-epithelialization.

Bone marrow mesenchymal stem cells undergo nemosis and induce keratinocyte wound healing utilizing the HGF/c-Met/PI3K pathway

We previously showed cell-cell contacts of human dermal fibroblasts to induce expression of the hepatocyte growth factor/scatter factor (HGF) in a process designated as nemosis. Now we report on nemosis initiation in bone marrow mesenchymal stem cells (BMSCs). Because BMSCs are being used increasingly in cell transplantation therapy we aimed to demonstrate a functional effect and benefit of BMSC nemosis for wound healing. Nemotic and monolayer cells were used to stimulate HaCaT keratinocyte migration in a scratch-wound healing assay. Both indicators of nemosis, HGF production and cyclooxygenase-2 expression, were induced in BMSC spheroids. When compared with a similar amount of cells as monolayer, nemotic cells induced keratinocyte in vitro scratch-wound healing in a concentration-dependent manner. The HGF receptor, c-Met, was rapidly phosphorylated in the nemosis-stimulated keratinocytes. Nemosis-induced in vitro scratch-wound healing was inhibited by an HGF-neutralizing antibody as well as the small molecule c-Met inhibitor, SU11274. HGF-induced in vitro scratch-wound healing was inhibited by PI3K inhibitors, wortmannin and LY294002, while LY303511, an inactive structural analogue of LY294002, had no effect. Inhibitors of the mitogen-activated protein kinases MEK/ERK1/2 (PD98059 and U0126), and p38 (SB203580) attenuated HGF-induced keratinocyte in vitro scratch-wound healing. We conclude that nemosis of BMSCs can induce keratinocyte in vitro scratch-wound healing, and that in this effect signaling via HGF/c-Met is involved.

Brain response to induced peripheral cancer development in rats: dual fos-tyrosine hydroxylase and fos-oxytocin immunohistochemistry

OBJECTIVE

During last few decades a considerable number of data has emerged supporting the hypothesis that central nervous system might monitor and modulate tumor growth. This assumption is based on two facts: 1. immune system plays a crucial role in the development and progression of cancer; 2. immune and nervous systems communicate tightly and bidirectionally. The aim of present study was to elucidate whether tumor growth may induce detectable changes in brain structures that are involved in the response to immune challenges.

METHODS

Using Fos immunohistochemistry, we investigated whether the advanced stage of cancer, induced by a single intraperitoneal injection of BP6-TU2 fibrosarcoma cells to male Wistar rats, could activate Fos expression in the nucleus of the solitary tract (NTS), amygdala and parabrachial nuclei (PBN) and also activate some of neuronal phenotypes including tyrosine hydroxylase (TH) neurons in the brainstem noradrenergic cell groups and hypothalamic oxytocinergic neurons.

RESULTS

Twenty eight days after the initiation of tumor process we found increased Fos expression in NTS/A2, A1 noradrenergic cells, PBN as well as in the hypothalamic paraventricular, supraoptic and accessory oxytocinergic neurons. These structures are involved in the transmission of signals related to immune challenges within the brain and consequent elaboration of neuro-endocrine responses.

CONCLUSIONS

The data obtained are supporting the view that the information on peripheral tumor development might be transmitted to the brain. However, further studies are necessary to be performed to reveal whether our findings can be attributed to specific effect of cancer or whether observed changes in the activity of brainstem and hypothalamic neurons reflex processes that only accompany the cancer progression.

Does incorporation of gene for green fluorescent protein in BP6 fibrosarcoma tumor cells depress their intraperitoneal growth in rats? (In honour of Nobel Prize laureates 2008--Osamu Shimomura, Martin Chalfie, Roger Y. Tsien)

This manuscript was in honour of Nobel Prize in chemistry "for the discovery and development of the green fluorescent protein, GFP" to Osamu Shimomura, Martin Chalfie, and Roger Y. Tsien, simultaneously a brief information about experience with GFP in experimental tumorigenesis used this study is also presented. The experimental data have showed that BP6 cells incorporated with GFP gene have had smaller ability to induce both experimental intraperitoneal and subcutaneous tumor process. It was anticipated that incorporation of GFP gene might change physiological properties of cytoskeleton and worsen adhesive characteristics of tumor cells. It was also supposed that aftertime GFP will enable to monitor proliferation of cells not only within experimental work, but also in human medicine. GFP could help (supposedly) as reporter of proliferation, but also can serve as "target" for guide of tumorigenesis inhibiting substances. These ideas which are consequences of our experiments we append as congratulation to Nobel Prize in chemistry of the 2008 (Fig. 2, Ref. 44). Full Text (Free, PDF) www.bmj.sk.

Effective gene transfer to melanoma cells using bacterial ghosts

Bacterial ghosts (BG) are cell envelopes preparations of Gram-negative bacteria devoid of cytoplasmic content produced by controlled expression of PhiX174 plasmid-encoded lysis gene E. Eight melanoma cell lines were investigated for their capacity to bind and phagocyte BG derived from Escherichia coli NM522 and Mannheimia haemolytica A23. High capability to bind BG was observed in almost all of the analyzed cell lines, furthermore cells were able to take up BG independently of the used bacterial species. Further, transfection efficiency of BG loaded with DNA in vitro was measured. The Bowes cells exhibited a high expression level of GFP and the incubation of cells with plasmid loaded BG led up to 82% transfection efficiency.

Neural-endocrine-immune complex in the central modulation of tumorigenesis: facts, assumptions, and hypotheses

For the precise coordination of systemic functions, the nervous system uses a variety of peripherally and centrally localized receptors, which transmit information from internal and external environments to the central nervous system. Tight interconnections between the immune, nervous, and endocrine systems provide a base for monitoring and consequent modulation of immune system functions by the brain and vice versa. The immune system plays an important role in tumorigenesis. On the basis of rich interconnections between the immune, nervous and endocrine systems, the possibility that the brain may be informed about tumorigenesis is discussed in this review article. Moreover, the eventual modulation of tumorigenesis by central nervous system is also considered. Prospective consequences of the interactions between tumor and brain for diagnosis and therapy of cancer are emphasized.

Cell-cell contact activation of fibroblasts increases the expression of matrix metalloproteinases

BACKGROUND

We recently found that direct homotypic cell-cell contacts between human dermal fibroblasts induce a novel form of cell activation leading to non-apoptotic programmed cell death. As the major features of this process we identified massive induction of cyclo-oxygenase-2 and production of inflammatory prostaglandins. On the surface of the decomposing spheroids, activation of the major extracellular proteolytic cascade, plasminogen activation, associated with surface exposure of alpha-enolase, took place.

AIM

To further characterize pericellular proteolysis by cell-cell contact-activated fibroblasts we studied the role of the other major extracellular proteolytic system, matrix metalloproteinases (MMPs).

METHODS

MMP expression in fibroblast clusters and monolayers was compared using mRNA microarrays and immunoblot analyses. The activities of MMPs were confirmed using MMP inhibitors and caseinolysis.

RESULTS

In microarrays MMP-1, -10, and -14 (MT1-MMP) were induced 5.8-, 106-, and 5.6-fold, respectively. These findings were confirmed by immunoblotting. Radial caseinolysis showed low level of proteolytic activity in spheroid-conditioned media; ilomastat, a general inhibitor of MMPs, suppressed 50% of the proteolytic activity thus confirming it to be at least in part due to MMPs. A cocktail of tetracycline-derived MMP inhibitors suppressed lactate dehydrogenase (LDH) release only 11%, and if combined with aprotinin 28%.

CONCLUSIONS

Cell-cell contact activation of fibroblasts induced MMP-1, -10, and MT1-MMP expression, suggesting similar signaling to that in inflammation and cancer.

Bacterial ghosts as a novel advanced targeting system for drug and DNA delivery

Although there are powerful drugs against infectious diseases and cancer on the market, delivery systems are needed to decrease serious toxic and noncurative side effects. In order to enhance compliance, several delivery systems such as polymeric micro- and nanoparticles, liposomal systems and erythrocyte ghosts have been developed. Bacterial ghosts representing novel advanced delivery and targeting vehicles suitable for the delivery of hydrophobic or water-soluble drugs, are the main focus of this review. They are useful nonliving carriers, as they can carry different active substances in more than one cellular location separately and simultaneously. Bacterial ghosts combine excellent natural or engineered adhesion properties with versatile carrier functions for drugs, proteins and DNA plasmids or DNA minicircles. The simplicity of both bacterial ghost production and packaging of drugs and/or DNA makes them particularly suitable for the use as a delivery system. Further advantages of bacterial ghost delivery vehicles include high bioavailability and a long shelf life without the need of cold-chain storage due to the possibility to freeze-dry the material.

Induction of Hepatocyte Growth Factor/Scatter Factor by Fibroblast Clustering Directly Promotes Tumor Cell Invasiveness

For determining the malignant behavior of a tumor, paracrine interactions between stromal and cancer cells are crucial. We previously reported that fibroblast clustering induces cyclooxygenase-2 (COX-2), plasminogen activation, and programmed necrosis, all of which were significantly reduced by nonsteroidal anti-inflammatory drugs (NSAID). We have now found that tumor cell-conditioned medium induces similar fibroblast clustering. Activation of the necrotic pathway in clustering fibroblasts, compared with control monolayer cultures, induced a massive >200-fold production of bioactive hepatocyte growth factor/scatter factor (HGF/SF), which made human carcinoma cells spread and invade a collagen lattice. This response occurred only if a functional, properly processed c-Met receptor was present, which was then rapidly phosphorylated. The invasion-promoting activity was inhibited by a neutralizing HGF/SF antibody. NSAIDs, if added early during fibroblast aggregation, inhibited HGF/SF production effectively but had no effect at later stages of cell aggregation. Our results thus provide the first evidence that aggravated progression of tumors with necrotic foci may involve paracrine reciprocal signaling leading to stromal activation by direct cell-cell contact (i.e., nemosis).

Bacterial ghosts as novel efficient targeting vehicles for DNA delivery to the human monocyte-derived dendritic cells

Recombinant bacterial ghosts loaded with plasmids were tested as an antigen delivery system and as a potential mediator of maturation for human monocyte-derived dendritic cells (DCs). Bacterial ghosts are cell envelopes derived from Gram-negative bacteria; the intracellular content is released by the controlled expression of plasmid-encoded lysis gene E of PhiX174. All the cell surface structures of the native bacteria, including the outer membrane proteins, adhesins, LPS, lipid A, and peptidoglycans, are preserved. Co-incubation of immature DCs with ghosts resulted in decreased expression of CD1a, CD80, and CD83 molecules, while addition of maturation mix (TNF-alpha, IL-1 beta, IL-6, and PGE2) to the cultures enhanced expression of these molecules. No marked changes were observed in the expression of the CD11c, CD40, and CD86 surface molecules. The exposure of DCs to ghosts in combination with maturation mix resulted in a nonsignificant increase in their ability to activate T cells. DCs co-incubated with bacterial ghosts carrying plasmids encoding GFP in combination with maturation mix exhibited high expression levels of GFP (up to 85%). These results indicate that in addition to their well-established use as vaccines, bacterial ghosts can also be used as carriers of nucleic acid-encoded antigens.

T cell-specific immune response induced by bacterial ghosts

BACKGROUND

Bacterial ghosts, genetically inactivated Gram-negative bacterial pathogens, possess significant advantages over commonly used vaccination technologies. The autolysis of the bacteria, by the expression of a cloned viral gene, results in empty bacterial envelopes through the expulsion of cytoplasmic content. Immunostimulatory properties are generally presented through the targeting of professional antigen-presenting cells (APCs), such as macrophages and dendritic cells (DCs).

MATERIAL/METHODS

This study investigated the interactions between porcine antigen-presenting cells and bacterial ghosts derived from the bacterial pathogen Actinobacillus pleuropneumoniae. The maturation process of DCs and their generation of immune responses to bacterial ghosts was shown by the expression of activation markers on their surface, as well as in the functional tests.

RESULTS

A population of porcine APCs was generated from PBS by incubation with rpo-GMCSF and rh-IL-4. The cells expressed SWC3, MIL-2, CD80/86 molecules, as well as a high level of MSA3 molecules. The internalization of bacterial ghosts by the cells resulted in increased expression of MSA3 molecules. The capacity of T cells to proliferate when induced by bacterial ghosts was 4 times higher in the cultures including APCs than in cultures stimulated with bacterial ghosts only.

CONCLUSIONS

We found that antigen-presenting cells have the capacity to stimulate specific T cells after the internalization and processing of Actinobacillus ghosts, as demonstrated by a strong specific T-cell response generated against the ghost antigens.

Cell-cell contacts trigger programmed necrosis and induce cyclooxygenase-2 expression

Necrosis was induced by cell-cell contacts of human dermal fibroblasts in three-dimensional culture. Dramatic induction of cyclooxygenase-2 (COX-2) expression was found throughout these necrotizing cell clusters, whereas no increase in expression of apoptosis markers was seen. The cells were rapidly committed to necrosis, and the process could not be reversed by allowing them to spread and adhere on a solid substrate. Induction of COX-2 expression was accompanied by greatly enhanced production of the prostaglandins E(2), I(2), and F(2alpha). When applied exogenously on necrotizing clusters, these prostaglandins delayed cell clustering and further enhanced COX-2 expression. Abolishing prostaglandin production by NS-398 or indomethacin reduced cell membrane damage (as measured by lactate dehydrogenase release into the culture medium). We also identified alpha-enolase-mediated plasminogen activation as the major extracellular proteolytic executor of necrotic cell death. In contrast to inhibition of COX-2, inhibition of plasminogen activation failed to inhibit membrane damage associated with necrosis. Intracellular proteolysis, by caspases, was shown to take part in COX-2 induction. Taken together, our results indicate that cell-cell contacts induce an actively programmed necrotic process that functionally involves COX-2, a known hallmark of inflammation and cancer.

The 'Abtropfung phenomenon' revisited: Dermal nevus cells from congenital nevi cannot activate matrix metalloproteinase 2 (MMP-2)

Since Unna's Abtropfung hypothesis, the process of migration of nevus cells in the dermis remains unknown. To investigate its mechanisms, we studied the role of gelatinases in dermal nevus cells obtained from congenital pigmented nevi, which are major actors in the remodeling of basement membrane proteins. Our previous studies have shown that dermal nevus cells express pro-matrix metalloproteinase (MMP)-2 exclusively and cannot return to the dermis when seeded together with keratinocytes on top of the dermis in a skin reconstruction model. To examine why MMP-2 was not in its active form, we used Western blot to study the expression of members of the MMP-2 activation pathway (membrane type 1-MMP and tissue inhibitor of metalloproteinase-2), which proved to be normally expressed. To induce the dermal passage of nevus cells artificially, we also tried to activate gelatinases with phorbol-12-myristate-13-acetate and epidermal growth factor, using epidermis reconstructed with nevus cells. No migration in the dermis could be triggered. We conclude that the absence of active MMP-2 is due to a functional blockade of its activation pathway and may prevent dermal nevus cells from reaching the dermal compartment in skin reconstructs. Furthermore, our findings reinforce the concept that dermal nevus cells originating from congenital nevi are in a quiescent status.

Conditioned medium from HeLa cells enhances motility of human monocyte-derived dendritic cells but abrogates their maturation and endocytic activity

Progressive tumor proliferation may be associated with suppression of the immune response. Several different mechanisms can contribute to immune evasion. It is generally proposed that inhibition of dendritic cell functions would be a key mechanism by which tumors could escape immune surveillance. Therefore, the purpose of this study was to evaluate the capacity of HeLa cells conditioned medium (HeLa-CM) to modulate phenotypic and functional parameters of human peripheral blood monocyte-derived dendritic cells (DCs). Two types of reference DCs population were generated in vitro, the first cultured in the presence of IL-4 and GM-CSF which represented immature DCs (iDCs) and the second, representing mature DCs (mDCs), was raised from the iDCs by additional stimulation with a maturation cocktail - TNF-alpha, IL-1beta, IL-6, PGE2. In parallel, the iDCs were treated with HeLa-CM collected from the tumor cells. The analysis of DC populations demonstrated that the HeLa-CM prevented maturation of these cells and also impaired their capacity to uptake an antigen and stimulate proliferation of allogeneic T cells. In contrast, HeLa-CM modulated DCs exhibited a 3-fold increase mobility over iDCs. The latter functional capacity did not correlate with the levels of matrix metalloproteinase expression in the analysed cells. Altogether, our results provide evidence that HeLa cells produce soluble factors that might dramatically alter basic phenotypic and functional characteristics of DCs.

Dermal nevus cells from congenital nevi cannot penetrate the dermis in skin reconstructs

Congenital nevi are composed of pigment cells bearing common features with melanocytes but showing altered differentiation which leads to nesting and dermal involvement. Using a dead de-epidermized dermis seeded with a combination of keratinocytes and various sources of pigment cells (normal melanocytes, dermal nevus cells from congenital nevi, Bowes melanoma cells), we have studied the formation of nests and the dermal migration of pigment cells together with their secretion profiles of matrix metalloproteinases (MMP). Dermal fibroblasts were also used as control cells in epidermal reconstructs. Besides their morphologic features, the absence of pigment donation to keratinocytes was the major characteristic of dermal nevus cells. A positive correlation was established between the increasing percentage of seeded nevus cells and the patchy pigmentation of reconstructs, as well as the clustering of cells in junctional nests. However, the presence of nevus cells in the dermis of reconstructs was never detected, whereas melanoma cells and dermal fibroblasts could invade the dermis during the time span of the experiments. MMP9 was never expressed in congenital dermal nevus cells but pro-MMP2 was constitutively expressed by all strains of congenital nevus cells and dermal fibroblasts. Melanocytes produced comparable amounts of both pro-MMP2 and pro-MMP9, and Bowes melanoma cells secreted a marginal level of pro-MMP2. In view of their three-dimensional behaviour and secretion of MMPs, we propose that dermal congenital nevus cells correspond to an intermediate status of differentiation between normal melanocytes and melanoma cells. Activation of MMPs by a cofactor or the activation of another signalling pathway seems necessary to induce the dermal passage of nevus cells.

The level of urokinase-type plasminogen activator receptor is increased in serum of ovarian cancer patients

Ascites and serum of patients with ovarian carcinoma contain a soluble form of urokinase-type plasminogen activator receptor (uPAR). We now report that pro-uPA-Sepharose-purified uPAR from ascites of patients with ovarian carcinoma is the full-length molecule missing the glycosyl-phosphatidylinositol anchor, as determined by its amino acid composition. We next examined the significance of determining serum soluble uPAR (suPAR) levels in ovarian cancer patients using a specific ELISA and compared the results with serum concentrations of CA-125, an established diagnostic marker. Serum from pre- and postoperative ovarian cancer patients was assayed for suPAR and CA-125. The majority of the patients with ovarian cancer had enhanced preoperative serum levels of suPAR compared with healthy controls, but suPAR concentrations decreased after operation. Although uPAR was associated with most ovarian carcinomas, it appeared to be a less specific indicator for ovarian cancer than CA-125. On the other hand, suPAR was more specific for other types of solid tumors. Moreover, we have observed some cases of ovarian cancer that showed increase of suPAR but not of CA-125. The prognostic significance of serum suPAR assay for survival of ovarian carcinoma patients was evaluated using Cox's proportional hazards analysis. Our preliminary data show that high preoperative levels of suPAR were associated with worse survival of the patients, whereas CA-125 had no prognostic implications. This is the first report evaluating the assay of serum suPAR levels in ovarian cancer and analyzing its value as a tumor or prognostic marker.

Spatial orientation of tissue-type plasminogen activator bound at the melanoma cell surface

Human melanoma cells produce tissue-type plasminogen activator (tPA) which is bound to the cell surface where it effectively mediates generation of plasmin. The present study is focused on analysis of involvement of the tPA domains in binding of the enzyme to the cell surface. The extent of plasminogen activation by tPA of melanoma cells was measured using an immunocapture assay. The activator anchored to solid surface via monoclonal antibodies directed to the individual domains of the activator exhibited variable enzymatic activity. The tPA was the most effective when bound by the antibodies against kringle-1 or kringle-2. Accessibility of the epitopes within cell surface-bound tPA was probed by the same set of monoclonal antibodies. FACS analysis showed that the epitopes within the finger/growth factor domain one part of the kringle-2 domain and the active site epitope were the most exposed. The kringle-1 domain epitope and the protease region epitope appeared partially exposed. Full-length melanoma-derived tPA and three recombinant domain-deletion variants of tPA were compared for their capacity to bind to the melanoma cells. The estimated IC50 value for the melanoma-derived tPA was 2.3 +/- 0.25 microM. Comparable IC50 values were found for the tPA variant lacking the finger domain (3.6 +/- 0.6 microM) as well as for the variants consisting only of the kringle-2 and protease domains (7.5 +/- 0.45 microM). In contrast the value found for a tPA variant lacking the kringle-2 domain was > 100 microM. The consistent results obtained by the three different experimental approaches provide evidence that tPA binds to melanoma cells via its kringle-2 domain but binding sites within kringle-1 domain and protease domain may support the interaction. The finger domain did not contribute to the binding.

The proteolytic potential of normal human melanocytes: comparison with other skin cells and melanoma cell lines

To understand the contribution of epidermal melanocytes in the proteolytic potential of human skin, we have studied melanocytes grown in a low-serum medium deprived of phorbol esters, cholera toxin, and other non-physiological supplements. We focused on the plasminogen activation system and certain matrix metalloproteinases (gelatinases). Supposing that the proteolytic activity of cells can influence binding to collagen matrix and its reorganization, we have analyzed these parameters as well. We found that human melanocytes secreted tissue-type plasminogen activator and utilised it to generate cell-bound plasmin. No urokinase-type plasminogen activator was detected in the cultures but its receptor was found in cell extracts. Both the 72 kDa and 92 kDa gelatinases were secreted by the cells and in equal amounts. In addition, melanocytes secreted the wide-spectrum proteinase inhibitor alpha-2-macroglobulin. Melanocytes cast into collagen matrices retained a rounded morphology, did not extend processes, and were unable to contract collagen lattices. As a control, these parameters were investigated in parallel in cultures of human keratinocytes, dermal fibroblasts, and two melanoma cell lines. The obtained characteristics suggest that normal human melanocytes are proteolytically active cells. This function may pertain to skin physiology and pathophysiology.

Active transforming growth factor-beta in human melanoma cell lines: no evidence for plasmin-related activation of latent TGF-beta

Cultured human melanoma cells were found to secrete TGF-beta mostly in latent biologically inactive form but in addition five of six melanoma cell lines studied produced in conditioned culture medium active TGF-beta in the range from 370 to 610 pg per 10(6) cells per 24 h. A distinct characteristic of these melanoma cell lines is that they form active surface-bound plasmin by the activation of plasminogen with surface-bound tissue-type plasminogen activator. The present study was performed to assess the role of plasmin in the process of latent TGF-beta activation in the melanoma cell lines. No direct correlation was found between cell-associated plasmin activity and the amount of active TGF-beta present in the conditioned medium of individual cell lines. The melanoma cell lines exhibited diverse responses to exogenous active TGF-beta 1; three cell lines were growth-stimulated, two were growth-inhibited, and one had a very low sensitivity to the growth factor. The active TGF-beta produced by the melanoma cells was found to inhibit the natural killer cell function of peripheral blood lymphocytes, suggesting that it may have an immunosuppressive effect and a role in the development of melanomas.

Binding of tissue-type plasminogen activator to human melanoma cells

We have shown (Bizik et al., Cell Regul 1:895-905, 1990) that tPA can activate plasminogen on the surface of human melanoma cells in the presence of alpha 2-macroglobulin (alpha 2M) secretion. In the present study, we investigated the binding of tPA on the surface of Bowes melanoma cells, selected since they lacked production of PAI-1 and alpha 2M. Elution of tPA from the cell layers indicated that polylysine (5 micrograms/ml) and tranexamic acid (10 mM), an analog of lysine, were the most efficient agents for disrupting the interaction between tPA and cell surface component(s). Using a panel of monoclonal antibodies against individual domains of tPA revealed that an antibody directed to the kringle-2 domain of tPA interfered most significantly with cell-surface plasmin generation. As tPA is a glycoprotein, interactions between the tPA sugar moieties and cell surface were also tested by the use of a series of monosaccharides. N-acetyl-D-glucosamine (100 mM) was the most potent sugar to release tPA from melanoma cells, but the results indicated that the oligosaccharides of tPA play only a supportive role in the binding of tPA to the cell surface. Quantitative comparison of the cell surface localized tPA, which was eluted by tranexamic acid, with the total cellular tPA showed that cell surface bound tPA could represent up to 10%. We conclude that tPA interacts with the melanoma cell surface in a similar manner as has been described for binding of tPA to fibrin and to the putative endothelial cell surface receptor.

Alpha 2-macroglobulin restricts plasminogen activation to the surface of RC2A leukemia cells

Human RC2A myelomonocytic leukemia cells are able to activate the prourokinase (pro-u-PA) they secrete so that active u-PA is present both in serum-free conditioned medium from these cells, as well as on the cell surface. When the cells are grown in serum-containing medium, no u-PA activity can be found in the medium but active u-PA is found bound to the cell surface where it can generate bound plasmin. This distribution of u-PA activity was shown to be, first, the net result of slow inactivation of free active u-PA by serum inhibitor(s) and simultaneous rapid uptake of u-PA onto the cell surface. Binding to cells was at least six times faster than inactivation by 10% serum. The principal serum inhibitor of u-PA was identified as alpha 2-macroglobulin (alpha 2M), and prior inactivation of u-PA by purified human alpha 2M was also shown to prevent uptake of u-PA activity onto cells. Second, although endogenous u-PA could form covalent complexes with purified alpha 2M in the culture medium of RC2A cells, covalent alpha 2M complexes were not formed by u-PA on the cell surface; the u-PA taken up in this compartment was protected against alpha 2M inhibition. u-PA anchored to plastic surfaces via monoclonal antibodies to the amino-terminal region of u-PA was also protected against alpha 2M, suggesting that the protection of cell surface u-PA results from a steric effect. These results provide evidence as to how the active u-PA produced by leukemia cells can contribute to proteolytic activity on their cell surface in the presence of serum inhibitors.

Direct evidence for methylation of arginine residues in high molecular weight forms of basic fibroblast growth factor

Basic fibroblast growth factor (bFGF) is a heparin-binding angiogenic polypeptide mitogen. Protein sequence analysis of bFGF isolated from tissue sources initially established that it is composed of 146 amino acids (apparent Mr 18,000). More recently larger apparent molecular weight forms have been identified and partially characterized. In addition, these high molecular weight forms (apparent Mr 22,000 and 25,000) have been shown to localize preferentially to nuclear fractions of transfected cells. In this report we demonstrate that the higher molecular weight, amino terminally extended forms of bFGF contain methylated arginine residues. The demonstration is based on 1) amino acid sequence analysis of a protein known to contain methylated arginine (myelin basic protein) and a comparison with amino acid sequence analysis of trypsin-derived fragments of the high molecular weight bFGF purified from guinea pig brain and 2) the ability to label in vivo the high molecular weight forms of bFGF with S-adenosyl-L-(methyl-3H)-methionine, the substrate of arginine-protein methylase I. These results are suggestive of a role of arginine methylation in directing nuclear localization of certain forms of bFGF.

Growth factor control of extracellular proteolysis

The involvement of proteases and growth factors in angiogenesis is complex. The angiogenic factor basic fibroblast growth factor (bFGF) induces increased synthesis of both plasminogen activator and collagenase in endothelial cells. In addition, bFGF increases the number of plasminogen activator receptors on the cell surface. Increased production of plasmin may be responsible for the release of soluble complexes of heparan sulfate-bFGF which may be the active form of bFGF. The activity of a negative regulator of angiogenesis, transforming growth factor beta (TGF-beta), is also regulated by proteases since the released latent form of TGF-beta is activated by a surface proteolytic assembly plasminogen activator and plasmin. Since TGF-beta induces an inhibitor of plasminogen activator, the activation reaction is self-regulatory.

Plasminogen activation by t-PA on the surface of human melanoma cells in the presence of alpha 2-macroglobulin secretion

Several human melanoma cell lines produced tissue-type plasminogen activator (t-PA), as detected by zymography and immunocapture assay of culture media and cell lysates. Urokinase (u-PA) was found at only less than or equal to 1% the level of t-PA. Acid eluates of the cell surface indicated that the melanoma cells had t-PA bound on their surface, but no u-PA, and also had a very low capacity to bind exogenous u-PA. After incubation of the melanoma cells with 10% plasminogen-depleted fetal calf serum and human plasminogen, bound plasmin activity could be eluted from the cell surface with tranexamic acid, an analogue of lysine. This indicated that plasminogen was activated on the cell surface. The cell-surface plasmin formation was inhibited by an anti-catalytic monoclonal antibody to human t-PA, and not by an anti-catalytic antibody to u-PA. The melanoma cells also synthesized and secreted alpha 2-macroglobulin (alpha 2M), as shown by alpha 2M-specific mRNA in Northern blotting and detection of alpha 2M protein in conditioned cell culture media. The media were found to inhibit u-PA but not t-PA. This inhibition was related to their alpha 2M content, and immunoabsorption of alpha 2M removed the inhibitory activity. These studies suggest that t-PA can bind to the surface of melanoma cells and generate surface-bound plasmin. Because t-PA and cell-bound plasmin are unaffected by alpha 2M, t-PA may, in the case of melanoma cells, serve an analogous function to u-PA in supporting tumor cell invasion.

Localization of alpha 2-macroglobulin in human primary sarcomas and synthesis in established cell lines

The presence of alpha 2-macroglobulin (alpha 2M) was detected with the avidin-biotin technique in more than 20-yr-old paraffin blocks from human sarcomas. alpha 2M was found mainly in the cytoplasm of the tumor cells, and almost all tumor cells were positive. This serum glycoprotein, which is a major plasma proteinase inhibitor with a wide specificity, was also shown to be synthesized and secreted by all three cell lines derived from primary sarcomas but was not detected in cultures of the autologous skin fibroblasts. For the detection of alpha 2M in situ and in vitro an antiserum to tumor-associated alpha 2-macroglobulin was used.