Variation in EGF-induced EGF receptor downregulation in human hepatoma-derived cell lines expressing different amounts of EGF receptor

Oncolytic herpes viral therapy is effective in the treatment of hepatocellular carcinoma cell lines

The rising incidence of hepatocellular carcinoma (HCC) in western countries, along with the poor prognosis offered by present-day treatment modalities, makes novel therapies for this disease necessary. Oncolytic herpes simplex viruses (HSV) are replication-competent viruses that are highly effective in the treatment of a wide variety of experimental models of human malignancies. This study seeks to investigate the effectiveness of oncolytic herpes viruses in the treatment of primary HCC cell lines. Sixteen commercially available human HCC cell lines were studied. G207 is an attenuated, replication-competent, oncolytic HSV engineered to selectively replicate within cancer cells. Cell lines were tested for viral sensitivity to G207 and their ability to support viral replication using standard cytotoxicity and viral replication assays. Eleven of 16 cell lines were moderately to highly sensitive to G207 viral oncolysis. HCC cell lines additionally demonstrated the ability to support viral replication in vitro with as high as 800-fold amplification of the administered viral dose observed. G207 is cytotoxic to, and efficiently replicates within, HCC cell lines in vitro. From these data, we suggest that oncolytic HSV therapy may have a role in the treatment of HCC, and in vivo studies are warranted.

Novel biphasic traffic of endocytosed EGF to recycling and degradative compartments in lacrimal gland acinar cells

The purpose of this study was to delineate the traffic patterns of EGF and EGF receptors (EGFR) in primary cultured acinar epithelial cells from rabbit lacrimal glands. Uptake of [(125)I]-EGF exhibited saturable and non-saturable, temperature-dependent components, suggesting both receptor-mediated and fluid phase endocytosis. Accumulation of [(125)I] was time-dependent over a 120-min period, but the content of intact [(125)I]-EGF decreased after reaching a maximum at 20 min. Analytical fractionation by sorbitol density gradient centrifugation and phase partitioning indicated that within 20 min at 37 degrees C [(125)I] reached an early endosome, basal-lateral recycling endosome, pre-lysosome, and lysosome. Small components of the label also appeared to reach the Golgi complex and trans-Golgi network. Intact [(125)I]-EGF initially accumulated in the recycling endosome; the content in the recycling endosome subsequently decreased, and by 120 min increased amounts of [(125)I]-labeled degradation products appeared in the pre-lysosomes and lysosomes. Confocal microscopy imaging of FITC-EGF and LysoTrackerRed revealed FITC enriched in a dispersed system of non-acidic compartments at 20 min and in acidic compartments at 120 min. Both confocal immunofluorescence microscopy and analytical fractionation indicated that the intracellular EGFR pool was much larger than the plasma membrane-expressed pool at all times. Cells loaded with [(125)I]-EGF released a mixture of intact EGF and [(125)I]-labeled degradation products. The observations indicate that in lacrimal acinar cells, EGFR and EGF-EGFR complexes continually traffic between the plasma membranes and a system of endomembrane compartments; EGF-stimulation generates time-dependent signals that initially decrease, then increase, EGF-EGFR traffic to degradative compartments.

Membrane-anchored heparin-binding epidermal growth factor-like growth factor acts as a tumor survival factor in a hepatoma cell line

Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF), which belongs to the EGF family, is produced as a membrane-anchored form (pro-HB-EGF) and later processed to a soluble form (sHB-EGF). It is known that high expression of pro-HB-EGF occurs in hepatoma tissues, although its biological meaning remains unknown. We established two types of hepatoma cell lines (AH66tc), which stably produce pro-HB-EGF and sHB-EGF, respectively. While sHB-EGF-producing cells (sHB-AH) showed rapid growth, pro-HB-EGF-producing cells (pHB-AH) showed markedly suppressed cell growth as compared with the parental cells. Transforming growth factor beta or serum-starved conditions induced apoptosis of mock and sHB-AH as well as the parental cells, but not of pHB-AH. The resistance to apoptosis upon serum-starved treatment was correlated with an increase in the rate of the G1 phase in the cell cycle due to up-regulation of the cyclin-dependent kinase inhibitor p21. The mechanism underlying this resistance of pHB-AH to apoptosis was thought to be related to the prolonged half-life of the EGF receptor followed by continuous phosphorylation of the tyrosine residues. These observations demonstrate a unique function of pro-HB-EGF that is not observed for the mature form and show that pro-HB-EGF may act as a tumor survival factor in hepatoma cells.

Epidermal growth factor and transforming growth factor alpha characteristics of human oral carcinoma cell lines

This study examined the expression of epidermal growth factor (EGF) cell-surface receptors, the response to exogenous ligand and the autocrine production of transforming growth factor alpha (TGF-alpha) in normal and carcinoma-derived human oral keratinocytes. One of eight malignant cell lines overexpressed EGF receptors, while the remainder expressed receptor numbers similar to normal cells. Exogenous EGF stimulated incorporation of tritiated thymidine in a dose-dependent manner. In keratinocytes expressing normal numbers of EGF receptors, the cellular response to exogenous EGF correlated positively with total EGF receptor number. SCC-derived keratinocytes produced more TGF-alpha than normal cells. There was no statistical correlation between the autocrine production of TGF-alpha, EGF cell-surface receptor expression and cellular response to exogenous EGF. While the growth-stimulatory effects of exogenous TGF-alpha were inhibited by the addition of a neutralising antibody, the presence of this antibody in conditioned medium failed to produce a similar decrease in growth. The results indicate that overexpression of EGF receptors is not an invariable characteristic of human oral squamous carcinoma-derived cell lines. Further, the contribution of TGF-alpha to the growth of normal and carcinoma-derived human oral keratinocytes in vitro may be less significant than previously documented.

Tyrosine phosphorylation of mitogen-activated protein kinases is necessary for activation of murine macrophages by natural and synthetic bacterial products

The purpose of these studies was to determine the intracellular signal transduction pathways of bacterial products in murine macrophages from lipopolysaccharide (LPS)-responder C3H/HeN and LPS-nonresponder C3H/HeJ mice. Both LPS and synthetic lipopeptide CGP 31362 (LPP) induced production of tumor necrosis factor alpha (TNF-alpha) in C3H/HeN macrophages. In C3H/HeJ macrophages, however, TNF-alpha was induced only by incubation with LPP. Both LPS and LPP induced tyrosine phosphorylation on proteins with apparent molecular masses of 39, 41, and 45 kD (p35, p41, and p45) in C3H/HeN macrophages, whereas in C3H/HeJ macrophages, tyrosine phosphorylation was induced only by LPP. 20-h incubation with LPS or LPP downregulated TNF-alpha production/secretion and tyrosine phosphorylation in C3H/HeN macrophages induced by additional LPS or LPP. In C3H/HeJ macrophages, however, the downregulation of TNF-alpha production and tyrosine phosphorylation were observed only with LPP. Protein kinase assays, Western blotting analyses, phenyl-Sepharose chromatography, and immunocomplex kinase assay suggested that p45 and p39 were similar or identical to mitogen-activated protein (MAP) kinase 1 and 2, respectively. Pretreatment of macrophages with LPS or LPP did not change the amount of kinase proteins but inhibited the stimulation of kinase activity by the agents. These data suggest that MAP kinases are among target proteins involved in the transduction of LPS and LPP signals that lead to activation of murine macrophages to produce/secrete TNF.