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R J Coffey

Publications and source records attributed to R J Coffey.

At least 37 records · Page 2Linked to original sources
PubMed1999

Decrease in cranial nerve complications after radiosurgery for acoustic neuromas: a prospective study of dose and volume.

PURPOSE: To determine whether tumor control can be maintained, and cranial nerve complications decreased by reducing the radiosurgical dose to acoustic neuromas. METHODS AND MATERIALS: Forty-two consecutive patients with acoustic neuromas were treated prospectively using an initial standard-dose protocol in which the tumor-margin dose (50% isodose) was 20, 18, and 16 Gy for tumor diameters < or =2 cm, 2.1-3 cm, and 3.1-4 cm, respectively. After analysis of tumor control and complications, the next 40 patients were treated using a reduced-dose protocol in which the tumor-margin dose was 16, 14, and 12 Gy for tumor volumes < or =4.2 cm3, 4.2-14.1 cm3, and > or =14.1 cm3, respectively. RESULTS: Median follow-up was 2.3 years (range 0.1-6) for 80 of 82 patients. The actuarial incidence (Kaplan-Meier) of facial neuropathy at 2 years was 38% (95% confidence interval [CI], 23-53%) for the standard-dose protocol and 8% (95% CI, 0-17%) for the reduced-dose protocol (p = 0.006). Univariate analysis revealed an association between risk of facial neuropathy and use of CT planning, higher radiosurgical dose, and neurofibromatosis, type 2. Multivariate analysis revealed that the only factor associated with increased risk of post-treatment facial neuropathy was a tumor margin dose > or =18 Gy. The incidence of trigeminal neuropathy at 2 years was 29% (95% CI, 15-43%) for the standard-dose protocol and 15% (95% CI, 3-27%) for the reduced-dose protocol (p = 0.17). Univariate analysis revealed an association between maximal tumor diameter and increased risk of trigeminal neuropathy; multivariate analysis revealed no additional statistically significant associations between tumor and dosimetric and patient characteristics and risk of trigeminal neuropathy. Two tumors in the standard-dose protocol required salvage surgery for progression. To date, no tumor in the reduced-dose protocol has shown progression. CONCLUSION: Our analysis suggests that a tumor margin dose of > or =18 Gy is the most significant risk factor for facial nerve complications after acoustic neuroma radiosurgery. Patients receiving a minimal tumor dose of < or =16 Gy are at significantly lower risk for permanent facial neuropathy after radiosurgery. Longer follow-up is required before definitive conclusions can be made about the ultimate rate of tumor control using reduced radiosurgical doses.

Adult↗
PubMed1999

Expansion of Pdx1-expressing pancreatic epithelium and islet neogenesis in transgenic mice overexpressing transforming growth factor alpha.

BACKGROUND & AIMS: The progenitor cells responsible for transforming growth factor (TGF)-alpha-induced pancreatic ductal metaplasia and neoplasia remain uncharacterized. During pancreatic development, differentiated cell types arise from ductal progenitor cells expressing the Pdx1 homeodomain transcription factor. The aims of this study were, first, to evaluate the role of Pdx1-expressing stem cells in MT-TGFalpha transgenic mice, and second, to further characterize cell proliferation and differentiation in this model. METHODS: To assess Pdx1 gene expression in normal and metaplastic epithelium, we performed in vivo reporter gene analysis using heterozygous Pdx1(lacZ/+) and bigenic Pdx1(lacZ/+)/MT-TGFalpha mice. RESULTS: Pdx1(lacZ/+)/MT-TGFalpha bigenics showed up-regulated Pdx1 expression in premalignant metaplastic ductal epithelium. In addition to Pdx1 gene activation, TGF-alpha-induced metaplastic epithelium demonstrated a pluripotent differentiation capacity, as evidenced by focal expression of Pax6 and initiation of islet cell neogenesis. The majority of Pdx1-positive epithelial cells showed no expression of insulin, similar to the pattern observed during embryonic development. CONCLUSIONS: Overexpression of TGF-alpha induces expansion of a Pdx1-expressing epithelium characterized by focal expression of Pax6 and initiation of islet neogenesis. These findings suggest that premalignant events induced by TGF-alpha in mouse pancreas may recapitulate a developmental program active during embryogenesis.

Animals↗
PubMed1999

Pharmacological inhibition of Ras-transformed epithelial cell growth is linked to down-regulation of epidermal growth factor-related peptides.

BACKGROUND & AIMS: Posttranslational farnesylation is required for Ras activation. Farnesyl transferase inhibitors (FTIs) selectively block protein farnesylation and reduce the growth of many Ras-transformed cells in vitro and in vivo. Activated Ras transforms rat intestinal epithelial (RIE-1) cells by a mechanism distinct from NIH 3T3 fibroblasts in that an epidermal growth factor receptor (EGFR) autocrine loop contributes significantly to the Ras-transformed RIE-1 phenotype. METHODS: The ability of FTIs to block growth of Ras-transformed RIE-1 cells was evaluated, and these results were correlated with decreased EGFR ligand production. RESULTS: FTI L744,832 caused a selective, dose-dependent, reversible blockade in proliferation of H-Ras-transformed RIE-1 cells, whereas control cell lines, K-Ras-transformed cells, and activated raf-transfected RIE cells were unaffected. The growth-inhibitory effects of L744,832 correlated with loss of farnesylated H-Ras protein and a marked reduction in transforming growth factor (TGF)-alpha and amphiregulin expression. Inhibition of proliferation of H-Ras RIE-1 cells by L744,832 was overcome by exogenous TGF-alpha, and enhanced growth inhibition was achieved by EGFR blockade in combination with L744,832. + CONCLUSIONS: These data suggest that one mechanism by which FTIs inhibit growth of H-Ras-transformed epithelial cells is by reducing Ras-induced EGFR ligand production.

Animals↗
PubMed1999

Amphiregulin acts as an autocrine growth factor in two human polarizing colon cancer lines that exhibit domain selective EGF receptor mitogenesis.

Colonic enterocytes, like many epithelial cells in vivo, are polarized with functionally distinct apical and basolateral membrane domains. The aims of this study were to characterize the endogenous epidermal growth factor (EGF)-like ligands expressed in two polarizing colon cancer cell lines, HCA-7 Colony 29 (HCA-7) and Caco-2, and to examine the effects of cell polarity on EGF receptor-mediated mitogenesis. HCA-7 and Caco-2 cells were grown on plastic, or as a polarized monolayer on Transwell filters. Cell proliferation was measured by 3H-thymidine incorporation and EGF receptor (EGFR) binding was assessed by Scatchard analysis. EGFR ligand expression was determined by Northern blot analysis, reverse transcription polymerase chain reaction, metabolic labelling and confocal microscopy. We found that amphiregulin (AR) was the most abundant EGFR ligand expressed in HCA-7 and Caco-2 cells. AR was localized to the basolateral surface and detected in basolateral-conditioned medium. Basolateral administration of neutralizing AR antibodies significantly reduced basal DNA replication. A single class of high-affinity EGFRs was detected in the basolateral compartment, whereas the apical compartment of polarized cells, and cells cultured on plastic, displayed two classes of receptor affinity. Basolateral administration of transforming growth factor alpha (TGF-alpha) or an EGFR neutralizing antibody also resulted in a dose-dependent stimulation or attenuation, respectively, of DNA replication. However, no mitogenic response was observed when these agents were added to the apical compartment or to confluent cells cultured on plastic. We conclude that amphiregulin acts as an autocrine growth factor in HCA-7 and Caco-2 cells, and EGFR ligand-induced proliferation is influenced by cellular polarity.

Amphiregulin↗
PubMed1999

Stimulatory actions of insulin-like growth factor-I and transforming growth factor-alpha on intestinal neurotensin and peptide YY.

Proliferation of the gastrointestinal mucosa is stimulated by the growth factors, insulin-like growth factor-I (IGF-I) and transforming growth factor-alpha (TGF-alpha), or the closely related epidermal growth factor (EGF), as well as the gastrointestinal hormones, gastrin, neurotensin (NT), and peptide YY (PYY). The stimulatory actions of these growth factors or gastrointestinal hormones on the gastrointestinal mucosa may be direct or mediated in part by gastrointestinal peptides or the growth factors, respectively. The purpose of these studies therefore was to examine the effects of IGF-I and TGF-alpha on stomach gastrin and intestinal NT and PYY gene expression [i.e. messenger RNA (mRNA), peptide levels] and secretion. Mice were given recombinant human IGF-I (3, 6 mg/kg BW/day x 14 days). Transgenic mice with the rat TGF-alpha gene linked to a metallothionein promoter were used as a model of chronic TGF-alpha excess. IGF-I and TGF-alpha did not affect gastrin gene expression. Steady-state intestinal NT and PYY mRNA and peptide levels were elevated in a dose-related manner by IGF. TGF-alpha also increased intestinal expression of NT and PYY peptide, but not mRNA levels. Basal serum levels of PYY were elevated by IGF-I and TGF-alpha. IGF-I and TGF-alpha did not increase intestinal chromogranin A (CGA) gene expression, a marker of endocrine cells, or the density of PYY-containing cells in the colon, indicating that the elevations in intestinal gut peptide gene expression by IGF-I and TGF-alpha are not due simply to an increased number of enteroendocrine cells. IV infusion of EGF also stimulated release of PYY in the dog. Together, these findings indicate that IGF-I and TGF-alpha may cause secretion of gut hormones and exert a major upregulatory influence on the regulation of intestinal peptide hormone homeostasis.

Animals↗
PubMed1999

The dynamic expression of the epidermal growth factor receptor and epidermal growth factor ligand family in a differentiating intestinal epithelial cell line.

The Caco-2 intestinal epithelial cell line differentiates when cultured on plastic or permeable filters, and offers a valuable system to study events associated with enterocytic differentiation in vitro. Little is known as to whether the expression of the epidermal growth factor receptor (EGFR) and its ligands changes as intestinal epithelial cells differentiate. We found that total cellular EGFR protein and mRNA transcript levels were relatively unchanged during Caco-2 cell differentiation, but the expression of surface EGFR and patterns of steady state epidermal growth factor (EGF)-family ligand expression changed significantly. EGFR affinity, surface EGFR expression levels, and the repertoire of expressed EGF-family ligands, were different between Caco-2 cells cultured on plastic and filters. Functionally, EGFR-mediated cell proliferation and tyrosine phosphorylation of the signal transduction protein SHC could be inhibited in Caco-2 cells cultured on filters, but not on plastic. Thus, the substrate on which the cells were grown and the degree of cell differentiation strongly modulate EGFR affinity, EGFR surface expression, the steady state expression of EGF-family ligands, as well as, EGFR-mediated cellular responses. Our results suggest that the EGFR system is regulated during intestinal epithelial cell differentiation primarily at the level of ligand expression.

Amphiregulin↗
PubMed1999

Risk of injury to cranial nerves after gamma knife radiosurgery for skull base meningiomas: experience in 88 patients.

OBJECT: In this study the authors sought to determine the neurological risks and potential clinical benefits of gamma knife radiosurgery for skull base meningiomas. METHODS: A consecutive series of 88 patients harboring skull base meningiomas were treated between 1990 and 1996 by using the Leksell gamma knife in a prospective clinical study that included a strict dose-volume protocol. Forty-nine patients had previously undergone surgery, and six had received external-beam radiotherapy. The median treatment volume was 10 cm3, and the median dose to the tumor margin was 16 Gy. The radiosurgical dosage to the optic nerve, the cavernous sinus, and Meckel's cave was calculated and correlated with clinical outcome. The median patient follow-up time was 35 months (range 12-83 months). Two tumors (2.3%) progressed after radiosurgery; the progression-free 5-year survival rate was 95%. At last follow-up review, 60 (68%) tumors were smaller and 26 (29.5%) remained unchanged. Clinical improvement (in vision, trigeminal pain, or other cranial nerve symptoms) occurred in 15 patients. Functioning optic nerves received a median dose of 10 Gy (range 1-16 Gy), and no treatment-induced visual loss occurred. Among nine patients with new trigeminal neuropathy, six received doses of more than 19 Gy to Meckel's cave. CONCLUSIONS: Gamma knife radiosurgery appeared to be an effective method to control the growth of most skull base meningiomas in this intermediate-term study. The risk of trigeminal neuropathy seemed to be associated with doses of more than 19 Gy, and the optic apparatus appeared to tolerate doses greater than 10 Gy. Considering the risks to cranial nerves associated with open surgery for comparable tumors, the authors believe that gamma knife radiosurgery is a useful method for the management of properly selected recurrent, residual, or newly diagnosed skull base meningiomas.

Adult↗
PubMed1999

Treatment with farnesyl-protein transferase inhibitor induces regression of mammary tumors in transforming growth factor (TGF) alpha and TGF alpha/neu transgenic mice by inhibition of mitogenic activity and induction of apoptosis.

Mouse mammary tumor virus-transforming growth factor alpha (MMTV-TGF alpha) and MMTV-TGF alpha/neu transgenic mice develop mammary tumors after a long latency and therefore provide useful model systems for breast cancer with its recognized activation of receptor tyrosine kinase signaling. We used these mice to study the antitumor effect of L-744,832 (FTI), a potent and selective inhibitor of farnesyl-protein transferase, and hence of Ras function. A total of 55 mice were assigned randomly to treatment with FTI or vehicle, and one-half of the mice were crossed over after initial treatment to the opposite group. L-744,832 induced reversible regression of mammary tumors that was paralleled by a decrease in serum levels of TGF alpha secreted by the tumor cells. There was no difference in response to treatment with FTI between MMTV-TGF alpha mice, in which tumorigenesis was accelerated by multiparity or the chemical carcinogen 7,12-dimethylbenzanthracene, and MMTV-TGF alpha/neu mice. The tumor histological type had no impact on FTI sensitivity. For mechanistic analyses, tumor excision biopsies were obtained from 12 mice before and after treatment with L-744,832. In these samples, tumor regression was paralleled biochemically by inhibition of mitogen-activated protein kinase activity and biologically by an increase in G1-phase and decrease in S-phase fractions, as well as induction of apoptosis. These results suggest that the potential clinical use of FTI could be expanded to include cancers harboring activated receptor tyrosine kinases as well as those containing activated Ras.

Alkyl and Aryl Transferases↗
PubMed1998

Prolonged activation of the mitogen-activated protein kinase pathway promotes DNA synthesis in primary hepatocytes from p21Cip-1/WAF1-null mice, but not in hepatocytes from p16INK4a-null mice.

In primary rat hepatocytes, prolonged activation of the p42/44 mitogen-activated protein kinase (MAPK) pathway is associated with a decrease in DNA synthesis and increased expression of the cyclin-dependent kinase inhibitor (CKI) proteins p21Cip-1/WAF1 and p16INK4a. To evaluate the relative importance of these CKIs in mediating this response, we determined the impact of prolonged MAPK activation on DNA synthesis in primary cultures of hepatocytes derived from mice embryonically deleted (null) for either p21Cip-1/WAF1 or p16INK4a. When MAPK was activated in wild-type mouse hepatocytes for 24 h, via infection with a construct to express an inducible oestrogen receptor-Raf-1 fusion protein (DeltaRaf:ER), the expression of p21Cip-1/WAF1 and p16INK4a CKI proteins increased, cyclin-dependent kinase 2 (cdk2) and cdk4 activities decreased, and DNA synthesis decreased. Inhibition of RhoA GTPase function increased the basal expression of p21Cip-1/WAF1 and p27Kip-1 but not p16INK4a, and enhanced the ability of MAPK signalling to decrease DNA synthesis. Ablation of the expression of CCAATT enhancer-binding protein alpha (C/EBPalpha), but not of the expression of C/EBPbeta, decreased the ability of MAPK signalling to induce p21Cip-1/WAF1. When MAPK was activated in p16INK4a-null hepatocytes for 24 h, the expression of p21Cip-1/WAF1 increased, cdk2 and cdk4 activities decreased and DNA synthesis decreased. In contrast with these findings, prolonged activation of the MAPK pathway in hepatocytes from p21Cip-1/WAF1-null mice enhanced cdk2 and cdk4 activities and caused a large increase in DNA synthesis, despite elevated expression of p16INK4a. Inhibition of RhoA GTPase activity in p21Cip-1/WAF1-null cells partly blunted both the basal levels of DNA synthesis and the ability of prolonged MAPK signalling to increase DNA synthesis. Expression of anti-sense p21Cip-1/WAF1 in either wild-type or p16INK4a-null hepatocytes decreased the ability of prolonged MAPK signalling to increase the expression of p21Cip-1/WAF1, and permitted MAPK signalling to increase both cdk2 and cdk4 activities and DNA synthesis. These results argue that the ability of prolonged MAPK signalling to inhibit DNA synthesis in hepatocytes requires the expression of p21Cip-1/WAF1, and that the increased expression of p16INK4a has a smaller role in the ability of this stimulus to mediate growth arrest. Our results also suggest that RhoA function can modulate DNA synthesis in primary hepatocytes via the expression of p21Cip-1/WAF1 and p27Kip-1.

Animals↗
PubMed1998

Active signaling by Neu in transgenic mice.

Transgenic mice engineered to overexpress the HER-2/neu/erbB-2 protooncogene under the control of a mammary-specific promoter develop mammary tumors and are a model for human breast cancer. Signal transduction by Neu was examined in situ in the tumors of these transgenic mice. This was accomplished using the PN2A monoclonal antibody, which recognizes Neu only in the phosphorylated, and therefore actively signaling, state. Immunohistochemistry using PN2A demonstrated that Neu actively signals in the tumors of Neu transgenic mice. Expression of Neu was always accompanied by co-overexpression of the endogenous epidermal growth factor receptor. Qualitatively similar results were found in mammary tumors from mice bitransgenic for the neu and transforming growth factor-alpha genes (both driven by the mouse mammary tumor virus promoter). Early mammary lesions demonstrated distinctive patterns of Neu activation relative to expression levels. Overexpression and activation were separable both temporally and spatially. These results refine the multi-step model for the role of Neu in mammary neoplasia and establish phosphorylation-state specific antibodies as a powerful tool for investigating tumor progression.

Animals↗
PubMed1998

Cell surface ectodomain cleavage of human amphiregulin precursor is sensitive to a metalloprotease inhibitor. Release of a predominant N-glycosylated 43-kDa soluble form.

Biosynthesis and processing of amphiregulin (AR) have been investigated in human colorectal (HCA-7, Caco-2) and mammary (MCF-7) cancer cell lines, as well as in Madin-Darby canine kidney cells stably expressing various human AR precursor (pro-AR) forms. Both cells expressing endogenous and transfected AR produce multiple cellular and soluble forms of AR with an N-glycosylated 50-kDa pro-AR form being predominant. Our results demonstrate that sequential proteolytic cleavage within the ectodomain of the 50-kDa pro-AR form leads to release of a predominant N-glycosylated 43-kDa soluble AR, as well as the appearance of other cellular and soluble AR forms. Cell surface biotinylation studies using a C-terminal epitope-tagged pro-AR indicate that all cell surface forms are membrane-anchored and support that AR is released by ectodomain cleavage of pro-AR at the plasma membrane. We also show that pro-AR ectodomain cleavage is a regulated process, which can be stimulated by phorbol 12-myristate 13-acetate and inhibited by the metalloprotease inhibitor, batimastat. In addition, we provide evidence that high molecular mass AR forms may retain the full-length N-terminal pro-region, which may influence the biological activities of these forms.

Amino Acid Sequence↗
PubMed1998

Increased intestinal epithelial proliferation in metallothioneine-transforming growth factor alpha transgenic mice.

BACKGROUND AND AIM: The epidermal growth factor (EGF) peptide family includes six closely-related proteins, all of which bind to the EGF receptor. In the intestinal epithelium, transforming growth factor alpha (TGFalpha) appears to be the most physiological ligand for the EGF receptor. The present studies were designed to examine the effect of TGFalpha overexpression on duodenal epithelial proliferation using a metallothioneine-inducible promoter/enhancer transgenic mouse (MT-TGFalpha). The MT-TGFalpha mouse model was further studied to determine the in vivo effect of unregulated TGFalpha production on the physiological proliferative responses to fasting and refeeding. METHODS: MT-TGFalpha mice were given 25 mM oral ZnSO4 to induce transgene expression and were studied 1 to 2 months later. Duodenal histology was analyzed morphometrically in well-oriented transverse sections. The vincristine metaphase-arrest technique was used to assess proliferation in duodenal crypts. Immunohistochemical staining and in situ hybridization were used to assess transgenic TGFalpha protein and mRNA expression, respectively. RESULTS: Normally fed MT-TGFalpha mice had deeper crypts (0.12 vs. 0.08 mm), longer villi (0.66 vs. 0.54 mm), and greater luminal diameters (2.65 vs. 2.19 mm) compared to controls (P<0.05 for all three dimensions). The crypt cell mitotic index in normally fed transgenic mice was 1.5 fold greater than the index in normally fed controls (20+/-2 vs. 35+/-4 mitoses per crypt; P <0.05). Fasting and refeeding MT-TGFalpha mice resulted in no significant change in their high baseline rate of crypt proliferation, while proliferation in control mice rose from a lower baseline during fasting to a level with refeeding that approximated rates in MT-TGFalpha mice. Transgenic TGFalpha protein and mRNA were localized to the villus epithelial compartment with little or no evidence of mRNA or protein expression in the crypt epithelium. CONCLUSION: Overproduction of TGFalpha in the mouse duodenal epithelium results in a pronounced increase in crypt epithelial cell proliferation and a resulting increase in the dimension of the crypt/villus unit. This appears to be mediated through a paracrine and/or juxtacrine effect on crypt cells by TGFalpha produced in the villus epithelium. Fasting and refeeding experiments suggest that TGFalpha may also play a role in the proliferative response to refeeding or that the full potential for proliferation is realized by TGFalpha overexpression alone. Collectively, these studies suggest that TGFalpha is a physiological autocrine and paracrine regulator of small intestinal epithelial proliferation.

Animals↗
PubMed1998

Antioxidants reduce cyclooxygenase-2 expression, prostaglandin production, and proliferation in colorectal cancer cells.

Increased expression of cyclooxygenase (COX) and overproduction of prostaglandins (PGs) have been implicated in the development and progression of colorectal cancer (CRC). Recent observations suggest that reactive oxygen intermediates play a role in tumor cell growth regulation and expression of the inducible COX, COX-2. We therefore evaluated the effects of various antioxidants on COX expression and cellular growth in the human CRC cell line HCA-7. The antioxidants pyrrolidinedithiocarbamate (PDTC), N-acetylcysteine, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox), and U74006 decreased PG production, intracellular redox status, and cellular growth in a concentration-dependent manner. The decrease in cellular growth was associated with the induction of apoptosis. Unlike the selective COX inhibitors 1-[(4-methylsulfonyl)phenyl]-3-trifluoromethyl-5-[(4-fluoro)phenyl]pyraz ole (SC 58125) and (2-cyclohexyloxy-4-nitrophenyl)methanesulfonamide (NS 398) that inhibit COX-2 catalytic activity, these antioxidants decreased COX-2 expression at the transcriptional level. Combined treatment of HCA-7 cells with PDTC and SC 58125 resulted in an additive decrease in PG levels and anchorage-dependent and -independent growth. Furthermore, whereas antioxidants or SC 58125 reduced tumor growth in vivo, coadministration of PDTC and SC 58125 resulted in actual tumor regression. These results suggest that combined therapy with NSAIDs and antioxidants might be useful in the prevention and/or treatment of CRC.

Animals↗
PubMed1998

Helicobacter pylori upregulates expression of epidermal growth factor-related peptides, but inhibits their proliferative effect in MKN 28 gastric mucosal cells.

Acute exposure to Helicobacter pylori causes cell damage and impairs the processes of cell migration and proliferation in cultured gastric mucosal cells in vitro. EGF-related growth factors play a major role in protecting gastric mucosa against injury, and are involved in the process of gastric mucosal healing. We therefore studied the acute effect of H. pylori on expression of EGF-related growth factors and the proliferative response to these factors in gastric mucosal cells (MKN 28) derived from gastric adenocarcinoma. Exposure of MKN 28 cells to H. pylori suspensions or broth culture filtrates upregulated mRNA expression of amphiregulin (AR) and heparin-binding EGF-like growth factor (HB-EGF), but not TGFalpha. This effect was specifically related to H. pylori since it was not observed with E. coli, and was independent of VacA, CagA, PicA, PicB, or ammonia. Moreover, H. pylori broth culture filtrates stimulated extracellular release of AR and HB-EGF protein by MKN 28 cells. AR and HB-EGF dose-dependently and significantly stimulated proliferation of MKN 28 cells in the absence of H. pylori filtrate, but had no effect in the presence of H. pylori broth culture filtrates. Inhibition of AR- or HB-EGF- induced stimulation of cell growth was not mediated by downregulation of the EGF receptor since EGF receptor protein levels, EGF binding affinity, number of specific binding sites for EGF, or HB-EGF- or AR-dependent tyrosine phosphorylation of the EGF receptor were not significantly altered by incubation with H. pylori broth culture filtrates. Increased expression of AR and HB-EGF were mediated by an H. pylori factor > 12 kD in size, whereas antiproliferative effects were mediated by both VacA and a factor < 12 kD in size. We conclude that H. pylori increases mucosal generation of EGF-related peptides, but in this acute experimental model, this event is not able to counteract the inhibitory effect of H. pylori on cell growth. The inhibitory effect of H. pylori on the reparative events mediated by EGF-related growth factors might play a role in the pathogenesis of H. pylori-induced gastroduodenal injury.

Adenocarcinoma↗
PubMed1998

Ras, but not Src, transformation of RIE-1 epithelial cells is dependent on activation of the mitogen-activated protein kinase cascade.

Src transformation of NIH3T3 mouse fibroblasts has been shown to be dependent on Ras function. Since we recently showed that the signaling pathways that mediate Ras transformation of RIE-1 rat intestinal epithelial cells are distinct from those that cause Ras transformation of fibroblasts, we utilized three approaches to determine if Src transformation of RIE-1 cells is dependent on Ras. First, although both Ras and Src cause upregulation of an epidermal growth factor (EGF) receptor-dependent autocrine growth loop, only Ras transformation required this activity. Second, whereas both Src and Ras caused upregulation of the p42 and p44 mitogen-activated protein kinases (MAPKs), only Ras transformation was blocked by the inhibition of MAPK activation by treatment with the PD 98059 MEK inhibitor. Third, treatment with the farnesyltransferase inhibitor FTI-277 blocked Ras, but not Src, transformation. Taken together, these observations suggest that Src transformation of RIE-1 cells is not dependent on Ras. Finally, we determined that Ras activation of Raf-independent pathways alone is sufficient to cause growth transformation of RIE-1 cells. Thus, both Ras and Src cause transformation of RIE-1 cells via pathways distinct from those required to cause transformation of NIH3T3 cells.

Alkyl and Aryl Transferases↗
PubMed1998

Identification of rCop-1, a new member of the CCN protein family, as a negative regulator for cell transformation.

By using a model system for cell transformation mediated by the cooperation of the activated H-ras oncogene and the inactivated p53 tumor suppressor gene, rCop-1 was identified by mRNA differential display as a gene whose expression became lost after cell transformation. Homology analysis indicates that rCop-1 belongs to an emerging cysteine-rich growth regulator family called CCN, which includes connective-tissue growth factor, CYR61, CEF10 (v-src inducible), and the product of the nov proto-oncogene. Unlike the other members of the CCN gene family, rCop-1 is not an immediate-early gene, it lacks the conserved C-terminal domain which was shown to confer both growth-stimulating and heparin-binding activities, and its expression is lost in cells transformed by a variety of mechanisms. Ectopic expression of rCop-1 by retroviral gene transfers led to cell death in a transformation-specific manner. These results suggest that rCop-1 represents a new class of CCN family proteins that have functions opposing those of the previously identified members.

Aging↗
PubMed1997

The role of stereotactic radiosurgery in the treatment of malignant skull base tumors.

PURPOSE: To determine the efficacy and toxicity of stereotactic radiosurgery in the treatment of malignant skull base tumors. METHODS AND MATERIALS: Thirty-two patients with 35 newly diagnosed or recurrent malignant skull base tumors < or = 33.5 cm3 were treated using the Leksell Gamma unit. Tumor histologies included: adenoid cystic carcinoma [12], basal cell carcinoma [1], chondrosarcoma [1], chordoma [8], nasopharyngeal carcinoma [3], osteogenic sarcoma [2], and squamous cell carcinoma [8]. RESULTS: After a median follow-up of 2.3 years, 83% +/- 15% (+/-95% confidence interval) of patients experienced a symptomatic response to treatment. Local control at the skull base was 95 +/- 9% at 2 years and 78 +/- 23% at 3 years. Local-regional control above the clavicles was 75 +/- 15% at 1 year and 51 +/- 20% at 2 years. Overall and cause specific survival were identical, 82 +/- 13% at 1 year, 76 +/- 14% at 2 years, and 72 +/- 16% at 3 years. One patient developed a radiation-induced optic neuropathy 12 months after radiosurgery. CONCLUSION: Stereotactic radiosurgery using the Leksell Gamma Unit can provide durable tumor control and symptomatic relief with acceptable toxicity in the majority of patients with malignant tumors 4 cm or less in size involving the skull base. Further evaluation of more patients with longer follow-up is warranted.

Adolescent↗