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R J Coffey

Publications and source records attributed to R J Coffey.

At least 91 records · Page 5Linked to original sources
PubMed1995

Roles for transforming growth factor-alpha in the stomach.

The gastric mucosa maintains its integrity despite the harsh environment of an acidic luminal pH and strong mechanical stresses secondary to peristalsis of ingested contents. The mucosa has marshalled a battery of both protective and reparative mechanisms which, in general, prevent the deleterious effects of these factors that, if unchecked, may result in untoward consequences such as gastritis and peptic ulcer disease. An increasing body of evidence suggests that transforming growth factor-alpha (TGF alpha) produced by the gastric mucosa is a critical mediator of gastric mucosal homeostasis. TGF alpha inhibits acid secretion, stimulates mucosal restitution after injury (cell migration and proliferation), and augments gastric mucin levels. We review the data that support a role for this endogenously produced growth factor in both protective and reparative actions in the stomach. In addition, we discuss a possible role for overproduction of TGF alpha in the pathogenesis of Ménétrier's disease, a premalignant disorder of the stomach characterized by fundic gland hyperplasia, hypochlorhydria, increased gastric mucus, and hypoalbuminemia.

Animals↗
PubMed1994

Auto- and cross-induction within the mammalian epidermal growth factor-related peptide family.

Several polypeptide growth factors related to epidermal growth factor (EGF) have been identified recently, including transforming growth factor-alpha (TGF-alpha), amphiregulin (AR), heparin-binding EGF-like growth factor (HB-EGF), and betacellulin (BTC). These peptides all bind to the EGF receptor (EGFr). In an effort to understand redundancy within this peptide family and interactions among these related peptides, we compared the biological activities of EGF, TGF-alpha, AR, and HB-EGF in an EGF-responsive, nontransformed intestinal epithelial line (RIE-1) and also determined the effect of individual EGF-related peptides on the expression of related family members in these cells. TGF-alpha, AR, HB-EGF, and EGF were equipotent in stimulating [3H]thymidine incorporation by RIE-1 cells and bound the EGFr with equivalent affinity. Each EGF-related peptide induced the mRNA expression of the remaining family members, including BTC. HB-EGF and AR mRNAs were induced rapidly (within 30 min) and to a greater extent than TGF-alpha and BTC mRNAs, suggesting heterogeneity in the molecular mechanisms for induction. This same pattern was observed for all EGF-related peptides tested. A similar pattern of mRNA induction was observed in secondary cultures of human keratinocytes and in LIM1215 colon adenocarcinoma cells. Nuclear run-on analysis showed that induction of AR and HB-EGF is, at least in part, regulated at the level of gene transcription. Concurrent treatment with HB-EGF and cycloheximide resulted in superinduction of HB-EGF and AR, suggesting that these peptides are immediate early genes in RIE-1 cells. Our results demonstrate an equivalent biological response to EGF-related peptides in RIE-1 cells and further indicate that extensive auto-induction and cross-induction occur within the EGF-related peptide family in several EGF-responsive epithelial cell types.

Amphiregulin↗
PubMed1994

Basolateral targeting and efficient consumption of transforming growth factor-alpha when expressed in Madin-Darby canine kidney cells.

To investigate the trafficking of transforming growth factor-alpha precursor (pro-TGF-alpha) in polarized epithelial cells, wild type and membrane-fixed human pro-TGF-alpha were introduced into Madin-Darby canine kidney (MDCK) cells. We show that wild type pro-TGF-alpha was synthesized and processed normally to release mature 5.6-kDa TGF-alpha into the basal medium while membrane-fixed pro-TGF-alpha remained cell-associated. Antibody (mAb-528) receptor blockade experiments demonstrated the efficient consumption of basally released TGF-alpha by basolateral epidermal growth factor receptors, indicating that TGF-alpha can act in an autocrine manner in these polarized epithelial cells. Biochemical analysis showed pro-TGF-alpha was expressed on the basolateral surface as either a 17- or 30-kDa species; the 17-kDa forms of both pro-TGF-alpha constructs had basolateral/apical ratios of > 20:1. By confocal microscopy, membrane-fixed pro-TGF-alpha was immunolocalized to lateral membrane surfaces. In pulse-chase experiments combined with cell surface immunoprecipitation, we demonstrated that newly synthesized wild type and membrane-fixed pro-TGF-alpha are delivered directly to the basolateral surface with 94 and 96% efficiency, respectively. These results also provide direct evidence for sequential cleavage of pro-TGF-alpha at the basolateral membrane surface. Thus, pro-TGF-alpha is sorted intracellularly and vectorially targeted to the basolateral membrane domain in these polarized epithelial cells. The MDCK cell line provides an ideal in vitro model to examine the molecular basis for trafficking of pro-TGF-alpha and other epidermal growth factor-like growth factors in polarized epithelial cells and their potential interactions with basolateral epidermal growth factor receptors.

Animals↗
PubMed1994

Acceleration of mammary neoplasia in transforming growth factor alpha transgenic mice by 7,12-dimethylbenzanthracene.

A mouse mammary tumor virus enhancer/promoter-transforming growth factor alpha transgenic mouse model has been described in which mammary tumors develop (Y. Matsui et al., Cell, 61: 1147-1155, 1990). In Line 29, spontaneous mammary tumors do not develop before 300 days of age in virgin females. Herein, Line 29 virgin females and their nontransgenic littermates have been treated with 7,12-dimethylbenzanthracene (DMBA) at varying dosages and times. Orogastric instillation of a single dose of DMBA (0.5 mg) dramatically accelerates mammary tumor formation when administered to 21- and 56-day-old virgin transgenic females compared to their nontransgenic littermates. The latency period for tumor formation is significantly shorter in transgenic mice treated with DMBA at 56 days compared to transgenic mice treated with DMBA at 21 days when results are analyzed by time from DMBA administration. To determine whether differences in the proliferative state of the mammary gland may contribute to these findings, bromodeoxyuridine incorporation was examined in the mammary glands of untreated 21- and 56-day-old mice. No differences in bromodeoxyuridine incorporation were detected between 21-day-old transgenic and nontransgenic mice. However, there was a marked increase in bromodeoxyuridine incorporation in the epithelial cells comprising the smaller ducts of 56-day-old transgenic mice compared to their nontransgenic littermates. These data indicate an enhancing interaction between a growth factor and a genotoxic carcinogen in mammary tumorigenesis and provide evidence that the transforming growth factor alpha transgene acts as a tumor promoter in this experimental model.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1994

A multi-institutional experience with stereotactic radiosurgery for solitary brain metastasis.

PURPOSE: A multi-institutional experience in radiosurgery for solitary brain metastases was combined to identify factors associated with safety, efficacy, tumor control, and survival. MATERIALS AND METHODS: A review of 116 patients with solitary brain metastases who underwent gamma knife stereotactic radiosurgery at five institutions was performed. The median follow-up was 7 months following radiosurgery and 12 months following diagnosis. Minimum tumor doses varied from 8-30 Gy (mean, 17.5 Gy). Forty-five patients failed prior radiotherapy and 71 had no prior brain irradiation. Fifty-one patients had radiosurgery alone and 65 underwent combined radiosurgery with fractionated large-field radiotherapy (mean dose, 33.8 Gy). RESULTS: Median survival was 11 months after radiosurgery and 20 months after diagnosis. Follow-up documented local tumor control in 99 patients (85%), tumor recurrence in 17 (15%), and documented radiation necrosis in one (1%). The 2-year actuarial tumor control rate was 67 +/- 8%. Tumor histology affected survival (better for breast cancer, p = .004) and local control (better for melanoma and renal cell, p = .0003) in multivariate analyses. Combined fractionated radiotherapy and radiosurgery improved local control (p = 0.111), but not survival in multivariate testing. CONCLUSION: Radiosurgery is effective in controlling solitary brain metastases with low morbidity. Further study is needed to better define optimum treatment parameters for radiosurgery.

Adult↗
PubMed1994

Effect of transforming growth factor-alpha on gastric acid secretion in rats and monkeys.

The effect of transforming growth factor-alpha was studied in histamine-stimulated gastric acid secretion in monkeys and in pylorus-ligated rats. In monkeys, transforming growth factor-alpha given intravenously in a stepwise manner gradually reduced gastric acid secretion. A dose of 0.1 mmol/kg induced about a 50% inhibition of gastric acid output, while about 100% inhibition of the same parameter, was observed after a dose of 1 nmol/kg. Following a single administration of 1 nmol/kg intravenously in monkey, the maximum inhibitory effect on gastric acid output was reached 60 min after the administration of the drug, when a 91.8% inhibition was observed. Pretreatment values were reached 210-240 min after transforming growth factor-alpha administration. In pylorus-ligated rats, transforming growth factor-alpha, at doses of 9 and 18 nmol/kg produced an almost complete inhibition of gastric acid secretion. In this model, the ED50 was calculated to be 4.5 nmol/kg. Comparison with epidermal growth factor on the same models of gastric acid secretion showed that these two compounds have similar inhibitory potency. However, the effect of transforming growth factor-alpha on gastric acid secretion in monkeys was shorter lasting than that of epidermal growth factor.

Animals↗
PubMed1994

Up-regulation of cyclooxygenase 2 gene expression in human colorectal adenomas and adenocarcinomas.

BACKGROUND/AIMS: Several clinical, epidemiological, and animal studies indicate that nonsteroidal anti-inflammatory drugs (NSAIDs) may alter the incidence of colorectal cancer. A likely target for NSAIDs is cyclooxygenase, a key enzyme in arachidonic acid metabolism. Two isoforms of this enzyme have been identified; cyclooxygenase (COX) 1 and COX-2. The present study was undertaken to determine if there is differential expression of these isoforms in colorectal neoplasia, and, if so, at what stage in malignant transformation this occurs. METHODS: COX-1 and COX-2 messenger RNA (mRNA) levels were determined by Northern blot analysis of poly(A)+ RNA isolated from human colorectal cancers, adenomas, and accompanying normal mucosa. RESULTS: There was a marked increase in COX-2 mRNA levels in 12 of 14 carcinomas (86%) compared with paired normal mucosa. In contrast, there was equivalent intensity of the COX-1 mRNA transcript between the normal mucosa and cancer in all 14 cases. In six pairs of colorectal adenomas and normal mucosa, three showed up-regulation of COX-2 in the adenoma compared with the normal mucosa. Because COX-2 expression is low to undetectable in normal colorectal mucosa, 14 unpaired adenomas were examined for COX-2 expression; a clearly detectable transcript was identified in six (43%). CONCLUSIONS: COX-2, but not COX-1, gene expression is markedly elevated in most human colorectal cancers compared with accompanying normal mucosa. Furthermore, COX-2 expression seems to be increased in a subset of adenomas. COX-2 may provide an attractive therapeutic target in colorectal neoplasia.

Adenocarcinoma↗
PubMed1994

Brain metastatic lesions.

OBJECTIVE: To describe current concepts in the diagnosis and treatment of brain metastases. RESULTS: More than 25% of all autopsy-proven brain metastases have a pulmonary source. Most brain metastases manifest with a combination of focal and generalized symptoms and signs. Typically, patients have subacute, progressive symptoms. In most situations, a computed tomographic scan of the head provides sufficient neuroimaging and allows one to monitor the effects of therapy. Magnetic resonance imaging has become increasingly useful in the diagnosis and management of brain metastases. It can detect computed tomographic occult metastases, identify associated leptomeningeal disease, and reveal early therapeutic complications. CONCLUSION: Treatment options for patients with brain metastases include corticosteroids, whole-brain radiation therapy (WBRT), surgical intervention, stereotactic radiosurgical techniques, and chemotherapy. Corticosteroids produce prompt improvement in most patients; however, prolonged use is associated with considerable risks. For most patients, WBRT is the preferred treatment. Nonetheless, it has associated nonneurologic and neurologic complications, some of which are serious. In patients with a single metastasis, surgical removal should be considered. Recent studies have suggested that resection of a single metastatic lesion followed by radiation therapy offers better survival than does radiation therapy alone. The subsequent administration of WBRT after radiosurgical treatment has become standard practice. The role of chemotherapy is uncertain.

Brain Neoplasms↗
PubMed1994

Expression and distribution of transforming growth factor-alpha within melanocytic lesions.

Stimulation of epidermal growth factor (EGF) receptor by ligands such as transforming growth factor (TGF) alpha may be associated with cell proliferation or transformation in both nevocytes and keratinocytes. Previously, EGF receptors have been identified within a variety of pigmented lesions, suggesting a possible responsiveness to ligands such as TGF alpha. In the present study, we characterize the intralesional expression and distribution of immunoreactive TGF alpha protein by avidin-biotin immunoperoxidase localization in benign nevi, congenital nevi, dysplastic nevi, and malignant melanomas. In situ hybridization techniques with TGF alpha riboprobes confirmed the constitutive production of TGF alpha in all types of pigmented lesions. The localization of TGF alpha expression to nevocytes when coupled with the previous reports of expression in basal keratinocytes suggests the possibility of either an autocrine mechanism of action for TGF alpha or a paracrine interplay of TGF alpha between keratinocytes and nevocytes within melanocytic lesions. An increase in immunoreactive TGF alpha in nevocytes was noted in both benign and dysplastic nevi from dysplastic nevus patients, as compared to benign nevi from normal patients. Congenital nevi and malignant melanomas showed an intermediate and variable level of TGF alpha immunoreactivity. When coupled with previous studies the data suggest linkage of the TGF alpha/EGF receptor pathway in the evolution of melanocytic lesions.

Adolescent↗
PubMed1994

Cause of failure of lactation in mouse mammary tumor virus/human transforming growth factor alpha transgenic mice.

Transgenic female mice bearing human transforming growth factor-alpha (TGF alpha) cDNA under the control of the mouse mammary tumor virus enhancer/promoter became pregnant but failed lactation. TGF alpha mRNA was detected in the mammary glands of these mice by the reverse transcriptase-polymerase chain reaction. By the use of collagenase-dissociated mammary epithelial cells, the binding of prolactin to its receptor was determined before and after parturition. At the end of pregnancy, the binding in TGF alpha transgenic (TGF alpha [+]) mice was small and its amount was comparable to that in the TGF alpha negative (TGF alpha [-]) mice. On the day of parturition, prolactin binding in TGF alpha (+) mice increased approximately 1.9-fold (insignificant), while that in TGF alpha (-) mice elevated over 5.3-fold (P < 0.01). The binding sites per cell were also higher in TGF alpha (-)mice. Radioimmunoassay of prolactin suggested that in TGF alpha (+) mice the low level of prolactin binding after parturition was not due to masking effect of serum prolactin. Among six TGF alpha (+) mice assayed, one mother with the highest prolactin binding activity (3.7-fold increase) initiated lactation, but the others did not. As there was little difference between groups in the growth and synthesis in the mammary glands, it was concluded that the failure of lactation in TGF alpha (+) mice is principally due to the lack of elevation of mammary prolactin receptor after parturition. At present, the role of TGF alpha in this process is obscure; however, TGF alpha was revealed not to interfere with the binding of prolactin to the receptor.

Animals↗
PubMed1994

Comparison between transforming growth factor alpha and epidermal growth factor in the protection of rat gastric mucosa against drug-induced injury.

This study was designed to compare the protective effect of recombinant human TGF alpha or EGF against drug-induced damage to the rat gastric mucosa. Parenteral administration of TGF alpha and EGF prevented 100% ethanol-induced mucosal injury to a similar extent. Furthermore, both peptides, in non-antisecretory doses, significantly decreased the gastric mucosal damage brought about by acidified aspirin. TGF alpha and EGF did not afford significant protection of the gastric mucosa when administered orogastrically. We also evaluated the effect of TGF alpha and EGF on insoluble (adherent) gastric mucin and found that both compounds dose-dependently stimulated adherent mucin in a time frame consistent with their protective effect. In conclusion, TGF alpha and EGF are equally effective in preventing drug-induced injury to the rat gastric mucosa.

Animals↗
PubMed1994

Keratinocyte growth factor receptor ligands induce transforming growth factor alpha expression and activate the epidermal growth factor receptor signaling pathway in cultured epidermal keratinocytes.

Epidermal growth factor receptor (EGFR) ligands are fundamental regulators of epithelial growth, differentiation, and neoplastic transformation. In addition to being potent mitogens for murine epidermal keratinocytes in vitro, transforming growth factor alpha (TGF alpha) and EGF elicit distinctive changes in keratin expression: Ca(2+)-mediated induction of the differentiation-specific keratins K1 and K10 is blocked, while simple epithelial keratins K8 and K18 are expressed aberrantly (C. Cheng et al., Cell Growth, & Differ., 4: 317-327, 1993). We have evaluated several additional growth factors to determine the specificity of this response for EGFR ligands. TGF alpha, keratinocyte growth factor (KGF), and acidic fibroblast growth factor (aFGF), but not basic fibroblast growth factor (bFGF) or insulin-like growth factor type I, block Ca(2+)-mediated expression of K1 while inducing K8. Since KGF and aFGF (but not bFGF) are ligands for the KGF receptor (KGFR), we explored the possibility that the TGF alpha/EGFR pathway is an intermediary in signaling through the KGFR. TGF alpha mRNA was increased in cells treated with KGF, aFGF, or TGF alpha but not bFGF or insulin-like growth factor type I. Similar changes were detected at the protein level; TGF alpha in conditioned medium (CM) from control, KGF-, TGF alpha-, and aFGF-treated cultures was 54 (+/- 8, SEM), 365 (+/- 50), 146 (+/- 20), and 120 (+/- 50) pg/ml, respectively. KGF and TGF alpha also increased expression of cell-associated TGF alpha measured in keratinocyte lysates. KGF increased TGF alpha secretion and mRNA levels in human as well as mouse keratinocytes. CM from KGF-treated cultures stimulated cell growth when added to cultures of normal keratinocytes. Preincubation with neutralizing antibodies to both TGF alpha and KGF, but not KGF antibody alone, blocked cell growth in cultures treated with KGF CM, suggesting that the predominant keratinocyte mitogen in KGF CM is TGF alpha. In support of this hypothesis, treatment of keratinocytes for 5 min with either KGF CM or purified TGF alpha resulted in EGFR autophosphorylation. Furthermore, after approximately 24 h, KGF as well as TGF alpha induced EGFR down-regulation based on Western blot analysis and 125I-EGF binding. Induction of TGF alpha in KGF-treated keratinocytes, coupled to activation and down-modulation of the EGFR, suggests that TGF alpha may be a proximal effector of KGF action for at least certain aspects of epidermal growth and differentiation.

Animals↗
PubMed1994

Inhibition of estrogen-induced breast cancer cell proliferation by reduction in autocrine transforming growth factor alpha expression.

Breast cancer cell lines have been shown to secrete transforming growth factor alpha (TGF alpha) and other polypeptide growth factors in response to estrogen (E2) stimulation. In this study, we investigated whether cellular-derived TGF alpha mediates the growth-stimulatory effects of E2 in ER-positive breast cancer cells. To test this hypothesis, we introduced an antisense TGF alpha mRNA expression vector under control of a human metallothionein promoter into E2-responsive T47D human breast cancer cells. In stably transfected cells, cadmium induced antisense mRNA and reduced expression of TGF alpha mRNA and protein in antisense clones (AS1). TGF alpha expression was increased in sense clones (S2), while wild-type T47D cells (W3) or pSV2 neomycin resistance-transfected cells showed no change in TGF alpha expression in response to cadmium. The basal proliferative capacity of antisense transfected cells was equivalent to that of the wild-type. E2 increased TGF alpha synthesis and cell proliferation in transfected and wild-type cells. In AS1 cells, the simultaneous addition of cadmium with E2 blocked most of the E2-induced increase in TGF alpha mRNA and protein and nearly abolished the stimulatory effects of E2 on DNA synthesis and cell number. In contrast, no reduction in cell proliferation was observed with cadmium in antisense-transfected cells with a low level of antisense expression or in the S2 or W3 cells. Our results are compatible with the hypothesis that autocrine production of TGF alpha may be an important contributor to E2-induced growth in T47D cells.

Breast Neoplasms↗
PubMed1994

Therapeutic manipulation of cytokines: transforming growth factor beta-1 protects mice treated with lethal doses of cytarabine.

We have developed a mouse model to utilize the specific regulatory effects of Transforming Growth Factor Beta-1 (TGF beta 1), the prototype for a family of growth inhibitory cytokines. A vital factor in the regulation of normal cellular growth for many cell types, TGF beta 1 prevents proliferation by reversibly arresting cells at the G1/S border of the cell cycle, thus delaying DNA synthesis and cell division. Since the dose of cytotoxic chemotherapy is limited by its adverse effects on bone marrow and gut cells, we proposed that a TGF beta 1-induced block at G1/S would diminish the S phase toxicity of high dose cytarabine (ara-C). The dosage of ara-C required to kill 90 per cent of 4-week old DBA/2 males was determined to be 3200 mg/kg every 12 hours x 2. Pretreatment with TGF beta 1 6-24 hours before the first dose of ara-C proved to be significantly protective; 8/9 TGF beta 1-pretreated mice survived versus 1/9 treated with TGF beta 1 for 3 hours or less or with ara-C alone (chi2 = 10.89 P = 0.001). A second experiment confirmed this effect; TGF beta 1 pretreatment for 6-24 hours protected 9/9 versus 0/9 survivors in the group treated with TGF beta 1 for 3 hours or less or with ara-C alone (chi2 = 18.0, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Transforming growth factor-alpha production and autoinduction in a colorectal carcinoma cell line (DiFi) with an amplified epidermal growth factor receptor gene.

The DiFi colorectal carcinoma cell line, derived from a patient with familial adenomatous polyposis, was examined for gene expression and production of the autocrine growth factor transforming growth factor alpha (TGF-alpha) and for epidermal growth factor receptor (EGFR) gene expression and gene copy number. DiFi cells expressed TGF-alpha transcripts as identified on Northern (RNA) blots. Addition of TGF-alpha (10 ng/ml) or EGF (10 ng/ml) to DiFi cell cultures (lacking EGF or serum) up-regulated DiFi cell basal TGF-alpha mRNA levels, suggesting that autoinduction of TGF-alpha occurs in these cells. DiFi cell cultures in log phase growth secreted measurable amounts of TGF-alpha (347 pg/10(6) cells/24 h) into their culture medium, as determined by radioimmunoassay. DiFi cells showed strong overexpression of the EGFR gene on Northern blots relative to three other colon cancer cell lines examined. Immunoperoxidase staining showed enhanced EGFR expression in a cell subpopulation among the original (uncultured) ascitic fluid cells from which the DiFi cell line was established. This cell subpopulation was observed to expand dramatically between passages 1 and 25. Immune complex kinase assay of DiFi cells showed that EGFR were functional as determined by their ability to autophosphorylate. The EGFR gene in these cells was not found to be rearranged or genetically altered using Southern blot analysis. Dot blot analysis of DiFi cell DNA revealed EGFR gene amplification in the range of 60-80 copies/cell, which is approximately twice the copy number seen in A-431 epidermoid carcinoma cells. To our knowledge DiFi cells represent the first example of EGFR gene amplification in a colorectal adenocarcinoma. Because DiFi colorectal cancer cells uniquely show production and auto-induction of TGF-alpha in addition to amplification and overexpression of the EGFR gene, these cells represent a valuable tool for studying the role(s) of the EGFR in the regulation of tumor cell growth.

Blotting, Northern↗
PubMed1993

Transforming growth factor-alpha (TGF alpha) inhibition of parietal cell secretion: structural requirements for activity.

Parietal cells of the gastric fundus produce transforming growth factor-alpha (TGF alpha) which functions as a potent inhibitor of acid secretion. We have previously demonstrated that TGF alpha can inhibit aminopyrine uptake in isolated rabbit parietal cells. In this study, we have evaluated the components of TGF alpha structure which determine its ability to inhibit parietal cell function. Both human and rat TGF alpha inhibited histamine stimulation by increasing the EC50 for agonist stimulation. Three fragments containing the third loop domain of TGF alpha (rat TGF alpha 34-43, human TGF alpha 34-43 and human TGF alpha 34-50) all inhibited histamine stimulation with IC50 values 20, 33 and 4-fold higher, respectively, than that of the native molecule. Rat TGF alpha inhibited carbachol stimulation throughout an agonist dose response. Human TGF alpha was only effective in inhibiting carbachol if incubations were performed in the presence of air rather than 100% O2. In air incubation, all three of the TGF alpha fragments inhibited carbachol stimulation but, in contrast to the effects on histamine, the peptides all were virtually equipotent with the native molecule. The human sequence fragments, like the native human TGF alpha, elicited no inhibition when incubations were performed in the presence of 100% O2. The results suggest that there are pharmacological differences in the response of isolated parietal cells to TGF alpha-mediated inhibition of histamine and carbachol. In addition, in contrast with previous investigations on the mitogenic action of TGF alpha, third loop fragments of TGF alpha retain the capacity to inhibit aminopyrine accumulation.

Amino Acid Sequence↗
PubMed1993

Characterization of the DiFi rectal carcinoma cell line derived from a familial adenomatous polyposis patient.

The DiFi human colorectal cancer cell line was recently established from a familial adenomatous polyposis patient with extracolonic features characteristic of the Gardner syndrome. These cells have now been propagated for 150 passages in standard culture media and vessels without feeder layers or collagen coatings. They retain features of colonic epithelial cells such as surface microvilli, secretory vesicles, and desmosomes. Cytosol of DiFi cells contains a high level (502 U/mg protein) of the mucin CA 19-9. In addition, DiFi cells produce carcinoembryonic antigen, and induce tumors in athymic mice. Cytoskeleton analysis of DiFi cells by fluorescence microscopy showed a pronounced disorganization of actin cable structure. The isozyme genetic signature of DiFi cells is unique (0.01 probability of finding the same genetic signature in a different cell line), differs from that of HeLa cells, and has expressional features seen in other colorectal cell lines. The DiFi cell karyotype is tetraploid, contains many marker chromosomes, and shows numerous episomal particles. Two copies of chromosome 18 were absent, and only a single normal chromosome 17 was found. This parallels detection of allelic losses from DiFi cell DNA at loci on chromosomes 17p and 18 using molecular (cDNA) probes. DiFi cells clearly express transcripts for the c-myc proto-oncogene, the c-myb proto-oncogene, and the p53 tumor suppressor gene. Transforming growth factor beta inhibits DiFi cell growth in soft agar and suppresses c-myc expression in these cells. The value of this cell line in the study of genetic alterations in colorectal cancer is discussed.

Actins↗