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Biomedical subjects

J C Thompson

Publications and source records attributed to J C Thompson.

At least 91 records · Page 5Linked to original sources
PubMed1994

Growth-regulatory effect of gastrin on human colon cancer cell lines is determined by protein kinase a isoform content.

Cell growth is regulated by various peptide growth factors through receptor-linked multiple intracellular signal-transduction pathways, such as the cyclic adenosine monophosphate (cAMP) pathway. cAMP activates cAMP-dependent protein kinase A (PKA) either to stimulate or inhibit cell growth. The effect on growth is determined by the presence of two isoforms of the regulatory (R) subunit of PKA; activation of RI alpha-type PKA leads to stimulation of growth, activation of RII beta-type inhibits cell growth. We determined whether the effect of gastrin on the growth of human colon cancer cells is determined by cell-specific content of PKA. We utilized two human colon cancer cell lines: LoVo, growth of which is stimulated by gastrin, and HCT116, growth of which is inhibited by gastrin. Activation of both types of PKA with 8-Br-cAMP mimicked the regulation of growth by gastrin; preferential activation of RII beta-type PKA with 8-Cl-cAMP inhibited growth of both cell lines. LoVo cells possess the predominantly RI alpha isoform of PKA at the mRNA and protein level; HCT116 cells possess predominantly the RII beta-type PKA. The cAMP-mediated regulation of growth (either stimulatory or inhibitory) by gastrin on these human colon cancer cells was determined by the predominant isoform of PKA.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1994

Gastrin stimulates growth of human colon cancer cells via a receptor other than CCK-A or CCK-B.

Two receptors for cholecystokinin (CCK) have been isolated which also bind gastrin: CCK-A type and CCK-B type, both are coupled to phospholipase C (PLC) activation. However, identification of the "true" gastrin receptor remains controversial. We determined which CCK receptor mediated the trophic effect of gastrin on human colon cancer cells (LoVo). LoVo cells lack mRNA for either CCK receptor by Northern hybridization. Gastrin stimulated cyclic AMP production, not PLC activity, in LoVo cells. The trophic effect was not blocked by receptor antagonists for CCK-A (L364,718) or CCK-B (L365,260). The gastrin receptor pharmacology on LoVo cells and the lack of appropriate transcripts suggest that gastrin stimulated growth of these cells by a receptor other than CCK-A or CCK-B type and there likely exists another receptor for gastrin.

Cell Division↗
PubMed1994

Effects of gastrin on 3',5'-cyclic adenosine monophosphate, intracellular calcium, and phosphatidylinositol hydrolysis in human colon cancer cells.

Gastrin is a trophic factor for some human colon cancer cells. However, the signal-transduction pathways by which gastrin regulates growth are still unknown. We examined the effect of synthetic human gastrin-17 (G-17) on signal-transduction pathways and cell growth using 4 different human colon cancer cell lines (LoVo, COLO 320, HT-29, and HCT116). G-17 stimulated the production of cyclic AMP in LoVo, COLO 320, and HCT116 cells, while G-17 stimulated phosphatidylinositol hydrolysis and mobilization of intracellular calcium in HT-29 cells. The growth-regulatory effect of G-17 on these colon cancer cells (stimulatory on LoVo, COLO 320, and HT-29 cells; inhibitory on HCT116 cells) was well correlated with the effect of G-17 on the signal-transduction pathway in each cell line. We further examined the effect of a selective cholecystokinin-B type receptor antagonist, JMV 320, on G-17-induced signal-transduction pathways and G-17-regulated growth. In each cell line, the effect of JMV 320 on G-17-induced signal-transduction pathways was well correlated with that on G-17-regulated growth. G-17 appears to regulate, at least to some extent, growth of human colon cancer cells through gastrin receptor-linked signal-transduction pathways that are cell-specific.

Calcium↗
PubMed1994

Bombesin stimulates the in vitro growth of a human gastric cancer cell line.

Bombesin (BBS) and its mammalian equivalent, gastrin-releasing peptide (GRP), exhibit diverse biological functions, including that of a neurotransmitter, a regulator of gastrointestinal hormone release, and a trophic factor for various normal and neoplastic tissues. Bombesin stimulates the growth of normal cells of the stomach, pancreas, and bronchial epithelium as well as cells in breast cancer, gastrinoma, and small cell lung cancer. The purpose of this study was to determine whether BBS regulates the growth of a human gastric cancer cell line (SIIA) in vitro, and if so, to examine the mechanisms of signal-transduction that are involved. We found that BBS stimulated the growth of SIIA cells in vitro. The GRP receptor antagonists, BIM 26189 and BIM 26226, had no effect on growth of SIIA cells. Although these antagonists blocked the BBS-induced increase of [Ca2+]i, they failed to block the growth-stimulatory effect of BBS. BBS stimulated intracellular tyrosine phosphorylation of multiple proteins, with a predominant protein of apparent molecular weight of 125 kDa. Inhibition of intracellular tyrosine kinases by tyrphostin blocked the growth-stimulatory effect of BBS on SIIA cells. These results indicate that BBS exerts its trophic effect on SIIA cells through a receptor(s) linked to tyrosine kinase pathway, but not to the phospholipase C (PLC) pathway.

Adenocarcinoma↗
PubMed1994

Transforming growth factor-beta inhibits rat intestinal cell growth by regulating cell cycle specific gene expression.

Transforming growth factor-beta 1 (TGF-beta 1) inhibits the growth of intestinal cells, but the mechanisms involved are unknown. Using a rat intestinal crypt cell line (IEC-6), we determined the site of action in the cell cycle that TGF-beta 1 acts to suppress proliferation. We also examined the effect of TGF-beta 1 on the expression of proliferation-associated "immediate early" genes (zif268, jun-B, c-myc) during the early G1 phase and the cdc2 gene during the transition from the G1 phase to the S phase of the cell cycle. Cell cycle progression was determined by incorporation of 3H-thymidine, and gene expression was analyzed by Northern blot analysis. We found that TGF-beta 1 acts to inhibit proliferation of rat intestinal crypt cells by blocking cell cycle progression at the middle G1 phase. The genes activated during G1 can be divided into TGF-beta 1 insensitive (zif268, jun-B, and c-myc) and TGF-beta 1 sensitive (the cdc2 gene). TGF-beta 1 suppresses the induction of the cdc2 gene during the G1/S transition without inhibiting the activation of immediate early genes during the early G1 phase.

Animals↗
PubMed1994

Cytocidal effect of high energy shock wave on tumour cells enhanced with larger dose and multiple exposures.

Cultured LLC-WRC256 (Walker rat carcinoma) cells were exposed to different doses of high energy shock waves (HESW). The immediate viabilities were 98% in the control cells, and 74%, 53% and 18% following 400, 800, and 1500 HESW treatment, respectively. Surviving cells in the 400 and 800-treated HESW demonstrated delayed upward growth rate curves, and the 1500 HESW-treated a downward curve. Agar clonogenic efficiencies for surviving cells were 36% (control), 20% (400 HESW), 15% (800 HESW) and 3% (1500 HESW). LLC-WRC256 tumours in Wistar rats were treated once every other day with 1500 HESW on a total of three occasions. Tumours treated with HESW grew more slowly (4.9 cm3) than those in the control (13.5 cm3). HESW fragmented cells and destroyed cell membranes and intracellular organelles. A histological examination of tumours treated with HESW demonstrated local haemorrhage with necrosis in the HESW focus area. Damage to the surrounding skin and soft tissue was slight and transient. These findings suggest that the growth of tumour cells can be suppressed in vitro and in vivo by treatment with HESW.

Animals↗
PubMed1994

Organ physiology of aging.

With improvements in medical care over the last several decades, individuals are living longer and, as a result, more surgical procedures will be performed in the geriatric patient. Normal physiologic aging is characterized by a gradual loss of reserve capacity. The effects of the aging process on various organ systems do not usually affect function in the normal state; however, during periods of stress (such as with a surgical procedure or illness), the elderly patient may not be able to meet the increased metabolic demand. This loss of reserve capacity is the single most important factor that decreases the elderly patient's ability to tolerate operations. It is imperative that the surgeon identify the elderly patient who is at increased risk for complications. Specific consideration must be given to proper management of fluid and electrolyte replacement, respiratory management to prevent atelectasis and pneumonia, and monitoring for possible cardiac complications.

Aging↗
PubMed1994

Gastrinomas demonstrate amplification of the HER-2/neu proto-oncogene.

OBJECTIVE: This study determined whether genomic amplification of HER-2/neu or mutations of the p53 and ras genes were present in gastrinomas. SUMMARY BACKGROUND DATA: Amplification of HER-2/neu, a proto-oncogene related to the epidermal growth factor receptor, and mutation of the ras proto-oncogene and p53 tumor suppressor gene appear to play a role in the pathogenesis of some human cancers. Little is known about possible molecular alterations in gastrinomas, tumors that may be particularly virulent because of gastrin overproduction, resulting in the severe ulcer diathesis, the Zollinger-Ellison syndrome. METHODS: The differential polymerase chain reaction (PCR) procedure was used to detect amplification of the HER-2/neu gene in DNA samples from the novel human gastrinoma cell line (PT) and from paraffin-embedded samples of gastrinomas. Sequencing techniques were used to determine whether mutations of the p53 or ras (Ha-ras, N-ras, Ki-ras) genes were present. RESULTS: Amplification (> twofold) occurred in all gastrinoma tumor samples. Compared with normal pancreas or ileum, a 4- to 12-fold amplification of HER-2/neu was found in 3 gastrinomas, 3 to 3.3-fold in four samples and 2.1- to 2.4-fold in the remaining five tumors. A heterozygous point mutation in the p53 gene (codon 273) was found in a single sample; none of the gastrinomas contained a mutation of the ras genes. CONCLUSIONS: Amplification of the HER-2/neu gene, but not alterations of either p53 or ras, may be involved in the pathogenesis of gastrinomas. The unique PT cell line will be a useful model to further elucidate the molecular mechanisms that contribute to gastrinoma formation and growth.

Base Sequence↗
PubMed1994

Expression of the neurotensin gene in fetal human liver and fibrolamellar carcinoma.

OBJECTIVE: This study determined whether the neurotensin gene (NT/N) is expressed in the normal adult liver and focal nodular hyperplasia (FNH) and confirmed NT/N expression in fibrolamellar carcinoma; whether NT/N or the neurotensin receptor is expressed in the fetal liver; and whether hepatic resection leads to expression of NT/N. SUMMARY BACKGROUND DATA: Neurotensin (NT), a gut tridecapeptide localized in the gastrointestinal tract of the adult to the small bowel, is an important hormone-regulating gut motility, secretion, and mucosal growth. Expression of the NT/N gene has been identified in fibrolamellar carcinomas, but NT/N is not known to be expressed in the normal liver. METHODS: Sensitive ribonuclease (RNase) protection assays were used to determine whether NT/N is expressed in fibrolamellar carcinoma, FNH, or healthy fetal and adult livers. The authors also determined whether the receptor for NT was present in the fetal liver and whether liver resection and subsequent regeneration could lead to re-expression of NT/N in the rat. RESULTS: Neurotensin is expressed in fibrolamellar carcinoma and in the fetal human liver, but not in the adult liver or the samples of FNH. In addition, the authors were not able to detect expression of the NT receptor in the fetal liver and did not identify NT/N gene activation in the regenerating liver of the rat. CONCLUSIONS: The NT/N gene will be a useful molecular marker to differentiate fibrolamellar carcinoma from other liver tumors. The finding of NT/N expression in the fetal liver suggests a stem cell descendant that is common to both the liver and gut. The absence of NT/N expression in the regenerating liver suggests that NT does not play a role in this rapid growth process.

Animals↗
PubMed1994

Bombesin improves survival from methotrexate-induced enterocolitis.

OBJECTIVE: The authors determined whether bombesin could improve survival from methotrexate (MTX)-induced enterocolitis. SUMMARY BACKGROUND DATA: Bombesin prevents gut mucosal atrophy, which is produced by feeding rats an elemental diet. Administration of MTX produces a lethal enterocolitis in rats fed an elemental diet. METHODS: On treatment day 0, 60 rats were divided randomly into three groups and fed an elemental diet (Vivonex TEN, Sandoz, Minneapolis, MN) as the only source of nutrition. Groups were subdivided further to receive either saline or bombesin (10 micrograms/kg, subcutaneously, three times a day) beginning either on day 0 or day 14. Methotrexate (20 mg/kg, intraperitoneally) was given to all rats 14 days after the start of an elemental diet. RESULTS: Bombesin prevented the mucosal atrophy in the ileum produced by the elemental diet and significantly decreased mortality in rats given MTX (whether given as a pretreatment or at the time of MTX administration). CONCLUSION: Bombesin significantly improved survival in a lethal model of MTX-induced enterocolitis, possibly by maintaining gut mucosal structure. Administration of bombesin to patients receiving chemotherapy may be clinically useful in preventing the severe enterocolitis induced by various chemotherapeutic agents.

Animals↗
PubMed1994

Characterization of a human pancreatic carcinoid in vitro: morphology, amine and peptide storage, and secretion.

The study of functioning human endocrine tumors has been hampered by a lack of suitable in vitro models. We have established the first permanent cell line of a human pancreatic carcinoid tumor (BON) in culture. BON cells grow in monolayer culture and form colonies in soft agar. Injection of BON cells into nude mice produces transplantable tumors in a dose-dependent fashion. The histology of tumors in athymic mice from injection of dispersed, cultured BON cells is similar to the original histology of the resected tumor. Significant amounts of neurotensin, pancreastatin, and serotonin (5-HT) are demonstrated in the cells by radioimmunoassay (RIA) and the presence of chromogranin A, bombesin, and 5-HT is confirmed by immunocytochemistry. Numerous round and pleomorphic dense-core neurosecretory granules are present on electron microscopy. Functional receptors for acetylcholine, 5-HT, isoproterenol, and somatostatin are present on cultured cells. BON cells possess a specific transport system for uptake of 5-HT from the medium; this uptake system may be a route for regulation of autocrine effects of 5-HT on carcinoid cells. This unique human carcinoid tumor cell line should provide the opportunity for new insight into the biology of carcinoid tumors and of specific intracellular mechanisms for secretagogue action in the release of amines and peptides.

Adult↗
PubMed1994

Inhibitory effect of calcium channel blockers on growth of pancreatic cancer cells.

Calcium, which binds to calmodulin inside the cells, is an important mediator of various intracellular processes, including cell proliferation. We speculated that blockade of Ca2+ influx into the cells by Ca(2+)-channel blockers, such as phenytoin and verapamil, might affect the Ca(2+)-calmodulin pathway leading to suppression of cell growth. In this study, we examined the effect of phenytoin and verapamil on growth of two human pancreatic cancer cell lines, MIA PaCa-2 and CAV, in vitro and in vivo. Both phenytoin and verapamil inhibited growth of the two cell lines in a dose-dependent fashion. Phenytoin and verapamil each significantly prolonged doubling time of MIA PaCa-2 and the combination of the two drugs acted synergistically. The activity of ornithine decarboxylase, which is a rate-limiting enzyme of the polyamine pathway that is closely related to cell proliferation, was significantly inhibited by both drugs in a time-dependent fashion. Phenytoin, but not verapamil, inhibited growth of MIA PaCa-2 tumors xenotransplanted into nude mice, whereas both phenytoin and verapamil inhibited the growth of CAV tumors. Since phenytoin and verapamil are known to have fewer side effects than conventional antineoplastic drugs, these results suggest their possible use in novel therapeutic strategies.

Calcium Channel Blockers↗
PubMed1994

Bombesin inhibits growth of pancreatic ductal adenocarcinoma (H2T) in nude mice.

Bombesin (BBS), a tetradecapeptide, stimulates growth of various types of cells, including fibroblasts and human small cell lung cancer, and has been termed the universal "on-switch" due to its ability to stimulate the release of numerous hormones. In addition, BBS receptors have been identified in normal and neoplastic pancreatic tissue. A pancreatic ductal adenocarcinoma cell line (H2T), established in our laboratory, possesses specific binding sites for BBS. The purpose of this study was to examine the effect of BBS on the growth of H2T tumors transplanted into athymic nude mice. H2T cells (5 x 10(6) cells/mouse) were injected s.c. into the interscapular region of the nude mice and then the mice were randomized into two groups (n = 10/group). Mice received either 0.1 ml of saline with 0.1% bovine serum albumin (BSA) (control) or 0.1 ml BBS (5 micrograms/kg) intraperitoneally, three times/day. Tumor area was measured twice weekly until the mice were killed (day 32), when tumor and normal pancreas were removed, weighted, and assayed for DNA and protein content. Administration of BBS significantly inhibited H2T tumor area, weight, and DNA and protein content. Conversely, growth of normal pancreas, removed as an in vivo bioassay so as to ensure the efficacy of BBS, was stimulated. We conclude that BBS is a growth inhibitory factor for H2T tumors and that different mechanisms may be responsible for the differential growth effects elicited by normal and neoplastic pancreas in response to BBS.

Animals↗
PubMed1994

Lovastatin inhibits pancreatic cancer growth regardless of RAS mutation.

Lovastatin, an inhibitor of the rate-limiting enzyme of cholesterol synthesis, inhibits growth of pancreatic cancer cells. A possible mechanism of this inhibition is that lovastatin inhibits the activity of RAS protein by depleting farnesyl (an intermediate of cholesterol synthesis). The K-ras gene is frequently mutated in pancreatic cancers and RAS protein requires farnesyl to be bound to the cell membrane and thereby activated. To investigate whether lovastatin inhibition of cell growth depends upon the presence of ras mutation, codons 12/13 and 61 of ras genes were examined by the dideoxynucleotide chain-terminating method in five pancreatic cell lines (human CAPAN2, CAV, MIA Paca2, PANCi, and hamster H2T) on which lovastatin exerted a growth-inhibitory effect. These codons play a major role in tumorigenic mutation of ras genes. Lovastatin inhibited cell growth by 99% (MIA), 97% (H2T), 78% (CAV), 41% (CAPAN2), and 23% (PANC1), respectively, when cells were treated with 2.5 micrograms/ml lovastatin for 6 days. Activating point mutations were found in codon 12 of the K-ras gene (wild type:GGT) in MIA (GTT), H2T (GAT), CAPAN2 (TGT), and PANC1 (GAT) but not in CAV. In addition, the CAV cell line did not have a mutation in either H- or N-ras genes. Lovastatin inhibited the growth of CAV cells even though this cell line did not have ras mutation, suggesting that lovastatin inhibition of pancreatic cancer cell growth is not directly dependent on the presence of ras mutation.

Animals↗
PubMed1994

Effect of aging on neurotensin-stimulated growth of rat small intestine.

The proliferative activity of gut mucosa is altered with aging; the potential for the aged gut to respond to trophic stimuli is not known. The purpose of this study was to determine whether there are age-related differences in the effects of the trophic gut peptide neurotensin (NT) on the structure and function of small bowel mucosa. NT (300 micrograms/kg) or saline (control) was injected subcutaneously at 8-h intervals for 5 days in rats of two age groups, young (2 mo) and aged (24 mo). On day 6, rats were killed, and the gut mucosa (proximal and distal small bowel) was scraped, weighed, and analyzed for DNA, RNA, and protein content and for disaccharidase (sucrase and maltase) activity. In a second experiment, the groups of rats and the protocol for NT administration were identical; however, when the rats were killed, the distal gut was removed for histological evaluation of crypt and villus length (mm) and density (no./cm gut segment) and bromodeoxyuridine immunohistochemistry. NT produced significant increases in mucosal growth (wt, DNA, RNA, and protein) in both age groups when compared with age-matched controls; the increase of growth measurements was the greatest in the small bowel mucosa of the aged rats. In addition, NT increased crypt density in both groups; only the aged group treated with NT demonstrated increases in crypt depth and villus height. Specific activities of sucrase and maltase did not change with NT treatment in either of the age groups. We conclude that the proliferative potential of small bowel mucosa is maintained with aging in response to administration of NT.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

Temporal-specific and spatial-specific patterns of neurotensin gene expression in the small bowel.

Expression of the neurotensin/neuromedin N (NT/N) gene is developmentally regulated in a temporal- and spatial-specific pattern in the small bowel. The purpose of our study was to determine 1) whether the temporal expression of NT/N could be altered by ectopic placement of small bowel and 2) whether the spatial-specific expression of NT/N could be altered by different diets. We found that the relative temporal pattern of NT/N expression was unchanged in rat jejunal and ileal xenografts implanted into the flanks of athymic nude mice. To determine whether the spatial-specific pattern of NT/N expression could be altered by different luminal nutrients, 28-day-old rats were randomized to receive chow or chemically defined liquid diets for 60 days at which time the jejunoileum was divided into eight equal segments, and NT/N expression was analyzed. The normal pattern of increasing levels of NT/N mRNA along the jejunum-to-ileum axis was not altered by any of the liquid diets. In contrast to NT/N, we found that expression of sucrase-isomaltase varied greatly depending on both location and type of luminal nutrients. We conclude that the strict temporal- and spatial-specific pattern of NT/N expression is not affected by either location or luminal contents, thus suggesting an intrinsic program of NT/N gene expression. Furthermore, we speculate that the NT/N gene may provide a useful endocrine paradigm to investigate the factors regulating the establishment and maintenance of certain cell lineage-specific patterns along the cephalocaudal axis of the gut.

Aging↗
PubMed1994

Experimental gene therapy of human colon cancer.

BACKGROUND: Gastrin regulates growth of human colon cancer cells by activation of the cyclic adenosine monophosphate (cAMP)-dependent protein kinase A (PKA). Gastrin and 8-Br-cAMP, a membrane-permeable cAMP analog, inhibit growth of HCT116 cells; both stimulate growth of LoVo cells. This dual effect on growth may be explained by relative amounts of the regulatory subunit (RI alpha or RII beta) of PKA within the cancer cells. Antisense oligodeoxynucleotides (ASO) to either RI alpha or RII beta inhibit protein translation of the target mRNA by sequence-specific binding; subsequently, cellular PKA content and the cAMP-mediated growth may be altered. We determined whether ASO to either the RI alpha or RII beta subunit altered the cAMP-mediated growth of HCT116 and LoVo human colon cancer cells. METHODS: HCT116 cells were treated with RII beta ASO (15 mumol/L, 4 days) and then treated with 8-Br-cAMP (25 mumol/L); tritiated thymidine incorporation was measured after 24 hours, and the cell number was determined on alternate days. Protein and mRNA levels of the RII beta subunit were determined by Western and Northern blotting, respectively. Similar studies with an ASO against the RI alpha subunit were performed on LoVo cells. RESULTS: RII beta ASO reversed the cAMP-mediated inhibition of growth of HCT116 cells, and RII beta ASO decreased the protein level of the RII beta subunit. RII beta ASO did not alter the basal growth of HCT116 cells. RI alpha ASO reversed the cAMP-mediated stimulation of growth of LoVo cells. CONCLUSIONS: The regulatory subunits of PKA are potential targets to alter growth of human colon cancer cells. Gene therapy directed to alter specific steps in signal transduction pathways may provide new therapeutic strategies.

8-Bromo Cyclic Adenosine Monophosphate↗