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Query: UMLS:C0596263 (carcinogenesis)
 64,820 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Alterations in large gut associated lymphatic tissues (LGALT) were studied histologically during 20-methylcholanthrene (MCA) induced colorectal carcinogenesis. Precancerous changes in LGALT included hyperplasia, hyperchromasia of lymphocytes and enlargement of lymphoid follicles. In addition, follicular invasion in muscular layer and cellular disorganization of diffuse lymphatic tissues were observed in neoplasia. Since, LGALT showed remarkable changes during carcinogenesis, this aspect may be considered during assessment of preneoplastic lesions, along with other histologic features of early neoplasia.
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PMID:Alterations in large gut associated lymphatic tissues (LGALT) during experimental colorectal carcinogenesis. 827 29

Dietary fat, protein and fibre have been shown to modulate cancer risk in humans and the present study examined the biological effects in human-flora-associated (HFA) rats of altering intake levels within the normal human range. Two control groups, one HFA and the other germfree (GF), consumed a human diet low in fat, fibre and beef for 4 weeks; three other groups consumed human diets similar except for independent 3-fold increases in fat, beef protein or fibre. After 2 weeks on the diets, magnetically recoverable microcapsules were given orally to the rats and subsequently recovered from the faeces to assess endogenous cross-linking agents. After 4 weeks, measurements were made of gut microfloral enzyme activities, hepatic activation of dietary mutagens and hepatic DNA adducts by 32P-postlabelling. Activation in vitro of the dietary mutagens 2-amino-3-methyl-3H-imidazo[4,5-f]quinoline (IQ) and 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) by hepatic S9, formation of endogenous hepatic DNA adducts in vivo and the beta-glucuronidase activity of caecal contents were all increased in the sequence high fat > high fibre > high beef = control. Of the two DNA adducts found in all HFA rats, only one was present in GF controls, indicating that the human gut microflora (subject to human dietary modulation) either releases a DNA-adducting product able to act outside the gastrointestinal tract, or stimulates the generation of such a product by mammalian processes. Caecal nitrate reductase activity was highest in rats fed the high beef diet, whilst entrapment of cross-linking agents was highest in those fed the high fibre diet. These results show that risk-related components of human diets interact with human gut microflora to modulate the production of endogenous DNA-adducting and cross-linking substances.
Carcinogenesis 1993 Jan
PMID:Effects of risk-associated human dietary macrocomponents on processes related to carcinogenesis in human-flora-associated (HFA) rats. 838 Oct 55

Several studies carried out during the past two decades have investigated the effect of dietary and surgical manipulation on pancreatic growth and carcinogenesis. Diets high in trypsin inhibitor stimulate pancreatic growth and increase the formation of preneoplastic lesions and carcinomas in the rat pancreas. Cholecystokinin (CCK) is the key intermediary in this response, since both natural and synthetic trypsin inhibitors increase circulating levels of the hormone and CCK antagonists largely prevent these changes. Fatty acids enhance pancreatic carcinogenesis in both rats and hamsters, whereas protein appears to have a protective role in the rat, but to increase tumour yields in the hamster. Several surgical operations affect the pancreas. Pancreatobiliary diversion and partial gastrectomy stimulate pancreatic growth and enhance carcinogenesis, probably by means of increased CCK release. Complete duodenogastric reflux has similar effects on the pancreas but the gut peptide involved is gastrin. Although massive small bowel resection increases pancreatic growth, the marked reduction in caloric absorption probably explains its failure to enhance carcinogenesis. CCK and enteroglucagon might work in concert to modulate the tropic response of the pancreas to small bowel resection. In the pancreas, as in the large intestine, hyperplasia appears to precede and predispose to neoplasia.
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PMID:Experimental pancreatic hyperplasia and neoplasia: effects of dietary and surgical manipulation. 849 19

Mutations in the adenomatous polyposis coli (APC) gene cause the hereditary cancer syndrome familial adenomatous polyposis and are implicated in the early stages of sporadic colorectal carcinogenesis. APC is therefore a promising candidate for use in prophylactic gene therapy of intestinal tissues at high risk of becoming malignant. The aim of the study was to discover if functional full length APC gene can be introduced into somatic gut epithelial cells and to define the optimum conditions for such transfer. Copies of the normal APC gene were introduced into SW480 cells, a colonic epithelial cell line with an APC gene mutation, using plasmid DNA combined with liposomes. Reverse transcriptase polymerase chain reaction and restriction enzyme digestion allowed the endogenous gene to be distinguished from the transgene. It was shown that the normal APC gene is expressed at high levels for 72 hours after transfection and disappears within one week. This study shows that short-term expression of normal APC gene can be achieved after transfection with liposome-DNA complexes at sufficiently high levels to permit assessment of biological effects.
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PMID:Expression of the APC gene after transfection into a colonic cancer cell line. 853 55

Gut peptides are involved in the growth and carcinogenesis of the exocrine pancreas of rats after treatment with azaserine. However, little is known about the influence of azaserine on expression of gut peptide receptors in the pancreas of the rat. Cholecystokinin, bombesin, somatostatin, secretin, and vasoactive intestinal peptide receptors were therefore visualized and quantified by storage phosphor autoradiography in pancreata of either saline control or azaserine-treated rats. As expected, putative preneoplastic lesions were formed in the pancreata of the azaserine-treated but not in the control animals. The pancreata of control rats contained receptors for cholecystokinin, bombesin, somatostatin, secretin, and vasoactive intestinal peptide. Cholecystokinin receptors were of the A-type and showed, in contrast to the other receptors, a heterogeneous expression due to variability of the high-affinity receptors. In the pancreata of azaserine-treated animals a significantly increased binding capacity of high-affinity receptors fro cholecystokinin was found not only in atypical acinar cell nodules but also in non-nodular pancreas when compared to pancreas of control rats (P < 0.05). Neither atypical acinar cell nodules nor non-nodular pancreas of rats treated by azaserine were shown to possess receptors for the other four types of gut peptide receptors. The spectrum of peptide receptors in pancreas of control and azaserine-treated rats in this study may help to understand the mechanism whereby gut hormones may modulate pancreatic carcinogenesis.
Carcinogenesis 1995 Dec
PMID:Gut peptide receptors in pancreata of azaserine-treated and normal control rats. 860 69

Localised folate deficiency has been implicated in colonic carcinogenesis and supplementation has been proposed for certain populations at risk. However, identifying those groups that may benefit is difficult as the relation between blood folate and gut epithelial cell values is unknown. The aim of this study was to define this relation. Epithelial cells mean (SEM) (sigmoid: 5.35 (0.56) x 10(6) cells, caecum: 6.6 (0.71) x 10(6) cells, duodenum: 4.0 (0.62) x 10(6) cells) were isolated from four endoscopic mucosal biopsy specimens (n = 25) by incubation with dithiothreitol (three hours) and EDTA (one hour). Lamina propria contamination was < 1%, with < 6% intraepithelial lymphocytes. Folate assay of isolates showed sigmoid colon folate content to be 20.1 (1.8) pg/micrograms DNA (10.2-46.6). In the same subject, caecal folate concentrations were lower (p < 0.01, n = 11) than sigmoid values, whereas duodenal isolates mirrored those of the sigmoid (19.4 (2.9) v 20.5 (3.2), n = 5). Sigmoid folate values were consistent over one to three weeks (n = 3). In a single case with blood folate deficiency, colonic values were normal. Serum folate and red cell folate correlated poorly with sigmoid epithelial cell folate content (r = 0.41, p = 0.063 and r = 0.17, p > 0.05 respectively). This study reports a modified ion-chelation isolation method for colonic biopsy specimens that yields large numbers of viable epithelial cells. Cell folate values remain constant with time though vary with intestinal region. The inability of serum or red cell folate values to predict those of the sigmoid epithelium suggests that they cannot identify those patients that might benefit from folate supplements.
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PMID:Folate status of gastrointestinal epithelial cells is not predicted by serum and red cell folate values in replete subjects. 867 95

The growth of pancreatic cancers may be influenced by certain gut peptides. However, the alteration of gut peptide receptors in the progress of pancreatic carcinogenesis is largely unknown. With storage phosphor autoradiography, this study visualized and characterized receptors for cholecystokinin (CCK), somatostatin (SST), bombesin (BBS), secretin and vasoactive intestinal peptide (VIP) in pancreata of control hamsters (n = 7) and pancreatic preneoplastic lesions (n = 10) or adenocarcinomas (n = 10) of N-nitrosobis(2-oxopropyl)amine (BOP)-treated hamsters. The specific CCK-A and secretin receptors expressed in normal pancreata were markedly reduced in pancreatic preneoplastic lesions and absent in adenocarcinomas. In the development of pancreatic tumours, the subgroup of SST receptors did not change, but both the affinity and binding capacity declined. In comparison with the binding of VIP to normal pancreata, specific VIP binding was significantly lower in preneoplastic lesions and almost absent in pancreatic adenocarcinomas. No specific binding for BBS was detected in normal pancreas or (pre)neoplastic lesions of hamster pancreas. The reduction or absence of receptors for CCK, secretin, SST and VIP in hamster pancreas with the progress of carcinogenesis suggests that in BOP-treated hamsters, pancreatic adenocarcinomas have, to a large extent, lost the hormone-dependent characteristics of the original tissue.
Carcinogenesis 1996 Oct
PMID:Expression of receptors for gut peptides in pancreata of BOP-treated and control hamsters. 889 85

The practice of medicine-both past and present-often involves the prescription of specific foods (almost always plants) or their potent derivatives, to treat a wide spectrum of illnesses. Foods that have been ascribed healing properties include the Cruciferae, the allium family, celery, cucumber, endive, parsley, radish and legumes. Review of the epidemiological data, including both cohort and case-control studies, of all cancer sites strongly suggests that plant foods also have preventive potential and that consumption of the following groups and types of vegetables and fruits is lower in those who subsequently develop cancer: raw and fresh vegetables, leafy green vegetables, Cruciferae, carrots, broccoli, cabbage, lettuce, and raw and fresh fruit (including tomatoes and citrus fruit). Other data suggest that foods high in phytoestrogens, particularly soy (which contains isoflavones), or high in precursor compounds that can be metabolized by gut bacteria into active agents, particularly some grains and vegetables with woody stems (which contain precursors to lignans), are plausibly associated with a lower risk of sex-hormone-related cancers. The human evidence for these latter associations is not strong. There are many biologically plausible reasons why consumption of plant foods might slow or prevent the appearance of cancer. These include the presence in plant foods of such potentially anticarcinogenic substances as carotenoids, vitamin C, vitamin E, selenium, dietary fibre (and its components), dithiolthiones, isothiocyanates, indoles, phenols, protease inhibitors, allium compounds, plant sterols, and limonene. Phytoestrogens are also derived from some vegetables and berries as well as grains and seeds. Most of the data for the observations on the anticarcinogenic potential of all of these compounds have come from animal and in vitro studies. At almost every one of the stages of the cancer process, identified phytochemicals are known to be able to alter the likelihood of carcinogenesis-occasionally in a way that enhances risk but usually in a favourable direction. For example, glucosinolates and indoles, thiocyanates and isothiocyanates, phenols, and coumarins can induce a multiplicity of phase II (solubilizing and usually inactivating) enzymes; ascorbate and phenols block the formation of carcinogens such as nitrosamines; flavonoids and carotenoids act as antioxidants, essentially disabling the carcinogenic potential of specific compounds; lipid-soluble compounds such as carotenoids and sterols may alter membrane structure or integrity; some sulphur-containing compounds suppress DNA and protein synthesis; carotenoids can suppress DNA synthesis and enhance differentiation; and phytoestrogens compete with estradiol for estrogen receptors in a way that is generally antiproliferative. Consumption of diets low in plant foods results in a reduced intake of a wide variety of those substances that can plausibly lower cancer risk. In the presence of a diet and lifestyle high in potential carcinogens (whether derived from fungal contamination, cooking or tobacco) or high in promoters (such as salt and alcohol), overall risk of cancer at many epithelial sites is elevated. Plant foods appear to exert a general risk-lowering effect; the patterns of exposure to cancer initiators and promoters and of genetic susceptibility may determine the variations in the site-specific risks of cancer seen across populations.
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PMID:Vegetables, fruit and phytoestrogens as preventive agents. 892 20

C57BL/6J-Min/+ mice, which are heterozygous for a non-sense mutation in the Apc gene, provide a model for both familial adenomatous polyposis and sporadic colon cancers. In our study, gut tumors and small intestine lymphoid nodules were counted in Min mice fed fiber-enriched diets for 6 weeks. Neither starch-free wheat bran nor resistant starch modified the number of tumors. However, short-chain fructo-oligosaccharides dramatically reduced the incidence of colon tumors and concomitantly developed gut-associated lymphoid tissue. Our experiment shows that short-chain fructo-oligosaccharides counteract advanced stages of colon carcinogenesis, possibly via stimulation of antitumoral immunity by modulation of the colonic ecosystem.
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PMID:Short-chain fructo-oligosaccharides reduce the occurrence of colon tumors and develop gut-associated lymphoid tissue in Min mice. 900 May 59

The effects of 1,8-dihydroxyanthraquinone (DHAQ), a stimulant laxative named danthron, on cell kinetics and prostaglandin (PG) biosynthesis in the gastrointestinal tract were investigated in male 8-week-old F344 rats divided into three groups, each consisting of 10 animals. The animals in groups one, two and three were respectively given diets supplemented with 0%, 0.1% and 0.2% DHAQ for 24 days. PGE2 levels in the colorectal mucosa were significantly (P < 0.05 and 0.001) elevated after DHAQ treatment and showed some evidence of a dependence of DHAQ dose, consistent with the plasma PGE2 levels. BrdU-labeling indices in the large intestinal epithelium were also significantly (P < 0.01) increased, although the other portions of the gut such as the stomach and small intestine were not significantly affected. Excretion of the main urinary metabolite of PGE (PGE-MUM) was significantly (P < 0.001 or 0.01) increased whereas the urinary PGE2 concentration and total PGE2 excretion were not changed. Thus the results of the present study clearly indicate enhancement of cell proliferation by DHAQ in the large intestine epithelia, correlated with increased PGE2 levels in the large intestinal mucosa as well as the plasma, and possible support for the conclusion that quantitative analysis of urinary PGE-MUM, but not PGE2 itself, offer a useful approach for biomonitoring exposure to such stimulant laxatives.
Carcinogenesis 1997 Jun
PMID:Enhancement of cell proliferation and prostaglandin biosynthesis by 1,8-dihydroxyanthraquinone in the rat large intestine. 921 11


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