Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0699790 (colon cancer)
 28,837 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase activity, was evaluated in vivo and in vitro on the growth of a gastrin-sensitive human colon carcinoma (WiDr). In vivo, mice bearing the tumor treated with pentagastrin had larger tumors with higher ornithine decarboxylase activity and polyamine content (P < 0.05) than mice not treated with pentagastrin. Difluoromethylornithine treatment significantly decreased ornithine decarboxylase in both the pentagastrin-treated and the untreated animals; however, DFMO had no effect on tumor volume, weight, protein, or DNA content. In cell culture, gastrin treatment increased WiDr cell number and [3H]thymidine incorporation in the presence or absence of serum. In serum-free conditions, however, gastrin stimulated cell growth without concomitantly increasing ODC activity. DFMO, on the other hand, decreased both ODC activity and growth. These studies suggest that the trophic effect of gastrin on WiDr human colon cancer is independent of ODC activity. Since gastrin treatment increased ODC activity in vivo, gastrin may interact in vitro with other factors present in serum that can alter ODC activity.
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PMID:Effects of gastrin and difluoromethylornithine on growth of human colon cancer. 844 85

In our attempts to evaluate the influence of chemopreventive agents on intermediate biomarkers of colon cancer, we have investigated the effect of D,L-alpha-difluoromethylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase and piroxicam, a non-steroidal anti-inflammatory drug (NSAID) on the expression levels of biochemically active p21ras, the protein product of cellular ras protooncogenes during the development of azoxymethane (AOM) induced colon carcinogenesis in male F344 rats in order to explore the plausibility of using p21ras as an intermediate biochemical marker of colon cancer. Groups of male F344 rats were fed the modified AIN-76A diets containing 0 or 150 p.p.m. piroxicam or 4000 p.p.m. DFMO and administered s.c. AOM dissolved in normal saline at a dose of 15 mg/kg body wt/week, once weekly, for 4 weeks. Vehicle control groups received s.c. equal vol of normal saline. Groups of animals were then killed at 0, 4, 16, 24 and 32 weeks after the last injection of AOM or saline and their colonic mucosa and tumors analyzed for biochemically active p21ras levels. AOM treatment significantly increased the expression of biochemically active p21ras. The AOM-induced expression of biochemically active p21ras was significantly suppressed by dietary DFMO and piroxicam. DFMO exerted a more pronounced inhibitory effect on AOM-induced colon tumor development as well as the expression of biochemically active p21ras. These results indicate that the determination of biochemically active p21ras may be effectively used in clinical chemoprevention trials as an intermediate end-point to monitor the colon carcinogenesis.
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PMID:Intermediate biomarkers of colon cancer: modulation of expression of ras oncogene by chemopreventive agents during azoxymethane induced colon carcinogenesis. 847 34

Juvenile polyps (JP) are the most common colonic tumor in children. Although considered benign, malignant transformation has been reported in JP. Ornithine decarboxylase (ODC) and tyrosine kinase (TyK) enzymes are markers for a rapid cell proliferation index. DNA aneuploidy score and p53 gene expression are late malignant changes seen in patients with colon cancer. In this study, we investigated ODC and TyK activities as well as DNA aneuploidy score and p53 expression in juvenile polyps compared with the adjacent normal colonic mucosa. Results showed that ODC was significantly increased in JP compared with the adjacent normal colonic mucosa. TyK activity was increased in 3/5 polyps and decreased in 2/5 polyps compared with the mucosa. Mean TyK activity was higher in JP compared with normal mucosa but did not reach significance (707 and 632 pmol/mg pmol, respectively). Moreover, changes in phosphorylization of TyK proteins was also observed in JP but not in normal mucosa. JP had a normal DNA aneuploidy score and showed no expression of p53 gene. We conclude that JP do not express p53 gene and aneuploidy but had higher activity of ODC and TyK enzymes, suggesting a higher stage of cell proliferation.
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PMID:Ornithine decarboxylase and tyrosine kinase activity in juvenile polyps of childhood. 855 12

Weekly administrations of the potent carcinogen 1,2-dimethylhydrazine (DMH) predominantly induce carcinoma of the colon by nearly 100% after six months' treatment in rats. Polyamines, and especially the key enzyme of polyamine de novo synthesis ornithine decarboxylase (ODC) are well-known to play an important role in cell growth and tumor carcinogenesis. Male Wistar rats were s. c.-injected with a single dose of 20 mg DMH/kg b. wt. and five to eight animals were sacrificed 4, 8, 12, 24, 72, 120, 168, and 240 hours after injection of DMH or the basic solution, respectively. Additionally, seven animals were simultaneously treated with the ODC inhibitor alpha-difluoromethylornithine (DFMO) and sacrificed seven days after a single DMH injection. A single s. c.-dosage of the colon carcinogen DMH resulted in dissimilar activation patterns of polyamine metabolism in the various organs studied: in distal and less pronounced in proximal colonic mucosa ODC and putrescine are significantly increased seven days after application of DMH and DNA polymerase after ten days; in small intestinal mucosa ODC activity is significantly elevated after seven days and especially S-adenosylmethionine decarboxylase activity is significantly and prolonged increased between twelve and 72 hours after DMH injection; while spermidine/spermine N1-acetyltransferase activity is significantly elevated in liver after 168 and 240 hours, no changes compared to controls are found in the pancreas. DFMO treatment completely prevents DMH-induced activation of polyamine de novo synthesis and DNA polymerase in colon and small intestine. These data prove completely different and -interestingly-late appearing activation patterns of DMH on intracellular polyamine metabolism in various organ systems and further elucidate the complex metabolic changes following carcinogen treatment.
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PMID:Dissimilar activation patterns of the carcinogen dimethylhydrazine (DMH) on intracellular polyamine metabolism in various organs. 901 96

Didemnins are cytotoxic agents belonging to a depsipeptide family isolated from marine tunicates. In the present study, a new member, dehydrodidemnin B (DDB), isolated from the mediterranean tunicate Aplidium albicans, was used. The effect of the drug on human colon cultured cell lines was tested using multiple approaches: proliferation studies, long term survival after three hours of exposure to DDB by means of a clonogenic assay and the decrease of the protooncogen, ornithine decarboxylase, activity. A dehydrodidemnin B concentration of 10(-8) M completely inhibited cell growth. The IC50 obtained using the MTT proliferation test, indicated that the most proliferative cell line (CT-2) was the most sensitive to the drug. Using a clonogenic assay a clear dose-response was obtained for the three cell lines used; HT-29 cell line showed the minimum survival after 3 hours of dehydrodidemnin B treatment. A dose-dependent decrease in ornithine decarboxylase activity was also observed in three cell lines assayed. The data presented indicate that the dehydrodidemnin B is a potent cytotoxic agent on rapidly dividing human colon cancer cells.
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PMID:Effect of dehydrodidemnin B on human colon carcinoma cell lines. 906 73

Experimental models have several advantages in the study of colon cancer. They can be used to tightly control diet, examine putative intermediate markers, test hypotheses about mechanisms of carcinogenesis, and quantify development of tumors in a short time. Dietary issues that have been studied in animal models but are unresolved include the concept of the effects of total fat compared with energy intake, composition of the basal diet, linoleic acid requirements, and interactions of fat with other nutrients. Intermediate markers that have been probed in animal or in vitro studies include cytokinetics, aberrant crypt foci, eicosanoids and hydroxyoctadecadienoic acids, ornithine decarboxylase, tyrosine kinase, protein kinase C, and gene expression. Colon cancer is studied in animals primarily with use of chemicals that are relatively specific inducers of these tumors, but transplantable models and transgenic animals are also used. Total dietary fat is generally thought to affect colon tumorigenesis, but there does not appear to be any specific fatty acid that promotes the development of colon cancer. Several studies indicate that n-3 fatty acids from marine sources alter a variety of biological intermediates and inhibit colonic tumorigenesis; this is probably mediated via the eicosanoid pathway. Although there are undoubtedly multiple cellular changes elicited by certain fatty acids, our current knowledge of this area suggests that specific fatty acid metabolites or their targets are the likely mediators in this sequence.
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PMID:Fatty acids and colon cancer in experimental models. 939 11

The polyamine analogue N1,N12bis(ethyl)spermine (BESpm) is a potent inhibitor of cell proliferation and is representative of a class of agents currently in clinical trials. Previous studies have demonstrated that BESpm treatment can produce a decrease in the mRNA levels of the protooncogene c-myc resulting from decreased transcription. Investigation into the mechanism of the antiproliferative effect of BESpm in the colon cancer cell line CaCO2 indicated that significant reduction in MYC protein, but not c-myc mRNA levels, preceded cytostasis. Specificity of the downregulation of MYC expression by BESpm treatment was demonstrated by comparison to effects on the polyamine catabolic enzyme spermidine/spermine N1-acetyltransferase (SSAT) and the polyamine biosynthetic enzyme ornithine decarboxylase (ODC). SSAT activity rapidly increased while levels of ODC activity decreased after BESpm treatment. Measurement of intracellular polyamines demonstrated significant uptake of the analogue after 24 hours, which was concurrent with a reduction of spermine and spermidine levels. Thus, cellular uptake of BESpm mediated a reduction of polyamine levels that was associated with a decrease of MYC protein at the post-transcriptional level.
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PMID:Inhibition of cell growth in CaCO2 cells by the polyamine analogue N1,N12-bis(ethyl)spermine is preceded by a reduction in MYC oncoprotein levels. 946

Chemoprevention of colorectal cancer has been extensively investigated in animal models and in high-risk human populations with inherited or acquired genetic changes, using anticarcinogenic agents from natural and synthetic sources. To understand active agents using a short-term assay, reliable intermediate biomarkers other than cancer are required as end-points. Endoscopically detectable aberrant crypt foci and adenomas are useful biomarkers in human intervention trials. Indomethacin and other nonsteroidal antiinflammatory drugs (NSAIDs) inhibit carcinogen-induced colon cancer development in rats. It was reported that a number of colorectal polyps in familial adenomatous polyposis patients regress after several months of sulindac treatment. Epidemiological studies have shown that regular use of aspirin and other NSAIDs reduces the risk of colorectal cancers and adenomas. In addition, ursodeoxycholic acid and alpha-difluoromethylornithine, a selective inhibitor of ornithine decarboxylase, have been employed in human intervention trials. Vegetable antioxidants such as carotenoids and flavonoids, omega-3 fatty acids, lactic acid bacteria, and indigestible oligosaccharides may also be promising chemopreventive agents.
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PMID:[An overview on chemoprevention of colorectal cancer]. 969 73

A two-step Phase I study of piroxicam (PXM) and a-difluoromethylornithine (DFMO) alone and in combination was initiated to assess toxicity and the impact of these drugs on several biological markers. In step 1, 12 subjects with a history of skin cancers were assigned to receive PXM 10 mg every day (q.d.) or 10 mg every other day (q.o.d.). The dosage of PXM 10 mg q.o.d. was tolerated. No changes were seen in 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC) or urinary polyamine levels. Steady-state serum levels of PXM were consistent with the oral dose level. In step 2, 31 subjects with stage 0 or I nonmelanoma skin cancers, stage A or B prostate or colon cancer, or stage I breast cancer or who had a family history of cancer were randomized to receive DFMO 0.5 g/m2, PXM 10 mg q.o.d., or the combination of DFMO and PXM. In addition to the biological markers of TPA-induced ODC activity in skin biopsies and urinary polyamine levels, we measured urinary 11-dehydrothromboxane B2, a specific metabolite of thromboxane A2. Of the 12 subjects on DFMO/PXM, 2 dropped out for non-drug-related reasons. Three developed grade-2 drug-related toxicities. One subject developed dyspnea that resolved and was able to continue on the study for 6 months. One subject who developed diarrhea that resolved after 5 days was also able to restart the drug without a recurrence. A third subject described intermittent episodes of tinnitus starting 4 h after taking PXM that lasted only 5 s and did not progress on treatment. Comparing the 6-month measurements with pretreatment, DFMO/PXM or DFMO significantly reduced TPA-induced ODC levels (Ps, 0.03 and 0.05). Urinary polyamine levels of spermidine decreased slightly with the DFMO/PXM or DFMO alone, whereas putrescine decreased with PXM alone. Levels of 11-dehydrothromboxane B2 were depressed by PXM and PXM/DFMO. The doses of DFMO/PXM determined in step 2 are potential starting dosages for Phase IIa and IIb chemoprevention trials.
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PMID:Phase I chemoprevention study of piroxicam and alpha-difluoromethylornithine. 979 36

DFMO is an irreversible inhibitor of ornithine decarboxylase (ODC), the key enzyme in mammalian polyamine biosynthesis. The goal of this study was to determine the effects of DFMO 0.5 g/m2/day as a single oral dose on polyamine and ODC levels in rectal, rectosigmoidal, and cecal colonic mucosae of individuals at risk for colon cancer because of a personal history of adenomatous polyps of the colon or a family history of colon cancer in at least one first-degree relative. A second goal was to determine toxicity of this treatment given over 1 year. Forty-five randomized subjects had a flexible sigmoidoscopy with no preparation and a colonoscopy after lavage preparation at baseline, a sigmoidoscopy with no preparation after 3 months, and both procedures (as at baseline) after 12 months, with mucosal biopsies taken from the rectosigmoid area (sigmoidoscopy) or rectal and cecal areas (colonoscopy) for evaluations of ODC and polyamine levels. Significantly decreased levels of putrescine and spermidine were found in rectosigmoid colonic mucosae of DFMO-treated (n = 24) compared with placebo (n = 21) subjects at 3 months (P = 0.03 and 0.04) and 12 months (P = 0.005, P = 0.004). Similar trends, none reaching statistical significance, were found for individual polyamine levels in rectal and cecal mucosae. No significant differences in ODC levels were detected marginally. There was evidence of global suppression of ODC and polyamine levels in the treatment group (P = 0.035). Three DFMO recipients (12.5%) developed clinically noticeable and audiologically demonstrated hearing loss, which was reversible and attributed to DFMO after 3 months (two subjects) and 12 months (one subject). The tissue polyamine changes demonstrated in this study are consistent with findings in other studies in colon and other tissues. The ototoxicity findings here suggest that investigation of other DFMO schedules, such as ones with a drug "holiday," will be a necessary step before Phase III chemoprevention studies can be pursued.
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PMID:A randomized, placebo-controlled trial of low-dose alpha-difluoromethylornithine in individuals at risk for colorectal cancer. 982 6


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