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)

Two colon cancer cell lines, HT-29 (human) and DHD/K12/TRb (rat), were grown as monolayer cultures to various confluence degrees. The cytotoxic efficacies of doxorubicin and 4'-deoxydoxorubicin, evaluated by a survival assay, and the nuclear drug concentrations, measured by microspectrofluorometry, were shown to progressively decrease with the augmentation of confluence. This confluence dependent resistance (CDR) to anthracyclines was demonstrated independent of the multidrug resistance drug efflux mechanism. The cellular uptake of three compounds (sodium [51Cr]chromate, D-[14C]alanine, L-[14C]glucose) known to passively diffuse across the cell membrane as anthracyclines do was also reduced in confluent cells. After trypsin cell detachment, the kinetics of reversion of the sodium [51Cr]chromate uptake decrease and that of CDR were similar. Therefore, CDR may be attributed to a reduction of anthracycline cell intake due to a general alteration of passive diffusion across the cell membrane. However, CDR is only partly explained by this phenomenon since a reduced sensitivity of confluent cells was observed compared with nonconfluent cells for a similar amount of drug in their nuclei. CDR could explain the high resistance to anthracyclines of some solid tumors, such as colon tumors, in which cancer cells are tightly aggregated.
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PMID:Mechanisms of resistance of confluent human and rat colon cancer cells to anthracyclines: alteration of drug passive diffusion. 220 25

We have previously shown the superiority of tumor-associated antigens (TAA) to function as effective immunogens when administered with bilayer membrane vesicles called liposomes. The ability of liposomes to target TAA to host antigen-presenting cells is analyzed here. 1-Butanol extracted TAA from two syngeneic rat colon cancer tumors (WB 2054 and W 1756) was radioiodinated (131I-TAA). Free 131I and 131I-TAA (2.8 X 10(7) cpm and 75 micrograms TAA per rat) were used as tracers, with or without incorporation into liposomes (composition: sphingomyelin, cholesterol, dicetyl phosphate at 70:24:6 molar ratio). Six groups of male rats (BN X WF for WB2054 and Wistar/Furth for W1756, n = 18 each group) were injected iv with either free tracers or the tracers incorporated into liposomes. Whole blood clearance curve was biphasic (half-life alpha = 5 min; half life beta = 12 hr), suggesting a two-compartmental model of distribution. Seven animals from each group were sacrificed at set times (15 min to 48 hr), organs harvested and cpm/g of tissue estimated. Liposome 131I and liposome 131I-TAA were targeted to and retained preferentially in liver and spleen. Four animals from each group were imaged serially using a gamma camera. Matched pair analysis of regions showed persistently higher activity in liver-spleen area when liposomes were used (P less than 0.001). The uptake of radiolabeled antigens by plastic adherent mononuclear cells in liver and spleen was significantly higher when presented with liposomes (macrophage uptake index: liver = 1.65 vs 0.55; spleen = 5.85 vs 1.15; with and without liposomes, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Targeting of tumor-associated antigens (TAA) in experimental immunotherapy. 374 91

Curcumin and quercetin were evaluated in rats for their ability to modulate the carcinogenic activity of azoxymethane (AOM) in the colon and 7,12-dimethylbenz[a]anthracene (DMBA) in the mammary gland. In the AOM-induced colon cancer model, male Fischer 344 rats at 8 weeks of age started to receive either curcumin (8 and 16 g/kg) or quercetin (16.8 and 33.6 g/kg) in the diet and 1 week later, were administered AOM (30 mg/kg body wt.) by subcutaneous injection. The animals continued to receive the two agents in the diet until sacrificed 45 weeks later. Curcumin mediated a dose-dependent inhibition of the incidence and multiplicity of adenomas from 47% and 0.58 +/- 0.12 adenomas/rat in the AOM-treated control group to 19% and 0.22 +/- 0.08 and 0.06% and 0.08 +/- 0.06 adenomas/rat for the low and high dose groups, respectively. A low yield of adenocarcinomas (0.06 +/- 0.04 adenocarcinomas/rat) was induced by AOM which was not significantly altered by curcumin. Treatment with quercetin caused a dose-dependent increase in the yield of AOM-induced tumors in the colon from 0.06 +/- 0.04 adenocarcinoma/rat to 0.64 +/- 0.12 and 1.14 +/- 0.17 for the low and high dose groups, respectively. In the DMBA-induced mammary cancer model, curcumin or quercetin was administered at either 10 or 20 g/kg diet, beginning 7 days prior to DMBA and continually throughout the remainder of the experiment. Neither curcumin nor quercetin significantly altered the incidence of animals with tumors or the tumor multiplicity, while the high concentration of both agents significantly increased tumor latency. These results demonstrate different responses to these agents in the two models. While curcumin was highly effective as a chemopreventive agent in the colon model, it was only weakly effective in the mammary model. In contrast, quercetin which was also only weakly effective in the mammary model, caused a dose-dependent enhancement of tumors induced by AOM in the colon model.
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PMID:Effects of the phytochemicals, curcumin and quercetin, upon azoxymethane-induced colon cancer and 7,12-dimethylbenz[a]anthracene-induced mammary cancer in rats. 868 47

We showed the possibility of significant decreasing of the frequency of chemically induced colon cancer in rats by vaccination with polyclonal rabbit IgG generated against purified tumor-associated antigens (TAA). TAA were isolated from benign rat colon tumors by the method developed in our laboratory (Zusman et al 1994) using affinity chromatography columns with gel fiberglass membranes (R. Zusman, 1992) containing anti-tumor IgG. The IgG was isolated from rabbits following their vaccination with TAA. Sprague Dawley rats were vaccinated with anti-TAA IgG (100 micrograms/rat) suspended in Freunds adjuvant by weekly subcutaneous injections for 5 weeks. The induction of colon cancer was caused by weekly injections with 1,2-dimethylhydrazine (DMH) (20 mg/kg) for 7 weeks and was started one week after the end of the vaccination. The results of experiments were evaluated 6 months after the start of cancer induction. IgG protected against the carcinogenic effects of DMH. The number of tumor-bearing rats decreased to 64% as compared with 90% in the control group. In vaccinated rats, the incidence of tumors was almost 3 times less than of control, i.e. 3.6 and 9.3, respectively. The number of malignant tumors was also significantly smaller in vaccinated rats than in controls, being 24% and 58%, respectively. Metastases were found only in controls, 4 of 30 rats. The results of our experiments have shown that anti-TAA IgG not only has anti-tumor effects but also prevents the malignization of benign tumors. As one of the main components of TAA which was isolated from colon cancer rats was soluble p53 antigen (Zusman et al 1994), we suggest that the vaccine which has been generated in our experiments may be regarded as acting mainly against p53 antigen, and its antitumor effects should also be considered as effects of p53 antibodies. The further studies will be performed to clarify this.
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PMID:IgG generated against benign tumor-associated antigens prevented the effects of 1,2-dimethylhydrazine in rats. 870 33

Significant alarm has existed among the general public in the past few years that eating red meat may cause human colon cancer. Iron in beef has been hypothesized as one of the factors in the etiology of this cancer. The present study was designed to test the hypothesis that dietary iron solely from beef would enhance colon tumorigenesis induced in rats. Tumors were induced in Sprague-Dawley rats with 1,2-dimethylhydrazine (20 mg/kg body weight for 10 weeks). Seventy male weanling rats were randomized to two dietary treatment groups with two iron sources (very lean beef vs. iron citrate) as the factor. The rats were allowed free access to the respective diet and deionized water for 27 weeks. At termination of the study, the rats were examined for location, size and type of colon or extracolonic lesions. No significant differences were found in total incidence and number of colon tumors between the beef (51.7%, 0.8 tumors/rat) and casein (62.1%, 0.9 tumors/rat) diets, although the serum iron levels of rats fed the beef diet were higher than for those fed the casein diet. The results demonstrate that, when lean beef is used as an iron source, the risk for colon carcinogenesis is not increased.
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PMID:Non-promoting effects of iron from beef in the rat colon carcinogenesis model. 902 73

In order to increase the understanding of the factors responsible for causing human colon cancer, a technique was developed to detect genotoxic effects of chemicals in human colon cells. Risk factors suspected to be associated with the aetiology of human colon cancer were subsequently investigated: the method is based on the measurement of DNA damage in primary cells freshly isolated from human colon biopsies with the single cell microgel ectrophoresis technique ('Comet Assay'). 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3-methyl-3H-imidazo[4,5f]quinoline (IQ), N-methyl-N-nitro-N-nitrosoguanidine (MNNG), dinitrosocaffeidine (DNC) lithocholic acid (LCA), hydrogen peroxide (H2O2) and benzo[a]pyrene (B[a]P) were investigated for their genotoxic and cytotoxic effects following 30 min incubation with colon cells of human, and for comparative purposes also of the rat colon. The nitrosamides (MNNG, DNC) were very genotoxic in human colon cells. MNNG was more genotoxic in human than in rat colon cells. In contrast, the rat colon carcinogens PhIP and IQ were not genotoxic in human colon cells. PhIP did induce DNA damage in rat colon cells, which correlates to its capacity of inducing tumors in this animal tissue. LCA was toxic (rat > human) and concomitantly caused DNA damage in higher concentrations. The widespread contaminant B[a]P was not genotoxic in colon cells of either species using this system. H2O2 was found to be a potent genotoxic agent to both rat and human colon cells (human > rat). In summary, those compounds chosen as representatives of endogenously formed risk factors (MNNG, H2O2, LCA) have a higher toxic and/or genotoxic potency in human colon tissue than in rat colon. They are also more effective in this system than the contaminants tested so far (B[a]P, PhIP, IQ). The newly developed technique is rapid and yields relevant results. It is a novel and useful approach to assess different chemical compounds for genotoxic activities in tumour target tissues of the human.
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PMID:Induction of DNA damage by risk factors of colon cancer in human colon cells derived from biopsies. 920 21

Evidence is accumulating that a diet high in plant-derived foods may be protective against cancer. One class of plant component under increasing investigation is the phytoestrogens of which there are two main groups: the isoflavones, found mainly in soy products, and the lignans, which are more ubiquitous and are found in fruit, vegetables and cereals with high levels being found in flaxseed. In this study, we have used carefully balanced high-fat (40% energy) diets: a control diet (containing low isoflavone soy protein as the sole protein source), a rye diet (the control diet supplemented with rye bran) and a soy diet (containing as protein source a high isoflavone soy protein). The effect of these diets on the development of colonic cancer was studied in F-344 rats treated with the carcinogen, azoxymethane (two doses of 15 mg/kg given 1 week apart). Colons from treated animals were examined for aberrant crypt foci (ACF) and tumours after 12 and 31 weeks. Results after 12 weeks showed no differences in the total number of ACF in the control, soy or rye bran groups. However, the soy group had increased numbers of small ACF (less than four crypts/focus) while the rye group had decreased numbers of large ACF (greater than six crypts/focus). Examination of colons after 31 weeks gave similar low numbers of ACF in each group with no differences in multiplicity. There were no differences in the number of tumours between the control (1.36 tumours/rat) and soy (1.38 tumours/rat) groups. However, there was a significant decrease in the number of tumours in the rye group (0.17 tumours/rat). These results suggest that soy isoflavones have no effect on the frequency of colonic tumours in this model while rye bran supplementation decreases the frequency of colon cancer. This effect is due not to a decrease in early lesions but in their progression to larger multi-crypt ACF. The study also supports the hypothesis that larger ACF are more predictive of subsequent tumorigenicity.
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PMID:Effects of soy or rye supplementation of high-fat diets on colon tumour development in azoxymethane-treated rats. 1035 69

Organ-specific tumor cell adhesion within the microcirculation of host organs is an important step in the metastatic cascade. Circulating tumor cells have to adhere within the microcirculatory vessels, quickly stabilize their adhesion and probably leave the circulation to avoid toxic effects of hydrodynamic shear forces of circulating blood. Using intravital fluorescence microscopy we established a new model for the intravital observation of colon carcinoma cell adhesion within the hepatic microcirculation. HT-29 (human) and CC531 (rat) colon carcinoma cells were fluorescence labeled using CalceinAM. Single cell suspensions were injected intraarterially in Sprague-Dawley rats. Using intravital fluorescence microscopy adhesive interactions of circulating tumor cells within the hepatic microcirculation were observed at the liver surface. These interactions were analyzed regarding their time course and the localization within the vascular tree. Autofluorescence of liver parenchyma was sufficient for distinction of hepatic sinusoids. Intravital microscopy enabled the differentiation of early events in adhesion formation within hepatic sinosoids, adhesion stabilization, and extravasation of the tumor cells into the liver parenchyma. Tumor cell adhesion occurred almost exclusively within sinusoidal capillaries; however, the diameter of these vessels was usually larger than that of the tumor cells leaving remaining perfused lumen of the capillaries. Colon carcinoma cells rapidly migrated into the liver parenchyma after successful adhesion within the sinusoids. In contrast to common endpoint assays of the metastatic cascade, this in vivo model allows investigations of metastatic colon carcinoma cell adhesion within the liver microcirculation as specific steps during the formation of hematogenous metastasis and their underlying mechanisms.
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PMID:An intravital model to monitor steps of metastatic tumor cell adhesion within the hepatic microcirculation. 1501 35

The multistage model of colon carcinogenesis is well established in both humans and experimental animals, and aberrant crypt foci (ACF) are generally assumed to be putative preneoplastic lesions of the colon. However, morphological analyses of ACF have suggested that they are highly heterogeneous in nature and their role in tumorigenesis is still controversial. To better understand the biological significance of ACF in carcinogenesis, morphological and genetic analyses were performed using a rat colon cancer model induced by a food-borne colon carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). ACF of different sizes were collected at weeks 6, 18, 25, and 32 after three cycles of 2-week PhIP feeding (400 ppm in diet) with 4-week intervals on a high-fat diet, and a total of 110 ACF, representing approximately three-quarters of the total ACF, were subjected to histological evaluation. Thirty (27%) were diagnosed as dysplastic ACF, based on cytological and structural abnormalities of crypts. Dysplastic ACF were detected even at week 6 (0.4 per rat), and the numbers increased slightly at later time points, being 0.8, 1.4, and 0.8 per rat at weeks 18, 25, and 32, respectively. The sizes of these dysplastic ACF varied widely from 1 to 16 crypts and 50% (15 of 30) were composed of less than 4 crypts. Immunohistochemical analysis revealed that 83% (25 of 30) of dysplastic ACF demonstrated beta-catenin accumulation; 22 only in the cytoplasm and 3 in both the cytoplasm and nucleus, the latter manifesting a higher grade of dysplasia as compared with the former. Seven dysplastic ACF harbored beta-catenin mutations at codon 32, 34, or 36 in exon 2, and one had an Apc mutation at the boundary of intron 10 and exon 11. Mutations at these sites were also commonly found in colon tumors induced by PhIP. The results of our present study indicate that dysplastic ACF, which accounted for approximately one-fourth of the total ACF, are preneoplastic lesions of colon cancers induced by PhIP in rats.
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PMID:Characterization of dysplastic aberrant crypt foci in the rat colon induced by 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine. 1450 67

We have shown the different effects of rabbit IgG generated against various types of p53 tumor-associated protein on chemically induced colon cancer in rats. p53 protein was isolated in the form of cytoplasmic, soluble, protein from sera obtained from: a) rats with colon cancer and b) rats with benign colon tumors. The isolation was performed using the affinity chromatography columns with,eel fiberglass membranes. Anti-p53 IgG were obtained from rabbits vaccinated with the above mentioned types of p53. Sprague Dawley rats were vaccinated with anti-p53 IgG (100 mu g/rat) at two-week intervals for 2 months and then monthly for 3 months. The induction of colon cancer was caused by weekly injections with 1,2-dimethylhydrazine (20 mg/kg) for 7 weeks and was initiated 8 weeks after the start of the vaccination. Results of experiments were evaluated 6 months after the start of cancer induction. It was found that vaccination of rats with IgG generated against the p53 protein isolated from cancer-bearing rats did not exhibit significant protective effect. Only IgG generated against p53 protein from benign tumor-bearing rats significantly prevented the carcinogenic effect of DMH. The number of tumor-bearing rats in vaccinated group decreased to 44% as compared with 93% in the control group. In vaccinated rats, the number of tumors/rat was 0.8 as compared to 9.3 in controls. The number of malignant tumors in vaccinated rats was half that in controls: 29% and 58%, respectively. In the controls, metastases were found in 6 of 45 rats (13%). Anti-p53 IgG not only has an anti-tumor effect but also prevented benign tumors from becoming malignant. We suggest that the anticancer role of a vaccine generated against p53 protein from benign tumor-bearing rats is related to a wild-type p53 protein. Further studies will be performed to clarify this hypothesis.
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PMID:High tumor-preventive effects of polyclonal IgG generated against p53 tumor-associated protein obtained from benign-tumor bearing rats. 2159 94


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