Role In Development Of Colon Cancer Research Articles

Dietary supplementation of resveratrol suppresses colonic tumour incidence in 1,2-dimethylhydrazine-treated rats by modulating biotransforming enzymes and aberrant crypt foci development

Diet-induced changes in the activities of bacterial enzymes are known to play a role in colon cancer development. Resveratrol has been implicated as a protective agent in carcinogenesis. In the present study, the effect of resveratrol on the activities of faecal and colonic biotransforming enzymes such as beta-glucuronidase, beta-glucosidase, beta-galactosidase, mucinase, nitroreductase and faecal sulfatase activity was assessed. The total number of aberrant crypt foci and their distribution in the proximal, medial and distal colon were observed in 1,2-dimethylhydrazine (DMH)-induced rats (group 3) and other treatment groups (groups 4-6). DMH (0.02 g/kg body weight) was given subcutaneously once a week for 15 consecutive weeks, and the experiment was terminated at 30 weeks. DMH-treated rats showed elevated levels of cancer-associated bacterial enzyme activities, whereas on resveratrol supplementation in three different regimens, rats showed lowered activities. Resveratrol supplementation throughout the experimental period (group 6) exerted a more pronounced effect (P < 0.01) by modulating the development of aberrant crypt foci and the activities of bacterial enzymes than did the other treatment regimens (groups 4 and 5). Thus, the present results demonstrate the inhibitory effect of resveratrol on DMH-induced colon carcinogenesis in rats.

Osteopontin regulates multiple functions contributing to human colon cancer development and progression

Osteopontin (OPN) is a secreted phosphoglycoprotein known to interact with a number of integrin receptors. While increased OPN expression has been reported in a number of human cancers, and its cognate receptors (alphav-beta3, alphav-beta5, and alphav-beta1 integrins and CD44) have been identified, its role in colon cancer development and progression has not been extensively studied. We previously identified, using a combination of gene expression and tissue microarrays, that increased OPN expression is concordant with tumor stage. The current study examined the functional role of OPN in colon cancer progression and metastatic potential. The principal findings of this study were that both endogenous OPN expression (via stable transfection) as well as exogenous OPN (added to culture medium) enhanced the motility and invasive capacity of human colon cancer cells in vitro. OPN appeared to regulate motility though interaction with CD44. OPN expression also reduced intercellular (homotypic) adhesion, an important characteristic of metastatic cancer cells. Stable transfection of four poorly tumorigenic human colon cancer cell lines with OPN also resulted in enhanced tumorigenicity in vivo with increased proliferation and increased CD31 positive microvessel counts, concordant with the degree of OPN expression. Collectively, these results suggest that OPN may affect multiple functional components contributing to human colon cancer progression and solidifies its role in this process.

Lipoxygenase expression in colon polyps and inhibition of colon cancer growth by lipoxygenase blockade

Abstract Introduction: Expression of 5-lipoxygenase (5-LOX) has been shown to be up-regulated in early pancreatic cancer, but has not been characterized in early colon neoplasms. We hypothesize that there is upregulation of 5-LOX in colon polyps and that inhibition of 5-LOX in colon cancer cell lines would inhibit cell growth and induce apoptosis. Methods: Tissue samples of normal colonic mucosa and neoplastic polyps were collected from 20 patients. Immunohistochemistry was used to compare 5-LOX expression between patient's normal colonic mucosa and polyps. Effects of the specific 5-LOX inhibitor, Rev 5901, on cell proliferation were studied in 3 colon cancer cell lines (LoVo, HT-29, HCT-116). Results: Intense 5-LOX staining was evident in polyps from 20/20 specimens. Adjacent areas of normal colonic mucosa did not express 5-LOX. Specific 5-LOX blockade with Rev 5901 showed concentration and time-dependent inhibition of cell proliferation (85% reduction relative to control with 15uM at 24 hours, p Conclusions: These results demonstrate that 1) 5-LOX is up-regulated in colon polyps compared to normal mucosa, and 2) treatment with 5-LOX inhibitor Rev 5901 results in decreased cell proliferation and increased apoptosis. These findings provide evidence that 5-LOX plays a role in colon cancer development and may be an early target for chemoprevention of colon cancer.

The NBL1 tumor suppressor gene is downregulated in colon cancer by promoter methylation

Abstract Introduction: We have recently identified the novel finding that TSG is a tumor suppressor gene that is down-regulated in v-Srctransformed rat fibroblasts through the mechanism of promoter hypermethylation and gene silencing. We hypothesized that the human homologue of TSG, NBL1 (Neuroblastoma, suppression of tumorigenicity 1), might be affected through a similar mechanism in human cancer. Thus, NBL1 may represent a new candidate tumor suppressor gene regulated by promoter hypermethylation through DNA methyltransferases. Methods: We evaluated colon cancers (n = 10) of similar stage and grade and their matched normal tissues for NBL1 expression by real-time RT-PCR and western blots. In addition, we assessed the promoter region of NBL1 for presence of CpG islands and for hypermethylation of these regions though bisulfite sequencing and methylation specific PCR. Results: The mRNA levels and protein of the expressed NBL1 gene were significantly reduced in 70% tumors with respect to their normal matched controls. Evaluation identified NBL1 promoter site to be CpG island rich. Methylation analysis of human colon cancer specimens confirmed hypermethlation of NBL1 promoter site. Conclusions: NBL1 is a transcription factor that plays a role in the negative regulation of the cell cycle. Our data suggest, for the first time, that the down regulation of NBL1 in human colon cancer through promoter hypermethylation may play an important role in colon cancer development and/or progression.

Isolation of a novel member of small G protein superfamily and its expression in colon cancer.

APMCF1 is a novel human gene whose transcripts are up-regulated in apoptotic MCF-7 cells. In order to learn more about this gene's function in other tumors, we cloned its full length cDNA and prepared its polyclonal antibody to investigate its expression in colon cancers with immunohistochemistry. With the method of 5' rapid amplification of cDNA end (RACE) and EST assembled in GenBank, we extended the length of APMCF1 at 5' end. Then the sequence encoding the APMCF1 protein was amplified by RT-PCR from the total RNA of apoptotic MCF-7 cells and cloned into the prokaryotic expression vector pGEX-KG to construct recombinant expression vector pGEX-APMCF1. The GST-APMCF1 fusion protein was expressed in E. coli and used to immunize rabbits to get the rabbit anti-APMCF1 serum. The specificity of polyclonal anti-APMCF1 antibody was determined by Western blot. Then we investigated the expression of Apmcf1 in colon cancers and normal colonic mucosa with immunohistochemistry. A cDNA fragment with a length of 1 745 bp was obtained. APMCF1 was mapped to chromosome 3q22.2 and spanned at least 14.8 kb of genomic DNA with seven exons and six introns contained. Bioinformatic analysis showed the protein encoded by APMCF1 contained a small GTP-binding protein (G proteins) domain and was homologous to mouse signal recognition particle receptor beta(SRbeta). A coding region covering 816 bp was cloned and polyclonal anti-APMCF1 antibody was prepared successfully. The immunohistochemistry study showed that APMCF1 had a strong expression in colon cancer. APMCF1 may be the gene coding human signal recognition particle receptor beta and belongs to the small-G protein superfamily. Its strong expression pattern in colon cancer suggests it may play a role in colon cancer development.

COX-2 and colon cancer: potential targets for chemoprevention.

Evidence derived from several lines of investigation suggest that prostaglandins, metabolites of arachidonic acid, play an important role in colon cancer development. Elevated prostaglandin levels are found in colon cancers and their precursor lesions, adenomatous polyps. Agents such as aspirin and NSAIDs, which inhibit the generation of these arachidonic acid metabolites, are associated with a decreased risk of developing or dying from colon cancer. Both the amount of the agent used and the duration of exposure seem to be important variables. In animals, NSAIDs are among the most potent agents discovered for the reduction of tumors in both genetic and carcinogen-induced models. Data from human trials also suggests that NSAIDs such as sulindac can reduce the size and number of polyps in individuals with familial adenomatous polyposis (FAP). In parallel with the above findings, it is now understood that at least two forms of the enzyme responsible for the metabolism of arachidonic acid exist. One of these forms, COX-1, is generally considered a constitutive form that is responsible for maintaining normal physiologic function. Inhibition of COX-1 leads to many of the clinically undesirable side effects associated with NSAID use. The other known form of the enzyme, COX-2, is an inducible form that is found in increased levels in inflammatory states and in many cancers and their associated pre-malignant lesions. Levels of COX-2 are increased by exposure to mitogens and growth factors. Agents that specifically inhibit COX-2 are now in clinical development and appear to be well-tolerated and effective for the treatment of osteoarthritis and rheumatoid arthritis. The potential for use of COX-2 specific NSAIDs in the prevention of colon cancer is suggested from the distribution of COX-2 in adenomatous polyps and colon cancer and the effectiveness of these agents in genetic and carcinogen-induced animal models of colon cancer. The development of these agents for the prevention of colon cancer will be discussed.

Effects of fish oil on fecal bacterial enzymes and steroid excretion in healthy volunteers: implications for colon cancer prevention.

Diet-induced changes in fecal excretion of secondary bile acids, certain neutral sterols, and bacterial enzyme activities are known to play a role in colon cancer development. Dietary fish oil (FO) has been implicated as a protective agent in colon carcinogenesis. In the present study, the effects of FO and corn oil (CO) on these fecal parameters were investigated in 24 healthy volunteers consuming a low- or a high-fat diet (30% or 50% of energy derived from fat). After four weeks of FO or CO supplementation (4.4 g of n-3 fatty acids/day), no significant differences were noted for fecal activities of beta-glucuronidase, beta-glucosidase, and sulfatase, nor was fecal bile acid excretion significantly affected by FO or CO consumption. However, daily excretion of the putative colon carcinogen 4-cholesten-3-one was significantly lower in the FO than in the CO period during low- and high-fat experiments. This may be another biochemical mechanism by which FO exerts its protective effect on colon cancer development.