A comprehensive strategy to combat colon cancer targeting the adenomatous polyposis coli tumor suppressor gene

Nutrient-Gene Interaction in Colon Cancer, from the Membrane to Cellular Physiology

The International Agency for Research on Cancer recently released an assessment classifying red and processed meat as "carcinogenic to humans" on the basis of the positive association between increased consumption and risk for colorectal cancer. Diet, however, can also decrease the risk for colorectal cancer and be used as a chemopreventive strategy. Bioactive dietary molecules, such as n-3 polyunsaturated fatty acids, curcumin, and fermentable fiber, have been proposed to exert chemoprotective effects, and their molecular mechanisms have been the focus of research in the dietary/chemoprevention field. Using these bioactives as examples, this review surveys the proposed mechanisms by which they exert their effects, from the nucleus to the cellular membrane. In addition, we discuss emerging technologies involving the culturing of colonic organoids to study the physiological effects of dietary bioactives. Finally, we address future challenges to the field regarding the identification of additional molecular mechanisms and other bioactive dietary molecules that can be utilized in our fight to reduce the incidence of colorectal cancer.

Chemoprotective epigenetic mechanisms in a colorectal cancer model: Modulation by n-3 PUFA in combination with fermentable fiber

Colorectal cancer is the third major cause of cancer-related mortality in both men and women worldwide. The beneficial role of n-3 polyunsaturated fatty acids (PUFA) in preventing colon cancer is substantiated by experimental, epidemiological, and clinical data. From a mechanistic perspective, n-3 PUFA are pleiotropic and multifaceted with respect to their molecular mechanisms of action. For example, this class of dietary lipid uniquely modulates membrane and nuclear receptors, sensors/ion channels, and membrane structure/cytoskeletal function, thereby regulating signaling processes that influence patterns of gene expression and cell phenotype. In addition, n-3 PUFA can synergize with other potential chemoprotective agents known to reprogram the chromatin landscape, such as the fermentable fiber product, butyrate. Nutri-epigenomics is an emerging field of research that is focused on the interaction between nutrition and epigenetics. Epigenetics refers to a group of heterogeneous processes that regulate transcription without changing the DNA coding sequence, ranging from DNA methylation, to histone tail modifications and transcription factor activity. One implication of the nutri-epigenome is that it may be possible to reprogram epigenetic marks that are associated with increased disease risk by nutritional or lifestyle interventions. This review will focus on the nutri-epigenomic role of n-3 PUFA, particularly DHA, as well as the combinatorial effects of n-3 PUFA and fermentable fiber in relation to colon cancer.

Differential control of growth, apoptotic activity and gene expression in human colon cancer cells by extracts derived from medicinal herbs, Rhazya stricta and Zingiber officinale and their combination

AIM

To investigate the effects of extracts from Rhazya stricta (R. stricta) and Zingiber officinale (Z. officinale) on human colorectal cancer cells.

METHODS

Human colorectal cancer cells (HCT116) were subjected to increasing doses of crude alkaloid extracts from R. stricta (CAERS) and crude flavonoid extracts from Z. officinale (CFEZO). Cells were then harvested after 24, 48 or 72 h and cell viability was examined by trypan blue exclusion dye test; clonogenicity and soft agar colony-forming assays were also carried out. Nuclear stain (Hoechst 33342), acridine orange/ethidium bromide double staining, agarose gel electrophoresis and comet assays were performed to assess pro-apoptotic potentiality of the extracts. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR), using gene-specific primers and Western blot analyses were performed to assess the impact of CAERS and CFEZO on the expression levels of key regulatory proteins in HCT116 cells.

RESULTS

Treatment with a combination of CAERS and CFEZO synergistically suppressed the proliferation, colony formation and anchorage-independent growth of HCT116 cells. Calculated IC50, after 24, 48 and 72 h, were 70, 90 and 130 μg/mL for CAERS, 65, 85 and 120 μg/mL for CFEZO and 20, 25 and 45 μg/mL for both agents, respectively. CAERS- and CFEZO-treated cells exhibited morphologic and biochemical features of apoptotic cell death. The induction of apoptosis was associated with the release of mitochondrial cytochrome c, an increase in the Bax/Bcl-2 ratio, activation of caspases 3 and 9 and cleavage of poly ADP-ribose polymerase. CAERS and CFEZO treatments downregulated expression levels of anti-apoptotic proteins including Bcl-2, Bcl-X, Mcl-1, survivin and XIAP, and upregulated expression levels of proapoptotic proteins such as Bad and Noxa. CAERS and CFEZO treatments elevated expression levels of the oncosuppressor proteins, p53, p21 and p27, and reduced levels of the oncoproteins, cyclin D1, cyclin/cyclin-dependent kinase-4 and c-Myc.

CONCLUSION

These data suggest that a combination of CAERS and CFEZO is a promising treatment for the prevention of colon cancer.

Docosahexaenoic fatty acid (DHA) in the regulation of colon cell growth and cell death: a review

BACKGROUND

Experimental, epidemiological and clinical data substantiate the beneficial role of n-3 polyunsaturated fatty acids (PUFAs) in preventing inflammation and cancer of the colon. This review covers the unsaturated docosahexaenoic fatty acid (DHA), describes some of its important cellular and molecular mechanisms, its interaction with another dietary lipid, butyrate and with endogenous apoptotic regulators of the tumour necrosis factor (TNF) family. We also discuss the clinical impact of this knowledge and the use of these lipids in colon cancer prevention and treatment.

RESULTS

From the literature, DHA has been shown to suppress the growth, induce apoptosis in colon cancer cells in vitro and decrease the incidence and growth of experimental tumours in vivo. Based on these data and our own experimental results, we describe and discuss the possible mechanisms of DHA anticancer effects at various levels of cell organization. We show that DHA can sensitize colon cancer cells to other chemotherapeutic/chemopreventive agents and affect the action of physiological apoptotic regulators of the TNF family.

CONCLUSION

Use of n-3 PUFAs could be a relatively non-toxic form of supportive therapy for improving colon cancer treatment and slowing down or preventing its recurrence. However, it is necessary to use them with caution, based on solid scientific evidence of their mechanisms of action from the molecular to the cellular and organism levels.

Phospho-sulindac (OXT-328) combined with difluoromethylornithine prevents colon cancer in mice

The nonsteroidal anti-inflammatory drug (NSAID) sulindac and the ornithine decarboxylase (ODC) antagonist difluoromethylornithine (DFMO), individually and together, are effective inhibitors of colon carcinogenesis. However, chronic use of sulindac is associated with significant side effects. We evaluated the chemopreventive efficacy of phospho-sulindac (P-S, OXT-328), an apparently safe derivative of sulindac, together with DFMO, in HT-29 human colon cancer xenografts. Nude mice were divided into four groups as follows: group 1 received vehicle (corn oil); group 2 received P-S (100 mg/kg/d) by oral gavage; group 3 received DFMO (2% in drinking water); and group 4 received P-S (100 mg/kg/d) by gavage plus DFMO (2% in drinking water; P-S/DFMO). Eighteen days after implantation, compared with controls, tumor volume was inhibited 65.9% by P-S, 52.9% by DFMO, and 70.9% by P-S/DFMO (P < 0.01 for all). P-S/DFMO reduced cell proliferation 27.1% and increased apoptosis 38.9% compared with controls (P < 0.05 for both). Compared with controls, P-S reduced the levels of thioredoxin-1 (Trx-1) and thioredoxin reductase (TrxR), whereas DFMO reduced polyamine content (putrescine and spermidine) and TrxR levels. Importantly, P-S/DFMO decreased putrescine and spermidine levels and the expression of Trx-1, TrxR, and cyclooxygenase (COX) 2. Of these molecular targets, TrxR most consistently correlated with tumor growth. Study results show that P-S/DFMO is an efficacious drug combination for colon cancer prevention and also show the safety of P-S, which may overcome the limiting side effects of conventional sulindac. P-S/DFMO has an intricate mechanism of action extending beyond polyamines and including the thioredoxin system, an emerging regulator of chemoprevention. P-S/DFMO merits further evaluation.

Hereditary and familial colon cancer

Between 2% to 5% of all colon cancers arise in the setting of well-defined inherited syndromes, including Lynch syndrome, familial adenomatous polyposis, MUTYH-associated polyposis, and certain hamartomatous polyposis conditions. Each is associated with a high risk of colon cancer. In addition to the syndromes, up to one-third of colon cancers exhibit increased familial risk, likely related to inheritance. A number of less penetrant, but possibly more frequent susceptibility genes have been identified for this level of inheritance. Clarification of predisposing genes allows for accurate risk assessment and more precise screening approaches. This review examines the colon cancer syndromes, their genetics and management, and also the common familial colon cancers with current genetic advances and screening guidelines.

Regulation of deoxycholate induction of CXCL8 by the adenomatous polyposis coli gene in colorectal cancer

Elevated deoxycholic acid (DCA), mutations in the adenomatous polyposis coli (APC) gene and chronic inflammation are associated with increased risk of colorectal cancer. APC status was manipulated to determine whether DCA mediates inflammatory molecules in normal or initiated colonic mucosa. DCA increased steady state mRNA and protein levels of CXCL8 in cells which do not express wild-type APC. Steady-state CXCL8 mRNA and protein were suppressed when cells with conditional expression of wild-type APC were exposed to DCA. Immunostaining did not detect CXCL8 in normal human colonic mucosa. CXCL8 was expressed in adenomatous polyps and adenocarcinomas. CXCL8 expression correlated with nuclear beta-catenin localization in epithelial cells of adenomas, but was associated with endothelial cells and neutrophils in the adenocarcinomas. DCA-mediated CXCL8 promoter-reporter activity was elevated in a mutant APC background. Wild-type APC suppressed this effect. Mutation of activator protein-1 (AP-1) or nuclear factor kappa B (NF-kappaB) sites suppressed the activation of the CXCL8 promoter-reporter by DCA. Chromatin immunoprecipitation revealed that AP-1 and NF-kappaB binding to the 5'-promoter of CXCL8 was induced by DCA. The beta-catenin transcription factor was bound to the 5'-promoter of CXCL8 in the absence or presence of DCA. Phenotypic assays determined that DCA-mediated invasion was blocked by antibody-directed against CXCL8 or wild-type APC. CXCL8 exposure led to matrix metalloproteinase-2 production and increased invasion on laminin-coated filters. These data suggest that DCA-mediated CXCL8 occurs in initiated colonic epithelium and neutralizing CXCL8 could reduce the invasive potential of tumors.

The effect of difluoromethylornithine on decreasing prostate size and polyamines in men: results of a year-long phase IIb randomized placebo-controlled chemoprevention trial

BACKGROUND

Prostate cancer is a major health issue, and prevention of prostate cancer and/or its progression will yield benefits for men. Difluoromethylornithine (DFMO) is an antiproliferative agent, inhibiting ornithine decarboxylase, the first enzyme in the polyamine pathway, and has been studied as a therapeutic and chemopreventive agent. The prostate has high levels of tissue polyamines and has shown sensitivity to DFMO both in vitro and in vivo.

METHODS

Eighty-one men participated in a 1-year randomized trial of placebo or DFMO. Prostate volume determination and biopsy of the prostate for histology and polyamine content were done at baseline and after 12 months. Other biomarker variables were assessed, including total and free prostate-specific antigen and prostate-specific antigen doubling time.

RESULTS

Compared with baseline, men receiving DFMO had a smaller increase in prostate volume (0.14 cm(3)) than those on placebo (2.95 cm(3); P = 0.0301) at 1 year. In addition, DFMO caused a 60.8% reduction of prostate putrescine levels compared with a 139.5% increase in the placebo arm (P = 0.0014). Stratification by ornithine decarboxylase genotype showed that DFMO reduced prostate volume (P = 0.029) and putrescine levels (P = 0.0053) in the AA + GA group but not in the GG group. There were no grade 3 or 4 toxicities. There was no clinical ototoxicity, with one subclinical grade 2 hearing decline on audiogram.

CONCLUSION

In this randomized placebo-controlled trial, DFMO induced a decrease of prostate putrescine levels and rate of prostate growth. The potential of this compound for prostate cancer or hyperplasia should be further studied.

Polyamines and the intestinal tract

Owing to their high turnover, the intestinal mucosal cells have a particularly high requirement for polyamines. Therefore, they are an excellent charcol for the study of polyamine function in rapid physiological growth and differentiation. After a cursory introduction to the major aspects of polyamine metabolism, regulation, and mode of action, we discuss the contribution of the polyamines to the maintenance of normal gut function, the maturation of the intestinal mucosa, and its repair after injuries. Repletion of cellular polyamine pools with (D,L)-2-(difluoromethyl)ornithine has considerably improved our understanding of how the polyamines are involved in the regulation of normal and neoplastic growth. Unfortunately, the attempts to exploit polyamine metabolism as a cancer therapeutic target have not yet been successful. However, the selective inactivation of ornithine decarboxylase appears to be a promising chemopreventive method in familial adenomatous polyposis. Presumably, it relies on the fact that ornithine decarboxylase is a critical regulator of the proliferative response of the protooncogene c-myc, but not of its apoptotic response.

Clinical, biological, and molecular aspects of metastasis in colorectal cancer

Colorectal cancer is one of the most frequent malignant tumors with a still increasing incidence in Western countries. Currently, colorectal cancer is the second most common cancer in Europe both in terms of incidence and mortality. Approximately 90% of all cancer deaths arise from the metastatic dissemination of primary tumors. Thus, metastasis is the most lethal attribute of colorectal cancer. Today, colorectal cancer and metastasis thereof are understood as the results of early changes during tumor progression that determine the metastasis capacity. Much is known about molecules contributing to the metastasis phenotype, the pathways they control, and the genes they regulate. However, patient prognosis is mainly defined by histopathological staging, a static description of the anatomical extent of tumor spread within a surgical specimen. This review demonstrates the need for and possibilities of molecular-based staging as an essential prerequisite for improved diagnosis, prognosis, and therapy. Molecular determinants for progression and metastasis of colorectal cancer are discussed representing both potential markers for metastasis prognosis and targets for intervention strategies aiming at the ultimate goal of metastasis prevention.

Distinct nuclear arrangement of active and inactive c-myc genes in control and differentiated colon carcinoma cells

Using sequential RNA-DNA fluorescence in situ hybridization, the nuclear arrangement of both the active and inactive c-myc gene as well as its transcription was investigated in colon cancer HT-29 cells induced to differentiate into enterocytes. Cytogenetic studies revealed the presence of two chromosomes 8 in HT-29 cells, of which the one containing c-myc gene amplicons was substantially larger and easily distinguished from the normal chromosome. This observation enabled detection of both activity and nuclear localization of c-myc genes in single cells and in individual chromosome territories. Similar transcriptional activity of the c-myc gene was observed in both the normal and derivative chromosome 8 territories showing no influence of the amplification on the c-myc gene expression. Our experiments demonstrate strikingly specific nuclear and territorial arrangements of active genes as compared with inactive ones: on the periphery of their territories facing to the very central region of the cell nucleus. Nuclear arrangement of c-myc genes and transcripts was conserved during cell differentiation and, therefore, independent of the level of differentiation-specific c-myc gene expression. However, after the induction of differentiation, a more internal territorial location was found for the single copy c-myc gene of normal chromosome 8, while amplicons conserved their territorial topography.