Deregulation of apoptosis in colorectal carcinoma: theoretical and therapeutic implications

Anticancer and Antimigration Effects of a Combinatorial Treatment of 5-Fluorouracil and Lactobacillus paracasei subsp. paracasei NTU 101 Fermented Skim Milk Extracts on Colorectal Cancer Cells

Colorectal cancer (CRC) is one of the most prevalent cancers worldwide. Metabolites of lactic acid bacteria (LAB) have anticancer and antimetastasis capacities. This study aimed to investigate the chemotherapeutic effects of Lactobacillus paracasei subsp. paracasei NTU 101-fermented skim milk (NTU101-FM) extracts in combination with the chemotherapeutic drug 5-fluorouracil (5-FU) in a cellular CRC model. The NTU101-FM extracts effectively reduced CRC cell viability but were not cytotoxic to colon epithelial cells. Moreover, they increased RAW 264.7 cell viability. Notably, the cell viability of CRC cells was decreased by 5-FU in combination with the NTU101-FM extracts; the combinatorial treatment inhibited cell viability significantly more than 5-FU alone ( p < 0.05). An ethanol extract of NTU101-FM effectively attenuated CT26 cell migration. In conclusion, the ethanol extract prepared from NTU101-FM has a potential application as an anticancer agent in CRC.

A polysaccharide from Lentinus edodes inhibits human colon cancer cell proliferation and suppresses tumor growth in athymic nude mice

The antitumor effect of Lentinan is thought rely on the activation of immune responses; however, little is known about whether Lentinan also directly attacks cancer cells. We therefore investigated the direct antitumor activity of SLNT (a water-extracted polysaccharide from Lentinus edodes) and its probable mechanism. We showed that SLNT significantly inhibited proliferation of HT-29 colon cancer cells and suppressed tumor growth in nude mice. Annxein V-FITC/PI, DAPI, AO/EB and H&E staining assays all showed that SLNT induced cell apoptosis both in vitro and in vivo. SLNT induced apoptosis by activating Caspase-3 via both intrinsic and extrinsic pathways, which presented as the activation of Caspases-9 and -8, upregulation of cytochrome c and the Bax/Bcl-2 ratio, downregulation of NF-κB, and overproduction of ROS and TNF-α in vitro and in vivo. Pretreatment with the caspase-3 inhibitor Ac-DEVD-CHO or antioxidant NAC blocked SLNT-induced apoptosis. These findings suggest that SLNT exerts direct antitumor effects by inducing cell apoptosis via ROS-mediated intrinsic and TNF-α-mediated extrinsic pathways. SLNT may thus represent a useful candidate for colon cancer prevention and treatment.

Cellular FLICE-like inhibitory protein secures intestinal epithelial cell survival and immune homeostasis by regulating caspase-8

BACKGROUND & AIMS

The intestinal epithelium generates a barrier that protects mammals from potentially harmful intestinal contents, such as pathogenic bacteria. Dysregulation of epithelial cell death has been implicated in barrier dysfunction and in the pathogenesis of intestinal inflammation. We investigated mechanisms of cell-death regulation in the intestinal epithelium of mice.

METHODS

Conditional knockout mice (either inducible or permanent) with deletion of cellular FLICE-inhibitory protein (cFlip) or caspase-8 in the intestinal epithelium were analyzed by histology and high-resolution endoscopy. We assessed the effects of cFlip or caspase-8 deficiency on intestinal homeostasis.

RESULTS

Expression of cFlip in the intestinal epithelium was required for constitutive activation of caspase-8 under steady-state conditions. Intestinal expression of cFlip was required for development; disruption of the gene encoding cFlip from the intestinal epithelium (cFlip(fl/fl) VillinCre(+) mice) resulted in embryonic lethality. When cFlip was deleted from the intestinal epithelium of adult mice (cFlip(iΔIEC) mice), the animals died within a few days from severe tissue destruction, epithelial cell death, and intestinal inflammation. Death of cFlip-depleted intestinal epithelial cells was regulated extrinsically and required the presence of death receptor ligands, such as tumor necrosis factor-α and CD95 ligand, but was independent of receptor-interacting protein 3. cFlip deficiency was associated with strong up-regulation of caspase-8 and caspase-3 activity and excessive apoptosis in intestinal crypts.

CONCLUSIONS

cFlip is required for intestinal tissue homeostasis in mice. It controls the level of activation of caspase-8 to promote survival of intestinal epithelial cells.

The study protocol for the Head Injury Retrieval Trial (HIRT): a single centre randomised controlled trial of physician prehospital management of severe blunt head injury compared with management by paramedics

BACKGROUND

The utility of advanced prehospital interventions for severe blunt traumatic brain injury (BTI) remains controversial. Of all trauma patient subgroups it has been anticipated that this patient group would most benefit from advanced prehospital interventions as hypoxia and hypotension have been demonstrated to be associated with poor outcomes and these factors may be amenable to prehospital intervention. Supporting evidence is largely lacking however. In particular the efficacy of early anaesthesia/muscle relaxant assisted intubation has proved difficult to substantiate.

METHODS

This article describes the design and protocol of the Head Injury Retrieval Trial (HIRT) which is a randomised controlled single centre trial of physician prehospital care (delivering advanced interventions such as rapid sequence intubation and blood transfusion) in addition to paramedic care for severe blunt TBI compared with paramedic care alone.

RESULTS

Primary endpoint is Glasgow Outcome Scale score at six months post injury. Issues with trial integrity resulting from drop ins from standard care to the treatment arm as the result of policy changes by the local ambulance system are discussed.

CONCLUSION

This randomised controlled trial will contribute to the evaluation of the efficacy of advance prehospital interventions in severe blunt TBI.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00112398.

Oral inoculation of probiotics Lactobacillus acidophilus NCFM suppresses tumour growth both in segmental orthotopic colon cancer and extra-intestinal tissue

Modulation of the cellular response by the administration of probiotic bacteria may be an effective strategy for preventing or inhibiting tumour growth. We orally pre-inoculated mice with probiotics Lactobacillus acidophilus NCFM (La) for 14 d. Subcutaneous dorsal-flank tumours and segmental orthotopic colon cancers were implanted into mice using CT-26 murine colon adenocarcinoma cells. On day 28 after tumour initiation, the lamina propria of the colon, mesenteric lymph nodes (MLN) and spleen were harvested and purified for flow cytometry and mRNA analyses. We demonstrated that La pre-inoculation reduced tumour volume growth by 50·3 %, compared with untreated mice at 28 d after tumour implants (2465·5 (SEM 1290·4) v. 4950·9 (SEM 1689·3) mm³, P<0·001). Inoculation with La reduced the severity of colonic carcinogenesis caused by CT-26 cells, such as level of colonic involvement and structural abnormality of epithelial/crypt damage. Moreover, La enhanced apoptosis of CT-26 cells both in dorsal-flank tumour and segmental orthotopic colon cancer, and the mean counts of apoptotic body were higher in mice pre-inoculated with La (P<0·05) compared with untreated mice. La pre-inoculation down-regulated the CXCR4 mRNA expressions in the colon, MLN and extra-intestinal tissue, compared with untreated mice (P<0·05). In addition, La pre-inoculation reduced the mean fluorescence index of MHC class I (H-2Dd, -Kd and -Ld) in flow cytometry analysis. Taken together, these findings suggest that probiotics La may play a role in attenuating tumour growth during CT-26 cell carcinogenesis. The down-regulated expression of CXCR4 mRNA and MHC class I, as well as increasing apoptosis in tumour tissue, indicated that La may be associated with modulating the cellular response triggered by colon carcinogenesis.

PTH inactivates the AKT survival pathway in the colonic cell line Caco-2

In previous works, we found that PTH promotes the apoptosis of human Caco-2 intestinal cells, through the mitochondrial pathway. This study was conducted to investigate the modulation of different players implicated in the AKT survival pathway in PTH-induced intestinal cell apoptosis. We demonstrate, for the first time, that PTH modulates AKT phosphorylation in response to apoptosis via the serine/threonine phosphatase PP2A. PTH treatment induces an association of AKT with the catalytic subunit of PP2A and increases its phosphatase activity. PTH also promotes the translocation of PP2Ac from the cytosol to the mitochondria. Furthermore, our results suggest that PP2A plays a role in hormone-dependent Caco-2 cells viability and in the cleavage of caspase-3 and its substrate PARP. The cAMP pathway also contributes to PTH-mediated AKT dephosphorylation while PKC and p38 MAPK do not participate in this event. Finally, we show that PTH induces the dissociation between 14-3-3 and AKT, but the significance of this response remains unknown. In correlation with PTH-induced Bad dephosphorylation, the hormone also decreases the basal association of 14-3-3 and Bad. Overall, our data suggest that in Caco-2 cells, PP2A and the cAMP pathway act in concert to inactivate the AKT survival pathway in PTH-induced intestinal cell apoptosis.

Pro-apoptotic effects of parathyroid hormone in intestinal cells

Apoptosis, a form of programmed cell death, is a process fundamental to normal growth and development, immune response, tissue remodeling after injury or insult, and homeostasis of the intestinal epithelium. Recently, it has become apparent that apoptosis is a crucial process in skeletal development and homeostasis, and that signaling by the parathyroid hormone (PTH) receptor can either promote or suppress apoptosis depending on the cellular context. In this study, we evaluated the role of PTH in intestinal apoptosis using human colonic Caco-2 cells. To that end, Caco-2 cells were exposed to PTH (10−8 mol/L) for 1–5 days. Evaluation of cell survival by use of resazurin staining, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) staining, and crystal violet staining revealed that PTH treatment diminishes the number of viable cells. Assessment of cells after PTH treatment by use of propidium iodide showed that the hormone increased the number of red-stained (dead) cells (178%, 5 days). Moreover, we found that the hormone induced disruption of actin filaments with changes to cellular shape, alteration of cell-to-cell junctions, externalization of membrane phosphatidylserine, chromatin condensation, and DNA fragmentation of the nucleus, which are morphological features consistent with apoptosis. In addition, PTH treatment revealed a cytosolic staining pattern of 14-3-3. However, the significance of such differential localization for 14-3-3 function remains unknown. Taken together, the present study suggests that PTH promotes apoptosis in Caco-2 intestinal cells.

Study of immune cells involved in the antitumor effect of kefir in a murine breast cancer model

Administration of kefir and a kefir cell-free fraction (KF) to mice injected with breast tumor cells produced, locally in the mammary gland, different profiles of cells secreting cytokines. Here, the immune cell populations in mammary glands affected by the cyclic consumption of kefir or KF for 2 or 7 d were evaluated using a breast tumor model. Apoptosis was also assayed as another mechanism involved in tumor growth delay. The rate development of tumor cells, IgA(+) cells, and CD4+ and CD8+ T lymphocytes was monitored in mammary gland tissues. The number of Bcl-2(+) cells in the mammary gland was compared with the apoptosis observed in the tumor. Two-day cyclical administration of both products delayed tumor growth and increased the number of IgA(+) cells in the mammary gland. Changes in the balance between CD4+ and CD8+ cells in the mammary gland were observed in mice from the group fed KF cyclically for 2 d, such that the number of CD4+ cells increased when the number of CD8+ cells remained constant. Mice that received 2-d cyclic administration of KF showed significant increases in the number of apoptotic cells and decreases in Bcl-2(+) cells in the mammary gland, compared with the tumor control group. The present study allows a better understanding of the mechanisms (immune and nonimmune) involved in the antitumor effect observed in mice administered kefir or KF. The importance of nonmicrobial components released during milk fermentation to obtain the beneficial antitumor effects is also reported.

Apoptosis in normal rectal mucosa, baseline adenoma characteristics, and risk of future adenomas

Low apoptosis in the normal rectal mucosa has been associated with colorectal adenomas in cross-sectional studies. It is unknown whether apoptosis can predict the occurrence of new adenomas. We evaluated whether apoptosis at baseline colonoscopy, as well as patient and adenoma characteristics, could predict future occurrence of adenomas. Study subjects were participants in the Diet and Health Study III, a cross-sectional study of adenoma risk factors between August 1998 and March 2000. At baseline, subjects underwent colonoscopy and provided normal rectal mucosal biopsies to evaluate apoptosis as well as information about diet and lifestyle. The present study includes 257 subjects who returned for follow-up colonoscopy between 2000 and 2005. Apoptosis, number of adenomas, size, and atypia at baseline colonoscopy were evaluated as predictors of new adenomas. Logistic regression was used to calculate odds ratios (OR) and 95% confidence intervals (95% CI). At baseline, low apoptosis was significantly associated with increased risk of adenomas (P = 0.0001). Compared with those in the lowest tertile, subjects with high apoptosis were less likely to have an adenoma at follow-up (crude OR, 0.25; 95% CI, 0.09-0.65; adjusted OR, 0.29; 95% CI, 0.08-1.06). Having three or more adenomas at baseline was associated with increased risk of new adenomas (crude OR, 2.46; 95% CI, 1.14-5.31; adjusted OR, 3.74; 95% CI, 1.01-13.83). This study suggests that lower apoptosis is associated with increased risk of future adenoma development. If confirmed in larger studies, apoptosis could potentially be used to identify patients at highest risk for developing new adenomas.

Potential role of apoptosis and apoptotic regulatory proteins in colorectal neoplasia: correlations with clinico-pathological parameters and survival

An imbalance between apoptotic and proliferative processes is believed to underlie colorectal neoplasia. We evaluated the expression of bcl-2, p53, mdm2 proteins, and apoptosis in colorectal neoplasms, as well as their correlation with clinico-pathological parameters, using image analysis. Biopsies from 46 colorectal cancers, 121 adenomas, and 25 controls were studied using monoclonal antibodies against p53, bcl-2, mdm2 and the terminal deoxynucleotidyl-transferase-mediated dUTP nick end labeling (TUNEL) method for apoptosis. P53 and bcl2 protein expression was higher in adenomas >or=1 cm (P < 0.03) and tubulovillous-villous adenomas (P < 0.03), and correlated with dysplasia (P < 0.03). In Cox regression analysis, Dukes' stage was the most significant independent prognostic indicator of a worse survival (P < 0.019), whereas when stage was eliminated, bcl-2 expression was also a powerful predictor for bad prognosis (P = 0.02). In conclusion, both bcl-2 and p53 immunohistochemical profiles may be useful adjuncts in detecting adenomas with a malignant potential, whereas bcl-2 could be used in combination with Dukes' stage as a predictor of prognosis in colorectal cancer.

Modification of Gene Products Involved in Resistance to Apoptosis in Metastatic Colon Cancer Cells: Roles of Fas, Apaf-1, NFκB, IAPs, Smac/DIABLO, and AIF

BACKGROUND

Colon cancer becomes resistant to apoptosis as it acquires metastatic potential. SW480 and SW620 colon cancer cells were established from the same patient at different stages of tumor progression. The stage III colorectal cancer cell line (SW620) is more resistant to apoptosis. In the present report, we investigated the apoptotic gene products that might account for colon cancer evasion of immune attack and chemoradioresistance-induced apoptosis.

METHODS

SW480 and SW620 cells were used for this experiment. Type 1 apoptosis was induced by CH-11. Type 2 apoptosis was induced by cisplatin and ionizing radiation. Apoptosis was determined by caspase-3 activity and terminal deoxynucleotidyl transferase mediated dUTP nick end labeling. Gene products Fas, TRAIL, c-FLIP, Bid, BAX, Bcl-2, Bcl-xL, Apaf-1, nuclear factor-kappa B, Smac/DIABLO, apoptosis inducing factor, and the inhibitors of apoptosis were investigated by immunocytochemistry and Western blot analyses.

RESULTS

SW620 cell lines were more resistant to both Type 1 and Type 2 apoptosis induced by CH-11, cisplatin, and ionizing radiation, respectively. Examination of the extrinsic pathway demonstrated Fas receptor to be down-regulated in SW620. Apaf-1 was decreased in SW620 cells; while other members of the mitochondrial pathway including Bax, Bid, Bcl-xL, and Bcl-2 demonstrated minimal alterations of protein levels in both cell lines. Survivin and XIAP protein levels were increased in SW620 cells, which correlated with nuclear expression of nuclear factor-kappa B in SW620 cells but not SW480. Mitochondrial-released factors including Smac/DIABLO and apoptosis inducing factor were increased in SW480 cells.

CONCLUSIONS

SW620 cells have acquired genetic defects both in the intrinsic and extrinsic pathways of apoptosis, which may explain in part the ability of colon cancer cells to escape the immune system and to become chemoradioresistant. These genes may be potential targets for chemoradiosensitization in advanced colorectal cancer.

Helix orientations in membrane-associated Bcl-XL determined by 15N-solid-state NMR spectroscopy

Controlled cell death is fundamental to tissue hemostasis and apoptosis malfunctions can lead to a wide range of diseases. Bcl-x(L) is an anti-apoptotic protein the function of which is linked to its reversible interaction with mitochondrial outer membranes. Its interfacial and intermittent bilayer association makes prediction of its bound structure difficult without using methods able to extract data from dynamic systems. Here we investigate Bcl-x(L) associated with oriented lipid bilayers at physiological pH using solid-state NMR spectroscopy. The data are consistent with a C-terminal transmembrane anchoring sequence and an average alignment of the remaining helices, i.e. including helices 5 and 6, approximately parallel to the membrane surface. Data from several biophysical approaches confirm that after removal of the C-terminus from Bcl-x(L) its membrane interactions are weak. In the presence of membranes Bcl-x(L) can still interact with a Bak BH3 domain peptide suggesting a model where the hydrophobic C-terminus of the protein unfolds and inserts into the membrane. During this conformational change the Bcl-x(L) hydrophobic binding pocket becomes accessible for protein-protein interactions whilst the structure of the N-terminal region remains intact.

Meta-analysis: antioxidant supplements for primary and secondary prevention of colorectal adenoma

BACKGROUND

Colorectal cancer may be prevented by reducing the development of adenomatous polyps.

AIM

To assess the benefits and harms of antioxidant supplements in preventing colorectal adenoma.

METHODS

Using the Cochrane Collaboration methodology we reviewed all randomized clinical trials comparing antioxidant supplements with placebo or no intervention. We searched electronic databases and the reference lists until October 2005. Outcome measures were development of colorectal adenoma adverse events. We analysed dichotomous outcomes with fixed- and random-effects model meta-analyses and calculated the relative risk with 95% confidence interval.

RESULTS

We identified eight randomized trials (17 620 participants). Neither fixed-effect (relative risk: 0.93, 95% CI: 0.81-1.1) nor random-effect model meta-analyses (0.82, 0.60-1.1) showed statistically significant effects of supplementation with beta-carotene, vitamins A, C, E and selenium alone or in combination. Antioxidant supplements seemed to increase the development of colorectal adenoma in three low-bias risk trials (1.2, 0.99-1.4) and significantly decrease its development in five high-bias risk trials (0.59, 0.47-0.74). The estimates difference is significant (P < 0.0001). There was no significant difference between the intervention groups regarding adverse events, including mortality (0.82, 0.47-1.4).

CONCLUSION

We found no convincing evidence that antioxidant supplements have significant beneficial effect on primary or secondary prevention of colorectal adenoma.

Colon cancer and apoptosis

BACKGROUND

The implementation of new therapeutic options for the management of metastatic colon cancer mandates a revisit to apoptosis and its role in colon cancer tumorigenesis with an emphasis on the mechanisms leading to chemotherapeutic resistance and immune system evasion of colon cancer cells.

DATA SOURCES

Literature regarding molecular apoptosis mechanisms and the role of apoptosis in colon cancer progression are reviewed by this article.

CONCLUSION

Programmed cell death has rapidly emerged as a potential target for cancer treatment at various stages of tumor progression. Chemoprevention, immuno-regulation, and metastasis are prospective targets by which apoptotic mechanisms could be utilized in the prevention and management of tumorigenesis. Understanding how defects in the death receptor pathway of apoptosis permit colon cancer cells to escape the immune system would allow for treatment options whereby the body's immune system could again recognize and eliminate unwanted cells.

Amarogentin can reduce hyperproliferation by downregulation of Cox-II and upregulation of apoptosis in mouse skin carcinogenesis model

Swertia chirata, is a bitter plant, used in the Indian system of medicine (Ayurveda) for various human ailments. Our laboratory was the first to report the chemopreventive effect of this plant. The antiproliferative and pro-apoptotic action of amarogentin rich fraction of S. chirata is now demonstrated on a mouse skin carcinogenesis model. Immunohistochemical localization revealed a reduction in proliferating and increase in apoptotic cells in skin lesion following treatment, also reflected in the expression of molecular markers--Cox-II and caspase-3 proteins. It may be possible to calculate relative risk, relative protection and attributable risk from the action of test agents on proliferation and apoptosis.

Effects of milk fermented by Lactobacillus helveticus R389 on a murine breast cancer model

Introduction

Antitumour activity is one of the health-promoting effects attributed to the lactic acid bacteria and their products of fermentation. Previous studies in mice demonstrated that bioactive compounds released in milk fermented by Lactobacillus helveticus R389 contribute to its immunoenhancing and antitumour properties. The aim of the present work was to study the effects of the consumption of milk fermented by L. helveticus R389 or its proteolytic-deficient variant, L. helveticus L89, on a murine hormone-dependent breast cancer model.

Methods

Mice were fed with milk fermented by L. helveticus R389 or L. helveticus L89, during 2 or 7 days. The tumour control group received no special feeding. At the end of the feeding period, the mice were challenged by a subcutaneous injection of tumour cells in the mammary gland. Four days post-injection, the mice received fermented milk on a cyclical basis. The rate of tumour development and the cytokines in serum, mammary gland tissue and tumour-isolated cells were monitored. Bcl-2-positive cells in mammary glands and cellular apoptosis in tumour tissue were also studied.

Results

Seven days of cyclical administration of milk fermented by either bacterial strain delayed or stopped the tumour development. Cytokines demonstrated that L. helveticus R389 modulated the immune response challenged by the tumour. IL-10 and IL-4 were increased in all the samples from this group. In comparison with the tumour control, all test groups showed a decrease of IL-6, a cytokine involved in oestrogen synthesis. Seven days of cyclical feeding with milk fermented by L. helveticus R389 produced an increase in the number of apoptotic cells, compared with all other groups.

Conclusion

This study demonstrated that 7 days of cyclical administration of milk fermented by both strains of L. helveticus diminishes tumour growth, stimulating an antitumour immune response. Compounds released during milk fermentation with L. helveticus R389 would be implicated in its immunoregulatory capacity on the immune response in mammary glands and tumour, which were correlated with the cytokines found at the systemic level. The milk fermented by L. helveticus R389 was able to modulate the relationship between immune and endocrine systems (by IL-6 diminution), which is very important in oestrogen-dependent tumour and induced cellular apoptosis.

Modulatory influence of garlic and tomato on cyclooxygenase-2 activity, cell proliferation and apoptosis during azoxymethane induced colon carcinogenesis in rat

Preventive intervention of colorectal cancer has become essential as a major portion of the population may develop the disease at some points during their lives. Diet and nutrition play an important role during this multistep colon carcinogenic process. Inhibitory activity of aqueous suspensions of garlic and tomato, individually and in combination, were tested on azoxymethane induced colon carcinogenesis in Sprague-Dawley rats. The effect was observed on aberrant crypt foci (ACF), the preneoplastic lesion. To investigate the mechanism of action of the agents used, cell proliferation and the level of apoptosis were determined and the expression of cyclooxygenase-2 (COX-2) protein was analyzed in the colon. Following treatment, significant inhibition of the level of cell proliferation (P<0.01 in garlic; P<0.001 in tomato and P<0.001 in combination treatment group with respect to the carcinogen control group), significant induction of apoptosis (P<0.01 in garlic treated; P<0.01 in tomato treated and P<0.001 in combination treatment group with respect to the carcinogen control group) and suppression of COX-2 expression among the treated groups resulted in significant reduction in the incidences of ACF (by 45.27% in garlic, 68.24% in tomato and 71.62% in combination treatment group). The preventive effect was better when the combination of garlic and tomato was administered in comparison to the individual treatment groups, suggesting the synergistic action of garlic and tomato.

Tomato and garlic can modulate azoxymethane-induced colon carcinogenesis in rats

Tomato (Lycopersicon esculentum) and garlic (Allium cepa) are important constituents of the human diet. Compounds like diallyl sulfides, diallyl disulfides and quercetin, which are active components of garlic, have known anti-inflammatory, antimutagenic activities. Similarly, active components in tomato, such as kaempferol and chlorogenic acid, have antimutagenic activities and lycopene is the most active oxygen quencher with potential chemopreventive activities. In view of this, an endeavour was made to evaluate the anticarcinogenic effect, if any, of tomato and garlic consumption individually and in combination on azoxymethane-induced colonic precancerous lesion, the aberrant crypt foci in animal model. Sprague-Dawley rats (4-5 weeks old) were injected with azoxymethane (15 mg/kg b.w.) and orally administered with 2% (w/v) of tomato, garlic and a combination of both. After 12 weeks of first azoxymethane injection, colons were assessed for aberrant crypt foci and compared with the carcinogen control group. Lipid peroxidation level and glutathione-S-transferase (GST) activity were assessed in liver as well as in colon. Furthermore, in situ cell proliferation and apoptosis were estimated using the Brdu incorporation method and TUNEL method respectively. It was observed that aberrant crypt foci were reduced in all treated groups (by 32.11% in garlic, by 76.14% in tomato and by 55.96% in the combination group). Among treated groups, GST activity was found to be induced in both liver and colon, whereas considerable reduction in lipid peroxidation level was observed in liver as well as in colon with respect to the carcinogen control group. Significant reduction in Brdu labelling index and increase in apoptotic index in colon was noted in the treated groups. These results suggest that tomato and garlic suspensions have a protective effect on colon carcinogenesis, which is mediated by modulation of different biological pathways during carcinogenesis.

Changes in apoptosis during the development of colorectal cancer: a systematic review of the literature

The development of colorectal cancer is characterised by an accumulation of molecular genetic alterations causing disorders in cell growth, differentiation and apoptosis. Although changes in apoptosis with colorectal cancer development have been studied extensively, a clear consensus of opinion has not yet emerged. In this review, the literature about changes in the frequency and distribution of apoptosis in tissue sections of normal and neoplastic colorectal tissues was reviewed systematically. Using a PUBMED search, 53 relevant articles were identified. Data from these studies are discussed with respect to the following aspects: methods used to detect apoptotic cell death; frequency and locoregional distribution of apoptosis in normal mucosa, adenomas and carcinomas; the correlation between levels of apoptosis and proliferation and the prognostic significance of the degree of apoptosis in colorectal cancer. Possible underlying mechanisms of dysregulation of apoptosis are discussed briefly. Finally, possible therapeutic implications of knowledge of the molecular regulation of apoptosis are discussed and potential options for further research are suggested.

Effect of yogurt on the inhibition of an intestinal carcinoma by increasing cellular apoptosis

Yogurt consumption has been associated with decreased risk of colon cancer. The apoptosis induced by yogurt as a mechanism involved in the inhibition of an experimental intestinal tumor induced by 1,2 dimethylhydrazine (DMH) in BALB/c mice, has been studied. An imbalance between apoptosis and mitosis or cell proliferation is believed to underlie colon cancer development and progression. We determined the effect of yogurt feeding in the induction of apoptosis and the relationship between mitosis and apoptosis in mice injected with the carcinogen DMH and in mice injected with DMH and fed with a diet supplemented with yogurt. The percentage of mitotic and apoptotic cells was analyzed every 2 weeks from week 8 to 16. They were analyzed on histological slices from the large intestine by colchicine, or Tunel test for mitosis and apoptosis determination, respectively. An increase in the mitosis during the first 4 weeks of tumor development with apoptosis negative and severe dysphasia, was observed in animals treated with the carcinogen. In those animals that received DMH and were given yogurt, a moderate cell proliferation with a significant increase in the number of apoptotic cells was determined. The increase in the apoptotic activity was also observed in the group of animals that received only a diet supplemented with yogurt. The results suggest that yogurt would influence the balance between mitosis and apoptosis, which was modified during the carcinogenesis process, by increasing cellular apoptosis. Dietary supplementation of yogurt may play a role in modulating cell proliferation or apoptosis during the development of colorectal carcinoma.

Beta-catenin--a linchpin in colorectal carcinogenesis?

An important role for beta-catenin pathways in colorectal carcinogenesis was first suggested by the protein's association with adenomatous polyposis coli (APC) protein, and by evidence of dysregulation of beta-catenin protein expression at all stages of the adenoma-carcinoma sequence. Recent studies have, however, shown that yet more components of colorectal carcinogenesis are linked to beta-catenin pathways. Pro-oncogenic factors that also release beta-catenin from the adherens complex and/or encourage translocation to the nucleus include ras, epidermal growth factor (EGF), c-erbB-2, PKC-betaII, MUC1, and PPAR-gamma, whereas anti-oncogenic factors that also inhibit nuclear beta-catenin signaling include transforming growth factor (TGF)-beta, retinoic acid, and vitamin D. Association of nuclear beta-catenin with the T cell factor (TCF)/lymphoid enhancer factor (LEF) family of transcription factors promotes the expression of several compounds that have important roles in the development and progression of colorectal carcinoma, namely: c-myc, cyclin D1, gastrin, cyclooxygenase (COX)-2, matrix metalloproteinase (MMP)-7, urokinase-type plasminogen activator receptor (aPAR), CD44 proteins, and P-glycoprotein. Finally, genetic aberrations of several components of the beta-catenin pathways, eg, Frizzled (Frz), AXIN, and TCF-4, may potentially contribute to colorectal carcinogenesis. In discussing the above interactions, this review demonstrates that beta-catenin represents a key molecule in the development of colorectal carcinoma.

Genetics--cellular basis

Colorectal carcinogenesis is a multistep process during which the specialised epithelial cells of intestinal mucosa surface (e.g. colonocytes) accumulate a series of genetic and epigenetic events which lead to a perturbation of their normal cellular functions and turnover. This review will address the mechanisms and biological effects of these abnormalities on the growth control, differentiation, adhesion and survival of the colonocytes.

Rat colon ornithine and arginine metabolism: coordinated effects after proliferative stimuli

Ornithine decarboxylase (ODC) catalyzes the first step in the polyamine biosynthetic pathway, a highly regulated pathway in which activity increases during rapid growth. Other enzymes also metabolize ornithine, and in hepatomas, rate of growth correlates with decreased activity of these other enzymes, which thus channels more ornithine to polyamine biosynthesis. Ornithine is produced from arginase cleavage of arginine, which also serves as the precursor for nitric oxide production. To study whether short-term coordination of ornithine and arginine metabolism exists in rat colon, ODC, ornithine aminotransferase (OAT), arginase, ornithine, arginine, and polyamine levels were measured after two stimuli (refeeding and/or deoxycholate exposure) known to synergistically induce ODC activity. Increased ODC activity was accompanied by increased putrescine levels, whereas OAT and arginase activity were reduced by either treatment, accompanied by an increase in both arginine and ornithine levels. These results indicate a rapid reciprocal change in ODC, OAT, and arginase activity in response to refeeding or deoxycholate. The accompanying increases in ornithine and arginine concentration are likely to contribute to increased flux through the polyamine and nitric oxide biosynthetic pathways in vivo.

M30 expression demonstrates apoptotic cells, correlates with in situ end-labeling, and is associated with Ki-67 expression in large intestinal neoplasms

CONTEXT

The monoclonal antibody M30 recognizes a neoepitope of cytokeratin 18 produced during apoptosis. It is reactive in formalin-fixed, paraffin-embedded tissue and has great potential in the study of apoptosis in clinical and experimental material.

OBJECTIVES

To compare the results of M30 immunoexpression with a more established technique of demonstrating apoptosis in tissue sections, in situ end-labeling. A secondary objective was to compare the results with immunoexpression of the proliferation-associated antigen Ki-67.

DESIGN

Retrospective analysis of adenomas and adenocarcinomas of the large intestine.

INTERVENTIONS

Immunohistochemistry for M30 and Ki-67, and in situ end-labeling. Formalin-fixed, paraffin-embedded tissue was used.

MAIN OUTCOME MEASURES

The number of cells positive for M30, Ki-67, and in situ end-labeling, expressed as a proportion of the total number of cells counted.

RESULTS

A strong positive correlation was found between in situ end-labeling and expression of M30, although the counts were widely scattered around the regression line. Counts of Ki-67 were strongly correlated with both M30 expression and in situ end-labeling. Immunoexpression of M30 was generally easier to interpret than in situ end-labeling, and the procedures for M30 immunohistochemistry were technically less exacting.

CONCLUSION

These findings support the application of M30 immunoreactivity in the study of apoptosis.

The effect of unfiltered coffee on potential biomarkers for colonic cancer risk in healthy volunteers: a randomized trial

BACKGROUND

Epidemiologic studies suggest that coffee use might protect against colorectal cancer. Inconsistencies as to the effect of coffee use and colorectal cancer between epidemiologic studies might be related to the type of coffee brew.

OBJECTIVE

We studied the effect of unfiltered coffee consumption on putative biomarkers for colonic cancer risk.

DESIGN

A total of 64 healthy volunteers (31 men and 33 women), with a mean age of 43 +/- 11 years were randomly assigned to two groups in a crossover design, with two intervention periods of 2 weeks separated by a washout period of 8 weeks. Treatments were 1 L of cafetière (French press) coffee daily or no coffee. At the end of each intervention period, fasting blood samples, colorectal biopsies and 48 h faeces were collected.

RESULTS

No effect of coffee on colorectal cell proliferation, assayed by estimating the Proliferating Cell Nuclear Antigen labelling index, was seen. Additionally, no effects were seen on the concentrations of faecal soluble bile acids and colorectal mucosal glutathione S-transferase activity. However, unfiltered coffee significantly increased the glutathione content in the colorectal mucosa by 8% and in plasma by 15%. Other aminothiols in plasma also increased on coffee.

CONCLUSION

Unfiltered coffee does not influence the colorectal mucosal proliferation rate, but might increase the detoxification capacity and anti-mutagenic properties in the colorectal mucosa through an increase in glutathione concentration. Whether this effect indeed contributes to a lower colon cancer risk remains to be established.

Phytic acid in wheat bran affects colon morphology, cell differentiation and apoptosis

Wheat bran (WB) and its component phytic acid (PA) have both been shown to decrease early biomarkers of colon carcinogenesis, i.e. the PCNA labeling index of cell proliferation and certain aberrant crypt foci parameters. However, it is not known how WB and PA alter other biomarkers of colon cancer risk, such as rate of apoptosis and degree of differentiation, or how they affect colon morphology. Thus, the objectives of this study were to determine the effects of WB on these parameters, to see if PA contributes to these effects and whether there is a difference between endogenous and exogenously added PA. Five groups of azoxymethane-treated male Fischer 344 rats were fed a basal control diet (BD) or BD supplemented with either 25% wheat bran, 25% dephytinized wheat bran (DWB), 25% DWB plus 1.0% PA or 1.0% PA for 100 days. The WB, DWB and PA diets significantly increased the rate of apoptosis and cell differentiation in the whole crypt and the top 40% of the crypt. The WB, DWB and PA diets also significantly increased cell apoptosis in the bottom 60% of the crypt, while all the treatment groups significantly increased cell differentiation versus the BD group in the bottom 60% of the crypt. In addition, the WB, DWB and PA diets decreased the number of crypts per millimeter of colon, while the DWB and PA diets also decreased crypt height measured as number of cells. It is concluded that WB, partly due to its dietary fiber and endogenous PA, and exogenous PA when added to a low fiber diet can increase cell apoptosis and differentiation and favorably affect colon morphology.

Apoptosis in the intestinal epithelium: its relevance in normal and pathophysiological conditions

Apoptosis is now recognized as an important process responsible for maintenance of the cellular balance between proliferation and death. Apoptosis is distinct from necrosis in that it is a programmed form of cell death and occurs without any accompanying inflammation. This form of cell death can be induced by a wide range of cellular signals, which leads to activation of cell death machinery within the cell and is characterized by distinct morphological changes. Apoptosis is especially relevant in the gastrointestinal tract, as the mammalian intestinal mucosa undergoes a process of continual cell turnover that is essential for maintenance of normal function. Cell proliferation is confined to the crypts, while differentiation occurs during a rapid, orderly migration up to the villus. The differentiated enterocytes, which make up the majority of the cells, then undergo a process of programmed cell death (apoptosis). Although apoptosis is essential for the maintenance of normal gut epithelial function, dysregulated apoptosis is seen in a number of pathological conditions in the gastrointestinal tract. The cellular mechanisms regulating this tightly regimented process have not been clearly defined and this topic represents an area of active investigation as delineation of this process will lead to a better understanding of normal gut mucosal growth.

Promoter region methylation does not account for the frequent loss of expression of the Fas gene in colorectal carcinoma

Expression of the apoptosis-promoting Fas gene is frequently reduced or lost during the development of colorectal carcinoma. However, loss of heterozygosity at the Fas locus or Fas gene rearrangements do not account for the loss of expression of Fas, raising the possibility that methylation of the Fas promoter may inhibit gene expression in colorectal carcinomas. We have examined the Fas promoter region CpG island for evidence of hypermethylation in colorectal tumours. Forty-seven specimens of colorectal adenoma and carcinoma, as well as six samples of normal colonic mucosa, were examined by Southern blotting for methylation at HpaII and Cfol sites in this region. No methylation was detected in any of the specimens, suggesting that hypermethylation is not primarily responsible for the loss of expression of the Fas gene during colorectal tumorigenesis.

Reactive nitrogen species in colon carcinogenesis

The role of reactive nitrogen species (RNS) in colon carcinogenesis is multifactorial and affects diverse processes, such as proliferation, apoptosis, differentiation, tumorigenesis, and metastases. This review describes the stages in colon carcinogenesis where nitric oxide (NO) and inducible NO synthase (NOS2) may influence the progression of a normal mucosa to overt metastatic cancer. Overexpression of NOS2 and an increase in the generation of NO and other RNS may lead to apoptosis resistance, DNA damage, mutation, up-regulation of COX-2, increased proliferation, an increase in oxidative stress and an increase in tumor vascularity and metastatic potential. Therefore, future goals are to establish mechanistically based biomarkers to assess individuals at risk for colon cancer and to implement chemopreventive and dietary strategies that reduce colon cancer risk. An understanding of NO signaling pathways in colon epithelial cells should provide the basis for novel biomarker development. Colon cancer prevention may be achieved effectively by chemically interfering with key components of the NO signaling pathways, changing dietary habits to reduce fat and increase antioxidant-containing vegetables, and dietary supplementation to increase DNA repair.