Chemoprevention of pancreatic cancer: a review of the molecular pathways involved, and evidence for the potential for chemoprevention

Areca nut extract demonstrated apoptosis-inducing mechanism by increased caspase-3 activities on oral squamous cell carcinoma

Background: Oral squamous cell carcinoma is a neoplasm of keratinocyte cells of oral mucosa epithelium that can potentially spread through lymphatic tissue or blood vessel. Although areca nut is one of the plants with a risk of inducing that cancer, areca nut is believed to have high antioxidant properties. Due to the current interest in the apoptosis effects from areca nut for oral cancer treatment, we investigated its ability to induce apoptosis and caspase-3 activity in oral cancer cell lines: HSC-2 and HSC-3. Methods: We examined the effect of areca nut on apoptosis and caspase-3 activity in HSC-2 and HSC-3 cells. Flow cytometry was conducted for the quantification of the cells that were apoptotic and expressing the caspase-3 enzyme for 24 and 48 hours. Results: Areca nut induced a significant increase (p<0.01) in late apoptosis of HSC-2 cells and mostly occurred over 48 hours. The study also found that in HSC-3, there were significant increases (p<0.01) the percentage of cells in early apoptosis after 24 hours and late apoptosis at 48 hours. Caspase-3 activity increased after 24 and 48 hours of areca nut exposure in both cells. Conclusions: The study showed that areca nut could be considered as a potential anticancer agent through its capability in inducing a caspase-dependent apoptosis.

Areca nut extract demonstrated apoptosis-inducing mechanism by increased caspase-3 activities on oral squamous cell carcinoma

Background: Oral squamous cell carcinoma is a neoplasm of keratinocyte cells of oral mucosa epithelium that can potentially spread through lymphatic tissue or blood vessel. Although areca nut is one of the plants with a risk of inducing that cancer, areca nut is believed to have high antioxidant properties. Due to the current interest in the apoptosis effects from areca nut for oral cancer treatment, we investigated its ability to induce apoptosis and caspase-3 activity in oral cancer cell lines: HSC-2 and HSC-3. Methods: We examined the effect of areca nut on apoptosis and caspase-3 activity in HSC-2 and HSC-3 cells. Flow cytometry was conducted for the quantification of the cells that were apoptotic and expressing the caspase-3 enzyme for 24 and 48 hours. Results: Areca nut induced a significant increase (p<0.01) in late apoptosis of HSC-2 cells and mostly occurred over 48 hours. The study also found that in HSC-3, there were significant increases (p<0.01) the percentage of cells in early apoptosis after 24 hours and late apoptosis at 48 hours. Caspase-3 activity increased after 24 and 48 hours of areca nut exposure in both cells. Conclusions: The study showed that areca nut could be considered as a potential anticancer agent through its capability in inducing a caspase-dependent apoptosis.

Areca nut extract demonstrated apoptosis-inducing mechanism by increased caspase-3 activities on oral squamous cell carcinoma

Background: Oral squamous cell carcinoma is a neoplasm of keratinocyte cells of oral mucosa epithelium that can potentially spread through lymphatic tissue or blood vessel. Although areca nut is one of the plants with risk of inducing that cancer, areca nut is believed to have high antioxidant properties. Due to the current interest in the apoptosis effects from areca nut for oral cancer treatment, we investigated its ability to induce apoptosis and caspase-3 activity in oral cancer cell lines: HSC-2 and HSC-3. Methods: We examined the effect of areca nut on apoptosis and caspase-3 activity in HSC-2 and HSC-3 cells. Flow cytometry was conducted for the quantification of the cells that were apoptotic and expressing the caspase-3 enzyme for 24 and 48 hours. Results: Areca nut induced a significant increase (p<0.01) in late apoptosis of HSC-2 cells and mostly occurred over 48 hours. The study also found that in HSC-3, there were significant increases (p<0.01) the percentage of cells in early apoptosis after 24 hours and late apoptosis at 48 hours. Caspase-3 activity increased after 24 and 48 hours of areca nut exposure in both cells. Conclusions: The study showed that areca nut could be considered as a potential anticancer agent through its capability in inducing a caspase-dependent apoptosis.

Areca nut extract demonstrated apoptosis-inducing mechanism by increased caspase-3 activities on oral squamous cell carcinoma

Background: Oral squamous cell carcinoma is a neoplasm of keratinocyte cells of oral mucosa epithelium that can potentially spread through lymphatic tissue or blood vessel. Although areca nut is one of the plants with a risk of inducing that cancer, areca nut is believed to have high antioxidant properties. Due to the current interest in the apoptosis effects from areca nut for oral cancer treatment, we investigated its ability to induce apoptosis and caspase-3 activity in oral cancer cell lines: HSC-2 and HSC-3. Methods: We examined the effect of areca nut on apoptosis and caspase-3 activity in HSC-2 and HSC-3 cells. Flow cytometry was conducted for the quantification of the cells that were apoptotic and expressing the caspase-3 enzyme for 24 and 48 hours. Results: Areca nut induced a significant increase (p<0.01) in late apoptosis of HSC-2 cells and mostly occurred over 48 hours. The study also found that in HSC-3, there were significant increases (p<0.01) the percentage of cells in early apoptosis after 24 hours and late apoptosis at 48 hours. Caspase-3 activity increased after 24 and 48 hours of areca nut exposure in both cells. Conclusions: The study showed that areca nut could be considered as a potential anticancer agent through its capability in inducing a caspase-dependent apoptosis.

Areca nut extract demonstrated apoptosis-inducing mechanism by increased caspase-3 activities on oral squamous cell carcinoma

Background: Oral squamous cell carcinoma is a neoplasm of keratinocyte cells of oral mucosa epithelium that can potentially spread through lymphatic tissue or blood vessel. Although areca nut is one of the plants with a risk of inducing that cancer, areca nut is believed to have high antioxidant properties. Due to the current interest in the apoptosis effects from areca nut for oral cancer treatment, we investigated its ability to induce apoptosis and caspase-3 activity in oral cancer cell lines: HSC-2 and HSC-3. Methods: We examined the effect of areca nut on apoptosis and caspase-3 activity in HSC-2 and HSC-3 cells. Flow cytometry was conducted for the quantification of the cells that were apoptotic and expressing the caspase-3 enzyme for 24 and 48 hours. Results: Areca nut induced a significant increase (p<0.01) in late apoptosis of HSC-2 cells and mostly occurred over 48 hours. The study also found that in HSC-3, there were significant increases (p<0.01) the percentage of cells in early apoptosis after 24 hours and late apoptosis at 48 hours. Caspase-3 activity increased after 24 and 48 hours of areca nut exposure in both cells. Conclusions: The study showed that areca nut could be considered as a potential anticancer agent through its capability in inducing a caspase-dependent apoptosis.

Repurposing of metformin and aspirin by targeting AMPK-mTOR and inflammation for pancreatic cancer prevention and treatment

Pancreatic cancer, as the fourth leading cause of cancer-related deaths, carries a poor prognosis with a median survival of 6 months and a dismal 5-year survival rate of 3% to 5%. These statistics highlight an urgent need for novel chemopreventive and therapeutic strategies for this malignancy. Metformin and aspirin have been explored as two emerging cancer chemoprevention agents for different types of cancers, including pancreatic cancer. Here, we review the effects of both metformin and aspirin on pancreatic tumorigenesis and their potential actions in pancreatic cancer. Special attention is paid to their effects on the important signaling pathways of pancreatic cancer development as well as possible mechanisms for synergy between these two agents. For metformin, the most important mechanism may involve the inhibition of mTOR signaling via AMP-activated protein kinase (AMPK)-dependent and -independent pathways. For aspirin, the major mechanism is the anti-inflammatory action through the inhibition of COX-1/COX-2 and modulation of the NFκB or STAT3 pathway. In addition, aspirin may activate AMPK, and both agents may affect Notch, Wnt/β-catenin, and other signaling pathways. The combination of metformin and aspirin will provide additive and possibly synergistic effects for the prevention and treatment of pancreatic cancer.

Molecular binding of black tea theaflavins to biological membranes: relationship to bioactivities

Molecular dynamics simulations were used to study the interactions of three theaflavin compounds with lipid bilayers. Experimental studies have linked theaflavins to beneficial health effects, some of which are related to interactions with the cell membrane. The molecular interaction of theaflavins with membranes was explored by simulating the interactions of three theaflavin molecules (theaflavin, theaflavin-3-gallate, and theaflavin-3,3'-digallate) with a mixed bilayer composed of 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) and 1-palmitoyl-2-oleoyl phosphatidylethanolamine (POPE). The simulations show that the theaflavins evaluated have an affinity for the lipid bilayer surface via hydrogen bonding. The molecular structure of theaflavins influenced their configuration when binding to the bilayer surface, as well as their ability to form hydrogen bonds with the lipid headgroups. The theaflavin-bilayer interactions studied here help to define structure-function relationships of the theaflavins and provide a better understanding of the role of theaflavins in biological processes. The significance of the results are discussed in the context of black tea composition and bioactivity.

Synthetic triterpenoids prolong survival in a transgenic mouse model of pancreatic cancer

Pancreatic cancer is the fourth leading cause of cancer-related deaths in the United States and is nearly always fatal. Whereas early detection offers the most promising approach for reducing the mortality of this disease, there is still a need to develop effective drugs for the prevention and treatment of pancreatic cancer. We tested two promising classes of noncytotoxic drugs, synthetic oleanane triterpenoids and rexinoids, for the prevention of carcinogenesis in the highly relevant LSL-Kras(G12D/+);LSL-Trp53(R127H/+);Pdx-1-Cre (KPC) mouse model of pancreatic cancer. KPC transgenic mice closely recapitulate the genetic mutations, clinical symptoms, and histopathology found in human pancreatic cancer. Beginning at 4 weeks of age, mice were fed powdered control diet or a diet containing the triterpenoids CDDO-methyl ester (CDDO-Me) or CDDO-ethyl amide, the rexinoid LG100268 (LG268), or the combination, until the mice displayed overt symptoms of pancreatic cancer. CDDO-Me, LG268, the combination of CDDO-Me and LG268, and the combination of CDDO-ethyl amide and LG268, all significantly (P < 0.05) increased survival in the KPC mice by 3 to 4 weeks. Recent studies have shown that gemcitabine, the current standard of care for human pancreatic cancer, does not extend survival in KPC mice. In cell lines developed from the KPC mice, the triterpenoids directly interact with both signal transducer and activator of transcription 3 and IκB kinase (IKK) to decrease constitutive interleukin-6 secretion, inhibit constitutive signal transducer and activator of transcription 3 phosphorylation, and block the degradation of IκBα when challenged with tumor necrosis factor α. These results suggest that oleanane triterpenoids and rexinoids have the potential to prevent pancreatic cancer.

Fabrication of gold nanoparticles for targeted therapy in pancreatic cancer

The targeted delivery of a drug should result in enhanced therapeutic efficacy with low to minimal side effects. This is a widely accepted concept, but limited in application due to lack of available technologies and process of validation. Biomedical nanotechnology can play an important role in this respect. Biomedical nanotechnology is a burgeoning field with myriads of opportunities and possibilities for advancing medical science and disease treatment. Cancer nanotechnology (1-100 nm size range) is expected to change the very foundations of cancer treatment, diagnosis and detection. Nanomaterials, especially gold nanoparticles (AuNPs) have unique physico-chemical properties, such as ultra small size, large surface area to mass ratio, and high surface reactivity, presence of surface plasmon resonance (SPR) bands, biocompatibility and ease of surface functionalization. In this review, we will discuss how the unique physico-chemical properties of gold nanoparticles may be utilized for targeted drug delivery in pancreatic cancer leading to increased efficacy of traditional chemotherapeutics.

Homeobox gene CDX2 inhibits human pancreatic cancer cell proliferation by down-regulating cyclin D1 transcriptional activity

OBJECTIVES

Homeobox gene caudal related homeobox gene 2 (CDX2) is an intestine-specific tumor suppressor gene. This study is intended to investigate the effect of CDX2 expression on cell proliferation and cyclin D1 expression in pancreatic cancer cells.

METHODS

Four pancreatic ductal adenocarcinoma cell lines (PancQGO-1, BxPC-3, MIAPaCa-2, CFPAC-1), 1 islet carcinoma cell line (QGP-1), and 1 adenosquamous carcinoma cell line (KP-3) were analyzed for CDX1 and CDX2 expression using real-time reverse transcription-polymerase chain reaction and Western blot analysis. Proliferation of pancreatic cancer cells was analyzed using WST-1 assay after CDX2 transfection. Luciferase assay was performed to examine the effects of CDX2 on cyclin D1 transcriptional activity.

RESULTS

CDX2 was expressed at a significantly higher level in QGP-1 cells than in KP-3 cells. Moreover, CDX2 was expressed at a middle level in 4 pancreatic ductal adenocarcinoma cells. Cell proliferation and cyclin D1 mRNA level were inhibited significantly after CDX2 transfection in pancreatic cancer cells. Furthermore, CDX2 inhibited exogenous nuclear factor kappaB-p65-induced luciferase gene expression in a dose-dependent manner. In addition, CDX2 inhibited pGL2HIVD1kappaB2-luciferase activity.

CONCLUSIONS

CDX2 might play a role in inhibiting cell proliferation and repressing cyclin D1 transcriptional activity through the proximal nuclear factor kappaB binding site in pancreatic cancer cells.

Diagnosis of pancreatic adenocarcinoma using protein chip technology

BACKGROUND

To develop a serum-specific protein fingerprint which is capable of differentiating samples from patients with pancreatic cancer and those with other pancreatic conditions.

METHODS

We used SELDI-TOF-MS coupled with CM10 chips and bioinformatics tools to analyze a total of 118 serum samples in this study; 78 serum samples were analyzed to establish the diagnostic models and the other 40 samples were analyzed on the second day as an independent test set.

RESULTS

The analysis of this independent test set yielded a specificity of 91.6% and a sensitivity of 91.6% for pattern 1, which distinguished pancreatic adenocarcinoma (PC) from healthy individuals and a specificity of 80.0% and a sensitivity of 90.9% for pattern 2, which distinguished PC from chronic pancreatitis.

CONCLUSION

This study indicated that the SELDI-TOF-MS technique can facilitate the discovery of better serum tumor biomarkers and a combination of specific models is more accurate than a single model in diagnosis of PC.

Systematic review: primary and secondary prevention of gastrointestinal cancers with antioxidant supplements

BACKGROUND

The evidence on whether antioxidant supplements prevent gastrointestinal cancers is contradictory.

AIM

To assess the beneficial and harmful effects of antioxidant supplements in preventing gastrointestinal cancers.

METHODS

Using the Cochrane Collaboration methodology, we reviewed the randomized trials comparing antioxidant supplements with placebo or no intervention on the occurrence of gastrointestinal cancers. We searched electronic databases and reference lists until October, 2007. Our outcome measures were gastrointestinal cancers, overall mortality and adverse events. Outcomes were reported as relative risks (RR) with 95% confidence intervals (CI) based on random-effects and fixed-effect models meta-analyses.

RESULTS

We identified 20 randomized trials (211,818 participants) assessing beta-carotene, vitamin A, vitamin C, vitamin E, and selenium. The trial quality was generally high. The antioxidant supplements were without a significant effect on the occurrence of gastrointestinal cancers (RR 0.94, 95% CI 0.83-1.06, I(2) = 54.0%). The heterogeneity seemed to be explained by bias risk (low-bias risk trials RR 1.04, 95% CI 0.96-1.13 compared to high-bias risk trials RR 0.59, 95% CI 0.43-0.80, test of interaction P < 0.0005) and type of antioxidant supplement (beta-carotene potentially increasing and selenium potentially decreasing cancer risk). Antioxidant supplements had no significant effect on mortality in a random-effects model meta-analysis (RR 1.02, 95% CI 0.97-1.07, I(2) = 53.5%) but significantly increased mortality in a fixed-effect model meta-analysis (RR 1.04, 95% CI 1.02-1.07).

CONCLUSIONS

We could not find evidence that the studied antioxidant supplements prevented gastrointestinal cancers. On the contrary, they seem to increase overall mortality.

Expression and clinical significance of CacyBP/SIP in pancreatic cancer

AIMS

Calcyclin-binding protein or Siah-1-interacting protein (CacyBP/SIP), a component of the ubiquitin-mediated proteolysis, could bind SKP1-CUL1-F box protein complex and participate in beta-catenin degradation, which was found to be related to the malignant phenotypes of gastric cancer and renal cancer. However, the role of CacyBP/SIP in pancreatic cancer progression still remains unclear. Therefore, the aim of the present study was to investigate the expression and clinical significance of CacyBP/SIP in pancreatic cancer.

METHODS

Immunohistochemistry was carried out on paraffin-embedded sections of pancreatic cancer and normal pancreatic tissues. In addition, Western blot and semiquantitative RT-PCR were carried out to analyze mRNA and protein expression of CacyBP/SIP in 8 pairs of freshly resected pancreatic cancer and their adjacent nontumorous tissue.

RESULTS

CacyBP/SIP expression was significantly increased in pancreatic cancer tissue (28/68 or 41.2%) and correlated with differentiation degree, higher TNM (tumor, node, metastasis) stage and distance metastasis. Also, mRNA and protein expression of CacyBP/SIP were found to be at higher levels in almost all cancer tissues compared to adjacent tissues.

CONCLUSIONS

CacyBP/SIP protein might play an important role in the process of pancreatic carcinogenesis and high-level CacyBP/SIP expression might be related to the malignant potential of pancreatic cancer.

Antioxidant supplements for preventing gastrointestinal cancers

BACKGROUND

Oxidative stress may cause gastrointestinal cancers. The evidence on whether antioxidant supplements are effective in preventing gastrointestinal cancers is contradictory.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements in preventing gastrointestinal cancers.

SEARCH STRATEGY

We identified trials through the trials registers of the four Cochrane Review Groups on gastrointestinal diseases, The Cochrane Central Register of Controlled Trials in The Cochrane Library (Issue 2, 2007), MEDLINE, EMBASE, LILACS, SCI-EXPANDED, and The Chinese Biomedical Database from inception to October 2007. We scanned reference lists and contacted pharmaceutical companies.

SELECTION CRITERIA

Randomised trials comparing antioxidant supplements to placebo/no intervention examining occurrence of gastrointestinal cancers.

DATA COLLECTION AND ANALYSIS

Two authors (GB and DN) independently selected trials for inclusion and extracted data. Outcome measures were gastrointestinal cancers, overall mortality, and adverse effects. Outcomes were reported as relative risks (RR) with 95% confidence interval (CI) based on random-effects and fixed-effect model meta-analysis. Meta-regression assessed the effect of covariates across the trials.

MAIN RESULTS

We identified 20 randomised trials (211,818 participants), assessing beta-carotene (12 trials), vitamin A (4 trials), vitamin C (8 trials), vitamin E (10 trials), and selenium (9 trials). Trials quality was generally high. Heterogeneity was low to moderate. Antioxidant supplements were without significant effects on gastrointestinal cancers (RR 0.94, 95% CI 0.83 to 1.06). However, there was significant heterogeneity (I(2) = 54.0%, P = 0.003). The heterogeneity may have been explained by bias risk (low-bias risk trials RR 1.04, 95% CI 0.96 to 1.13 compared to high-bias risk trials RR 0.59, 95% CI 0.43 to 0.80; test of interaction P < 0.0005), and type of antioxidant supplement (beta-carotene potentially increasing and selenium potentially decreasing cancer risk). The antioxidant supplements had no significant effects on mortality in a random-effects model meta-analysis (RR 1.02, 95% CI 0.97 to 1.07, I(2) = 53.5%), but significantly increased mortality in a fixed-effect model meta-analysis (RR 1.04, 95% CI 1.02 to 1.07). Beta-carotene in combination with vitamin A (RR 1.16, 95% CI 1.09 to 1.23) and vitamin E (RR 1.06, 95% CI 1.02 to 1.11) significantly increased mortality. Increased yellowing of the skin and belching were non-serious adverse effects of beta-carotene. In five trials (four with high risk of bias), selenium seemed to show significant beneficial effect on gastrointestinal cancer occurrence (RR 0.59, 95% CI 0.46 to 0.75, I(2) = 0%).

AUTHORS' CONCLUSIONS

We could not find convincing evidence that antioxidant supplements prevent gastrointestinal cancers. On the contrary, antioxidant supplements seem to increase overall mortality. The potential cancer preventive effect of selenium should be tested in adequately conducted randomised trials.

Green tea consumption and the risk of pancreatic cancer in Japanese adults

OBJECTIVE

Green tea polyphenols have been shown to inhibit tumor growth in animal and in vitro studies. We examined the relationship between green tea consumption and the risk of death from pancreatic cancer in a large Japanese cohort.

METHODS

At baseline (1988-1990), study participants reported the frequency and amount of green tea consumption during the past year. They were followed-up for mortality until December 31, 2003. Relative risk and 95% confidence intervals were calculated from Cox proportional hazard models.

RESULTS

During an average follow-up of 13 years, we observed 292 pancreatic cancer deaths. In men and women combined, the relative risk was 1.23 (95% confidence interval, 0.84-1.80) for participants who consumed 7 or more cups of green tea per day as compared with those who consumed less than 1 cup per day, after adjustment for potential confounding factors. No significant trend in risk reduction was noted, with increasing consumption of green tea. We found no inverse association between cups of green tea consumed per day and the risk of pancreatic cancer in either men or women.

CONCLUSIONS

Our findings do not support the hypothesis that green tea consumption is associated with decreased risk of pancreatic cancer in humans.

Pancreatic carcinogenesis

Pancreatic cancer is an almost universally lethal disease. Research over the last two decades has shown that pancreatic cancer is fundamentally a genetic disease, caused by inherited germline and acquired somatic mutations in cancer-associated genes. Multiple alterations in genes that are important in pancreatic cancer progression have been identified, including tumor suppressor genes, oncogenes, and genome maintenance genes. Furthermore, the identification of noninvasive precursor lesions of pancreatic adenocarcinoma has led to the formulation of a multi-step progression model of pancreatic cancer and the subsequent identification of early and late genetic alterations culminating in invasive cancer. In addition, an increased understanding of the molecular basis of the disease has facilitated the identification of new drug targets enabling rational drug design. The elucidation of genetic alterations in combination with the development of high-throughput sensitive techniques should lead to the discovery of effective biomarkers for early detection of this malignancy. This review focuses mainly on the current knowledge about the molecular insights of the pathogenesis of pancreatic ductal adenocarcinoma.

Pancreatogram findings for carcinoma in situ (CIS) of the pancreas seen on endoscopic retrograde cholangiopancreatography and postoperative pancreatography of resected specimens: can CIS be diagnosed preoperatively?

BACKGROUND/AIMS

From 1992 to 2003, 7 carcinomata in situ (CIS) were incidentally discovered during microscopical observation of resected materials for advanced carcinomas of peripancreatic organs, of which 4 had undergone endoscopic retrograde cholangiopancreatography (ERCP) or postoperative pancreatography of the resected specimen (POP). In addition, 7 of 79 invasive ductal carcinomata (IDC) of the pancreas were accompanied by CIS > or =2 cm long. A total of 11 patients were reviewed here for pancreatographic findings for CIS of the pancreas.

METHODS

All resected pancreatobiliary materials were sliced serially at 5- to 8-mm intervals in a plane at right angles to the main pancreatic duct, referring to POP images.

RESULTS

Irregularity (I), non-continuous narrowing (N), granular defects (G), and dilatation (D) were seen in 78, 67, 33 and 22% on ERCP, respectively, and in 90, 70, 60 and 40% on POP, respectively.

CONCLUSIONS

I, N, G, and D are most important pancreatographic findings in ERCP and highly suggestive of CIS of the pancreas, so that whenever they are encountered, cytological and/or pathological examination of the pancreatic duct should be actively performed.

Expression of orotate phosphoribosyltransferase (OPRT) in hepatobiliary and pancreatic carcinoma

The purpose of this study was to clarify the role of orotate phosphoribosyltransferase (OPRT) in the progression of hepatobiliary and pancreatic carcinomas. Representative sections from 8 surgically resected pancreatic carcinomas, 5 gallbladder carcinomas and 19 hepatocellular carcinomas (HCCs) were examined microscopically. Sites of pancreatic intraepithelial neoplasia (PanIN) were counted, and histologic subtypes of invasive ductal carcinoma of the pancreas (IDC) were determined. Gallbladder carcinomas and HCCs were examined histologically, and the subtypes and spread patterns were assessed. Expression of OPRT was examined immunohistochemically. A total of 75 PanINs were identified. Expression of OPRT increased as lesions progressed from early to high-grade PanINs (PanIN-1A and -1B versus PanIN-2 and -3, p=0.0004). Three (37.5%) of the 8 pancreatic IDCs were positive for OPRT. In the remaining 5 cases, OPRT was expressed only in the neoplastic ducts adjacent to PanIN-3s. In gallbladder carcinomas, mucosal neoplastic epithelium showed dense cytoplasmic expression in 4 of the 5 cases, but expression was absent in the deeply invasive lesions. Among HCCs, 15 of the 19 cases were negative for OPRT in the central area of the tumor, but 8 of the 19 cases expressed OPRT in vascularly invasive lesions. Our data suggest that OPRT is involved in early events of pancreatic and gallbladder carcinogenesis and invasion of HCC.

Overview of antibacterial, antitoxin, antiviral, and antifungal activities of tea flavonoids and teas

Tea leaves produce organic compounds that may be involved in the defense of the plants against invading pathogens including insects, bacteria, fungi, and viruses. These metabolites include polyphenolic compounds, the six so-called catechins, and the methyl-xanthine alkaloids caffeine, theobromine, and theophylline. Postharvest inactivation of phenol oxidases in green tea leaves prevents oxidation of the catechins, whereas postharvest enzyme-catalyzed oxidation (fermentation) of catechins in tea leaves results in the formation of four theaflavins as well as polymeric thearubigins. These substances impart the black color to black teas. Black and partly fermented oolong teas contain both classes of phenolic compounds. A need exists to develop a better understanding of the roles of polyphenolic tea compounds in food and medical microbiology. This overview surveys and interprets our present knowledge of activities of tea flavonoids and teas against foodborne and other pathogenic bacteria, virulent protein toxins produced by some of the bacteria, virulent bacteriophages, pathogenic viruses and fungi. Also covered are synergistic, mechanistic, and bioavailability aspects of the antimicrobial effects. Further research is suggested for each of these categories. The herein described findings are not only of fundamental interest, but also have practical implications for nutrition, food safety, and animal and human health.

Antioxidant supplements for preventing gastrointestinal cancers

BACKGROUND

Oxidative stress may cause gastrointestinal cancers. The evidence on whether antioxidant supplements are effective in preventing gastrointestinal cancers is contradictory.

OBJECTIVES

To assess the beneficial and harmful effects of antioxidant supplements in preventing gastrointestinal cancers.

SEARCH STRATEGY

We identified trials through the trials registers of the four Cochrane Review Groups on gastrointestinal diseases, The Cochrane Central Register of Controlled Trials on The Cochrane Library (Issue 1, 2003), MEDLINE, EMBASE, LILACS, and SCI-EXPANDED from inception to February 2003, and The Chinese Biomedical Database (March 2003). We scanned reference lists and contacted pharmaceutical companies.

SELECTION CRITERIA

Randomised trials comparing antioxidant supplements to placebo/no intervention examining the incidence of gastrointestinal cancers.

DATA COLLECTION AND ANALYSIS

Two reviewers independently selected trials for inclusion and extracted data. The outcome measures were incidence of gastrointestinal cancers, overall mortality, and adverse events. Outcomes were reported as relative risks (RR) with 95% confidence interval (CI) based on fixed and random effects meta-analyses.

MAIN RESULTS

We identified 14 randomised trials (170,525 participants), assessing beta-carotene (9 trials), vitamin A (4 trials), vitamin C (4 trials), vitamin E (5 trials), and selenium (6 trials). Trial quality was generally high. Heterogeneity was low to moderate. Neither the fixed effect (RR 0.96, 95% CI 0.88 to 1.04) nor random effects meta-analyses (RR 0.90, 95% CI 0.77 to 1.05) showed significant effects of supplementation with antioxidants on the incidences of gastrointestinal cancers. Among the seven high-quality trials reporting on mortality (131,727 participants), the fixed effect (RR 1.06, 95% CI 1.02 to 1.10) unlike the random effects meta-analysis (RR 1.06, 95% CI 0.98 to 1.15) showed that antioxidant supplements significantly increased mortality. Two low-quality trials (32,302 participants) found no significant effect of antioxidant supplementation on mortality. The difference between the mortality estimates in high- and low-quality trials was significant by test of interaction (z = 2.10, P = 0.04). Beta-carotene and vitamin A (RR 1.29, 95% CI 1.14 to 1.45) and beta-carotene and vitamin E (RR 1.10, 95% CI 1.01 to 1.20) significantly increased mortality, while beta-carotene alone only tended to do so (RR 1.05, 95% CI 0.99 to 1.11). Increased yellowing of the skin and belching were non-serious adverse effects of beta-carotene. In four trials (three with unclear/inadequate methodology), selenium showed significant beneficial effect on gastrointestinal cancer incidences.

REVIEWERS' CONCLUSIONS

We could not find evidence that antioxidant supplements prevent gastrointestinal cancers. On the contrary, they seem to increase overall mortality. The potential cancer preventive effect of selenium should be studied in adequately conducted randomised trials.