Modulation of methylcholanthrene-induced carcinogenesis in the uterine cervix of mouse by indomethacin

Comparison of serum and tissue levels of trace elements in different models of cervical cancer

Cervical cancer is a leading cause of death by cancer among women worldwide. It is necessary to develop and refine cervical cancer models to more accurately reflect human tumor type. The relevance of cervical cancer to trace element was studied in this paper. By means of quantitative trace element analysis in models and patients with cervical cancer, the tissue and serum levels of trace elements in papillomaviruses-induced cancer models were more similar to that of patients than the levels in models induced by HeLa cell and methylcholanthrene. The results reflect papillomaviruses model most accurately mimic in vivo carcinogenesis of patients with cervical cancer. It will have a superior predictive value over HeLa cell and methylcholanthrene models in pre-clinical trials. The papillomaviruses-induced cervical cancer can provide more reliable models for testing the efficacy of drugs in treating human cancers.

Potential role of probiotics on colorectal cancer prevention

Background

Colorectal cancer represents the most common malignancy of the gastrointestinal tract. Owing to differences in dietary habits and lifestyle, this neoplasm is more common in industrialized countries than in developing ones. Evidence from a wide range of sources supports the assumption that the link between diet and colorectal cancer may be due to an imbalance of the intestinal microflora.

Discussion

Probiotic bacteria are live microorganisms that, when administered in adequate amounts, confer a healthy benefit on the host, and they have been investigated for their protective anti-tumor effects. In vivo and molecular studies have displayed encouraging findings that support a role of probiotics in colorectal cancer prevention.

Summary

Several mechanisms could explain the preventive action of probiotics against colorectal cancer onset. They include: alteration of the intestinal microflora; inactivation of cancerogenic compounds; competition with putrefactive and pathogenic microbiota; improvement of the host’s immune response; anti-proliferative effects via regulation of apoptosis and cell differentiation; fermentation of undigested food; inhibition of tyrosine kinase signaling pathways.

Cancer-preventing attributes of probiotics: an update

Cancer is a serious global public health problem. Cancer incidence and mortality have been steadily rising throughout the past century in most places of the world. There are several epidemiological evidences that support a protective role of probiotics against cancer. Lactic acid bacteria and their probioactive cellular substances exert many beneficial effects in the gastrointestinal tract, and also release various enzymes into the intestinal lumen and exert potential synergistic (LAB) effects on digestion and alleviate symptoms of intestinal malabsorption. Consumption of fermented dairy products with LAB may elicit anti-tumor effects. These effects are attributed to the inhibition of mutagenic activity, the decrease in several enzymes implicated in the generation of carcinogens, mutagens, or tumor-promoting agents, suppression of tumors, and epidemiology correlating dietary regimes and cancer. Specific cellular components in lactic acid bacteria seem to induce strong adjuvant effects including modulation of cell-mediated immune responses, activation of the reticulo-endothelial system, augmentation of cytokine pathways, and regulation of interleukins and tumor necrosis factors. Studies on the effect of probiotic consumption on cancer appear promising, since recent in vitro and in vivo studies have indicated that probiotic bacteria might reduce the risk, incidence and number of tumors of the colon, liver and bladder. The protective effect against cancer development may be ascribed to binding of mutagens by intestinal bacteria, may suppress the growth of bacteria that convert procarcinogens into carcinogens, thereby reducing the amount of carcinogens in the intestine, reduction of the enzymes beta-glucuronidase and beta-glucosidase and deconjugation of bile acids, or merely by enhancing the immune system of the host. There are isolated reports citing that administration of LAB results in increased activity of anti-oxidative enzymes or by modulating circulatory oxidative stress that protects cells against carcinogen-induced damage. These include glutathione-S-transferase, glutathione, glutathione reductase, glutathione peroxidase, superoxide dismutase and catalase. However, there is no direct experimental evidence for cancer suppression in human subjects as a result of the consumption of probiotic cultures in fermented or unfermented dairy products, but there is a wealth of indirect evidence based largely on laboratory studies.

Intestinal microflora: probiotics and autoimmunity

Lactobacillus casei strain Shirota (LcS) has been demonstrated to have beneficial effects in numerous murine disease models via host immune modulation. It has also been reported that LcS induced recovery of host immune responses that were decreased by treatment with carcinogens and augmented the natural killer activity and T-cell functions of host immune cells. After LcS is ingested by the host, it is incorporated into M cells in Peyer's patches (PP) and digested to form active components. In PP, macrophages or dendritic cells that phagocytosed LcS gained the ability to produce several cytokines, especially tumor necrosis factor-alpha. The components of LcS digested in PP were then recognized through toll-like receptor 2 in antigen-presenting cells, resulting in the production of several cytokines that elicited varied responses in host immune cells. Also, it was observed by 2D-PAGE analyses that the expression level and/or the phosphorylation of some proteins in PP and mesenteric lymph nodes were definitely altered by the ingestion of LcS, providing more evidence of cellular responses. These results suggest that some probiotic bacteria have the potential to augment or modify the host immune function through the regulation of host immune cells.

High cyclooxygenase-2 expression in cervical adenocarcinomas

OBJECTIVE

The purpose of this study was to examine the relationships between cyclooxygenase-2 (COX-2) expression and prognostic factors in cervical carcinomas.

METHODS

We studied COX-2 expression in 53 women with cervical cancers, including 35 squamous cell carcinomas (SCCs), 1 adenosquamous cell carcinoma (ASCC), and 17 adenocarcinomas (ACs), using commercially available polyclonal antibodies on Formalin-fixed, paraffin-embedded tissues. Normal cervical tissues were obtained as from other patients with uterine myomas treated with a total hysterectomy (n = 16). The immunoreactivity was quantified using an immunohistochemical scoring system that approximates the use of an image analysis-based system.

RESULTS

Twenty-two cervical cancer tissues (41.5%), including 10 SCCs and 12 ACs, expressed COX-2 at a moderate to strong level, which significantly, differed from the negligible expression found in the control group of 16 normal cervical tissues (P = 0.001). Different cell types showed significantly different expression levels of COX-2 (SCC at 28.6% vs AC at 70.6%, P = 0.004). The presence of deep stromal invasion (n = 40) showed a significant inverse relationship to COX-2 expression (32.5% vs 69.2%, P = 0.02). The expression of COX-2 in well-differentiated carcinomas was significantly increased compared to that in moderately and poorly differentiated carcinomas (72.7% vs 33.3%, respectively, P = 0.018).

CONCLUSIONS

Overexpression of COX-2 was found in both SCC and AC, but SCCs showed infrequent and low expression. These findings suggest that increased COX-2 expression may play an important role in cervical adenocarcinomas.

Aspirin and epithelial ovarian cancer

BACKGROUND

Epidemiological evidence suggests that chronic inflammation may influence ovarian carcinogenesis. The study objective was to examine the association between the commonly used anti-inflammatory drug aspirin and epithelial ovarian cancer.

METHODS

The authors conducted a case-control study based in the New York University Women's Health Study cohort enrolled between 1985 and 1991 in New York City. After a median follow-up period of 12 years, 68 incident cases of epithelial ovarian cancer were identified. Data about regular aspirin use were collected during the 1994-1996 follow-up questionnaire. Using a case-control study design, 10 controls per case were randomly selected among study participants who matched the case by age and menopausal status. Conditional logistic regression analysis was used to study the relationships between aspirin and epithelial ovarian cancer by generating odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Relative to no aspirin use, the OR for epithelial ovarian cancer among women who reported aspirin use three or more times per week for a period of at least 6 months was 0.60 (95% CI 0.26, 1.38), after adjustment for age at menarche, parity, oral contraceptive use, and first-degree family history of breast cancer before age 50. Among recent, within the previous 5 years, users of aspirin, the adjusted OR was 0.36 (95% CI 0.11, 1.18).

CONCLUSION

Although confidence intervals included unity, the observed risk estimates seem to be compatible with previous studies suggesting that regular aspirin use could be inversely associated with risk of epithelial ovarian cancer.

Enhancement of natural killer cytotoxicity delayed murine carcinogenesis by a probiotic microorganism

Regulation of innate immunity may be an effective means of cancer control. Delaying cancer onset is regarded as an important mode of action in cancer prevention. We have been investigating the chemopreventive mechanisms of Lactobacillus casei Shirota (LcS), a probiotic strain. In this study, we evaluated the effect of LcS on tumor onset and the involvement of natural killer (NK) cells using a 3-methylcholanthrene-induced carcinogenesis model. C3H/HeN mice were divided into three groups, according to treatment: vehicle-treated, treated with vehicle only; control, 3-methylcholanthrene treated; LcS, 3-methylcholanthrene and LcS treated. 3-Methylcholanthrene was injected intradermally at 7 weeks of age. LcS was mixed into the diet (0.05%, w/w), which the mice were fed from the day of 3-methylcholanthrene injection onward. Tumor incidence was observed weekly. Profiles of splenic NK cells, in vitro cytotoxicity and the proportion, in the early stage of carcinogenesis were analyzed at 5 weeks after the injection. The tumor suppressive effect of LcS was also evaluated in a beige mouse model that is genetically deficient in NK cells. LcS delayed tumor onset and reduced tumor incidence in the results with C3H/HeN mice (P< 0.05). More specifically, tumor incidence in the control group was 33% at 6 weeks after the injection and 83% at 11 weeks as opposed to 0 and 42%, respectively, in the LcS group. NK cell cytotoxicity was significantly higher than in the control group, and the number of NK cells also increased in the LcS group of C3H/HeN mice. However, LcS failed to suppress tumorigenesis in the beige mouse. These findings suggest that enhancement of the cytotoxicity of NK cells by LcS delays tumor onset.

Indomethacin suppresses the growth of colon 26, Meth-A and FM3A tumors in mice by reducing the prostaglandin E2 content and telomerase activity in tumor tissues

The antitumor effect of indomethacin on Colon 26, Meth-A and FM3A tumors was investigated in mice. The prostaglandin E2 content in tumor tissues was assayed to find out if indomethacin acts on tumors, and the telomerase activity in tumors and somatic tissues (testis, liver, spleen and colon) was also monitored during indomethacin treatment. Growth of Colon 26, Meth-A and FM3A tumors was significantly (P < 0.001-0.05) suppressed by indomethacin compared to the untreated controls. The prostaglandin E2 content in the three tumors was markedly (P < 0.001) reduced by indomethacin. Telomerase activity in Colon 26 and FM3A tumors was significantly (P < 0.001) lower than that of untreated tumors (80% and 45% decrease versus the controls, respectively), and the activity in Meth-A tumor was slightly decreased (10% decrease versus the control) by indomethacin. Telomerase activity in the somatic tissues was not significantly affected by indomethacin. In summary, this study shows the effectiveness of indomethacin as an antitumor agent against three types of tumors, and suggests that indomethacin affects telomerase activity in tumors in vivo.

Effectiveness of indomethacin as an antitumor agent in Colon 26-bearing conventional and nude mice, and telomerase activity in the tumors

The antitumor effect of indomethacin on Colon 26 tumor was investigated in conventional (CDF1) and nude mice (BALB/c nu/nu), and the telomerase activity in the tumor tissues treated with indomethacin was monitored. Growth of Colon 26 tumor was significantly suppressed with indomethacin treatment compared to the controls both in conventional and nude mice. And telomerase activity in the tumor tissues noticeably declined in contrast to normal somatic tissues (testis, liver and colon), which were not affected by indomethacin treatment. We also showed that indomethacin can suppress tumor growth in association with a preferential decrease in telomerase activity in tumor tissues both in conventional and nude mice to the same extent. This study suggests a method for investigating the mechanism of tumor suppression by indomethacin, and suggests that indomethacin might be useful as a novel agent for human cancer therapy.

Recovery from 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone-induced immunosuppression in A/J mice by treatment with nonsteroidal anti-inflammatory drugs

BACKGROUND

We have previously reported that nonsteroidal anti-inflammatory drugs inhibit lung tumorigenesis induced by the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in mice.

PURPOSE

The aims of this study were to determine if NNK suppresses humoral (i.e., antibody) and cellular immune responses in mice and if nonsteroidal anti-inflammatory drugs could attenuate these immune responses.

METHODS

Female A/J mice (7-8 weeks old) were fed nonsteroidal anti-inflammatory drugs starting 2 weeks before the beginning of NNK treatment (9.1 mg per mouse in total) and continuing through the 7 weeks of NNK treatment. Eight groups (two control groups and six experimental groups) of 10 mice each were used per experiment. Animals in the two control groups received the same diet and water as animals in the six experimental groups; one control group received no nonsteroidal anti-inflammatory drugs or NNK and the other control group received only NNK. The primary humoral and cellular immune responses to the various treatments were assayed by the plaque-forming cell technique and by measurement of natural killer cell cytotoxic activity, respectively. At the end of each experiment, the animals were killed, blood was collected, plasma was prepared, and levels of the immune system modulator prostaglandin E2 were measured.

RESULTS

NNK treatment inhibited the plaque-forming cell response by approximately 50%; this inhibition was attenuated by treatment with sulindac or acetylsalicylic acid (P = .0001 for both). In contrast, treatment with naproxen, which had no chemopreventive (i.e., tumor inhibitory) efficacy, further increased by 26% (P = .05) the immunosuppressive effect of NNK. The cytotoxic activity of splenic natural killer cells against YAC-1 cells was reduced by 60% (P = .002); treatment with acetylsalicylic acid (254 mg/kg of diet) reduced the NNK-induced natural killer cell cytotoxicity inhibition by 50% (P = .02), whereas the administration of the specific cyclooxygenase-2 inhibitor NS-398 (7 mg/kg of diet) resulted in an almost complete recovery (approximately 95%, P = .04) of natural killer cell activity. The prostaglandin E2 plasma concentration was approximately 100% greater in NNK-treated mice than in untreated mice. Treatment of the mice with nonsteroidal anti-inflammatory drugs attenuated this elevation (from approximately 25% to 100%), and NS-398 (7 mg/kg of diet) was the most effective (100%).

CONCLUSIONS AND IMPLICATIONS

The ability of various nonsteroidal anti-inflammatory drugs to inhibit NNK-induced carcinogenesis appears to be directly related to the ability of these drugs to inhibit NNK-induced immunosuppression. Our results suggest that the chemopreventive effect of nonsteroidal anti-inflammatory drugs may be mediated through the modulation of prostaglandin E2 synthesis.

Effects of nonsteroidal antiinflammatory drugs on oxidative pathways in A/J mice

The tobacco-specific N-nitrosamine, NNK, is a potent carcinogen in laboratory animals. The authors have shown previously that NNK-induced lung tumorigenesis in A/J mice can be reduced significantly by certain nonsteroidal antiinflammatory drugs (NSAIDs), such as sulindac, ibuprofen, or piroxicam treatments. In this study, the authors investigated whether NSAIDs could reduce NNK-induced oxidative, DNA damage and/or inhibit endogenous lipid peroxidation, or prostaglandin E2 (PGE2) synthesis in A/J mice. In the first experiment, A/J mice were gavaged with NNK (112 mumol/kg b.w.) three times a week while being maintained on a diet to which either ibuprofen (263 mg/kg diet), naproxen (230 mg/kg), sulindac (123 mg/kg), piroxicam (25 mg/kg), indomethacin (5 mg/kg), or no NSAIDs had been added. Levels of 8-OH-dG in the DNA of lung and liver were measured by high-performance liquid chromatography with electron capture detector. Treatment with NSAIDs had no significant effects on the endogenous or NNK-induced formation of 8-OH-dG in the lung of the mice. In a second experiment, after treatment of A/J mice with NSAIDs for 2 weeks, lipid peroxidation was assayed by determining thiobarbituric acid-reactive substances (TBA-RS) in lung tissues, and prostaglandin E2 levels were measured in plasma by an enzyme immunoassay. Treatments with some NSAIDs lowered the levels of lipid peroxidation and plasma levels of PGE2 below basal levels. Taken together, these results suggest that the inhibition of NNK-induced lung tumorigenesis by NSAIDs is more likely related to an inhibition of prostaglandin synthesis than to a direct inhibition of lipid peroxidation or oxidative DNA damage induced by NNK.

Preclinical efficacy evaluation of potential chemopreventive agents in animal carcinogenesis models: methods and results from the NCI Chemoprevention Drug Development Program

In the NCI, Chemoprevention Branch drug development program, potential chemopreventive agents are evaluated for efficacy against chemical carcinogen-induced tumors in animal models. This paper summarizes the results of 144 agents in 352 tests using various animal efficacy models. Of these results, 146 were positive, representing 85 different agents. The target organs selected for the animals model are representative of high-incidence human cancers. The assays include inhibition of tumors induced by MNU in hamster trachea, DEN in hamster lung, AOM in rat colon (including inhibition of AOM-induced aberrant crypts), MAM in mouse colon, DMBA and MNU in rat mammary glands, DMBA promoted by TPA in mouse skin, and OH-BBN in mouse bladder. The agents tested may be classified into various pharmacological and chemical structural categories that are relevant to their chemopreventive potential. These categories include antiestrogens, antiinflammatories (e.g., NSAIDs), antioxidants, arachidonic acid metabolism inhibitors, GST and GSH enhancers, ODC inhibitors, protein kinase C inhibitors, retinoids and carotenoids, organosulfur compounds, calcium compounds, vitamin D3 and analogs, and phenolic compounds (e.g., flavonoids). The various categories of compounds have different spectra of efficacy in animal models. In hamster lung, GSH-enhancing agents and antioxidants appear to have high potential for inhibiting carcinogenesis. In the colon, NSAIDs and other antiinflammatory agents appear particularly promising. Likewise, NSAIDs are very active in mouse bladder. In rat mammary glands, retinoids and antiestrogens (as would be expected) are efficacious. Several of the chemicals evaluated also appear to be promising chemopreventive agents based on their activity in several of the animal models. Particularly, the ODC inhibitor DFMO was active in the colon, mammary glands, and bladder models, while the dithiolthione, oltipraz, was efficacious in all the models listed above (i.e., lung, colon, mammary glands, skin, and bladder).

Long term tumorigenicity of a single application of indomethacin or Amuno in adolescent and in adult male Sprague Dawley rats

200 adolescent (Group I) and 200 adult male Sprague Dawley rats (Group II) were divided into 4 subgroups of 50 animals each. Animals were treated on the 29th (Group I) or 98th day of life (Group II) either with acetone or Amuno carrier in acetone or Amuno on acetone (2.5 mg indomethacin/100 g animal weight in acetone) or with the pure substance indomethacin 2.5 mg/100 g of animal weight in acetone, giving a single application on the shaved dorsal skin. Subsequently the animals remained under observation until their deaths, followed by autopsy and histopathologic examination of several organs. The rats treated with Amuno of indomethacin in the adolescent stage showed lower body weights and a shorter total survival time. The adolescent animals treated with Amuno or indomethacin showed a significantly higher rate of interstitial testicular tumors of the Leydig tumor type, adenomas and adenocarcinomas of the small and large intestine as well as hepatocellular tumors. The total number of neoplasias was higher in the animals treated with Amuno or indomethacin compared to those treated with acetone or carrier with acetone. Application of Amuno or indomethacin also resulted in a higher rate of hyperplasias (sole of foot, lymph nodes, prostate). The impairment of the synthesis of prostaglandins caused by indomethacin apparently results in starting complex pathomechanisms which have effects until the late death of the animals. Adolescent animals were affected more frequently by the application of indomethacin as were already adult animals.

Effects of NSAIDs on NNK-induced pulmonary and gastric tumorigenesis in A/J mice

Non-steroidal anti-inflammatory drugs (NS-AIDs) are among the most widely prescribed drugs. In this study, we compared the efficacies of four NSAIDs to inhibit lung tumorigenesis in A/J mice. The tobacco-specific carcinogen, 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), was given in drinking water between week 0 and week +7. Groups of 25 mice were fed sulindac (123 mg/kg diet), ibuprofen (263 mg/kg), piroxicam (25 mg/kg) or naproxen (230 mg/kg) in AIN-76A diet from week -2 to the end of the bioassay (week +23). Sulindac was the most effective inhibitor and reduced lung tumor multiplicity by 51%. Ibuprofen and piroxicam reduced lung multiplicity by 38% and 30%, respectively. Naproxen demonstrated no inhibitory capacity. Forestomach tumor multiplicity and incidence were both reduced by sulindac and ibuprofen. Sulindac administered from week -2 to week +7 was less effective (28% inhibition) than when given throughout the bioassay. Sulindac induced more intestinal adhesions than any other NSAID and was directly related to the cumulative dose of sulindac. These results show that chemoprevention of lung tumorigenesis by NSAIDs is not limited to sulindac although it is the most effective.

Cancer chemoprevention. A review of ongoing clinical studies

The mass of experimental data on various possibilities of inhibiting the carcinogenic process is growing rapidly. However, the biological complexity of carcinogenesis and the intrinsic limitations of the animal models make it often very difficult to identify the real potentially effective agents among the hundreds currently being proposed. In fact, more than 600 potentially chemopreventive agents have been identified and approximately 30 of them are presently being tested in humans. The great heterogeneity of these compounds (they belong to over 20 different classes of chemicals) might be a positive feature as it indicates that a variety of approaches is possible and that the options for selecting effective compounds will be numerous. In recent years, what could be called 'clinical chemoprevention' (that is controlled studies to evaluate in human subjects the efficacy of potentially chemopreventive agents) has developed considerably: according to American estimates 4 chemopreventive agents were tested clinically in 1981, 10 in 1985 and 18 in 1988. The number of reported preclinical investigations was 10 in 1985 and 75 in 1988. This rapid expansion has obviously led to some confusion in terminology and in the evaluation of primary results; at present there is still a need for further investigations to better define clinical chemoprevention and to differentiate it from chemotherapy.