Chemoprevention of colorectal cancer

The cyclooxygenase-2-selective inhibitors rofecoxib and celecoxib prevent colorectal neoplasia occurrence and recurrence

BACKGROUND & AIMS

Colorectal cancer is one of the leading causes of cancer death. Most colorectal cancers are believed to develop from colorectal adenomas. We examined the effect of the selective cyclooxygenase-2 inhibitors rofecoxib and celecoxib, nonselective nonsteroidal anti-inflammatory drugs, aspirin, and acetaminophen on colorectal neoplasia (colorectal cancer, colorectal adenoma, or both).

METHODS

This was a nested case-control study, which used data from a government insurance database on patients 65 years and older who underwent a diagnostic test or procedure for colorectal neoplasia between January and June 2001. Logistic regression models were used to determine the effect of exposure to the drugs of interest for at least 3 months on the occurrence or recurrence of colorectal neoplasia.

RESULTS

The control group included 2568 patients found to be free of colorectal neoplasia; 730 patients were diagnosed with colorectal adenoma, and 179 were diagnosed with colorectal cancer. Patients more likely to have colorectal adenoma (odds ratio, 95% confidence interval) were those diagnosed with colorectal adenoma (4.12, 3.27-5.18) or colorectal cancer (3.74, 2.32-6.03) in the previous 1-3 years and those with hemorrhage of the rectum or unspecified anemia in the prior month (3.19, 2.46-4.12). Exposures to rofecoxib (0.67, 0.46-0.98) and nonselective nonsteroidal anti-inflammatory drugs (0.41, 0.21-0.83) reduced the risk of colorectal adenoma. Rofecoxib, celecoxib, and nonselective nonsteroidal anti-inflammatory drugs were all protective against both neoplasias (0.64, 0.45-0.91; 0.73, 0.54-0.99; and 0.47, 0.26-0.86, respectively).

CONCLUSIONS

Rofecoxib, celecoxib, and nonselective nonsteroidal anti-inflammatory drugs seem to protect against the development of colorectal neoplasia.

Gene modulation by the cyclooxygenase inhibitor, sulindac sulfide, in human colorectal carcinoma cells: possible link to apoptosis

The mechanisms underlying the anti-tumorigenic properties of cyclooxygenase inhibitors are not well understood. One novel hypothesis is alterations in gene expression. To test this hypothesis sulindac sulfide, which is used to treat familial adenomatous polyposis, was selected to detect gene modulation in human colorectal cells at physiological concentrations with microarray analysis. At micromolar concentrations, sulindac sulfide stimulated apoptosis and inhibited the growth of colorectal cancer cells on soft agar. Sulindac sulfide (10 microm) altered the expression of 65 genes in SW-480 colorectal cancer cells, which express cyclooxygenase-1 but little cyclooxygenase-2. A more detailed study of 11 genes revealed that their expression was altered in a time- and dose-dependent manner as measured by real-time RT-PCR. Northern analysis confirmed the expression of 9 of these genes, and Western analysis supported the conclusion that sulindac sulfide altered the expression of these proteins. Cyclooxygenase-deficient HCT-116 cells were more responsive to sulindac sulfide-induced gene expression than SW-480 cells. However, this response was diminished in HCT-116 cells overexpressing cyclooxygenase-1 compared with normal HCT-116 cells suggesting the presence of cyclooxygenase attenuates this response. However, prostaglandin E2, the main product of cyclooxygenase, only suppressed the sulindac sulfide-induced expression of two genes, with little known biological function while it modulated the expression of two more. The most likely explanation for this finding is the metabolism of sulindac sulfide to inactive metabolites by the peroxidase activity of cyclooxygenase. In conclusion, this is the first report showing sulindac sulfide, independent of cyclooxygenase, altered the expression of several genes possibly linked to its anti-tumorigenic and pro-apoptotic activity.

NO-NSAIDs and cancer: promising novel agents

Three potential applications of NO-donating NSAIDs in human cancer include their use: as chemopreventive agents; against already developed cancers (chemotherapy); and for the control of cancer symptoms, notably cancer pain. The evidence to date of greater safety and enhanced efficacy of NO-donating NSAIDs underscores their potential to prevent colon cancer and overcome the limitations of traditional NSAIDs. NO-donating NSAIDs affect several pathways critical to colon carcinogenesis and this may explain in part their greater efficacy in colon cancer prevention as assessed in preclinical models.

Current treatment for liver metastases from colorectal cancer

The liver is the commonest site of distant metastasis of colorectal cancer and nearly half of the patients with colorectal cancer ultimately develop liver involved during the course of their diseases. Surgery is the only therapy that offers the possibility of cure for patients with hepatic metastatic diseases. Five-year survival rates after resection of all detectable liver metastases can be up to 40%. Unfortunately, only 25% of patients with colorectal liver metastases are candidates for liver resection, while the others are not amenable to surgical resection. Regional therapies such as radiofrequency ablation and cryotherapy may be offered to patients with isolated unresectable metastases but no extrahepatic diseases. Hepatic artery catheter chemotherapy and chemoembolization and portal vein embolization are often used for the patients with extensive liver metastases but without extrahepatic diseases, which are not suitable for regional ablation. For the patients with metastatic colorectal cancer beyond the liver, systemic chemotherapy is a more appropriate choice. Immunotherapy is also a good option when other therapies are used in combination to enhance the efficacy. Selective internal radiation therapy is a new radiation method which can be used in patients given other routine therapies without effects.

Hereditary colorectal cancer: screening and management

Colorectal cancer (CRC) affects approximately 6% of the US population, with equal distribution between men and women. It is hereditary in a high proportion of cases and is one of the most preventable cancers. Detection and removal of its precursor lesions, the adenomatous polyps, is the foundation of preventive strategies. However, once CRC is diagnosed, surgical resection is the only cure. The likelihood of cure is higher when CRC is diagnosed at an early stage. Dietary and lifestyle modifications have little, if any, impact on CRC. Endoscopy with polypectomy prevents cancer deaths. The most important issues are screening and surveillance by any of the recommended modalities. Remaining concerns include the choice of screening tests, optimal testing intervals, and cost effectiveness. Patients may be stratified by personal and family risk and by the specific strategies used. Newer developments in genetic testing and imaging, including virtual colonoscopy, hold promise for future prevention. Chemoprevention with nonsteroidal anti-inflammatory drugs may have a role in high-risk populations. Colonoscopy is the most effective method of CRC prevention.

Cerivastatin enhances the cytotoxicity of 5-fluorouracil on chemosensitive and resistant colorectal cancer cell lines

Cerivastatin is one of the synthetic 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors used for the treatment and prevention of hypercholesterolaemia. The observation that patients receiving this drug had a lower incidence at cancer led to our interest in using it as a putative anticancer agent. In this study, we tested the cytotoxicity of cerivastatin on a panel of 5-fluorouracil (5FU) sensitive and resistant cell lines in vitro. Cerivastatin was cytotoxic to both 5FU sensitive and resistant cells. Cerivastatin significantly augmented the cytotoxic effect of 5FU on drug sensitive (6-22-fold) and resistant (229-310-fold) cell lines. Cerivastatin and 5FU acted synergistically. Cerivastatin inhibited nuclear factor kappaB DNA binding activity. The enhancing effect of cerivastatin on 5FU was partially mevalonate pathway independent. Cerivastatin may allow successful 5FU therapy in chemoresistant patients.

Reduction of the incidence and mortality of rectal cancer by polypectomy: a prospective cohort study in Haining County

AIM: To reduce the incidence and mortality of rectal cancer and address the hypothesis that colorectal cancer often arise from precursor lesion (s), either adenomas or non-adenomatous polyps, by conducting a population-based mass screening for colorectal cancer in Haining County, Zhejiang, PRC.

METHODS: From 1977 to 1980, physicians screened the population of Haining County using 15 cm rigid endoscopy. Of over 240000 participants, 4076 of them were diagnosed with precursor lesions, either adenomas or non-adenomatous polyps, which were then removed surgically. All individuals with precursor lesions were followed up and reexamined by endoscopy every two to five years up to 1998.

RESULTS: After the initial screening, 953 metachronous adenomas and 417 non-adenomatous polyps were detected and removed from the members of this cohort. Further, 27 cases of colorectal cancer were detected and treated. Log-rank tests showed that the survival time among those cancer patients who underwent mass screening increased significantly compared to that of other colorectal cancer patients (P < 0.0001). According to the population-based cancer registry in Haining County, age-adjusted incidence and mortality of rectal cancer decreased by 41% and 29% from 1977-1981 to 1992-1996, respectively. Observed cumulative 20-year rectal cancer incidence was 31% lower than the expected in the screened group; the mortality due to rectal cancer was 18% lower than the expected in the screened group.

CONCLUSION: Mass screening for rectal cancer and precursor lesions with protocoscopy in the general population and periodical following-up with routine endoscopy for high-risk patients may decrease both the incidence and mortality of rectal cancer.

Aspirin potently inhibits oxidative DNA strand breaks: implications for cancer chemoprevention

Epidemiological studies have suggested that the use of aspirin is associated with a decreased incidence of human malignancies, particularly colorectal cancer. Since reactive oxygen species (ROS) are critically involved in multistage carcinogenesis, this study was undertaken to examine the ability of aspirin to inhibit ROS-mediated DNA damage. Hydrogen peroxide (H2O2)+Cu(II) and hydroquinone (HQ) + Cu(II) were used to cause oxidative DNA strand breaks in phiX-174 plasmid DNA. We demonstrated that the presence of aspirin at concentrations (0.5-2 mM) compatible with amounts in plasma during chronic anti-inflammatory therapy resulted in a marked inhibition of oxidative DNA damage induced by either H2O2/Cu(II) or HQ/Cu(II). The inhibition of oxidative DNA damage by aspirin was exhibited in a concentration-dependent manner. Moreover, aspirin was found to be much more potent than the hydroxyl radical scavengers, mannitol and dimethyl sulfoxide, in protecting against the H2O2/Cu(II)-mediated DNA strand breaks. Since the reduction of Cu(II) to Cu(I) is crucially involved in both H2O2/Cu(II)- and HQ/Cu(II)-mediated formation of hydroxyl radical or its equivalent, and the subsequent oxidative DNA damage, we examined whether aspirin could inhibit this Cu(II)/Cu(I) redox cycle. It was observed that aspirin at concentrations that showed the inhibitory effect on oxidative DNA damage did not alter the Cu(II)/Cu(I) redox cycle in either H2O2/Cu(II) or HQ/Cu(II) system. In addition, aspirin was not found to significantly scavenge H2O2. This study demonstrates for the first time that aspirin potently inhibits both H2O2/Cu(II)- and HQ/Cu(II)-mediated oxidative DNA strand breaks most likely through scavenging the hydroxyl radical or its equivalent derived from these two systems. The potent inhibition of oxidative DNA damage by aspirin may thus partially contribute to its anticancer activities observed in humans.