Modulation of gene expression in subjects at risk for colorectal cancer by the chemopreventive dithiolethione oltipraz.

Prolonged exposure to mutagenic substances is strongly associated with an individual's risk of developing colorectal cancer. Clinical investigation of oltipraz as a chemopreventive agent is supported by its induction of the expression of detoxication enzymes in various tissues, and its protective activity against the formation of chemically induced colorectal tumors in animals. The goals of the present study were: to determine if oltipraz could induce detoxicating gene expression in human tissues; to identify effective non-toxic doses for more extensive clinical testing; and to establish a relationship between effects in the colon mucosa and those in a more readily available tissue, the peripheral mononuclear cell. 24 evaluable patients at high risk for colorectal cancer were treated in a dose-finding study with oltipraz 125, 250, 500, or 1,000 mg/m2 as a single oral dose. Biochemical analysis of sequential blood samples and colon mucosal biopsies revealed increases in glutathione transferase activity at the lower dose levels. These effects were not observed at the higher doses. More pronounced changes were observed in detoxicating enzyme gene expression in both tissues at all doses. Peripheral mononuclear cell and colon mRNA content for gamma-glutamylcysteine synthetase (gamma-GCS) and DT-diaphorase increased after dosing to reach a peak on day 2-4 after treatment, and declined to baseline in the subsequent 7-10 d. The extent of induction of gene expression in colon mucosa reached a peak of 5.75-fold for gamma-GCS, and a peak of 4.14-fold for DT-diaphorase at 250 mg/m2 ; higher doses were not more effective. Levels of gamma-GCS and DT-diaphorase correlated closely (P < or = 0.001) between peripheral mononuclear cells and colon mucosa both at baseline and at peak. These findings demonstrate that the administration of minimally toxic agents at low doses may modulate the expression of detoxicating genes in the tissues of individuals at high risk for cancer. Furthermore, peripheral mononuclear cells may be used as a noninvasive surrogate endpoint biomarker for the transcriptional response of normal colon mucosa to drug administration.

Glutathione S-transferase activity and glutathione S-transferase mu expression in subjects with risk for colorectal cancer.

The glutathione S-transferases (alpha, mu, and pi), a family of Phase II detoxication enzymes, play a critical role in protecting the colon mucosa by catalyzing the conjugation of dietary carcinogens with glutathione. We investigated the efficacy of using the glutathione S-transferase (GST) activity of blood lymphocytes and GST-mu expression as biomarkers of risk for colorectal cancer. GST activity was measured in the blood lymphocytes of control individuals (n = 67) and in the blood lymphocytes (n = 60) and colon tissue (n = 34) of individuals at increased risk for colon cancer. Total GST activity was determined spectrophotometrically with the use of 1-chloro-2,4-dinitrobenzene as a substrate. The ability to express the um subclass of GST was determined with the use of an ELISA. Although interindividual variability in the GST activity of blood lymphocytes was greater than 8-fold (range, 16.7-146.8 nmol/min/mg), the GST activity of blood lymphocytes and colon tissue within an individual was constant over time and was unrelated to sex, age, or race. The GST activity of blood lymphocytes from high-risk individuals was significantly lower than that of blood lymphocytes from control individuals (P < or = 0.004). No association was observed between the frequency of GST-mu phenotype and risk for colorectal cancer. Blood lymphocytes from high-risk individuals unable to express GST-mu had lower levels of GST activity than did those from control subjects with the GST-mu null phenotype; however, this difference was significant in male subjects only (P < or = 0.006). Analysis of paired samples of blood lymphocytes and colon tissue indicated a strong correlation between the GST activity of the two tissue types (Spearman's rank correlation, r = 0.87; P < or = 0.0001). The GST activity of blood lymphocytes may be used to identify high-risk individuals with decreased protection from this Phase II detoxication enzyme who may benefit from clinical trials evaluating GST modulators as chemopreventive agents for colorectal cancer. The GST activity of blood lymphocytes may also be used in colorectal cancer chemoprevention trials to monitor the responsiveness of colon tissue to regimens that modify Phase II detoxication enzymes.

Preclinical and clinical evaluation of broccoli supplements as inducers of glutathione S-transferase activity.

Previous studies suggest that cruciferous vegetables may provide protection against carcinogen exposure by inducing detoxification enzymes. ICR(Ha) mice were gavaged with broccoli tablets (1 g/kg), and colon tissues were collected after treatment. Glutathione S-transferase (GST) activity was assayed and peaked on days 1 and 2 after treatment, respectively (P = 0.03). Elevations in GST activity were attributed to the increased expression of mu and pi. These data supported a clinical assessment of broccoli supplements. Twenty-nine subjects at increased risk for colorectal cancer were randomized to group 1 (no cruciferous vegetables) or group 2 (broccoli supplements, 3 g/day) for 14 days. Blood samples and colon biopsies were obtained pre- and postintervention. No significant difference was observed between the GST activities of the control and broccoli supplementation groups posttreatment. Mean lymphocyte GST activity was 107% of baseline in the broccoli supplementation group (range, 79-158%) and 102% of baseline in the control group (range, 75-158 percent;). Correlation of the GST activities of blood lymphocytes and colon mucosa taken simultaneously suggested that the GST activity of blood lymphocytes may be used as a biomarker of the responsiveness of colon tissue to chemopreventive regimens. Future clinical studies evaluating cruciferous vegetables should consider using concentrated dietary supplements in subjects with a previous history of colorectal cancer.

Receptivity of African-American men to prostate cancer screening.

OBJECTIVE: The lifetime risk of prostate cancer among African-American men is two times higher than that of white men. Mortality from the disease is almost three times greater in African-Americans than in whites. This study assesses the receptivity of older (fifty to seventy-four years of age) African-American men (n = 86) in Chicago to periodic (annual and semiannual) prostate cancer screening. METHODS: A telephone survey conducted in January and February 1993, was used to collect data on subject sociodemographic background and medical history and to gather information on knowledge, attitudes, and beliefs about prostate cancer and screening. Univariate and multivariate analyses were carried out to identify factors associated with subject receptivity to annual and semiannual screening. RESULTS: Logistic regression analyses revealed that receptivity to annual and semiannual (every six months) examination is strongly associated with the degree to which screening is perceived as a salient and coherent (i.e., important, effective, and convenient) preventive health behavior. An additional factor independently associated with willingness to go through semiannual screening was subjects' awareness that African-American men are at increased risk for prostate cancer compared to white men. CONCLUSIONS: Findings from this study suggest that African-American men are willing to undergo prostate screening and are more receptive to annual than semiannual screening. Participation in screening may be facilitated by the provision of health education messages that emphasize the salience and coherence of early detection and elevated population risk.

Implications of fine-needle aspiration in patients with resectable pancreatic cancer.

A 9-year experience with fine-needle aspiration (FNA) in patients with resectable pancreatic adenocarcinoma was reviewed to determine whether this procedure is associated with positive peritoneal cytology, peritoneal recurrences, or decreased survival in patients who had pancreatic resection with curative intent. Forty-one patients underwent pancreatic resection for primary pancreatic adenocarcinoma from July 1987 to February 1996. Nine patients had open biopsies prior to definitive resection and were excluded from this study. Of the remaining 32 patients, 21 (66%) had preoperative computed tomography-guided or fluoroscopically guided FNA biopsy of the pancreas for diagnosis. FNA confirmed the diagnosis of adenocarcinoma in 17 of 21 patients (80%). Fifteen of 21 FNA biopsies were performed in patients who went on to receive neoadjuvant chemoradiation. Twenty-eight of 32 patients (87%) had peritoneal washings at the time of laparotomy. Five patients had suspicious or positive washings (18%), and 23 patients had negative washings (82%). Three of 18 patients (16.7%) who had both FNA and peritoneal washings and 2 of 10 patients (20%) who had no FNA but had peritoneal washings had positive or suspicious peritoneal cytology. Eight of 32 patients ultimately failed in the peritoneum. Six of 21 patients (28%) who had prior FNA and 2 of 11 (18%) who had no prior FNA failed in the peritoneum. Although the number of patients is small, none of these differences proved to be statistically significant. No difference in median survival was observed between the FNA and no FNA groups. We conclude that FNA is a safe and useful tool to confirm the diagnosis of pancreatic cancer when patients are to be treated with neoadjuvant chemoradiation.

Adherence to continuous screening for colorectal neoplasia.

Continuous screening is defined as the periodic provision of an opportunity for diagnostic testing to a population of individuals who are asymptomatic and at increased risk for disease. If screening is offered periodically irrespective of response to an earlier screening invitation, this situation may be referred to as serial screening. When continuous screening is made available only to individuals who had tested previously, population member response is referred to as repeat screening. This study assessed adherence to serial- and repeat-colorectal cancer screening among older adult members of an independent practice association-type health maintenance organization (HMO) in two consecutive rounds of screening. In the first screening round, fecal occult blood tests (FOBTs) were sent to 1,565 subjects who were randomly assigned to receive usual care or behavioral interventions intended to encourage testing. Overall, 647 (41%) subjects completed and returned their tests. In the second screening round, FOBTs were mailed again to all subjects; however, the interventions were discontinued. Logistic regression analysis results shows that first-round testing was a significant independent predictor of serial adherence for subjects older than 65 years of age (odds ratio[OR] = 10.8) and those younger than 65 years of age (OR = 10.9); and a significant negative association between exposure to first-round intervention and serial adherence (OR = 0.5) was found among younger subjects. Among first-round adherers, age was significantly and positively related to repeat adherence (OR = 1.6). However, exposure to first-round intervention and having an abnormal FOBT result were significantly and negatively associated with repeat adherence (OR = 0.5 and OR = 0.4, respectively). The results of this study reported here indicate that previous screening is a strong predictor of serial adherence, and special efforts may be required to achieve high levels of serial and repeat adherence among younger adults. Additional research is needed to understand why persons with abnormal screening test results are unlikely to engage in repeat screening.

Screening for colorectal neoplasia: physicians' adherence to complete diagnostic evaluation.

This prospective study was done in a health maintenance organization colorectal cancer screening program to determine whether 166 persons found to have abnormal fecal occult blood test results typically underwent complete diagnostic evaluation (i.e., either colonoscopy or barium enema x-ray plus flexible sigmoidoscopy). Chart audit data show that 137 (82%) subjects contacted a physician to discuss follow-up. A complete diagnostic evaluation was recommended to only 52 (38%) patients who talked with a physician. Forty-two (81%) patients who were advised to get a complete diagnostic evaluation actually complied. Significant differences in clinical findings were observed for patients who did and did not have a complete diagnostic evaluation.

Employee response to a company-sponsored program of colorectal and prostate cancer screening.

Studies done in the mid-1970s documented increased risk for respiratory cancer and leukemia among employees in a chemical company manufacturing plant where chloromethyl ethers were used in production from 1948 to 1971. In the late 1980s, the company informed current and former employees about the results of follow-up studies which showed a moderation of risk of respiratory cancer and leukemia. New data showing elevated rates of mortality from colorectal, prostate, bladder, and pancreatic cancer in the population were also reported. Via mailed correspondence, the company made a no-cost program of colorectal and prostate cancer screening available to employees upon request; and information about bladder and pancreatic cancer was made available. Thirteen percent of employees in the population indicated interest in colorectal and prostate cancer screening (response). Thirty-one percent of these responders were screened (adherence). Multivariate analyses showed that education and length of employment in the plant were positively associated with response. Being white was positively associated with response for younger workers; while among older workers being male was positively associated with response. In terms of adherence, we found that older, more highly educated workers were more likely to have a screening examination. Findings indicate that employee participation in workplace-sponsored colorectal and prostate cancer screening can vary according to worker sociodemographic factors and length of employment in areas of potential exposure.

Chronic dosing of oltipraz in people at increased risk for colorectal cancer.

The dithiolethione oltipraz is being developed as a chemopreventive agent for many malignancies, including colorectal cancer, on the basis of its in vivo protective activity against chemically induced tumors in a variety of animal models. This protection has been associated with an enhanced capacity to detoxify reactive carcinogens and, more recently, with increased DNA repair. In a previous single-dose study, elevated detoxification gene expression was observed in the days after oltipraz dosing. Now, in this clinical study, we evaluated the effects of oltipraz when given over a 3-month period. Fourteen individuals with increased risk for colorectal cancer were randomly assigned to one of two oral doses (125 or 250 mg/m2) of oltipraz twice weekly for 12 weeks. Two of seven subjects at the 250 mg/m2 dosage required dose reductions, owing to significant fatigue. The 125 mg/m2 dose level was well tolerated by all patients. Blood or colon tissue (or both) for evaluation of glutathione, glutathione S-transferase, DT-diaphorase activity, and DT-diaphorase mRNA expression were obtained prior to treatment and at weeks 6, 12, and 16. No significant modulation of phase II detoxification enzymes was seen at either dose studied during this period. Phase II trials evaluating a tolerable regimen of oltipraz (as demonstrated in this study) and other possible mechanisms that may be responsible for the protective activity of oltipraz should be pursued.