Tumor Promoters: Tennant's Response

This study was undertaken in an attempt to confirm the increased bile-acid concentration in association with nuclear dehydrogenating Clostridia (NDC) in the faeces of colorectal cancer patients. We have studied 37 patients with colorectal cancer and 36 control patients with no known gastrointestinal disease. Stool specimens were obtained for biochemical analysis (total faecal bile acid (FBA), lithocholic deoxycholic and cholic acids) and NDC isolation. The mean total FBA concentration (tmol/g) in the control group was 20-5 + 22 (s.e.) significantly higher (P <0.001) than the colorectal-cancer group (11-8 + 0.7). There was no statistically significant difference in the percentage distribution of the individual FBAs measured. NDC were isolated from the faeces of 640O/ of colorectal-cancer patients and 15% of control patients, this difference being statistically significant (P<0.001). These results suggest that bacteria capable of metabolizing steroids may be implicated in the aetiology of colorectal cancer. However, the relationship between FBA and colorectal cancer requires further evaluation. The disease is commonest in countries with a "Westernized" civilization , and at present Scotland has one of the highest recorded incidences of colo-rectal cancer in the world (36.2 per 100,000 population; Calman & Kemp, 1976). Epidemiological studies encompassing genetic, cultural, environmental and economic factors suggest that diet, in particular an increased intake of fat and animal protein, correlates best with the incidence of colorectal cancer (Haenzel et al. Although no ingested substance has been found to be carcinogenic to the large bowel mucosa (La Mont & O'Gorman, 1978), the observations of the epidemi-ologists could be explained by the hypothesis put forward by Hill and his colleagues (Aries et al., 1969; Hill et al., 19e71). Hill points out that diet has a significant influence on the intestinal substrate, digestive enzymes and large-bowel flora. He postulates that biochemically active bacteria in the bowel flora may degrade the intestinal substrate, thereby producing carcinogens or co-carcinogens. The bile acids have been a popular substrate for investigation, since their faecal content is related to fat intake (Antonis & Bersohn, 1962) and their acid steroid molecular structure is not far removed from that of the polycyclic aromatic carcinogens. In 1971 Hill and his colleagues published a study of healthy Scots and Ugandans, a population with a low incidence of colo-rectal cancer (Hill & Aries, 1971). They found that the Scots ate more fat, ex-creted more acid steroids in their faeces, degraded their faecal steroids further, and had more biochemically …