Chromosome sensitivity to bleomycin-induced mutagenesis in lymphocytes from colorectal cancer patients under 40 years of age.

PURPOSE: The incidence of colorectal cancer in young adults (under 40 years of age) is rare. The reason for the occurrence in these patients may lie in their genetic background.
METHODS: We studied chromosomal fragility in peripheral blood lymphocytes of patients under the age of 40 with large bowel cancer. Lymphocytes from 24 subjects were examined: 10 untreated large bowel cancer patients under the age of 40 and 14 age-matched and sex-matched controls.
RESULTS: The mean number of spontaneous chromosomal breaks per cells (b/c) was significantly higher in the right-sided large bowel cancer patients (0.23 +/- 0.12 b/c) compared with the control group (0.09 +/- 0.04 b/c; P < 0.01), but with no significant difference between the left-sided colorectal cancer patients and the control group. Lymphocytes exposed to the radiomimetic agent, bleomycin, were arrested in methaphase and analyzed for chromosome fragility. Mean chromosome breaks per cell in the left-sided colorectal cancer patients (1.60 +/- 0.49 b/c) were significantly higher than in either the controls (0.72 +/- 0.31 b/c; P < 0.001) or the right-sided, large bowel cancer patients (0.91 +/- 0.24 b/c; P < 0.05).
CONCLUSIONS: The increased spontaneous chromosomal breaks in the right colon, as opposed to the increased mutagen-induced chromosomal breaks in the left colon, might indicate that in young colon cancer patients the occurrence of right-sided colon cancer is more likely to be genetically determined, whereas in left-sided colon cancer, environmental carcinogens might play a greater role.