Mutagen sensitivity and p53 expression in colorectal cancer in China

Objective-This study was designed to investigate DNA damage and/or repair c apability, non-random chromatid breakage, and p53 expression in patients wi th colorectal cancer. Methods-The bleomycin sensitivity assay was used in a case-control study to compare the DNA damage repair system between colorectal cancer patients an d controls. G-banding was used to search for non-random chromatid breaks. I mmunocytochemistry was used to investigate p53 expression in tumour tissues and adjacent normal tissues. Results-It was found that cases typically had a higher number of chromosome breaks than controls (0.84 v 0.69 breaks/cell, p <0.01). After correction by sex and age, the difference was still significant (F=4.38, p <0.05). The correlation coefficient between mutagen sensitivity and age was 0.31(p <0. 05) in controls and 0.18 (p >0.05) in cases. The ratio of odds ratios among bleomycin resistant, sensitive, and hypersensitive classes was 1:2.31:3.85 . Overexpression of p53 was detected in 25 of 47 tumour tissues independent of tumour stage. Cases who had a family history of cancer were susceptible to the p53 aberration (p<0.05). Chromosomes lp, 5q, and 14q were susceptib le to breakage in patients with colorectal cancer. Conclusion-Patients with colorectal cancer show increased bleomycin induced chromatid breaks and may have minor DNA repair deficiencies. p53 aberratio n is an early event in the development of colorectal cancer, but no definit e correlation is found between p53 overexpression and mutagen sensitivity.