Objective To study the relationship between physical activity and onset of colorectal cancer in Chongqing populations.Methods In the hospital-based case-control study comprising 478 cases and 838 controls,who were local inhabitants admitted to 3 affiliated hospitals of the third military medical university during Jan 2002 to Jun 2004,with gender,age within 5 years and living places matched,the informations about diet and life styles were collected in manner of investigator-interviewing.The risk of disease was represented by using Odds Ratio and the 95% confidence interval.Results Heavy/very heavy labour intensity significantly increased risk of rectum cancer(OR=1.49,95%CI: 1.03-2.17),but did not associated with colon cancer risk.Keeping activity for a proper time each day(2-5 h/d) had a significant protective effect against rectum cancer(OR=0.6,95%CI: 0.36-0.99).Other factors such as BMI of 10-year-ago,exercise frequency,sleeping time,did not show significant association to colon or rectum cancer.Conclusion Physical activity can be likely to affect risk of colorectal cancer,especially rectal caner in two opposite direction depending on different intensity of activity performed.

To explore whether aberrant methylation in the promoter of p16 gene was associated with development and clinicopathological characteristics of colorectal cancer. Methylation-specific PCR(MSP) was used to detect hypermethylation of p16 gene in tumor tissues obtained from 32 patients with colorectal cancer. The results showed that the hypermethylation of p16 promoter was detected in 40.6% of tumor tissues. p16 hypermethylation in patients with Dukes stages of C and D tumors (63%) was higher than that in the stages of A and B tumors (25%). The highly and intermediately differentiated carcinomas had lower positive rate (30%) than the poorly differentiated carcinoma. Furthermore, the hypermethylation of p16 gene in tumor tissue from patients with the lymph node metastasis was different from that without lymph node metastasis (P