Loss of imprinting of insulin-like growth factor II is associated with increased risk of proximal colon cancer.

The aim of this study was to determine the clinicopathological features of sporadic colon cancers with loss of imprinting (LOI) of insulin-like growth factor II (IGF-II) in Chinese patients. DNA from peripheral blood leucocytes and RNA from tumours were amplified and then digested with ApaI to determine the LOI status. Of the 316 patients enrolled for analysis, 149 were informative for IGF-II LOI. The positive rate of IGF-II LOI of colon cancer tissue was 47% (70/149) in Chinese patients. Proximal colon (64%) cancers were more likely to have LOI of IGF-II in tumour than distal colon (40.9%) cancers (odds ratio (OR)=2.60, 95% confidence intervals (CI)=1.21-5.56, p=0.014). LOI of IGF-II in tumours was also associated with more advanced diseases (OR=2.90, 95% CI=1.05-8.04, p=0.04). IGF-II LOI is present in high frequency in Chinese colon cancer patients, especially those with proximal cancer.