Combined Bisulfite Restriction Analysis (COBRA) of LINE-1 loci was performed to examine the LINE-1 methylation statuses of PBMCs from 216 cancer patients with 6 different types of cancer compared with 144 normal controls.
Only colorectal and nasopharyngeal cancer samples were found to have lower levels of overall LINE-1 methylation compared with normal controls (p < 0.0001 and p = 0.0022). However,%uCuC in cancers of the colon, liver, lung and nasopharynx was significantly higher compared with normal controls (p < 0.0001, p < 0.0001, p = 0.01 and p = 0.001, respectively). Furthermore, ROC curve analyses of these four cancer types also demonstrated the potential of%uCuC as a biomarker for cancer diagnosis.
Changes in the levels and patterns of genome-wide methylation of PBMCs are associated with cancer risk. For LINE-1,%uCuC is a more effective tumour marker for determining cancer risk than overall methylation levels.