Given the difficulty in directly assessing whether and at what stage CD80 methylation takes place along the colorectal carcinogenesis pathway and in order to assess if hypermethylation plays a role in CD80 down-regulation in human colorectal tumorigenesis, we examined the correlation between expression of CD80 and the methylation of genes involved in the early stages of CRC carcinogenesis and the expression of DNMTs and attempted to verify our hypothesis by developing an in vitro assay. Here, CD80 is linked to colorectal carcinoma.