Although patients presenting with early disease (stage I-III) can be cured, prognosis varies from 90% in stage I to 50-80% in stage II and III. Therefore, prevention of metastases after early disease is of utmost importance. Extensive studies of the Wnt signal cascade have elucidated its role in colorectal cancer development and proliferation. Several well-known targets of the Wnt-cascade, like DKK1, APCDD1 and AXIN2, serve as feedback inhibitors and likely prevent pathway hyperactivation. Therefore, loss of these control mechanisms, for example due to repression of Wnt targets by CpG island methylation, serves as a potent proliferative signal. Recently, we identified a subset of colon cancers that are typified by CpG island methylation of specific Wnt target genes and have a poor prognosis. Moreover, in preclinical studies we showed that derepression of Wnt-targets by the demethylating agent decitabine resulted in tumor growth suppression. Thus, derepression of Wnt targets may provide a novel target for therapy. Objectives: The primary objective of the study is to assess in patients with primary colon cancer whether short-course pre-operative treatment with decitabine can increase Wnt target gene expression as measured in resected tumors compared to pretreatment biopsies. The secondary objective of the study is to assess in patients with primary colon cancer whether short-course pre-operative treatment with decitabine can revert CpG methylation and induce more favorable tumor characteristics as measured in resected tumors compared to pretreatment biopsies. The tertiary objective is to compare changes in Wnt target gene expression, CpG methylation and tumor characteristics for Wnt methylated and nonmethylated tumors as measured in resected tumors compared to pretreatment biopsies and identify new stratification markers.