Identified herein is a novel post-translational modification of Mcm2, wherein the residue of serines 53 and 108 are phosphorylated. DDK phosphorylates Mcm2 at serines 53 and 108 when stimulated by Treslin. DDK is overexpressed in many human cancers, including colorectal cancer, suggesting that monitoring the phosphorylation of Mcm2 at serines 53 and 108 may detect early cancer with high sensitivity and specificity. It was also found that the homologous modification in budding yeast is required for DNA replication, and the modification occurs in cells during active DNA replication only. In an embodiment, the current invention is an antibody specific for human Mcm2 that is phosphorylated at serines 53 and 108. This antibody was found to be overexpressed in colon cancer cell line HCT 116, as well as other cancer cell lines, compared to normal cells.
