Since genetic screening of colorectal polyposis patients for MUTYH mutations will continue to be performed worldwide, the same as genetic screening for APC mutations (reviewed in Lynch et al., 2008), our method of expression and purification of human MUTYH protein should be useful for assessing MUTYH variants newly identified by genetic screening as well as MUTYH variants that have not been examined. Here, APC is linked to polyp of large intestine.