Of the MSI-H cancers, only five multiple cancers demonstrated loss of MSH6 expression, four of these also failed to express MSH2 or MLH1. In two cases, the paired cancer continued to express MSH6 normally, while also failing to express MSH2, suggesting a secondary mutation possibly in the intragenic C8 mononucleotide repeat region of MSH6 as a result of loss of MLH1 or MSH2 function. This evidence concerns the gene MLH1 and cancer.