In this study, a functional assay was conducted using a human embryonic kidney fibroblast cell line (293T) that lacked MLH1 expression because of the hypermethylation of the promoter region. It was found that PMS2 was also dysfunctional in these cells. Demethylation of the promoter region and subsequent insertion of recombinant MLH1 and PMS2 genes (wild-type) restored full MMR function in these cells. When pathogenic mutations of MLH1 replaced the wild-type MLH1 gene, MMR activity was found to be deficient. When benign polymorphisms including I291V were introduced, MMR activity was normal.
This study investigated case-control numbers to determine the association of I219V with sporadic colorectal cancer susceptibility in Chinese patients.
This study utilized various methods of determining the pathogenicity of several MLH1 variants, including I219V. Yeast assays and in vitro MMR assays were performed to determine the effect of the I219V variant on MMR activity and MLH1 expression. The MLH1 structure of proteins with this variant was also analyzed, and the SIFT program was used to analyze the effect of the mutation on the protein’s function. The I219V variant was found to be associated with medium MMR activity (60.7%), low to medium MLH1 expression (25-75%), and 0.46 SIFT score.
This study performed a meta-analysis of 18 case-control studies to determine the association of the MLH1 I219V variant with cancer risk; no association was found.