MRC1 and neoplasm: Some of the papers dealt with the process of carcinogenesis in the lips and its relation to MMR dysfunctions: Souza et al. [55] tested (in normal, dysplastic and malignant lip epithelium) the tissue expression of hMSH2 and other DNA repair proteins (p53, a most important tumor suppressor gene, APE1, a multifunctional enzyme of the base excision repair pathway, and ERCC1, a component of the nucleotide excision repair mechanism), finding a significant reduction in epithelial cell expression of these proteins.