For the MTRR A66G genotype, there were 62 AA, 40 AG and 8 GG in normal group, 50 AA, 41 AG and 25 GG in CIN group, and 45 AA, 53 AG and 48 GG in cancer group for MTHFR A1298C genotype, respectively (Fig. 2e). Here, MTHFR is linked to cervical squamous intraepithelial neoplasia.