There was also a significant difference between serum SIRT1 levels in different tumor grades, graded according to the modified Bloom–Richardson system [27], as manifested by a higher SIRT1 level in grade 2 compared to grade 1 patients, and a higher value in grade 3 than in grade 2 patients (p < 0.05, Fig 1C). Here, SIRT1 is linked to neoplasm.