PPP1R21 and breast cancer: For example, the PPP1R21 gene (located in 2p16.3; the region of this gene is the BC-associated rs10454142, which, according to our in silico data, affects the epigenetic modifications, expression, and splicing of this gene) encodes the protein—regulatory subunit 1 of protein phosphatase 21—which belongs to the group widely represented in the organism and quite numerous in phosphoprotein phosphatase 1 (PPP1) (more than 200 PPP1 have been identified to date) [59].