MMP23B and breast cancer: We identified CpG dinucleotides prone to abnormal hypermethylation in BC in five MMP genes, MMP2, MMP23B, MMP24, MMP25, and MMP28, but failed to detect any association of their hypermethylation with clinical or molecular features of the tumors, except for the associations with HER2-positive phenotype and CpG island hypermethylated epigenetic subtype of BC.