For instance, the CpG islands in the promoter region of tumour suppressor genes, such as p16INK4A, CCND2, CDH1, BRCA1, ER and RARβ2 exhibit hypermethylation, thus leading to gene expression silencing and facilitating tumour initiation and progression of TNBC.7, 8. Here, BRCA1 is linked to neoplasm.