BMI1 and breast carcinoma: The epigenomic state of the p16/INK4A locus in the extended lifespan cells may be similar to that of other silenced tumour suppressor genes in immortalized cells, such as human MCF7 breast cancer cells, in which increased abundance in H3K27me3 marks and, in some cases, increased BMI1 binding, were frequently associated with relatively low levels of promoter DNA methylation.