In the present paper we aimed to characterize epigenetic aspects and analyze TP53 transcription in the 21 T series, composed of breast cell lines: non-cancerous H16N2;
Atypical Ductal Hyperplasia 21PT;
Ductal Carcinoma in situ 21NT and Invasive Metastatic
Carcinoma 21MT1. We detected a global genomic hypomethylation in 21NT and 21MT1. The
histone modification markers analysis showed an important global decrease of the active
chromatin mark H4Ac in 21MT1 relative to the other cell lines while the repressive mark H3K9Me3 were not significantly altered. The
mRNA levels of DNA methylation and
histone modification key
enzymes are consistent with the observed genomic hypomethylation and
histone hypoacetylation. The expression of DNMT3A/B increased at the initial stages of
oncogenesis and the expression of DNMT1 and HAT1 decreased at the advanced stages of
breast cancer. Using a confocal immunofluorescent assay, we observed that H4Ac was mostly located at the periphery and the repressive mark H3K9Me3, at the center of 21NT and 21MT1 cells nuclei. TP53 P1 promoter was found to be in an open
chromatin state, with a relatively high enrichment of H4Ac and similar TP53 transcription levels in all 21 T cell lines. In conclusion, we observed epigenetic alterations (global genome hypomethylation, global hypoacetylation and accumulation of pericentric
heterochromatin) in metastatic
breast cancer cells of the 21 T series. These alterations may act at later stages of
breast cancer progression and may not affect TP53 transcription at the P1 promoter.