Nature paper shows that removing estrogen from breast cancer induces a demethylation and remthylation cycle that repeats every hour and a half.
Epigenetic silencing by estrogen in breast cancer affect gene expression immediately and on a short timescale, according to researchers at the European Molecular Biology Laboratory (EMBL).
Methylation has traditionally been considered a long-term mechanism of gene regulation, because methylation marks are stable and maintained through cellular replication. The EMBL team found, however, that methylation marks occur rapidly in breast cancer cells in response to hormones such as estrogen or drug compounds.
Estrogen withdrawal or treatment with doxorubicin cause the methyl groups to be removed from regulatory regions of specific genes within 10s of minutes in human breast cancer cells, the scientists explain. They showed that the treatment sets off a cycle of events: initial demethylation renders silent genes active and subsequent remethylation shuts them down again. They found that this cycle repeats itself every 1.5 hours.
The study is reported in the March 6 issue of Nature.