For the first time, proof of what hormone replacement therapy does to genes involved in breast cancer

Researchers have measured activity of genes associated with breast cancer in women before and while, they took different types of HRT. They found that an HRT used in the WHI trial had a greater activating effect on these genes than a "natural" formulation applied via an estrogen gel applied to the skin in combination with oral progesterone. This shows that varying the HRT and the way it is taken can have very significant effects on the genes associated with breast cancer.