It is suspected that SIRT1 must also somehow be involved in the regulation of the expression of ERα because the blockade of SIRT1 action with sirtinol reduces ERα expression in MCF7 (Michigan Cancer Foundation—7) and T47D breast cancer cells; interestingly, silencing the expression of the gene encoding SIRT1 by the siRNA technique does not affect the level of receptor expression. The gene discussed is ESR1; the disease is breast cancer.