MCF7 cell lysate was prepared by homogenization in modified RIPA buffer (50 mM TrisHCl, pH 7.4, 1% Triton X-100, 0.2% sodium deoxycholate, 0.2% sodium dodecylsulfate (SDS), 1 mM sodium ethylenediaminetetraacetate, 1 mM phenylmethyl-sulfonyl fluoride, 5 ug/ml of aprotinin, 5ug/ml of leupeptin). Cell debris was removed by centrifugation. Protein concentration was determined with Bio-Rad protein assay. The lysate was boiled for 5 min in 1 x SDS sample buffer (50 mM Tris-HCl pH 6.8, 12.5% glycerol, 1% SDS, 0.01% bromophenol blue) containing 5% Beta-mercaptoethanol.