To determine the effects of Snail knockdown on p-ERK in T47-D and MDA-MB-231 breast cancer cells, we transiently transfected these cells with control siRNA or Snail siRNA and analyzed the expression of Snail, p-ERK, and EMT markers (E-cadherin and vimentin) by Western blot and immunofluorescence analyses. This evidence concerns the gene CDH1 and breast cancer.