This invention is based on the experimental finding that a potassium channel, SK3 is a new phenotypic marker of mammary epithelial cell malignant transformation, mediating cell migration, and represents a target for a new class of anticancer agents. This invention concerns a method for the in vitro screening of a compound that inhibits SK3 activity comprising (i) contacting a cell expressing a functional SK3 with a candidate compound and measuring the level of SK3 activity, (ii) comparing the level of SK3 activity which is measured at step (i) with the level of SK3 activity which is measured when step (i) is performed in the absence of said candidate compound, wherein a decrease level of SK3 activity in the presence of the candidate compound indicates that the candidate compound is a compound that inhibits SK3 activity.
