ESR1 and breast cancer: This phenotypic profiling using an Affymetrix Human Genome U133 plus 2.0 GeneChip is obtained by Sanaa Al Saleh using siRNA-mediated knockdown of the estrogen receptor α (ERα) in the breast cancer cell line MCF7 and it was observed that ERα knockdown resulted in estrogen/tamoxifen resistant cells with changed morphology, increased motility with the cytoskeleton rearrangement and the ability to invade simulated components of the extracellular matrix [41].