To determine if the loss of cell viability was due to apoptosis, CADM1 was knocked down in BC-1, BC-3, and BCBL-1 PEL cells and they were analyzed by Annexin V and propidium iodide (PI) staining; CADM1 knockdown resulted in significant apoptotic cell death in PEL cells after 96 hours (Fig 7C). This evidence concerns the gene CADM1 and breast cancer.