This study provided the first evidence that (a) PC-PLC, a phospholipase involved in mitogenic response, cell signalling, apoptosis, and survival [53-56], colocalizes with HER2 in membrane-raft domains of HER2-overexpressing breast cancer cells; and (b) PC-PLC inhibition induces in these cells enhanced HER2 internalization, followed by long-lasting HER2 accumulation in endosomal/lysosomal compartments and retarded HER2 reexpression on membrane. This evidence concerns the gene HSPG2 and breast carcinoma.