The role of CaSR in cancer cell migration and invasion has been studied before.1,21,24 Previous studies have shown that CaSR activation and signaling by elevated calcium concentrations resembling those found near resorbing bone could promote MDA-MB-231 cellular migration which is a breast cancer cell line with high metastasizing potential into bone compared to cells with a lower bone-metastasizing behavior such as MCF7 cells.1 These effects have been shown to be mediated via ERK1/2, phospholipase C beta 1 (PLC-β1) and mitogen-activated protein kinase. This evidence concerns the gene MAPK3 and breast cancer.