The CaSR suppresses cell proliferation and induces terminal differentiation in parathyroid and colon tumors, as shown by recent studies which provided abundant evidence that overexpressing the CaSR suppressed the proliferation of colorectal cancer cell both in vivo and in vitro [58,59], while inversely, it acts as an oncogene in prostate, testicular, ovarian, and breast cancer, especially bone metastasis in breast and prostate cancer [60,61]. Here, CASR is linked to breast cancer.