TNFSF11 and breast cancer: The OPG treatment did not alter the metastasis of B16F10 cells to other organs, such as the ovaries and adrenal glands, indicating that the chemotactic activity of RANKL is one of the primary causes of the preferential metastasis of RANK-expressing tumour cells to bone.15 In support of this hypothesis, the level of RANK expression is reported to be positively correlated with the bone metastatic potential of human primary breast cancer and renal cell carcinomas.19,20