Interestingly, depending on the metastasis origin, overexpression of ERRα in cancer cells either inhibits or stimulates osteoclasts by stimulating the expression of either the decoy receptor of RANKL, OPG (osteoprotegerin), a major inhibitor of osteoclast activity in BCa cells, or VEGF-A and WNT5a in PCa cells (62, 63). This evidence concerns the gene ESRRA and cancer.