SFRP4 and ocular melanoma: Whereas the actions of cytokines, such as OM, TNFα, and IL-6, and growth factors, such as TGFβ1, on bone are well described [44,45], SFRP4 is a phosphatonin that inhibits both tubular phosphate reabsorption and Wnt signaling, and whose expression has been reported to increase during adipose differentiation of MSCs and to be associated with lower bone density in mice [46-48].