ID1 and osteosarcoma: To analyse whether overexpression of Id-1 modulates prostate cancer cell-mediated bone cell differentiation, conditioned medium from LNCaP pBabe vector control cells and Id-1 overexpressing cells were collected and used for treating a human osteosarcoma cell line, SaOS-2, which is capable of undergoing mineralisation, and also a mouse macrophage-like cell line RAW264.7, which is capable of differentiating into osteoclast-like cells upon appropriate stimulation.