In contrast, bone metastases from breast cancer patients had a low expression of BSP compared to bone metastases from prostate cancer patients, suggesting that OPN and BSP expression are selective markers for the two types of metastases: osteolytic, more indicative of bone metastases from breast cancer patients and osteoblastic, more indicative of bone metastases from prostate cancer patients [93]. Here, SPP1 is linked to breast carcinoma.