Expression of parathyroid hormone-related protein and its receptor in bone metastases from prostate cancer

Studies of breast cancer suggest that parathyroid hormone-related protein (PTHrP) is important in the development of bone metastases. To determine whether PTHrP expression is important in prostate cancer metastasis, immunohistochemistry and in situ hybridization were used to assess the expression of PTHrP and its receptor in primary prostate cancer and bone metastases from both prostate and non-prostate cancers. PTHrP was expressed in more prostate primary tumours than bone metastases (p=0.003, Fisher's exact test). All bone metastases from non-prostate cancers expressed PTHrP. In contrast, PTHrP receptor was expressed in all bone metastases, but in only 19% of primary prostate tumours (p=0.001). The receptor to PTHrP was found to be highly expressed in bone metastases from prostate and other primaries, whereas PTHrP protein was found to have lower expression in the bone metastases than in the primary tumours. In conclusion, the expression of the receptor to PTHrP is increased in bone metastases from prostate cancer and may play an important role in their formation.