Loss of inhibition over master pathways of bone mass regulation results in osteosclerotic bone metastases in prostate cancer

Prostate cancer is the most common cancer among men in industrialised countries. Most patients with prostate cancer, however, will not die of it. As a result, many of them will experience symptomatic metastasis during the course of the disease. Prostate cancer has a high propensity to metastasize to bone. Unlike many other cancers prostate cancer cells induce a rather osteosclerotic than osteolytic reaction in the bone marrow by interfering with physiological bone remodelling. A proper understanding of the mechanisms of tumour cell-induced bone alterations and exaggerated bone deposition in prostate cancer may open new and urgently needed therapeutic approaches in the field of palliative care for affected patients. In this review we focus on the central role of two major regulators of bone mass, the wingless type integration site family members (WNTs) and the bone morphogenetic proteins (BMPs), in the development of osteosclerotic bone metastases.

Biology of Bone Metastases in Prostate Cancer

Advanced-stage prostate cancer (PCa) patients are often diagnosed with bone metastases. Bone metastases remain incurable and therapies are palliative. PCa cells prevalently cause osteoblastic lesions, characterized by an excess of bone formation. The prevailing concept indicates that PCa cancer cell secrete an excess of paracrine factors stimulating osteoblasts directly or indirectly, thereby leading to an excess of bone formation. The exact mechanisms by which bone formation stimulates PCa cell growth are mostly elusive. In this review, the mechanisms of PCa cancer cell osteotropism, the cancer cell-induced response within the bone marrow/bone stroma, and therapeutic stromal targets will be summarized.