The observed increase in bone resorption and the previously demonstrated spontaneous osteoclastogenesis in cancer Isoacteoside patients with osteolytic metastases prompted us to investigate osteoclastogenesis from CaP patients�� PBMC in vitro. OC formation was higher in bone metastatic patients compared to both non-bone metastatic patients and healthy controls. Otherwise the RANKL/OPG ratio was higher in bone metastatic patients, explaining the increased osteoclastogenesis and according to previous literature data. The interplay among the tumour cells, the Scopoletin immune system and the bone tissue has become a relevant object of intensive study. Since IL-7 involvement in bone metastasis was previously demonstrated in other tumours, we investigated this issue showing an increase in serum IL-7 levels in CaP patients with and without bone lesions. The increase of IL-7 might account for the RANKL/OPG augment, since IL-7 stimulates RANKL production from T cells. We evaluated IL-7 gene expression in CaP and normal prostate tissues, showing comparable IL-7 expression in prostate cancer and normal tissues. This result differs from our published data on lung cancer, where the tumour tissue expressed higher IL-7 levels compared with the normal counterpart. We suggest that this discrepancy might be due to the different tumour type and bone metastatic behaviour, as lung cancer causes osteolytic metastases, while CaP produces mainly bone forming lesions. The increased IL-7 serum level may depend on immune system activation against the tumour. In fact, it has been previously demonstrated that T and B cells produce IL-7, in both tumours and other pathologies associated to bone resorption. WNT signalling plays an important role in bone development, since it inhibits OC differentiation, stimulates osteoblastogenesis and mineralizing activity of osteoblasts. WNT proteins are also expressed by CaP and can promote tumour bone invasion. DKK is a soluble inhibitor of canonical WNT signalling. A recent study associates DKK-1 expression in breast cancer with the presence of bone metastases. Data regarding DKK-1 expression in CaP are scant: some authors report an increase DKK-1 expression in osteolytic lesions, but not in the primary tumours.