Stimulation of in vitro bone formation by canine prostate cancer

Abstract

Aim: Patients with prostate cancer frequently develop osteoblastic bone metastases. Canine models are important because dogs are the only mammal to develop spontaneous prostate cancer with osteoblastic bone metastases similar to men. The mechanism by which prostate cancer induces bone formation is unclear; however, it depends on the complex interaction between prostate cancer cells and bone microenvironment. This study investigated the effects of three canine prostate cancer cell lines (Ace-1, LuMa, and Probasco) on bone formation and resorption in vitro.

Methods: Mouse calvaria were treated with conditioned medium (CM) from cell lines. Calvaria were evaluated by histology, fluorescent calcein uptake at sites of bone mineralization, medium calcium assay, and alkaline phosphatase activity. The expression of bone-related genes was measured using quantitative reverse transcription-PCR.

Results: A novel calcein uptake assay was developed to measure bone formation and mineralization in vitro. Ace-1 CM induced predominantly bone resorption in calvaria, while Probasco CM induced marked bone formation, mineralization, and healing of calvaria defects. The expression of osteoblast-related genes in calvaria showed that Probasco CM stimulated the maturation and differentiation of osteoblasts and inhibited osteoclastogenesis. Both bone modeling and remodeling were involved in Probasco CM-induced bone formation and mineralization by inhibiting remodeling with zoledronic acid. Inhibition of WNT activity by DKK-1 decreased the osteoblastic activity of Probasco cells.

Conclusion: Probasco cells induced bone formation and mineralization in vitro that depended on the WNT signaling pathway. Probasco cells will serve as a valuable model for studying the mechanisms of osteoblastic bone metastasis in prostate cancer.

Keywords

Bone / canine / dog / metastasis / osteoblast / prostate cancer / zoledronic acid / DKK-1

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