Wnt1 induces osteoblastic changes in a well-established osteolytic skeletal metastatic model derived from breast cancer.

Background: Osteoblastic skeletal metastasis is frequently observed in prostate cancer. An effective therapy has not been developed due to the unclear molecular mechanism. The Wnt family is involved in various biological phenomena including bone metabolism. There is no direct evidence that the family causes osteoblastic skeletal metastasis.

Aims: The present study aims to evaluate whether overexpressed Wnt induces osteoblastic bone metastasis in a well-established osteolytic bone metastatic model.

Methods And Results: The breast cancer-derived 5a-D-Luc-ZsGreen cells were transfected with Wnt1, Wnt3A, and Wnt5A expression vectors, producing stably highly expressing cells. These cells were intracardially transplanted in nude mice. Bone metastasis development was confirmed by fluorescence imaging. Hind-limb bones including metastasis were dissected and visualized through micro-CT imaging. After imaging, sections were stained with hematoxylin and eosin (H&E), and immunohistochemically stained with an anti-SATB2 antibody. Luminescent imaging confirmed mice with bone metastases in the hind limbs. Micro-CT imaging found an osteoblastic change only in bone metastasis of mice transplanted with Wnt1-expressing cells. This was confirmed on H&E-stained sections. SATB2 immunostaining showed differentiated osteoblasts were at the site of bone metastases in the diaphysis. SATB2 in the Wnt/β-catenin pathway activated by overexpressed Wnt1 could induce osteoblastic change.

Conclusion: Our findings provided direct evidence Wnt1 is involved in osteoblastic bone metastasis development. Our model would be a powerful tool for further elucidating molecular mechanisms underlying the disease and developing effective therapies.