Abstract
Bones are the most common metastatic sites for prostate cancer (PCa). Receptor tyrosine kinase-like orphan receptor 2 (ROR2), a noncanonical Wnt receptor, plays crucial roles in skeletal morphogenesis, osteoblast differentiation, and bone formation. The role of ROR2 in PCa metastasis is unclear. We analyzed online datasets from Oncomine as well as using IHC staining on tissue array to determine the relationship between ROR2 expression level and disease outcome of PCa. To investigate how ROR2 regulates migration and invasion of PCa cells, we performed transwell assay and orthotopic xenograft model in nude mice. We then applied the Micro-Western Array (MWA), a high-throughput western blotting platform to analyze the downstream signaling pathways being regulated by ROR2. Compared with nonmalignant PZ-HPV-7 and RWPE-1 cells, PCa cell lines express lower level of ROR2 protein. Constitutive expression of ROR2 in PC-3, DU-145, or C4-2B PCa cells significantly suppressed the cell migration, invasion, and epithelial–mesenchymal transition (EMT) proteins. MWA, western blotting, and microRNA analysis showed that elevation of ROR2 suppressed the expression of miR-199a-5p, which in turn increased the expression of PIAS3. The upregulation of PIAS3 then decreased AKT2 and the phosphorylation of AKT, resulting in the inhibition of migration and invasion of PCa cells both in vitro and in orthotopic xenograft mice model. IHC staining of tissue array and Oncomine datasets analysis indicated that the gene and protein level of ROR2 is much lower in metastatic prostate tumors as compared with primary tumors or adjacent normal prostate tissues. Low level of ROR2 correlated to poor survival and high recurrent frequency in PCa patients. In conclusion, we discovered that ROR2 suppresses PCa metastasis via regulation of PIAS3–PI3K–AKT2 signaling axis.
Highlights
Bones and lymph nodes are the most common metastatic sites for prostate cancer (PCa)
As we demonstrated that receptor 2 (ROR2) is a novel tumor suppressor inhibiting the migration and invasion of PCa cells, we predicted that the protein level of ROR2 in advanced prostate tumors should be downregulated
All PCa datasets from Oncomine indicated that gene expression level of ROR2 was downregulated in prostate tumors as compared with normal tissues (Supplementary Fig. 1)
Summary
Bones and lymph nodes are the most common metastatic sites for prostate cancer (PCa). PCa metastases to bone are osteoblastic and induce extensive new bone deposition[1]. Official journal of the Cell Death Differentiation Association. DKK-1 expression is inhibited during the metastases progresses, allowing the initiation of Wnt-mediated osteoblast[3]. (ROR2) plays crucial roles in skeletal morphogenesis and promotes osteoblast differentiation and bone formation[4]. ROR2 binds with ligand Wnt5a and activates the noncanonical Wnt pathway by activating the Wnt–JNK pathway and inhibiting the β-catenin–TCF pathway[5,6]. Functional role of ROR2 in cancer progression depends on cancer types[7]. ROR2 is epigenetically inactivated in the early stages of colorectal cancer and the reduction of ROR2 contributes to the promotion of Wnt signaling, tumor growth, and cancer metastasis[8,9].
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