Knockdown of receptor tyrosine kinase-like orphan receptor 2 inhibits cell proliferation and colony formation in osteosarcoma cells by inducing arrest in cell cycle progression

Abstract

Abstract. Osteosarcoma (OS) is the most common malignant tumor of the bone, with a high mortality rate and poor prognosis. Receptor tyrosine kinase-like orphan receptor 2 (ROR2) has been reported to be dysregulated in human malignancies. More recently, ROR2 has been demonstrated to promote OS cell migration and invasion. However, the role of ROR2 in the regulation of OS cell proliferation, as well as the underlying molecular mechanism, remains unclear. The present study aimed to investigate the underlying mechanism of ROR2 in osteosarcoma growth. Reverse transcription-quantitative polymerase chain reaction analysis and western blot analysis were used to examine the mRNA and protein expression. MTT assay, colony formation assay and cell cycle analysis were conducted to explore the function of ROR2 in osteosarcoma cells. In the present study, the expression of ROR2 was found to be frequently upregulated in OS tissues compared with matched adjacent normal tissues. It was also upregulated in the OS cell lines Saos-2, MG-63 and U-2 OS, relative to normal osteoblast hFOB 1.19 cells. Knockdown of ROR2 expression by transfection with ROR2-specific siRNA markedly inhibited the proliferation and colony formation of OS cells. Data from the cell cycle distribution assay revealed an accumulation of ROR2-knockdown cells in the G0/G1 phase, indicating that knockdown of ROR2 leads to an arrest in cell cycle progression. Mechanistic investigation revealed that the protein levels of c-myc, a target gene of the Wnt signaling, as well as cyclin D1, cyclin E and cyclin-dependent kinase 4 were markedly reduced in the ROR2-knockdown OS cells, suggesting that the inhibitory effect of ROR2 knockdown on OS cell proliferation is associated with the Wnt signaling pathway. In summary, the current study indicates an important role for ROR2 in the proliferation of OS cells. Therefore, ROR2 may be a promising therapeutic target in OS.

Ellagic acid and Sennoside B inhibit osteosarcoma cell migration, invasion and growth by repressing the expression of c‑Jun

“…However, other factors can induce the cell cycle arrest of osteosarcoma cells. For example, the knockdown of ROR2 in osteosarcoma cells inhibited cell proliferation and colony formation by inducing cell cycle arrest ( 25 ). In addition, it was previously reported that the exogenous expression of miR-497 in human osteosarcoma MG63 cells suppressed cell proliferation, colony formation, migration and invasion, and induced apoptosis and arrest at the G 0 /G 1 phase of the cell cycle ( 26 ).…”

Critical role of Ror2 receptor tyrosine kinase in regulating cell cycle progression of reactive astrocytes following brain injury

“…How does Ror2 regulate proliferation of astrocytes? Although Ror2 has been implicated in the regulation of proliferation in several cell types, including NPCs and cancer cells (Endo et al, ; He et al, ; Huang et al, ; Shojima et al, ; Takiguchi et al, ; Wright et al, ; Yu et al, ), the underlying mechanism is still unclear. We show that induced expression of GFAP in reactive astrocytes is not affected by deletion of Ror2 (Fig.…”

E2F1‐Ror2 signaling mediates coordinated transcriptional regulation to promote G1/S phase transition in bFGF‐stimulated NIH/3T3 fibroblasts

“…23 Accumulating evidence further demonstrates that Ror2 is expressed highly in various types of cancer cells, and plays critical roles in regulating proliferation as well as migration and invasion of these cancer cells. [24][25][26][27] In cells stimulated with growth factors or cells harboring mutations in tumor suppressor genes like p53, retinoblastoma protein (Rb) is heavily phosphorylated by activated cyclin-dependent kinases (CDKs), leading to activation of E2F transcription factors to promote the cell cycle progression from G1 to S phase. [28][29][30][31][32][33] It has been shown that the suppressed expression of Ror2 results in reduced G1/S phase transition in astrocytes and cancer cells.…”

“…[28][29][30][31][32][33] It has been shown that the suppressed expression of Ror2 results in reduced G1/S phase transition in astrocytes and cancer cells. 23,26 However, it remains unclear about the molecular basis of how Ror2 expression is induced in proliferating cells, and how Ror2 regulates the cell cycle progression.…”