Abstract
Bone metastasis is positively associated with a poor prognosis in patients with colorectal cancer (CRC). CRC always leads to osteolytic change, which is regulated by aberrant activation of osteoclasts. MicroRNAs are remarkedly involved in metastasis of CRC; however, their role in bone metastasis of CRC is still unclear. The aim of this study is to find key microRNAs that are critical to bone resorption in bone metastasis of CRC. In this study, bone metastasis model was established through intratibially injecting CT-26 cells or MC-38 cells. Tartrate-resistant acid phosphatase (TRAP) staining was performed to explore the osteoclastogenesis of primary early osteoclast precursors (OCPs) after stimulation by CT-26 conditioned medium (CM). Then, microarray assay was performed to find differentially expressed miRNAs and mRNAs. The target gene of miRNA was confirmed by dual-luciferase analysis. The effect of miRNA, its target gene on osteoclastogenesis, and involved pathways were explored by Western blot, immunofluorescence analysis, and TRAP staining. Finally, the effect of miRNA on bone resorption in vivo was observed. miRNA-7062-5p was upregulated in early OCPs cultured in CT-26 CM or MC-38 CM. GPR65 was proven to be the target gene of miRNA-7062-5p. Overexpression of GPR65 can rescue the osteoclastogenesis caused by miRNA-7062-5p through activation of AMPK pathway. Local injection of miRNA-7062-5p inhibitors efficiently improved the bone resorption. Our study found the role of miRNA-7062-5p in regulating osteoclast formation, and our findings provided a potential therapeutic target in treatment of bone metastasis of CRC.
Highlights
The incidence of bone metastasis from colorectal cancer (CRC) is relatively rare in clinic, the prognosis is pessimistic
As expected, during osteoclastogenic induction treated with receptor activator of nuclear factor-κ B ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) for 6 days, early osteoclast precursors (OCPs) formed Tartrate-resistant acid phosphatase (TRAP)-positive multinuclear giant cells
We demonstrated that GPR65 is the target gene of miRNA7062-5p, and we performed rescue experiments to further assess that GPR65 is essential to miRNA-7062-5p–mediated osteoclastogenesis of OCPs
Summary
The incidence of bone metastasis from colorectal cancer (CRC) is relatively rare in clinic, the prognosis is pessimistic. Patients with CRC presenting with bone metastasis are often younger and have a poor prognosis; 5-year survival rate was only 5.7% (Kawamura et al, 2018). CRC is a kind of osteolytic tumors. For these types of tumors, aberrant activation of osteoclasts promotes the bone resorption and pathologic fractures (Clohisy et al, 1996; Li et al, 2019b). RANKL determines monocytes/macrophages to commit to osteoclast precursors (OCPs) (Liang et al, 2019). Cancer cells can directly promote the osteoclastogenesis of OCPs through RANKL-dependent or independent ways (Liang et al, 2019). Little is known on how the osteoclasts or its precursors change in CRC microenvironment
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