PLAC8 facilitates osteosarcoma growth and metastasis by upregulating CXCL5 expression via miR-363-3p

Abstract Background: Osteosarcoma (OS) is characterized by its highly aggressive nature and metastatic potential. Although dysregulated PLAC8 was reported in various cancers, its function and underlying mechanism in OS metastasis remains largely unknown. Methods: The expression of PLAC8 was detected by qRT-PCR and Western blot in OS clinical tissues and OS cell lines. CCK-8, colony formation, transwell and wound healing assays were performed to assess its effect on tumor cell proliferation and mobility. The relationship between PLAC8 and CXCL5 expression was analyzed by TIMER 2.0 database, qRT-PCR, Western blot and immunohistochemical staining. The qRT-PCR, Western blot, and luciferase reporter assays were performed to explore molecular mechanisms through which PLAC8 mediates the expression of miR-363-3p, thus modulating the expression of CXCL5.Subcutaneous transplantation, orthotopic tibia implantation, and tail-vein injection mouse model were employed to evaluate the role of PLAC8 on OS tumor growth and lung metastasis. Results: We found PLAC8 was upregulated in OS tissues and OS cell lines, and its overexpression facilitated the aggressive progression of OS. Besides, we identified CXCL5, as a downstream target gene of PLAC8, could potentiate OS cell proliferation, migration, and invasion. Mechanistically, PLAC8 down-regulated the levels of miR-363-3p which directly targeted CXCL5 3'-UTR, thus enhancing the proliferative and metastatic potency of OS cells. In subcutaneous transplantation and orthotopic tibia implantation mouse model, down-regulation of PLAC8 could markedly attenuate the OS tumorigenesis. In tail-vein injection mouse model, knockdown of PLAC8 could prominently restrain the OS lung metastasis. Moreover, we found that rhCXCL5 and miR-363-3p inhibitors significantly reversed the suppressive effect of PLAC8 silencing on OS growth and lung metastasis in vivo. Conclusions: PLAC8 is highly expressed in OS, which especially contributes to tumor growth and metastasis by regulating the miR-363-3p/CXCL5 axis. This study suggested that PLAC8 may serve as a promoter in OS and provided new insight into the treatment of OS lung metastasis.