Hsa_circ_0000073 promotes lipid synthesis of osteosarcoma through hsa-miR-1184/ FADS2 pathway.

PURPOSE: Osteosarcoma is one of the leading causes of cancer mortality in children and teenagers. Dysregulation of lipid metabolism has been reported to involve tumor progression. Our previous evidence has revealed that circular RNA hsa_circ_0000073 enhanced the proliferation and metastasis of osteosarcoma cells. However, the effect of hsa_circ_0000073 on the lipid metabolism of osteosarcoma remains unclear. In this paper, we focused on the effect of hsa_circ_0000073 in lipid metabolism and investigated a network among hsa_circ_0000073/ miR-1184 /FADS2 in osteosarcoma, which provides a new idea to treat osteosarcoma.

METHODS: The osteosarcoma and its adjacent tissue samples were collected for further validation. qRT-PCR or western blot was employed to detect the expression of hsa_circ_0000073, miR-1184, and FADS2 in OS cells and tissues. Microarray analysis, mass spectrometry, metabolomics analysis, and bioinformatics analysis were used to explore the potential function and target gene of hsa_circ_0000073. Oil red o, Nile red staining, and Triglyceride content assay were adopted to confirm the effect of hsa_circ_0000073 on the lipid metabolism of OS. Dual-luciferase reporter assays and RNA immunoprecipitation were applied to construct and validate the ceRNA network of hsa_circ_0000073. The xenograft mouse model was taken to verify the effect of hsa_circ_0000073 on lipid metabolism in vivo.

RESULTS: The results confirmed that hsa_circ_0000073 was raised in the tumor tissues more than its adjacent tissue. Moreover, the higher expression of hsa_circ_0000073 was associated with worse survival rates, advanced clinical stage, large tumor size, and metastasis. After hsa_circ_0000073 silence, the gene chip and metabolomics result implied that hsa_circ_0000073 expression is positively correlated with a 91 genes signature and 78 metabolites in MG-63 and Saos-2 cells. The bioinformatics analysis indicated that hsa_circ_0000073 might involve in the biological processes of lipid metabolism. Further loss and gain of function experiments affirmed that hsa_circ_0000073 could impact cell lipid synthesis. Mechanically, hsa_circ_0000073 favored the expression of FADS2 genes by sponging miR-1184. Consistent with these observations, silencing of hsa_circ_0000073 inhibited lipid synthesis in vivo xenograft mouse model.

CONCLUSIONS: Our study revealed that hsa_circ_0000073 contributed to the lipid synthesis of osteosarcoma by decreasing the expression of miR-1184, thereby increasing FADS2, which provides new insights into treating osteosarcoma.