Abstract: Objective To explore the mechanism of LINC00319 regulating PENK / PI3K / AKTsignal pathway in osteosarcoma (OS). Methods The expression levels of LINC00319 and PENK inthe peripheral blood RNAs from OS patients and non-OS patients were detected using qPCR, and the correlation between LINC00319 and PENK expression were analyzed. Knockdown or overexpression of LINC00319 were performed in the MG63 cells, and the mRNA and protein expression levels of PENK were detected using qPCR and Western blotting methods, respectively. The mouse OS transplanted tumor model was established and mice were divided into 2 groups: shNC group and shLINC00319 group. The tumor weight was measured, and the expression levels of PENK, AKT, p-AKT, and PI3K in the tumor tissues were detected through immunohistochemistry experiments. MG63 cells were divided into 3 groups: shNC group, shLINC00319 group, shLINC00319 + shPENK group. Cell proliferation was detected by EdU. Cell invasion was detected via transwell method. The protein expression levels of AKT, p-AKT, and PI3K were detected using Westernblotting. Results The expression level of LINC00319 was higher in the peripheral blood of OS patients, and the expression level of PENK was lower when compared to those in the peripheral blood of non-OS patients. The expression level of PENK was negatively correlated with the expression level of LINC00319. After knocking down LINC00319, PENK mRNA and protein levels were upregulated, while overexpression of LINC00319 resulted in decreased expression level of PENK mRNA and protein. Compared to mice in the shNC group, mice in the shLINC00319 group showed decreased tumor weight, unchanged expression level of AKT protein in tumor tissues, and deceased expression levels of p-AKT, PI3K protein. Compared to cells in the shNC group, MG63 cells in the shLINC00319 group showed decrease abilities in cell proliferation and invasion, the expression levels of p-AKT and PI3K proteins were decreased in the shLINC00319 group as well. Cells in the shLINC00319 + shPENK group showed increase abilities in cell proliferation and invasion, and the expression levels of p-AKT and PI3K proteins were increased when compared to those in theshLINC00319 group. Conclusion LINC00319 is highly expressed in the peripheral blood of OS patients, while PENK is lowly expressed in the peripheral blood of OS patients, and their expression levels are negatively correlated. LINC00319 promotes OS cell proliferation and invasion by inhibiting PENK levels and activating the PI3K / AKT signaling pathway.

Key words: osteosarcoma, LINC00319, proenkephalin, PI3K / Akt