Abstract: Objective To investigate the effects of the long non⁃coding RNA (lncRNA) ATPase secretory pathway Ca²⁺ transporting 2 antisense RNA 1 (ATP2C2⁃ AS1) on the proliferation andapoptosis of osteosarcoma cells， as well as to elucidate its underlying mechanism.  Methods The expression levels of ATP2C2⁃AS1 in human normal osteoblasts cell (hFOB 1.19) and human osteosarcoma cell lines (Saos⁃2， U2OS， 143B， and HOS) were quantified using qRT⁃PCR. Saos⁃2 osteosarcoma cells were transfected with either an ATP2C2⁃AS1 siRNA (si⁃ATP2C2⁃AS1) and its negative control (si⁃NC)， as well as ATP2C2⁃AS1 overexpression plasmid (oe⁃ATP2C2⁃AS1) or its negative control (Vector). Following the assessment of transfection efficiency， the PI3K inhibitor (NVP⁃BEZ235) was used to Saos⁃2 cells transfected with either the Vector or oe⁃ATP2C2⁃AS1. Cell proliferation activity was measured using the cell counting kit⁃8 (CCK⁃8) method， while apoptosis levels were assessed via flow cytometry. Western blot was used to detect the expression levels of apoptosis⁃related proteins (Bax， Bcl⁃2， and Cleaved⁃caspase⁃3) and proteins associated with the phosphatidylinositol 3⁃kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway. Results Compared with hFOB 1.19 cells， the expression levels of ATP2C2⁃AS1 were markedly elevated in Saos⁃2， U2OS， 143B and HOS cell lines(all P<0.001)， with the most pronounced expression observed in Saos⁃2 cells. The silencing of ATP2C2⁃AS1 reduced the proliferation activity in Saos⁃2 cells， an increase cell apoptosis， and a downregulation of PI3K (p85α)， Bcl⁃2 protein， and the p⁃Akt/Akt and p⁃mTOR/ mTOR proteins ratios， while it upregulated the expression of Bax and Cleaved⁃caspase⁃3 proteins (all P<0.05). Conversely， the overexpression of ATP2C2⁃AS1 enhanced the proliferation activity of Saos⁃2 cells， inhibited  apoptosis， and led to an upregulation of PI3K (p85α)， Bcl⁃2 protein， and the ratios of p⁃Akt/Akt and p⁃mTOR/mTOR protein ratios， while downregulating the expression of Bax and Cleaved⁃ caspase⁃3 proteins (all P<0.05). The intervention with NVP⁃BEZ235 significantly counteracted the proliferation effects of  ATP2C2⁃AS1 overexpression in Saos⁃2 cells， and induced apoptosis. Conclusions ATP2C2⁃AS1 may promote the proliferation and inhibit the apoptosis of osteosarcoma cells through the activation of the PI3K/Akt/mTOR signaling pathway.

Key words: Osteosarcoma, ATPase secretory pathway Ca²⁺ transporting 2, Long non?coding RNA, Proliferation, Apoptosis