Objective: The aim of this study was to explore the effect of long non-coding ribonucleic acid (lncRNA) FOXD2-adjacent opposite strand RNA 1 (FOXD2-AS1) on the sensitivity of osteosarcoma cells to cisplatin and its possible underlying mechanism. Our findings might help to provide a certain reference for clinically preventing the drug resistance of osteosarcoma cells.
Materials and methods: Cisplatin with a certain concentration gradient was used to induce the stable acquired resistance of human osteosarcoma U2-OS cell line. Subsequently, the expression level of lncRNA FOXD2-AS1 was determined in osteosarcoma cells in non-resistance group (Control group) and Cisplatin-resistance group (Cisplatin-RES group), respectively. Next, the cell line with stable lncRNA FOXD2-AS1 knockdown was constructed in Cisplatin-RES group using small interfering RNA (siRNA). The effects of stable knockdown of lncRNA FOXD2-AS1 on the proliferation of human osteosarcoma cells and the half-maximal inhibitory concentration (IC50) of cisplatin were detected by Cell Counting Kit-8 (CCK-8) assay. 5-ethynyl-2'-deoxyuridine (EdU) staining was performed to measure deoxyribonucleic acid (DNA) replication level in each group of cells. The protein expression levels of apoptosis-associated genes B-cell lymphoma 2 (Bcl-2) and Bcl-2 associated X protein (Bax) in each group of cells were measured via Western blotting. The migration and invasion abilities of cells in each group were determined using wound-healing assay and transwell assay. In addition, the expression of micro RNA (miR)-143 in each group of cells was detected via Reverse Transcription-Polymerase Chain Reaction (RT-PCR).
Results: Compared with Control group, the expression level of lncRNA FOXD2-AS1 rose significantly in cells in Cisplatin-RES group (p<0.05). Knockdown of FOXD2-AS1 evidently decreased the IC50 of cisplatin in human osteosarcoma cells (p<0.05). According to EdU staining results, the knockdown of FOXD2-AS1 distinctly inhibited the proliferation of osteosarcoma cells (p<0.05). Western blotting results demonstrated that the knockdown of FOXD2-AS1 remarkably upregulated the expression of pro-apoptotic protein Bax and repressed that of anti-apoptotic protein Bcl-2 in drug-resistant human osteosarcoma cells (p<0.05). Moreover, the knockdown of FOXD2-AS1 significantly weakened the migration and invasion abilities of drug-resistant human osteosarcoma cells (p<0.05). Finally, it was found that the expression level of miR-143 was distinctly elevated in drug-resistant human osteosarcoma cells after knockdown of FOXD2-AS1 (p<0.05).
Conclusions: LncRNA FOXD2-AS1 knockdown inhibits the resistance of human osteosarcoma cells to cisplatin, promotes their apoptosis and weakens their invasion and migration abilities. The possible underlying mechanism may be related to the inhibition of miR-143 expression by lncRNA FOXD2-AS1 in drug-resistant cell lines.