Silencing PPA1 promotes the survival of non-small cell lung cancer A549 cells under glucose-starved conditions.

BACKGROUND

Non-small cell lung cancer (NSCLC) is a malignant tumor with extremely high morbidity and mortality. The large demand for energy during its progression is highly dependent on glucose. The energy metabolism enzyme inorganic pyrophosphatase 1 (PPA1) can mediate the progression of NSCLC through various pathways. Bioinformatics analysis revealed a potential relationship between PPA1 and glycolysis pathway. This study further examined the regulatory effect of silencing PPA1 on the survival of A549 human NSCLC cells under glucose-starved conditions.

METHODS

The glycolysis-related gene set was obtained through the gene set enrichment analysis (GSEA) of the Molecular Signatures Database to form a glycolysis gene set, and the potential relationship between PPA1 and glycolysis pathway-related proteins was preliminarily examined via the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database. After A549 cells were treated with glucose-free RPMI-1640 medium for 0, 12, and 24 h, the expression level of PPA1 protein was detected via Western blotting (WB). Further stable silencing of PPA1 and cell proliferation activity were analyzed by Cell Counting Kit-8 (CCK-8), colony formation, and cell cycle assays, and cell apoptosis was analyzed via propidium iodide/annexin V cell flow cytometry. The expression of cell proliferation-related proteins p21, CDK2, Ki-67, and p53 and that of cell apoptosis-related proteins BAX, cleaved caspase-3, and cleaved PARP were detected via WB.

RESULTS

Bioinformatics was employed to examine the potential relationship between PPA1 and glycolysis pathway-related genes, and the results showed that there was a certain connection between PPA1 and the glycolysis pathway. With the extension of the treatment time of A549 cells with glucose-free medium, the expression of PPA1 showed a progressive increase. After further silencing of PPA1, the functional experiment results under glucose-free culture conditions showed that compared with those in the empty vector control (shCtrl) group, the cell viability, cell clone formation number, and S-phase cell percentage in the shPPA1-1 group and shPPA1-2 group were significantly increased under glucose-starved conditions, while the number of apoptotic cells was significantly reduced (P<0.05). Additionally, the WB results showed that compared with the shCtrl group, the shPPA1-1 group and shPPA1-2 group exhibited upregulated expression of Ki-67 and CDK2 proteins but downregulated expression of the p21, p53, cleaved PARP, cleaved caspase3, and BAX proteins (P<0.05).

CONCLUSIONS

Under glucose-starved conditions, silencing PPA1 can promote the survival of A549 cells.