Flavokawain A inhibits high glucose-induced malignant progression of lung cancer cells by suppressing PRMT5-mediated PTEN neddylation and nuclear translocation

Abstract

A high-glucose microenvironment is a key feature of tumor metabolic reprogramming that promotes lung cancer cell progression. Previous studies have revealed that protein arginine methyltransferase 5 (PRMT5) is overactivated in various cancers and regulates neddylation of the tumor suppressor phosphatase and tensin homolog (PTEN). This study established a high-glucose (25 mM) in vitro model using human non-small cell lung cancer A549 cells. Cell proliferation, invasion and cell cycle progression were assessed using the cell counting kit-8, Transwell, 5-ethynyl-2′-deoxyuridine and flow cytometry assays. The expression levels of neural precursor cells expressed developmentally downregulated protein 8 (NEDD8) and PTEN in total and nuclear protein fractions were analyzed using Western blotting and PTEN localization was determined using immunofluorescence. Cellular NEDD8 levels were manipulated by overexpressing Flag-NEDD8 and using MLN4924, an inhibitor of NEDD8-activating enzyme. The association between PTEN and NEDD8 was further assessed through co-immunoprecipitation. Finally, the mechanism underlying the action of flavokawain A (FKA) was explored by comparing its effects on high-glucose-induced PTEN neddylation with those of GSK3326595, a selective inhibitor of PRMT5. A high-glucose environment promoted A549 cell proliferation and viability while inhibiting cell apoptosis, accompanied by enhanced neddylation of PTEN and its nuclear translocation. NEDD8 overexpression promoted the nuclear import of PTEN; however, MLN4924 treatment effectively blocked this effect. FKA treatment markedly reduced PRMT5 activity, thereby reducing the neddylation modification of PTEN, limiting the nuclear localization of PTEN, ultimately inhibiting the proliferation and invasion ability of A549 cells and promoting cell apoptosis. Notably, GSK3326595 exhibited an inhibitory effect similar to that of FKA. The results indicated that FKA suppressed high glucose-induced carcinogenic effects by inhibiting PRMT5-mediated PTEN neddylation and subsequent nuclear translocation.