SRSF3 knockdown-induced cellular senescence as a possible therapeutic strategy for non-small cell lung cancer

Tyrosine kinase (TK) inhibitors improve clinical outcomes in non-small cell lung cancer (NSCLC) with targetable mutations. However, such NSCLC cases account for only about 50% in the western populations. Inhibition of the splicing factor SRSF3 has been reported to be tumor-suppressive in other cancer cell types. This study for the first time explores the tumor-suppressive activity of siRNA knockdown of SRSF3 in NSCLC cells. The cell lines used were A549 (no TK mutation; TP53 wild-type), NCI-H1975 (EGFR L858R/T790M; TP53 R273H mutant), NCI-H322 (no TK mutation; TP53 R248L mutant), and NCI-H596 (no TK mutation; TP53 G245C mutant). In all these cell lines, SRSF3 knockdown increased cellular senescence, as indicated by increased senescence-associated β-galactosidase activity and reduced cell proliferation. In A549 cells, increased apoptotic cleavage of caspase-3 and poly(ADP-ribose) polymerase was also observed. A tumor-suppressive p53 isoform, p53β, was shown to be upregulated by SRSF3 knockdown. However, overexpression of p53β did not induce cellular senescence or apoptosis, suggesting that this p53 isoform is not a primary effector of SRSF3 knockdown in NSCLC cells. Gene expression analyses suggested that the SRSF3 knockdown-induced senescence in NSCLC cells may be mediated by the downregulation of TOP2A, UBE2C or ASPM, which are known oncogenic factors associated with poor patient prognosis. We also generated SRSF3 siRNA-encapsulating lipid nanoparticles as a future therapeutic tool. This study proposes a therapeutic strategy for NSCLC that is independent of the mutation status of TP53 and TK-encoding genes.