Simvastatin inhibits PD-L1 via ILF3 to enhance CD8 + T cell-mediated ferroptosis in gastric cancer cells

Abstract

Background Immunotherapy is vital in the comprehensive treatment of gastric cancer (GC). However, the prognosis of GC patients remains unfavorable, necessitating to exploration of novel therapeutic approaches and medications. Methods PD-L1 expression was observed using small interfering RNA and plasmid to knock down and overexpress ILF3, respectively. The expression of ILF3, PD-L1, and ferroptosis marker molecules (SLC7A11 and GPX4) was detected upon simvastatin stimulation of gastric cancer cells co-cultured with activated CD8+ T cells. To assess the impact of ILF3 and simvastatin stimulation on the induction of ferroptosis in gastric cancer cells by CD8+ T cells, various assays including CCK8, MTT, ROS, Fe2+, MDA, GSH, and LPO were conducted. Cleavage under targets and Tagmentation (CUT&Tag) was employed to validate the mechanism of simvastatin by regulating ILF3 expression. Whole genome sequencing and KEGG analysis reveal that ILF3 regulates PD-L1 expression through the DEPTOR/mTOR signaling pathway. Results Statin treatment decreased the serum levels of ILF3 and PD-L1. This study found that ILF3 was positively correlated with the expression of PD-L1, and the knockdown of ILF3 effectively inhibited the expression of PD-L1, thus enhancing the cytotoxicity of CD8+ T cells to gastric cancer cells. Meanwhile, simvastatin inhibited the expression of PD-L1 through ILF3, which enhanced the induction of ferroptosis in gastric cancer cells by CD8+ T cells. Further studies found that simvastatin inhibited ILF3 expression by decreasing the acetylation level at residue site H3K14 in ILF3, while ILF3 inhibited PD-L1 expression through the DEPTOR/mTOR pathway. Conclusions Simvastatin further recruited CD8+ T cells to enhance anti-tumor immunity by inhibiting PD-L1 expression by ILF3 and induced GC cells to undergo ferroptosis to achieve synergistic immunotherapy. This study elucidated the new mechanism of statins to improve GC immunotherapeutic effect. It revealed a new theoretical basis for using statins in GC treatment to improve the prognosis of GC patients.