ASF1B promotes gastric cancer liver metastasis through inhibiting ZDHHC9/PCBP1/ SLC7A11 signaling axis mediated ferroptosis
Despite advances in comprehensive gastric cancer (GC) therapies, the prognosis of patients with liver metastasis remains poor. Identifying potential molecular targets for GC liver metastasis (GCLM) may provide new treatment avenues. Initially, clinical samples from patients with GCLM were analyzed through label-free proteomics screening, leading to the identification of ASF1B as a possible promoter of GCLM. This finding was further validated using in vitro experiments and in vivo spleen injection liver metastasis model, these results suggested that ASF1B significantly enhanced the metastasis ability of GC cells in vitro and in vivo. Subsequent transcriptome sequencing after ASF1B knockdown showed that ZDHHC9 and SLC7A11-mediated ferroptosis play crucial roles in the progression of GCLM. Mechanistically, ASF1B can recruit and bind to HOXB3, a transcription factor, thereby promoting the transcriptional level of ZDHHC9. Besides, ZDHHC9 is also involved in the regulation of SLC7A11-mediated ferroptosis levels in GC cells. To explore the role of ZDHHC9 in GC further, in vivo tumor metastasis experiments were constructed, which demonstrated ZDHHC9 could promote peritoneal metastases, pulmonary metastases, and hepatic metastases in GC. Then we found that the molecular interaction between ZDHHC9 and PCBP1 through immunoprecipitation and LC-MS analyses. As a palmitoyltransferase, ZDHHC9 was found to inhibit ferroptosis by palmitoylating PCBP1. Mechanistically, ZDHHC9 palmitoylates PCBP1 at the C109 residue, which inhibits PCBP1 ubiquitination and consequently suppresses SLC7A11-mediated ferroptosis. In line with these results, further experiments demonstrated that PCBP1 regulates ferroptosis by modulating the RNA stability of SLC7A11. Finally, IHC and immunofluorescenc demonstrated that ASF1B, ZDHHC9, PCBP1, and SLC7A11 exhibit significant clinical correlations. Furthermore, this signaling axis is strongly associated with PD-L1 expression rather than HER-2 expression. In conclusion, the study suggests that ASF1B promotes liver metastasis in GC by inhibiting ferroptosis via the ZDHHC9/PCBP1/SLC7A11 axis, providing a potential immunotherapeutic target for treating patients with GCLM.