The YAP1-IGFBP2 axis as a predictive biomarker and therapeutic target in gastric cancer metastasis

Background: Gastric cancer (GC) with peritoneal metastasis (PM) carries a poor prognosis, with a five-year survival rate of only 5%. Insulin-like growth factor binding protein 2 (IGFBP2) has been implicated in tumor proliferation, invasion, and metastasis through both IGF-dependent and independent mechanisms in various cancers. However, its role in GC progression and PM remains undefined. This study investigates the functional significance of the IGFBP2-YAP1 axis in GC tumorigenesis and metastasis, particularly to the peritoneum. Methods: Single-cell RNA sequencing (scRNA-seq) of GC primary tumors, matched normal tissues, and PM was performed to characterize IGFBP2 expression across cellular compartments. Bulk RNA sequencing of Yes-associated protein 1 (YAP1) knockout (KO) vs control GC cell lines, followed by quantitative PCR (qPCR) and enzyme-linked immunosorbent assay (ELISA), evaluated YAP1-dependent regulation of IGFBP2 transcription and secretion. Protein expression of IGFBP2 and YAP1 was assessed by Western blotting (WB) in multiple GC cell lines. IGFBP2 knockdown (KD) was achieved by short-hairpin RNA (shRNA) vectors in HGC27 and MKN7 cells. ELISA, migration, and invasion assays were conducted to determine the functional impact upon depletion of IGFBP2. Results: scRNA-seq revealed that both YAP1 and IGFBP2 are highly enriched in PM of GC compared to primary and normal gastric tissues, and their elevated expression correlates with poor prognosis. Among nine GC cell lines, AGS, GA0518, SNU16, HGC27, and MKN7 cells exhibited high expression of both YAP1 and IGFBP2 proteins. RNAseq of YAP1 KO vs control cells revealed significant downregulation of IGFBP2 upon YAP1 depletion, implicating YAP1 as an upstream regulator. Consistently, qPCR and ELISA confirmed reduced IGFBP2 transcription and secreted protein levels in YAP1 KO cells. Functionally, recombinant IGFBP2 (rIGFBP2) rescued the impaired invasiveness of YAP1 KO patient-derived GC PM cells (GA0518). IGFBP2 KD in HGC27 and MKN7 cells was validated by qPCR and WB, and these cell lines demonstrated reduced extracellular IGFBP2 levels along with diminished migration and invasion compared with controls. Conclusions: Our findings define the YAP1-IGFBP2 axis as a key driver of GC and PM. Elevated co-expression of IGFBP2 and YAP1 in PM, combined with loss of function studies demonstrating reduced migration and invasion upon IGFBP2 deletion, underscores their cooperative role in metastatic adaptation. These findings identify IGFBP2 as a YAP1-regulated effector that promotes tumor aggressiveness, highlighting the clinical potential of targeting the YAP1-IGFBP2 axis. Collectively, the YAP1-IGFBP2 axis may serve as both a predictive and prognostic biomarker and a promising therapeutic target for advanced GC patients with PM.