CircZFAND6 suppresses gastric cancer metastasis and reduces resistance to TKI therapy

Peritoneal metastasis, the most common mode of dissemination in gastric cancer (GC), is characterized by resistance to treatment and a poor prognosis. Accumulating evidence indicates that circular RNAs (circRNAs) play a significant role in tumor progression. However, the role of circRNAs in GC peritoneal dissemination (GCPD) remains unknown. CircRNA profiles in four clinical GCPD specimens were established using RNA-seq. Circular integrity was validated through Sanger sequencing, agarose gel electrophoresis, and RNase R resistance. The expression of Circ_0000643 (circZFAND6) in GC cells was determined by qRT-PCR. Functional assays, both in vitro and in vivo, assessed the suppressive effect of circZFAND6 in GC. Mechanistic studies that included AGO2-RIP, FISH, and luciferase reporter systems identified miR-6815-3p as a direct target of circZFAND6. RNA-seq and Western blotting were utilized to examine the impact of circZFAND6 on the Wnt/β-catenin signaling pathway. The construction of a FLAG-tagged circZFAND6 overexpression plasmid was performed to verify the coding potential of circZFAND6, while murine tumor models were employed to evaluate the synergy between circZFAND6 overexpression and gefitinib. The interaction between the circZFAND6 encoding protein and ERBB3 was demonstrated using co-IP. CircZFAND6 showed significant downregulation in GC tissues and cell lines, with its reduced expression independently linked to poor prognosis in GC patients. Functional analysis indicated that overexpression of circZFAND6 markedly inhibited GC cell proliferation, migration, and invasion in vitro, while also decreasing peritoneal dissemination in a xenograft mouse model. Mechanistically, circZFAND6 acted as a competitive endogenous RNA (ceRNA) that sponged miR-6815-3p, thus alleviating its post-transcriptional repression of APC mRNA. This resulted in decreased Wnt/β-catenin signaling activity. Our study revealed that circZFAND6 engaged in “rolling translation” to produce the circZFAND6-aa protein, which specifically interacts with ERBB3, thereby hindering EGFR tyrosine kinase activity and downstream AKT signaling pathways to overcome gefitinib resistance in GC. Our study shows that circZFAND6 acts as a tumor suppressor in gastric cancer by regulating the miR-6815-3p/APC/Wnt-β-catenin pathway. Additionally, its novel peptide helps reverse resistance to gefitinib. These findings highlight circZFAND6 as a promising prognostic marker and a potential therapeutic target for gastric cancer.