Abstract
Background: Peritoneal metastasis (PM) occurs frequently in patients with gastric cancer (GC) and confers poor survival. Lipid metabolism and epithelial-mesenchymal transition (EMT) play an important role in GC metastasis. As Apolipoprotein C-II (APOC2) is a key protein in lipid metabolism, few studies have investigated the role of APOC2 in PM. This study aims to elucidate the potential molecular mechanism of APOC2 in the PM of GC.Methods: The Tandem Mass Tagging (TMT) method followed by liquid chromatography-tandem mass spectrometry-based proteomics analysis was used to compare the levels of differentially expressed proteins between human PM and GC tissues. APOC2 expression was evaluated by immunoblotting, and immunohistochemistry analysis (n = 111). APOC2 over-expression and knock-down expression cell models were developed and tested in vitro. RNA sequencing analysis evaluated the changes in gene expression after APOC2 knockdown in GC cells. The Agilent Seahorse XF platform and lipid staining assay were used to evaluate the role of APOC2 in lipid metabolism of GC cells. Spheroid cell invasion assay, apoptosis assay, colony formation assay, wound-healing assays, and transwell assays were performed and peritoneal implants into nude mice were done to assess the biological effects of APOC2. The underlying mechanisms were investigated using Western blot, inhibitor or activator treatment assays.Results: APOC2 was highly abundant in GC cells and PM tissues. And high APOC2 levels in GC tissues correlated with poor patient prognosis. Knockdown of APOC2 inhibited the malignant phenotype of cancer cells and EMT significantly. Massive gene expression alterations after APOC2 knockdown, which were associated with various signaling pathways, especially the PI3K/AKT signaling pathway and lipid metabolism. Furthermore, the regulatory effects of APOC2 on the EMT were partially attributed to the PI3K/AKT/mTOR signaling pathway. The results in vivo also showed that APOC2 modulated GC PM.Conclusions: We verified that knockdown of APOC2 suppressed GC cell Lipid metabolism, proliferation, migration, invasion, and EMT, accompanied by inactivation of PI3K/AKT/mTOR signaling pathway. APOC2 overexpression had the opposite effects GC cell phenotypes and mechanisms. Collectively, our results identified APOC2 in PM as a potential therapeutic target.
Apolipoprotein C‐II induces EMT to promote gastric cancer peritoneal metastasis via PI3K/AKT/mTOR pathway
