Purpose: Previous studies have shown that non-SMC condensin I complex subunit G (NCAPG ) overexpression is correlated to poor prognosis of multiple cancer types. Herein, we explored the underlying mechanism of NCAPG -mediated cardia adenocarcinoma (CA) proliferation and cell cycle regulation.
Methods: The protein profiling technology was used to analyze the gene expression in 20 CA and adjacent tissue samples. Differential genes were identified by bioinformatic analysis. Western blot and qRT-PCR-based analysis assessed the NCAPG  expression levels in multiple CA cell lines. CA cell lines, SGC-7901 and AGS, were transfected with Lip 2000, and stably transfected cell lines were screened for NCAPG  overexpression and downregulation. MTT and clone formation assays were employed to detect cell proliferation, and cell cycle phases were analyzed using flow cytometry. Western blot was performed to determine the NCAPG  gene expression levels. Finally, we studied the tumorigenic effects of NCAPG  in the mouse model and validated the cell experiment results using immunohistochemistry.
Results: A significant overexpression of NCAPG  was found in CA tissues and CA cell lines. The outcomes of MTT and clone formation assays showed that NCAPG  upregulation promoted cell proliferation. The outcomes of these analyses were further validated using nude mice as an in vivo tumor model. As per the outcome of Western blot and flow cytometry analysis, NCAPG  regulated the G1 phase through the cyclins (CDK4, CDK6, and cyclin D1) overexpression and cell cycle inhibitors (P21 and P27) downregulation. Overexpressed NCAPG  and silenced NCAPG , both in vitro and in vivo, resulted in abnormal activation of the PI3K/AKT signaling pathway in CA cells. We observed that NCAPG  overexpression increased the levels of phosphorylated PI3K, AKT, and GSK3β; however, their total protein levels remained unchanged in CA cells.
Conclusion: As a CA oncogene, NCAPG  promoted cell proliferation and regulated cell cycle through PI3K/AKT signaling pathway activation.
Keywords: NCAPG , cardia adenocarcinoma, PI3K/AKT pathway, cell cycle, proliferation