A cascade via CD276/PI3K/SIRT1/E-Cad in overcoming contact inhibition of proliferation in hepatocellular carcinoma cells.

Contact inhibition of proliferation (CIP) halts normal cell proliferation upon confluence, a mechanism often lost in cancer cells, leading to disorganized proliferation. CD276, frequently overexpressed in cancers, promotes proliferation by activating the PI3K/AKT pathway; however, its role in CIP is unexplored. Human HCC cell lines and an immortalized human hepatocyte cell line were cultured under sparse or confluent conditions. Small interfering RNA was transfected to knockdown CD276 expression and plasmid DNA was transfected to overexpress CD276. The cell cycle was analyzed by flow cytometry. Western blotting was used to detect the expression of CD276, E-Cad, SIRT1 and cell cycle proteins. Analysis revealed higher CD276 levels in HCC lines than in HepLi5, with increased CD276 correlating with reduced CIP severity and lower E-Cad expression. Overexpression of CD276 alleviated G0/G1 phase arrest induced by high-density contact, while CD276 knockdown enhanced it. CD276 emerged as a critical regulator of E-Cad in confluent HCC cells through modulating SIRT1 protein via the PI3K/AKT pathway. The findings of the present study highlighted CD276's pivotal role in regulating the cell cycle under confluent culture conditions, revealing a novel regulatory cascade involving CD276/PI3K/SIRT1/E-Cad that may influence tumor progression. This insight into CD276's undisclosed function provides potential treatment strategies for HCC intervention.