Figure 5.

Regulatory role of circRNAs in the pathway for apoptosis of HCC. Apoptosis can be initiated by one of two pathways: extrinsic or intrinsic. Eventually, both pathways converge at the activation of executioner caspases that execute apoptosis. If PI3K is activated by cytokines or growth factors, it phosphorylates PIP2 to generate PIP3 and subsequently activates the PI3K/Akt signaling pathway. AKT signaling has a strong anti-apoptotic role through the phosphorylation and inhibition of key pro-apoptotic proteins (e.g., Bad). PTEN can dephosphorylate PIP3 to PIP2 and negatively regulates the PI3k/Akt pathway. These components involved in apoptosis can be regulated by circRNAs in HCC. circRNAs with anti-apoptotic effects are denoted as red circles whereas pro-apoptotic circRNAs are denoted as green circles.