Figure 2.

Insufficient immune surveillance after LRTs for HCC. Image-guided locoregional treatments (LRTs) such as radiofrequency ablation (RFA), microwave ablation (MWA), percutaneous ethanol injection (PEI), cryoablation, transarterial chemoembolization (TACE), and transarterial radioembolization (TARE) cause tumor-cell necrosis or apoptosis. LRT can induce immunogenic cell death, which can be characterized by increased tumor-antigen release, antigen presenting cell (APC) activation, and decrease of regulatory T (Treg) cell frequency. These phenomena result in the augmentation of anti-tumor T cell responses and tumor surveillance. However, LRT can also induce a non-immunogenic cell death, which increases the tumor-promoting inflammation, angiogenesis, and the expression of immune checkpoint molecules. Furthermore, incomplete T cell restoration despite antigen clearance and immune-tolerant liver environment might also affect the attenuation of immune surveillance; these factors might be associated with frequent tumor recurrence even after successful LRTs for HCC.