Nanobubble-based anti-hepatocellular carcinoma therapy combining immune check inhibitors and sonodynamic therapy

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, posing a global threat to human healthcare, and current approved treatment strategies do not produce satisfactory outcomes. Here, nanobubbles (NBs) were prepared that carried Immune Check Inhibitors (ICIs), PD-L1 antibody (PD-L1 Ab) and sonodynamic agent CHLORIN E6 (Ce(6)); the anti-cancer properties of these NBs were analyzed from the point of view of immune and sonodynamic therapies. The PD-L1 Ab/Ce(6)-NBs could inhibit tumor growth through regulating reactive oxygen species (ROS) production, apoptosis, and most importantly, the function of associated immunocytes, including natural killer cells and lymphocytes. The tumor tissues highly expressed markers of immunogenic tumor cell death (ICD) in which the expression of calreticulin (CRT) and ICD-related immune cytokines (CD80, CD86, INF-γ, and IL-2) were increased in PD-L1 Ab/Ce(6)-NB treated mice. PD-L1 Ab/Ce(6)-NBs also promoted murine spleen lymphocyte proliferation and cytotoxic activity, as well as CD8+ T cell infiltration in the tumor tissues, and downregulation of the PD-L1 protein and mRNA expression. Furthermore, Bax expression was increased and Bcl-2 was inhibited at the mRNA and protein levels in a murine subcutaneous transplanted tumor model. These results indicate that PD-L1 Ab/Ce(6)-NBs can induce ROS-dependent ICD to further boost anti-cancer immune responses under the action of targeting the PD-1/PD-L1 immune check point in the tumor microenvironment as a promising therapeutic agent for HCC.