Asiaticoside enhances the anti-tumor effect of anti-PDL1 by regulating T cell activity through increasing LCK activity

Abstract

Anti-PD-L1 antibody confers anti-tumor effects, but its long-term use can provoke resistance and adverse effects. Asiaticoside, a bioactive triterpene glycoside from Centella asiatica L., regulates immune function and induces apoptosis of hepatocellular carcinoma (HCC) cells. T cells play a vital role in killing tumor cells and require lymphocyte-specific protein tyrosine kinase (LCK) for activation. Here, we examined whether a combined asiaticoside and anti-PD-L1 treatment regulates T cells via LCK activation to enhance the anti-tumor effect in vivo. We established a subcutaneous mouse HCC model using Hepa1-6 cells and measured spleen and tumor weight. Morphological changes of tumor tissues were assessed by hematoxylin-eosin staining. Tumor cell apoptosis and proliferation were determined by TUNEL staining and KI67 immunohistochemistry. The proportion of activated T cells in the spleen was detected by flow cytometry, and the levels of phosphorylated p-LCK and p-AKT in the spleen were determined by Western blotting. Changes in the levels of serum inflammatory factors were detected with ELISA. Our results revealed that the combined asiaticoside and anti-PD-L1 treatment inhibited tumor growth by enhancing apoptosis and reducing tumor cell proliferation. The treatment activated T cells to increase the proportion of effector T cells in the spleen, evidenced by upregulated p-LCK and p-AKT levels. It also increased the level of TNF-α in the serum and decreased IL-6, implying an enhanced immune response. In conclusion, the combined asiaticoside and anti-PD-L1 treatment enhances the anti-HCC effect in vivo by promoting LCK activation to regulate T cells.

Keywords: Anti-PDL1; Asiaticoside; Hepatocellular carcinoma; Lymphocyte-specific protein tyrosine kinase (LCK); T cell.