Cabozantinib Combined with Anti-PD-L1 Antibody Produced Antitumor Effect on Mice Melanoma Xenograft and its Mechanism / 中山大学学报(医学科学版)

ABSTRACT

@#【Objective】The aim of this study was to investigate the effect and mechanism of cabozantinib combined with anti-PD-L1 antibody on the growth of subcutaneous transplanted malignant melanoma in mice.【Methods】Established mouse subcutaneous xenograft model using mouse melanoma cell line B16- F10，and then randomly divided into five groups：saline control group，vehicle control group，anti PD- L1 antibody group，cabozantinib group，cabozantinib in combined with anti- PD- L1 antibody group （combination group）. Tumor growth was observed and tumor volume was measured every 2 days. The research endpoint was defined as when the tumor volume reached 2 000 mm3 or the difference between the groups was statistically significant. Then the mice were sacrificed and tissue samples were taken at the endpoint of the study. Infiltrating immune cells including CD4 + ，CD8 + T lymphocytes and myelogenous suppressor cells （MDSC）were detected by flow cytometry. In addition，B16-F10 cells cultured in vitro were treated with different drugs， the apoptosis was detected by flow cytometry ，and the protein expressions of AKT ，p-AKT ，mTOR and p-mTOR were detected by western blot assay.【Results】B16- F10 melanoma xenograft model showed that anti- PD- L1 antibody group had no obvious antitumor effect ，while both cabozantinib group and combination group produced significant antitumor effect，and the combination group had more obvious antitumor effect compared to cabozantinib group（P=0.001 5）. B16- F10 cells were treated with different drugs in vitro，and the apoptosis rate of the combination group was significantly higher than that of cabozantinib group at 24 h and 48 h，respectively（24 hP=0.003 5；48 hP=0.002 9）. Western blot assay showed that the combination group and cabozantinib group had no significant effect on the protein expression of AKT and mTOR，but both could reduce their phosphorylation levels，and the combination group was more remarkable. 【Conclusion】Cabozantinib in combined with anti-PD-L1 antibody had synergistic anti-tumor effect，which might be achieved by promoting B16-F10 cells apoptosis and inhibiting of AKT/mTOR pathway.