The effects of anti-PD-L1 monoclonal antibody on the expression of angiogenesis and invasion-related genes.

Background/aim: The role of PD-L1 in regulating the immunosuppressive tumor microenvironment via its binding on PD-1 receptors is extensively studied. The PD-1/PD-L1 axis is a significant way of cancer immune escape, and PD-L1 expression on tumor cells is suggested as a predictive marker for anti-PD-1/PD-L1 monoclonal antibodies (MoAbs). However, the tumor-intrinsic role of PD-L1 is not known well. Therefore, we aimed to investigate the effects of anti-PD-L1 antibodies on the expression of angiogenesis and metastasis-related genes in tumor cells.

Materials And Methods: The experiments were done with prostate cancer and melanoma cells with low PD-L1 expression (<5%) and prostate and breast cancer cells with high PD-L1 expression (>50%). The gene and protein expressions of VEGFA, E-cadherin, TGFβ1, EGFR, and bFGF in tumor cells were assayed at the 3 different doses of the anti-PD-L1 antibody.

Results: We found that VEGFA, E-cadherin and TGFβ1 expressions increased in PD-L1 high cells but decreased in PD-L1 low cells after anti-PD-L1 treatment. EGFR expression levels were variable in PD-L1 high cells, while decreased in PD-L1 low cells upon treatment. Also, the anti-PD-L1 antibody was found to increase bFGF expression in the prostate cancer cell line with high PD-L1 expression.

Conclusion: Our results suggest that the binding of PD-L1 on tumor cells by an anti-PD-L1 monoclonal antibody may affect tumor-intrinsic mechanisms. The activation of angiogenesis and metastasis-related pathways by anti-PD-L1 treatment in PD-L1 high tumors might be a tumor-promoting mechanism. The decrease of VEGFA, TGFβ1 and EGFR upon anti-PD-L1 treatment in PD-L1 low tumor cells provides a rationale for the use of those antibodies in PD-L1 low tumors.