Vincristine upregulates PD-L1 and increases the efficacy of PD-L1 blockade therapy in diffuse large B-cell lymphoma.

Background: Some chemotherapy drugs have immunomodulatory effects on specific tumors. The potential of vincristine (VCR) in the R-CHOP regimen to act as both a chemotherapeutic and an immunomodulatory agent via PD-L1 in tumor cells remains unclear.

Methods: In vitro screening VCR showed that the IC50 value of VCR in the DLBCL cell lines was approximately 2 nM. Western blotting and q-PCR were used to detect the expression of PD-L1. The effect of VCR combined with PD-L1 mAb was tested in a co-culture system of LY-OCI-3 cells and peripheral blood mononuclear cells and in DLBCL xenograft mouse model. Flow cytometry was used to determine the proportion of T lymphocyte subsets. The effect of the STAT3 inhibitor nifuroxazide on VCR-induced PD-L1 expression was tested in LY-OCI-3 and SU-DHL-4 cells.

Results: VCR upregulated PD-L1 protein and mRNA expression in various DLBCL cell lines. PD-L1 Ab combined with VCR significantly increased the proportion of CD8 + Granzyme B + , INF-γ + or TNF-α + CD3 + T cells. VCR + PD-L1 Ab inhibited tumor growth more effectively than VCR monotherapy, whereas PD-L1 Ab alone had no significant effect. Survival time did not differ significantly between the PD-L1 Ab group and the control group, whereas it was significantly longer in the VCR monotherapy and combination groups which showed more longer survival compared with the former. Nifuroxazide downregulated p-STAT3 and PD-L1 protein levels.

Conclusions: VCR upregulated PD-L1 expression in DLBCL cells partially by promoting the p-STAT3; VCR combined with PD-L1 Ab activated effector T cells and increased the antitumor immune response in vitro and in vivo.