Background: Immune checkpoint blockade inhibitors have aroused great expectation on many types of tumor eradication. However, the therapeutic effect of anti-PD-L1 treatment on cervical cancer is unsatisfactory and the potential antagonist is not very clear. Here, we investigated the therapeutic effect of anti-PD-L1 in cervical tumor mouse model and identified the potential threats for anti-PD-L1 therapeutic efficacy.
Results: we found that PD-L1 had a moderate expression in human and mouse cervical tumor cell lines and clinical samples compared to other tumor types and para-tumor tissue. Interestingly, our results showed that the anti-PD-L1 treated mice were dichotomously divided into responsive and unresponsive group even with the same genome background C57BL/6 syngeneic tumor model. The unresponsive tumors showed less immune cell infiltration and higher Tregs population induced immunosuppression activity than the responsive ones. Furthermore, we found that anti-PD-L1 autonomously upregulated Tregs proliferation and frequency in multiple immune organs, and, most importantly, Tregs depletion more significantly depressed the tumor growth rate and tumor weight than either anti-PD-L1 or anti-CD25 alone. Finally, we observed that the upregulating effector CD8+ T cell is associated with the better therapeutic effect of anti-PD-L1 therapy post Tregs depletion.
Conclusion: In conclusion, anti-PD-L1 therapy upregulates Tregs frequency and proliferation in tumor model, and the depletion of Tregs may be a useful adjuvant strategy for anti-PD-L1 therapy in the immunotherapy of cervical cancer.