PD-1 blockade in combination with zoledronic acid to enhance the antitumor efficacy in the breast cancer mouse model

Abstract

Background: Blockade of PD-1 receptor may provide proof of concepts for the activity of an immune-modulation approach for the treatment of breast cancer (BC). Zoledronic acid (ZA) has been proven to inhibit angiogenesis, invasion, and adhesion of tumor cells. The aim of this study was to investigate the potential of monoclonal antibody against T cell checkpoint PD-1 in combination with chemotherapeutic drug ZA in BC mouse model.

Methods: The 4 T1-fLuc mouse BC model was used in this study. The anti-tumor efficacy of anti-PD-1 antibody alone or in combination with ZA was monitored by measuring bioluminescence imaging (BLI) and tumor volume. At the end of study, the flow cytometry was used to determine the immune cell population in tumors after different treatment.

Results: The results showed that mice treated with the combination therapy of anti-PD-1 antibody plus ZA exhibited better antitumor response compared to untreated controls or single therapy with no obvious toxicity.

Conclusion: Our study provides preclinical evidence for the enhanced BC treatment benefit through targeting co-signal molecules by combining anti-PD-1 antibody plus ZA treatment.

Keywords: Breast cancer; Checkpoint inhibitior; PD-1; Therapy; Zoledronic acid.

Fig. 1

Representative BLI and tumor volume after different treatments for 12 continuous days. a. The typical BLI images of each group after different treatments; b. Quantification of the BLI signal of tumors after different treatments; c. Tumor volume measurement at different time points. The data are presented as the means ± SEM (* p < 0.05)

Fig. 2

The mouse body weight changes after treatment for 15 continuous days

Fig. 3

Histological toxicity evaluation of major organs after treatment. H&E staining of the heart, liver, spleen, lung, and kidney harvested from different groups of mice at 15 day after different treatment

Fig. 4

The analysis of TILs in tumors after different treatments using flow cytometry and immunofluorescence staining. a Flow cytometry data for the CD3⁺ T cell population, CD8⁺ in the CD3⁺ T cell population, CD4⁺ in CD3⁺ T cells, and MDSC cells. *P < 0.05. b Immunofluorescence staining of CD8⁺ and CD11b⁺ MDSC cells in the tumor tissues from 4 T1 mice after different treatments

Fig. 5

The IFN-γ and IL-18 expression levels in the plasma was examined after different treatments using ELISA, *P < 0.05