Targeting tumorous Circ-E-Cadherinencoded C-E-Cad inhibits the recruitment and function of breast cancer-associated myeloid-derived suppressor cells.

We previously demonstrated that the C-E-cad protein encoded by circ-E-cadherin promotes the self-renewal of glioma stem cells. The expression pattern of C-E-cad in breast cancer and its potential function in the tumor microenvironment are unclear. The expression of circ-E-cadherin and C-E-cad was detected in breast cancer specimens. The influence of C-E-cad expression on MDSCs was assessed using FACS and in vivo tumorigenesis experiments. The synergistic effect of anti-C-E-cad and anti-PD-1 antibodies was validated in vivo. circ-E-cadherin and the encoded protein C-E-cad were found to be upregulated in breast cancer vs. normal samples. C-E-cad promotes the recruitment of MDSCs, especially PMN-MDSCs. C-E-cad activates EGFR signaling in tumor cells and promotes the transcription of CXCL8; moreover, C-E-cad binds to MDSCs and maintains glycolysis in PMN-MDSCs. Targeting C-E-cad enhanced anti-PD-1 efficiency. Our data suggested that C-E-cad is markedly overexpressed in breast cancer and promotes MDSC recruitment and survival. Targeting C-E-cad increases the efficacy of immune checkpoint inhibitor therapy.