IHC and IF staining for C5aR1 confirmed low expression in the tumour cells of the tissue from the C5aR1shRNA-treated group (Fig. 4h–m), and the number of cleaved caspase-3+ apoptotic cancer cells was significantly higher in the C5aR1shRNA-treated group than in the control group (Fig. 4n–q), thereby validating in vivo functional regulation of C5aR1 effectively suppressed tumour growth. Here, C5AR1 is linked to cancer.