Further study suggests that aberrant C5aR expression suppresses TAM antitumor activity, as C5aR knockout or pharmacologic inhibition enhanced the ability of macrophages to kill tumor cells in vitro and increased the abundance of M1-like TAMs in vivo, in agreement with previous reports showing the role of C5a-C5aR in regulating the phenotype of macrophages in colon cancer.25 Here, C5AR1 is linked to colonic neoplasm.