Objective      To determine the role of C5a/C5aR pathway in colon cancer

and investigate the regulatory mechanism of C5a/C5aR pathway in the expression of fibrinogen-like protein 2 (FGL2).       Methods      Fifteen colon cancer patients were recruited from general surgery department of Southwest Hospital and gastroenterology department of Xinqiao Hospital from December 2013 to July 2015. Immunohistochemical staining was used to assess the expression of complement activation fragments C5b-9

activated C3 and C5aR and the FGL2 deposition in colon cancer tissues to verify the complement activation. Western blotting was used to detect the phosphorylation level of P38 in MAPK signaling pathway and the FGL2 expression in colon cancer tissues to clarify the interaction of C5a/C5aR pathway and FGL2 expression.       Results      The activation fragments C5b-9

activated C3 and C5aR showed higher expression in colon cancer tissues than in the paratumor tissues. Furthermore

the expression of FGL2 in colon cancer tissues was higher than that in the paratumor tissues. Moreover

the MAPK signaling pathway was activated in the colon cancer tissues. C5a could promote the phosphorylation level of P38 in MAPK signaling pathway and the FGL2 expression in Raw264.7. However

C5aR antagonist could attenuate the expressions.       Conclusion      C5a/C5aR signaling pathway plays a significant role in the development of colon cancer via regulation of FGL2 expression.