Tumor associated macrophages are potential targets of the immune
therapy for patients with
colon cancer. PKCα acts as a
tumor suppressor in the intestine. However, the correlation between PKCα expressed in
colon cancer cells and tumor associated macrophages polarization has never been detected. In the present study, the correlation between PKCα expression and level of M1 macrophages was evaluated in human
colon cancer tissues. A xenograft mouse model of
colon cancer cells with different PKCα expression level was constructed to evaluate the effect of PKCα on M1 macrophages polarization in vivo. Co-culture of
colon cancer cells and differentiated macrophages was used to detect the potential interplay in vitro. PKCα regulated production of
cytokines which correlated with macrophage polarization and the underlying mechanism was further explored. Our study showed that high PKCα expression in human
colon cancer tissues correlated with better prognosis and high M1 macrophage content. PKCα expressed in
colon cancer cells inhibited the growth of
colon cancer in mice model. PKCα induced macrophages polarized to the M1-like phenotype both in vitro and in vivo. Mechanistically, PKCα targeted P38 via MKK3/6 to promote
IL12 and
GM-CSF expression which further enhanced M1-like macrophages polarization. In conclusion, this study provided evidence for the first time that PKCα in
colon cancer cells play an anticancer action by inducing the polarization of tumor associated macrophages to M1-like phenotype in the tumor microenvironment. PKCα promoted
IL12/
GM-CSF-mediated M1 polarization through MKK3/6-P38 signaling pathway. Our investigation suggested that modulation of the PKCα signaling pathway might serve as a novel strategy for
colon cancer therapy.