Icariin modulates the tumor microenvironment in colorectal cancer by targeting M2 macrophage polarization via PI3K/AKT pathway

Colorectal cancer (CRC) progression is influenced by intricate interactions in the tumor microenvironment (TME), with M2-polarized macrophages being key players in enhancing tumor growth and suppressing the immune response. Icariin (ICA), a bioactive flavonoid isolated from Epimedium brevicornu Maxim., exhibits potential antitumor properties. Nevertheless, its role in modulating macrophage-mediated immunosuppression in CRC remains unclear. To assess ICA's effects on CRC malignancy within an M2-enriched microenvironment, we established a CRC cell/M2 macrophage co-culture system. ICA suppressed CRC cell proliferation, migration, and invasion in co-culture with M2 macrophages. M2 polarization markers and PI3K/AKT pathway modulation were analyzed by western blot and qRT-PCR. Mechanistic studies revealed that ICA inhibited M2 polarization and suppressed the phosphorylation of PI3K and AKT. In vivo validation utilized two models, an AOM/DSS-induced CRC model and a syngeneic CT26-WT implantation system, evaluating both tumor progression and macrophage phenotype alterations. We found that ICA attenuated tumor growth and reduced M2 macrophage infiltration. Collectively, these finding demonstrated that ICA suppressed M2 macrophage polarization via PI3K/AKT signaling pathway, thereby inhibiting CRC progression. This study reveals a previously unrecognized mechanism by which ICA inhibits CRC and demonstrates its potential as a promising therapeutic agent for CRC treatment.