Overexpression of IL-12 reverses the phenotype and function of M2 macrophages to M1 macrophages

The characteristic of M2-polarized macrophage is IL-10(high)IL-12(low). Reports have shown that the combined application of CpG and anti-interleukin-10 receptor antibody could switch M2 to M1, while there are few literatures about the impact of over-expression of IL-12 on M2. After infected with the recombinant adenovirus Ad-IL-12-GFP for 60 h, the generated M2 macrophages were harvested for analysis of PCR/FCM/WB, and the supernatants were collected as conditioned media. HepG2 cells were examined by MTT assay and FCM following incubated with different conditioned media. After overexpression of IL-12, The PCR analysis showed that the M2 macrophages exerted a high level of M1 macrophage specific markers (such as IL-23, IL-1 beta, et al), a low level of M2 macrophage specific markers (IL-10, TGF-beta), the FCM analysis showed that CD86 was up-regulated while CD206 was down-regulated, and the WB showed a similar change trend. The conditioned medium of IL-12 overexpressed macrophages suppressed the proliferation, induced apoptosis, and caused G0/G1 cell cycle arrest in HepG2 cells compared to the control groups (P<0.05). To conclude, these results have indicated that the phenotype and function of M2 macrophages could be reversed by the overexprression of IL-12. It may be beneficial to explore the anti-cancer immunotherapy strategy switching the M2 macrophages to M1 macrophages.