Abstract: Objective To study if IRF1 could regulate the polarization by IRF1 and M1 status and affect M1 mediated antitumor function. Methods U937 derived M1 macrophage (U937-M1) model was established.The cells were devided into 4 groups, including: the PMA pretreated unpolarized macrophage (M0) , the PMA, IFN-γ and LPS stimulated M1 macrophage (M1), the siRNA of IRF1 knocked down M1 macrophage (siIRF1) and the negative control siRNA treated M1 macrophage (siC).Furthermore, the expression of CD86 and CD206 was detected by flow cytometry, the M1/M2 associated markers (IL-12p35，IL-12p40，IL-23p19，IL-6，TNF-α/IL-10) and IFNB1 were analyzed by qPCR, the expression of IL-12p70 and IL-10 was examined by ELISA, the expression of IRF1 and IRF5 was detected by Western blot, the proliferration and apoptosis of HCC were analyzed by CCK8 and flow cytometry, respectively. Results Compared with the U937-M1, the IRF1 knocked down group showed impaired CD86 expression, but enhanced CD206 expreesion (P < 0.05); the expression of M1 related cytokines including IL-12p35，IL-12p40，IL-23p19，IL-6，TNF-α and IFNB1 was decreased, but M2 related cytokine IL-10 level was increased (P < 0.01); the secretion of IFN-β and IL-12p70 was impaired, but IL-10 was enhanced (P < 0.05). In IRF1 knocked down U937-M1, the CCK8 analysis indicated that the M1 mediated anti-proliferation effects on hepatoma carcinoma cell was turned to pro-proliferation (P < 0.05); the flow cytometry showed that the M1 mediated pro-apoptosis effects was reversed to anti-apoptosis (P < 0.01). Interestingly, IRF5 and IFN-β were decreased at both mRNA and protein levels in IRF1 knocked down U937-M1 compared with the U937-M1 (P < 0.01). Conclusions IRF1 may partly modulate IRF5 and IFN-β, and further regulate M1 polarization and its antitumor effects.

Key words: IRF1, M1 polarization, antitumor, IRF5