CCAAT/enhancer binding protein δ inhibits invasion and metastasis of liver cancer by regulating M1 type macrophages polarization

Abstract

Objective: To explore the regulation of macrophage polarization and its effects on liver cancer invasion, metastasis and apoptosis by CCAAT/enhancer binding protein δ (CEBPD). Methods: THP-1 stable transfected cells with knockdown CEBPD (shCEBPD) and negative control shNC were constructed by lentviral transfection technique. THP-1 transfected cells were induced into macrophages, lipopolysaccharide (LPS) and interferon γ(IFNγ) by phorbol 12-tetradecanoate 13-acetate (PMA), and then the polarized macrophages were further induced to M1 type. The quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect M1 type macrophage related interleukin 1β (IL-1β) genes, IL-6, tumor necrosis factor α (TNFα), and inducible nitric oxide synthase (iNOS) mRNA expression level. Flow cytometry was used to detect M1 macrophage-specific surface marker CD80 expression levels. M1-induced macrophages were co-cultured with liver cancer MHCC97H cells using Transwell non-contact small sized co-culture dishes. MHCC97H cells invasion and metastasis were detected by Transwell and scratch assay under co-culture conditions, and the MHCC97H cells apoptosis was detected by flow cytometry. Results: The mRNA expression levels of M1 macrophage marker genes iNOS, TNFα, IL-6 and IL-1β in THP-1 derived macrophages were decreased after CEBPD knockdown. M1 macrophage-specific surface marker CD80 expression levels were decreased (23.7% ± 2.1% and 62.5% ± 2.0%, t = 9.58, P < 0.05). THP-1 were co-cultured with MHCC97H in shCEBPD and shNC group, respectively. Compared with shNC group, the invasion [(158.0 ± 3.5) and (75.0 ± 4.5), t = 39.87, P < 0.01] and metastatic ability (54.6% ± 1.5% and 24.3% ± 1.0%, P < 0.01) of MHCC97H cells co-cultured in shCEBPD group were stronger and the apoptosis rate was reduced [(9.4% ± 1.0%) vs. (23.7% ± 1.2%), t = 12.68, P < 0.01]. Conclusion: CEBPD can inhibit the invasion and metastasis and increase the apoptosis by amplifying M1 type macrophages polarization in liver cancer cells.