LncRNA TP73-AS1/miR-539/MMP-8 axis modulates M2 macrophage polarization in hepatocellular carcinoma via TGF-β1 signaling

Purpose: Our study aimed to study the role of lncRNA TP73-AS1/miR-539/MMP-8 axis in modulating M2 macrophage polarization in hepatocellular carcinoma (HCC).

Methods: The gene expression levels of TP73-AS1, miR-539 and MMP-8 were modified by transfection with the overexpression or knockdown vectors. The patient survival rate was analyzed using Kaplan-Meier method. The levels of TP73-AS1, miR-539, MMP-8 and M1/2 macrophage polarization markers were analyzed by qRT-PCR, western blot, and flow cytometry. The release of TGF-β1 in the supernatant was determined by ELISA assay. The interaction between TP73-AS1, miR-539 and MMP-8 was analyzed by bioinformatics analysis and dual-luciferase reporter assays. Mouse xenograft model was further established to examine the therapeutic effects of the TP73-AS1 knockdown and miR-539 overexpression in vivo.

Results: We found TP73-AS1 and MMP-8 upregulation, and miR-539 downregulation in HCC tissues and cell lines. Lower TP73-AS1 and MMP-8 expressions and higher miR-539 expression were associated with higher survival rate of patients. M2-macrophage markers CD206, Arg-1 and CD163 were significantly upregulated in the tumor tissues. TP73-AS1 negatively and directly regulated miR-539 and knockdown of TP73-AS1 inhibited MMP-8 expression and M2 macrophage polarization. Also, overexpression of miR-539 suppressed M2 macrophage polarization by negatively regulating MMP-8. Furthermore, knockdown of MMP-8 also restrained M2 macrophage polarization via inhibiting TGF-β1 signaling. We also found knockdown of TP73-AS1 or overexpression of miR-539 inhibited HCC tumor growth and M2 macrophage infiltration in vivo.

Conclusion: Our study demonstrated lncRNA TP73-AS1 negatively regulated miR-539 to promote MMP-8 expression, which activated TGF-β1 signaling to induce M2 macrophage polarization in HCC.