IGF2BP3 Enhances the Growth of Hepatocellular Carcinoma Tumors by Regulating the Properties of Macrophages and CD8+ T Cells in the Tumor Microenvironment

Background and Aims Overexpression of IGF2BP3 is associated with the prognosis of hepatocellular carcinoma (HCC). However, its role in regulating tumor immune microenvironment (TME) is not well characterized. Here, we investigated the effects of IGF2BP3 on macrophages and CD8 + T cells within the TME of HCC. Methods The relationship between IGF2BP3 and immune cell infiltration was analyzed using online bioinformatics tools. Knockout of IGF2BP3 in mouse hepatoma cell line Hepa1-6 was established using CRISPR/Cas9 technology. In vitro cell coculture and subcutaneously implanted hepatoma mice model were used to explore the effects of IGF2BP3 on immune cells. Expression of CCL5 or transforming growth factor beta 1 (TGF-β1) was detected with quantitative real-time polymerase chain reaction, western blotting, and enzyme-linked immunosorbent assay. The binding of IGF2BP3 and its target RNA was verified by trimolecular fluorescence complementation system and RNA immunoprecipitation followed by quantitative or semiquantitative polymerase chain reaction. Results IGF2BP3 expression was elevated in HCC and was positively correlated with macrophage infiltration. Patients with higher IGF2BP3 expression and lower macrophage infiltration had a better survival rate. We found that IGF2BP3 could bind to the mRNA of CCL5 or TGF-β1, increasing their expression, and inducing macrophage infiltration and M2 polarization while inhibiting the activation of CD8 + T cells. Furthermore, inhibition of IGF2BP3 combined with anti-CD47 antibody treatment significantly suppressed the growth of hepatoma in Hepa1-6 xenograft tumor mice. Conclusions IGF2BP3 promoted the infiltration and M2-polarization of macrophages and suppressed CD8 + T activation by enhancing CCL5 and TGF-β1 expression, which facilitated the progression of Hepa1-6 xenograft tumor.

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