Naringenin (4,5,7-trihydroxyflavonoid) is a naturally occurring bioflavonoid found in citrus fruits, which plays an important role in metabolic syndrome, neurological disorders, and cardiovascular diseases. However, the pharmacological mechanism and biological function of naringenin on anti-angiogenesis and anti-tumor immunity have not yet been elucidated. Our study firstly demonstrates that naringenin inhibits the growth of hepatocellular carcinoma (HCC) cells both in vivo and in vitro. Naringenin diminishes the ability of HCC cells to induce tube formation and migration of human umbilical vein endothelial cells (HUVECs) and suppresses neovascularization in chicken chorioallantoic membrane (CAM) assays. Meanwhile, in vivo results demonstrate that naringenin can significantly upregulate level of CD8⁺ T cells, subsequently increasing the level of immune-related cytokines in the tumor immune microenvironment. Mechanistically, we found that naringenin facilitate the K48-linked ubiquitination and subsequent protein degradation of vascular endothelial growth factor A (VEGFA) and mesenchymal-epithelial transition factor (c-Met), which reduces the expression of programmed death ligand 1 (PD-L1). Importantly, combination therapy naringenin with PD-L1 antibody or bevacizumab provided better therapeutic effects in liver cancer. Our study reveals that naringenin can effectively inhibit angiogenesis and anti-tumor immunity in liver cancer by degradation of VEGFA and c-Met in a K48-linked ubiquitination manner. This work enlightens the potential effect of naringenin as a promising therapeutic strategy against anti-angiogenesis and anti-tumor immunity in HCC.

Serine/arginine-rich splicing factor 7 (SRSF7), a known splicing factor, has been revealed to play oncogenic roles in multiple cancers. However, the mechanisms underlying its oncogenic roles have not been well addressed. Here, based on N⁶-methyladenosine (m⁶A) co-methylation network analysis across diverse cell lines, we find that the gene expression of SRSF7 is positively correlated with glioblastoma (GBM) cell-specific m⁶A methylation. We then indicate that SRSF7 is a novel m⁶A regulator, which specifically facilitates the m⁶A methylation near its binding sites on the mRNAs involved in cell proliferation and migration, through recruiting the methyltransferase complex. Moreover, SRSF7 promotes the proliferation and migration of GBM cells largely dependent on the presence of the m⁶A methyltransferase. The two m⁶A sites on the mRNA for PDZ-binding kinase (PBK) are regulated by SRSF7 and partially mediate the effects of SRSF7 in GBM cells through recognition by insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2). Together, our discovery reveals a novel role of SRSF7 in regulating m⁶A and validates the presence and functional importance of temporal- and spatial-specific regulation of m⁶A mediated by RNA-binding proteins (RBPs).
Humans ; Cell Line, Tumor ; Cell Proliferation ; Gene Expression Regulation, Neoplastic ; Glioblastoma/genetics* ; Methyltransferases/metabolism* ; RNA Splicing Factors/metabolism* ; RNA, Messenger/genetics* ; RNA-Binding Proteins/metabolism* ; Serine-Arginine Splicing Factors/metabolism* ; RNA Methylation/genetics*