FAT10 induces immune suppression by upregulating PD-L1 expression in hepatocellular carcinoma.

The upregulation of programmed death ligand 1 (PD-L1) plays a crucial role in facilitating cancer cells to evade immune surveillance through immunosuppression. However, the precise regulatory mechanisms of PD-L1 in hepatocellular carcinoma (HCC) remain undefined. The correlation between PD-L1 and ubiquitin-like molecules (UBLs) was studied using sequencing data from 20 HCC patients in our center, combined with TCGA data. Specifically, the association between FAT10 and PD-L1 was further validated at both the protein and mRNA levels in HCC tissues from our center. Subsequently, the effect of FAT10 on tumor progression and immune suppression was examined through both in vivo and in vitro experiments. Utilizing sequencing data, qPCR, and Western blotting assays, we confirmed that FAT10 was highly expressed in HCC tissues and positively correlated with PD-L1 expression. Additionally, in vitro experiments demonstrated that the overexpression of FAT10 fostered the proliferation, migration, and invasion of HCC cells. Furthermore, the overexpression of FAT10 in HCC cells led to an increase in PD-L1 expression, resulting in the inhibition of T cell proliferation and the enhancement of HCC cell resistance to T cell-mediated cytotoxicity. Moreover, in vivo experiments utilizing the C57BL/6 mouse model revealed that overexpression of FAT10 effectively suppressed the infiltration of CD8 + GZMB + and CD8 + Ki67 + T cells, as well as reduced serum levels of TNF-α and IFN-γ. Mechanistically, we further identified that FAT10 upregulates PD-L1 expression via activating the PI3K/AKT/mTOR pathway, but not in a ubiquitin-like modification. In conclusion, our findings indicate that FAT10 promotes immune evasion of HCC via upregulating PD-L1 expression, suggesting its potential as a novel target to enhance the efficiency of immunotherapy in HCC.

Identification of FOXP1 as a favorable prognostic biomarker and tumor suppressor in intrahepatic cholangiocarcinoma.

BACKGROUND: Forkhead-box protein P1 (FOXP1) has been proposed to have both oncogenic and tumor-suppressive properties, depending on tumor heterogeneity. However, the role of FOXP1 in intrahepatic cholangiocarcinoma (ICC) has not been previously reported. METHODS: Immunohistochemistry was performed to detect FOXP1 expression in ICC and normal liver tissues. The relationship between FOXP1 levels and the clinicopathological characteristics of patients with ICC was evaluated. Finally, in vitro and in vivo experiments were conducted to examine the regulatory role of FOXP1 in ICC cells. RESULTS: FOXP1 was significantly downregulated in the ICC compared to their peritumoral tissues (p < 0.01). The positive rates of FOXP1 were significantly lower in patients with poor differentiation, lymph node metastasis, invasion into surrounding organs, and advanced stages (p < 0.05). Notably, patients with FOXP1 positivity had better outcomes (overall survival) than those with FOXP1 negativity (p < 0.05), as revealed by Kaplan-Meier survival analysis. Moreover, Cox multivariate analysis showed that negative FOXP1 expression, advanced TNM stages, invasion, and lymph node metastasis were independent prognostic risk factors in patients with ICC. Lastly, overexpression of FOXP1 inhibited the proliferation, migration, and invasion of ICC cells and promoted apoptosis, whereas knockdown of FOXP1 had the opposite role. CONCLUSION: Our findings suggest that FOXP1 may serve as a novel outcome predictor for ICC as well as a tumor suppressor that may contribute to cancer treatment.

miR-424(322)-5p targets Ezh1 to inhibit the proliferation and differentiation of myoblasts.

The proliferation and differentiation of myoblasts are considered the key biological processes in muscle development and muscle-related diseases, in which the miRNAs involved remain incompletely understood. Previous research reported that miR-424(322)-5p is highly expressed in mouse skeletal muscle. Therefore, C2C12 cells are used as a model to clarify the effect of miR-424(322)-5p on the proliferation and differentiation of myoblasts. The data show that miR-424(322)-5p exhibits a decreasing trend upon myogenic differentiation. Overexpression of miR-424(322)-5p inhibits the proliferation of myoblasts, manifested by downregulation of proliferation marker genes ( CCNB1, CCND2, and CDK4), decreased percentage of EdU + cells, and reduced cell viability. In contrast, these phenotypes are promoted in myoblasts treated with an inhibitor of miR-424(322)-5p. Interestingly, its gain of function inhibits the expression of myogenic regulators, including MyoD, MyoG, MyHC, and Myf5. Additionally, immunofluorescence staining of MyHC and MyoD shows that overexpression of miR-424(322)-5p reduces the number of myotubes and decreases the myotube fusion index. Consistently, inhibition of its function mediated by an inhibitor promotes the expressions of myogenic markers and myotube fusion. Mechanistically, gene prediction and dual-luciferase reporter experiments confirm that enhancer of zeste homolog 1 ( Ezh1) is one of the targets of miR-424(322)-5p. Furthermore, knockdown of Ezh1 inhibits the proliferation and differentiation of myoblasts. Compared with NC and inhibitor treatment, inhibitor+si- EZH1 treatment rescues the phenotypes of proliferation and differentiation mediated by the miR-424(322)-5p inhibitor. Taken together, these data indicate that miR-424(322)-5p targets Ezh1 to negatively regulate the proliferation and differentiation of myoblasts.

Ablation of KDM2A Inhibits Preadipocyte Proliferation and Promotes Adipogenic Differentiation.

Epigenetic signals and chromatin-modifying proteins play critical roles in adipogenesis, which determines the risk of obesity and which has recently attracted increasing interest. Histone demethylase 2A (KDM2A) is an important component of histone demethylase; however, its direct effect on fat deposition remains unclear. Here, a KDM2A loss of function was performed using two unbiased methods, small interfering RNA (siRNA) and Cre-Loxp recombinase systems, to reveal its function in adipogenesis. The results show that the knockdown of KDM2A by siRNAs inhibited the proliferation capacity of 3T3-L1 preadipocytes. Furthermore, the promotion of preadipocyte differentiation was observed in siRNA-treated cells, manifested by the increasing content of lipid droplets and the expression level of adipogenic-related genes. Consistently, the genetic deletion of KDM2A by Adipoq-Cre in primary adipocytes exhibited similar phenotypes to those of 3T3-L1 preadipocytes. Interestingly, the knockdown of KDM2A upregulates the expression level of Transportin 1(TNPO1), which in turn may induce the nuclear translocation of PPARγ and the accumulation of lipid droplets. In conclusion, the ablation of KDM2A inhibits preadipocyte proliferation and promotes its adipogenic differentiation. This work provides direct evidence of the exact role of KDM2A in fat deposition and provides theoretical support for obesity therapy that targets KDM2A.

Immune-related genes response to stimulation of miR-155 overexpression in CIK (ctenopharyngodon idella kidney) cells and zebrafish.

MiR-155 regulates the development of germinal-center and the generation of immunoglobulin class-switched plasma cells. However, whether miR-155 is involved in immune response in fish is still unclear. Here, CIK cells transfected with miR-155 overexpressed plasmid inhibited mRNA expression of mIg and Rag2 (P < 0.05). Interestingly, mIg was predicted as a potential target gene of miR-155 by RNAhybrid, with a putative binding site in its CDS. Further, mIg luciferase reporter vectors with successive deletions of mIg cDNA sequence were constructed and dual luciferase reporter assay showed that vectors containing the sequence from 318 to 347 in CDS exhibited lower relative luciferase activity than others without predicted binding region (P < 0.05), which indicated mIg is the target gene of miR-155 and reveal bona fide targeted binding site of mIg for miR-155 in fish. In vivo, the zebrafish were respectively injected with miR-155 overexpressed and empty vector, and showed that miR-155 efficiently expressed in zebrafish (P < 0.01), which consistently decreased mRNA level of immune-related genes, including mIg (P < 0.01), sIg (P < 0.05), AID (P < 0.01), PU.1 (P < 0.05) and Rag2 (P < 0.05) at d 3 and d 6 post injection, comparing to control. Collectively, this work indicates that overexpression of miR-155 suppresses the mRNA level of immune-related genes in CIK cells and zebrafish, and mIg is a novel target gene of miR-155 in fish. These findings provide an insight into the miR-155 modulating adaptive immunity in grass carp and zebrafish.

CircNUP54 promotes hepatocellular carcinoma progression via facilitating HuR cytoplasmic export and stabilizing BIRC3 mRNA.

Circular RNAs (circRNAs) have been implicated in tumorigenesis and progression of various cancers. However, the underlying mechanisms of circRNAs in hepatocellular carcinoma (HCC) have not been fully elucidated. Herein, a new oncogenic circRNA, hsa_circ_0070039 (circNUP54), was identified to be significantly upregulated in HCC through circRNA sequencing. As verified in 68 HCC samples, circNUP54 overexpression was correlated with aggressive cancerous behaviors and poor outcomes. Moreover, the function experiments showed that knockdown of circNUP54 inhibited the malignant progression of HCC in vitro and in vivo, whereas overexpression of circNUP54 had the opposite role. Mechanistic investigations carried out by RNA pull-down, RNA immunoprecipitation, and immunofluorescence revealed that circNUP54 interacted with the RNA-binding protein Hu-antigen R (HuR) and promoted its cytoplasmic export. The cytoplasmic accumulation of HuR stabilized the downstream BIRC3 mRNA through its binding to the 3' UTR region. Consequently, the encoded protein of BIRC3, cellular inhibitor of apoptosis 2 (cIAP2), proceeded to activate the NF-κB signal pathway and ultimately contributed to HCC progression. In addition, depletion of BIRC3 rescued the pro-tumorigenic effect of circNUP54 on HCC cells. Overall, this study demonstrated that circNUP54 facilitates HCC progression via regulating the HuR/BIRC3/NF-κB axis, which may serve as a promising therapeutic target for HCC treatment.