Mutational landscape of hepatoblastoma goes beyond the Wnt-β-catenin pathway

Oncogenic Role of ADAM32 in Hepatoblastoma: A Potential Molecular Target for Therapy

Outcomes of pediatric hepatoblastoma (HBL) have improved, but refractory cases still occur. More effective and safer drugs are needed that are based on molecular mechanisms. A disintegrin and metalloproteases (ADAMs) are expressed with high frequency in various human carcinomas and play an important role in cancer progression. In this study, we analyzed expression of ADAMs in HBL with a cDNA microarray dataset and found that the expression level of ADAM32 is particularly high. To investigate the role of ADAM32 in cancer, forced expression or knockdown experiments were conducted with HepG2 and HBL primary cells. Colony formation, cell migration and invasion, and cell viability were increased in HepG2 expressing ADAM32, whereas knockdown of ADAM32 induced a decrease in these cellular functions. Quantitative RT-PCR demonstrated an association between ADAM32 expression and the expression of genes related to cancer stem cells and epithelial–mesenchymal transition (EMT), suggesting a role of ADAM32 in cancer stemness and EMT. Furthermore, knockdown of ADAM32 increased cisplatin-induced apoptosis, and this effect was attenuated by a caspase-8 inhibitor, suggesting that ADAM32 plays a role in extrinsic apoptosis signaling. We conclude that ADAM32 plays a crucial role in progression of HBL, so it might be a promising molecular target in anticancer therapy.

DNA methylation in Hepatoblastoma-a literature review

Hepatoblastoma (HB) is the most common malignant liver tumor in children. Abnormal activation of the Wnt/β-catenin signaling pathway plays an important role in the formation and development of HB. Genes in HB show a global hypomethylation change, accompanied by hypermethylation of specific tumor suppressor genes (TSGs). This article reviews the hypermethylation changes in several TSGs, such as RASSF1A, SOCS1, APC, HHIP, and P16, and analyzes the pathways and mechanisms of TSGs regulating gene expression. The role of the methylation-regulating enzymes DNA methyltransferases (DNMTs) and ten-eleven translocation (TET) family members enzymes in the methylation changes of HB was analyzed, and it was speculated that the occurrence of HB is partly due to the obstruction of liver differentiation in the early stage of differentiation. The origin cells may be incompletely differentiated hepatocytes remaining in the liver of children after birth. Therefore, further studying the role of methylation regulating enzymes in methylation changes in HB is a promising future research direction.

Down-regulation of dishevelled-2 inhibits cell proliferation and invasion in hepatoblastoma

BACKGROUND

Hepatoblastoma (HB) is the most common liver cancer found in early childhood. These patients suffer poor outcomes and need novel therapies. An abnormal activation of Wnt signaling is the hallmark of HB tumorigenesis, and its pathway is a potential candidate for a pharmacological intervention.

PROCEDURE

Tissue samples of patients with HB were collected for RNA-seq, quantitative real-time PCR, and immunohistochemistry to identify if disheveled-2 (Dvl-2) was a target gene. The correlation between Dvl-2 expression and different clinicopathological features was analyzed using statistical methods. Proliferation and invasion assays were applied after knocking down Dvl-2 by shRNA in HepG2 and Huh6 HB cell lines. The antitumor effect of niclosamide on HB was ascertained in vitro and in vivo.

RESULTS

Dvl-2 was overexpressed in 90% of patients with HB, and Dvl-2 expression was positively correlated with the age of patients with HB. Knockdown of Dvl-2 could inhibit proliferation and invasion of HB cell lines. Also, niclosamide, a Food and Drug Administration approved antihelminth compound, could effectively inhibit HB cell growth in vitro and in vivo via downregulation of Dvl-2 and β-catenin expression.

CONCLUSIONS

Our results implicate that Dvl-2 is a potential therapeutic target in HB, and niclosamide could have clinical potential to treat patients with HB.

MicroRNA-26-5p functions as a new inhibitor of hepatoblastoma by repressing lin-28 homolog B and aurora kinase a expression

Hepatoblastoma (HB) is the most common liver tumor in children. Despite recent improvements in treatment strategies, the survival of children with hepatoblastoma remains poor. In this study, we identified a novel role of microRNA‐26a‐5p (miR‐26a‐5p), lin‐28 homolog B (LIN28B), Ras‐related nuclear protein (RAN), and aurora kinase A (AURKA) in HB. The expression of LIN28B, RAN, and AURKA was significantly up‐regulated in human HB livers and cell lines. Knockdown of LIN28B and RAN by small interfering RNAs inhibited HB tumor cell proliferation and foci formation. We also elucidated miR‐26a‐5p‐mediated translational inhibition of LIN28B and AURKA in HB. Overexpression of miR‐26a‐5p markedly decreased LIN28B and AURKA 3′‐untranslated region activities and protein expression and repressed HB cell proliferation and colony formation. In contrast, re‐expression of LIN28B and AURKA rescued miR‐26a‐5p‐mediated suppression of HB cell growth and clonality. Importantly, a decreased miR‐26a‐5p expression correlated with the poor outcome of patients with HB. Conclusion: miR‐26a‐5p is a newly identified repressor of HB growth through its inhibition of the oncogenic LIN28B–RAN–AURKA pathway. (Hepatology Communications 2018;2:481‐491)

Central role of mTORC1 downstream of YAP/TAZ in hepatoblastoma development

Hepatoblastoma (HB) is the most common type of liver malignancy in children. Recent studies suggest that activation of Yes-associated protein (YAP) is a major molecular event in HB development, as activated YAP synergizes with mutant β-catenin to promote HB formation in mice (YAP/β-catenin). However, how YAP regulates HB development remains poorly defined. Similarly, de-regulation of mammalian target of rapamycin complex 1 (mTORC1) signaling has been implicated in multiple tumor types, but its functional role in HB development is scarcely understood. In the present study, we found that mTORC1 is activated in human HB cells and YAP/β-catenin-induced mouse HB tumor tissues. mTOR inhibitor MLN0128 significantly inhibits human HB cell growth in vitro. Furthermore, ablation of Raptor, the unique subunit of mTORC1, strongly delayed YAP/β-catenin-induced HB development in mice. At the molecular level, we found that expression of the amino acid transporter SLC38A1 is induced in mouse HB tissues, and amino acid deprivation leads to mTORC1 suppression in HB cell lines. Silencing of YAP and/or its paralog, transcriptional co-activator with PDZ binding motif (TAZ), decreased SLC38A1 expression as well as mTORC1 activation in HB cells. Furthermore, a frequent and concomitant upregulation of mTORC1 and SLC38A1 was detected in a collection of human HB specimens. Altogether, our study demonstrates the key role of mTORC1 in HB development. YAP and TAZ promote HB development via inducing SLC38A1 expression, whose upregulation leads to mTORC1 activation. Targeting mTOR pathway or amino acid transporters may represent novel therapeutic strategies for the treatment of human HB.