SP8 Promotes an Aggressive Phenotype in Hepatoblastoma via FGF8 Activation.

Alexandra Wagner,Beate Häberle,Roland Kappler,Markus Kaller,Thomas Schwarzmayr,Irene Schmid,Christian Vokuhl,Dietrich Von Schweinitz,Heiko Hermeking

doi:10.3390/cancers12082294

Alexandra Wagner, Beate Häberle + Show 7 more

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https://doi.org/10.3390/cancers12082294

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Abstract

Hepatoblastoma (HB) is the most common malignant liver tumor in childhood and it generally has a good prognosis. However, if associated with aggressive metastatic disease, outcome is still poor. The molecular mechanisms leading to metastatic spread in HB patients are still unknown. By combining RNA-sequencing and a genome-wide methylome analysis, we identified the transcription factor SP8 and the growth factor FGF8 among the most strongly upregulated genes in metastatic HB cases, with a concomitant robust demethylation of the respective promoter regions. Of note, high expression of both candidates was associated with the aggressive C2 subtype of the 16-gene signature and poor survival. Chromatin immunoprecipitation revealed a direct transcriptional regulation of FGF8 through binding of SP8 to the FGF8 promoter. Gain- and loss-of-function experiments proved promoting effects of SP8 on motility, self-renewal, migration, and the invasive potential of HB cells. Moreover, stable overexpression of SP8 in Hep3B cells resulted in the acquisition of a mesenchymal phenotype and a strong upregulation of epithelial-mesenchymal transition-associated genes. Using KRAB-mediated CRISPR-dCas9 interference directed against FGF8, we could show that FGF8 is essential for the SP8-mediated aggressive tumor behavior. Treatment of HB cell lines with the pan SP family inhibitor mithramycin A resulted in a significant inhibition of their clonogenic growth. In summary, we identified SP8 and FGF8 as key players in aggressive traits of HB and propose SP8 inhibiting drugs as a new effective treatment strategy especially for metastatic tumors.

Highlights

Hepatoblastoma (HB) is the most common pediatric liver tumor [1] with an annual incidence of1.2 cases per million children per year in Europe and is most commonly diagnosed under the age of three years [2]
In order to identify genes involved in metastatic spread, we performed RNA-sequencing of four primary hepatoblastomas with metastasis (M+) and seven primary hepatoblastomas without metastasis (M−), 11 matching normal liver (NL) specimens and four liver tumor cell lines (CL)
We found NAD(P)H quinone dehydrogenase 1 (NQO1), a gene that was recently identified by our group as an important factor for aggressive tumor behavior and poor prognosis in HB [13]

Summary

Introduction

Hepatoblastoma (HB) is the most common pediatric liver tumor [1] with an annual incidence of1.2 cases per million children per year in Europe and is most commonly diagnosed under the age of three years [2]. For patients with standard-risk HB, the prognosis is favorable with a 3-year overall survival rate of 95%, if a complete surgical resection of the tumor can be achieved, either with or without chemotherapy [4]. For high-risk HB patients, prognosis is worse and the 3-year overall survival rate shrinks to 69% [5]. To improve risk-stratification, the Children’s Hepatic tumors International Collaboration (CHIC) globally pooled and analyzed clinical data from 1605 HB cases [6]. They found that one of the main prognostic factors for high-risk HB was the existence of metastases [7]

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