Abstract 5420: Multiomics approach identifies the SP8-FGF8 axis as an important promoter of metastatic features in hepatoblastoma

Abstract

Abstract Introduction Hepatoblastoma (HB) is the most common pediatric liver tumor with a general good prognosis, but if associated with multifocal growth, vessel invasion or metastasis, outcome is still poor. The molecular mechanisms causing this high-risk profile are still unknown. The aim of our study was to gain insight into the neoplastic continuation towards more aggressive tumor phenotypes and to aid identification of biomarkers for high-risk patients. Experimental procedures Tumor specimens of seven non-metastasized and four metastasized HB patients were analyzed by RNA-sequencing and the Human Methylation 450 BeadChip microarray to assess global expression and methylation levels. Integration of both datasets identified new candidate genes, which were further verified in a cohort of 34 HB patients using real-time PCR. Gain and loss of function experiments of SP8 were conducted in five HB cell lines to evaluate its effects on proliferation, mobility, self renewal, migration and invasion. Chromatin-immunoprecipitation was used to assess binding of SP8 to the FGF8 promoter. Kaplan-Meier estimates of specific survival time in various groups were compared using the log-rank Mantel-Cox test. Results Global integration of expression and methylation levels identified the transcription factor SP8 and the fibroblast growth factor FGF8 as significantly upregulated genes accompanied with strong methylation changes in metastatic HB. In an independent cohort of 34 HB patients expression of both candidates was highly correlated (R² = 0.74, P < 0.0001) and could be positively associated with metastasis, the aggressive C2 subtype of the 16-gene signature and poor overall survival. Chromatin-immunoprecipitation identified binding of SP8 to the FGF8 promoter. Following SP8 overexpression in liver tumor cells, we found a significant increase in cell motility, self renewal and invasive growth together with the acquisition of a mesenchymal phenotype. In turn, CRISPRi-mediated knockdown of FGF8 rescued the phenotype. Conclusions We showed that elevated levels of SP8 induced cell motility, self renewal and mesenchymal characteristics by targeting FGF8, thereby implicating an important functional role of the SP8-FGF8 axis for the progression and metastasis of malignant childhood liver tumors. Moreover, SP8 might serve as a new biomarker in metastatic HB with poor prognosis. Citation Format: Alexandra Wagner, Beate Häberle, Irene Schmid, Christian Vokuhl, Dietrich von Schweinitz, Roland Kappler. Multiomics approach identifies the SP8-FGF8 axis as an important promoter of metastatic features in hepatoblastoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5420.