P0977 - Pathway to Personalized Therapy for Refractory Hepatoblastoma

Purpose: Hepatoblastoma (HB) is the most common pediatric primary liver tumor. Treatment-refractory disease has a less than 50% overall survival rate. Development of a pipeline for drug sensitivity testing with novel patient-derived cell line (PDCL) and animal models of refractory HB will lead to improved therapies for patients.

Methods: A patient derived xenograft (PDX) mouse model was generated with intrahepatic implantation of tumor thrombus from a non-metastatic stage 3 patient who recurred after transplantation. A stable PDCL was grown from the murine tumor, and 60 targeted agents were tested for efficacy with the PDCL with CellTiter-Glo Luminescent Viability Assays. Anti-oncogenic effects of the most efficacious agents were validated with HB cell lines with phenotypic assays for viability (MTT assays) and proliferation (CCK8 assays). Immunoblotting assays assessed changes in drug targets and induction of apoptosis (PARP cleavage) with cell lines. Gene expression was also screened in a cohort of 50 HB patients in comparison to six uninvolved liver samples with microarray analyses.

Results: The drug with the lowest IC50 identified in this drug screen was the histone deacetylase (HDAC) inhibitor panobinostat (0.06 M). Panobinostat showed strong effects in in vitro assays for viability (IC50 of 0.01-0.05 M) and proliferation. Immunoblotting with panobinostat-treated cells showed an increase in acetylated histone H3 and H4. Immunoblotting for PARP also showed that treatment with panobinostat causes cell death. Patient tumor samples showed clear differential expression of HDAC gene expression, including strong upregulation of HDAC1, HDAC2, HDAC3, and HDAC4.

Conclusions: Drug screening of a novel HB PDCL identified panobinostat, and validation in vitro assays supported the efficacy of this agent. Such a personalized medicine pipeline of development of PDCLs and testing them with targeted agents will lead to the identification of new drugs that can be used with patients that do not respond to standard therapies.