Abstract 1174: Avenue to personalized targeted therapy for hepatoblastoma
Authors: Srivastava Rohit Kumar , Patel Roma , Whitlock Richard S. , Larson Samuel R. , Badachhape Andrew , Woodfield Sarah E. , Vasudevan Sanjeev A. 
Published: July 2021

Abstract
Introduction: Hepatoblastoma (HB) is the most frequent liver malignancy of childhood with an annual incidence of 1.5 per million and a survival rate less than 50% for high-risk, relapse, and treatment refractory patients. The overall goal of this study is to assess the therapeutic efficacies and anti-cancer mechanisms of novel drugs with HB through a drug sensitivity testing pipeline utilizing multiple novel, clinically relevant preclinical patient-derived cell line (PDCL) and patient-derived xenograft (PDX) models.
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 by using CellTiter-Glo Luminescent Viability assays. Anti-oncogenic effects of the most efficacious agent, dinaciclib (cyclin-dependent kinase (CDK) inhibitor), were further assayed in vitro with HB cell lines (HepG2, HepT1, Huh6, HB17) with phenotypic assays for cell toxicity (MTT assay), proliferation (CCK-8 assay), and anchorage independent colony formation (soft agar assay). Immunoblotting assays were used to assess changes in drug targets and induction of apoptosis (PARP cleavage) with cell lines. Dinaciclib was also tested in vivo in our orthotopic PDX models of high-risk HB. The drug was administered three times a week by intraperitoneal injection (20 mg/kg, 100 µL) for 3 weeks. Magnetic resonance imaging (MRI) and Alpha-fetoprotein (AFP) ELISA were done to evaluate tumor growth throughout the study as tumor-bearing animals show expression of human serum AFP. Tumor weights and volumes, as well as immunohistochemistry for H&E, Ki-67, and TUNEL, were also used to assess effects of drug in vivo.
Results: The agent that showed the lowest IC50 value out of 60 tested agents was the CDK inhibitor, dinaciclib (0.7 µM). Dinaciclib suppressed cell proliferation and viability in a dose-dependent manner in all HB cell lines tested with IC50 values in the low micromolar range (HepG2 3.75 µM; HepT1 0.007 µM; Huh-6 1.42 µM; HB17 0.72 µM). Immunoblotting with dinaciclib-treated cells showed induction of PARP cleavage, indicating apoptosis, along with decreased protein expression of CDK1, 2, 5, and 9. Dinaciclib also showed significant in vivo inhibition of tumor growth compared to placebo (relative tumor volume p = 0.03, tumor weight p = 0.02).
Conclusions: Drug screening of a novel HB PDCL identified an agent, dinaciclib, that shows preclinical efficacy with refractory disease. Further in vitro and in vivo validation confirmed that dinaciclib is a promising therapeutic agent for the treatment of HB. 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.
Citation Format: Rohit Kumar Srivastava, Roma Patel, Richard S. Whitlock, Samuel R. Larson, Andrew Badachhape, Sarah E. Woodfield, Sanjeev A. Vasudevan. Avenue to personalized targeted therapy for hepatoblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1174.