Preclinical Evidence Supporting Novel Protein Phosphatase 2A Activators as Therapeutics in Hepatoblastoma

Abstract

INTRODUCTION: The tumor suppressor, protein phosphatase 2A (PP2A), is downregulated in hepatoblastoma. Our laboratory has shown that PP2A activation using the sphingosine analog, FTY720, decreased hepatoblastoma viability in vitro and tumor growth in vivo. Because FTY720 has significant immunosuppressive properties, we wished to examine the effects 2 novel compounds, ATUX-3364 (3364) and ATUX-8385 (8385), designed to activate PP2A without causing immunosuppression in hepatoblastoma. METHODS: The established human hepatoblastoma cell line, HuH6, and a human hepatoblastoma patient-derived xenograft, COA67, were used. Cells were treated with increasing doses of 3364 or 8385 for 24 hours. Proliferation and viability were investigated using CellTiter96 and alamarBlue assays, respectively. The ability of the COA67 cells to form tumor spheres, a marker of cancer cell stemness, was assessed following treatment with 3364 or 8385 (2 μM). RESULTS: Viability was significantly decreased following doses as low as 5 μM treatment in HuH6 (Fig. 1A, upper panel) and 0.5 μM treatment in COA67 (Fig. 1A, lower panel). Proliferation was significantly decreased in HuH6 after treatment with 3364 (7.5 μM, 57 ± 0.1%; p ≤ 0.01) and 8385 (12.5 μM, 54 ± 0.1%; p ≤ 0.01) vs 0 μM and COA67 cells at 4 μM (3364: 64 ± 0.7%; 8385: 93 ± 0.3%, vs 0 μM; p ≤ 0.05) after treatment. Both compounds significantly affected the ability of COA67 cells to form tumor spheres (Fig. 1B).CONCLUSION: The novel PP2A activators, 3364 and 8385, decreased proliferation, viability, and stemness in hepatoblastoma. These findings provide evidence for further investigation of these novel PP2A activators as potential therapeutics for hepatoblastoma.