J. R. Julson1, C. H. Quinn1, R. Marayati1, H. R. Markert1, J. S. Laue1, J. Stewart1, V. Atigadda1, E. A. Beierle1 1University Of Alabama at Birmingham, Pediatric Surgery, Birmingham, Alabama, USA
Introduction: Hepatoblastoma is the most common primary liver tumor in children and up to 20% have metastatic disease at the time of presentation. Due to the difficulty in managing metastatic disease, we previously established a metastatic human hepatoblastoma (HLM_2) cell line to evaluate the key drivers of hepatoblastoma metastases, with the goal of identifying potential therapeutic targets. We have previously demonstrated targeting the RXR pathway is beneficial in hepatoblastoma. Thus, we sought to investigate the effects of 9-cis-UAB30 (UAB30), a novel rexinoid agonist, on HLM_2 cells and the role it might play in treating hepatoblastoma metastases.
Methods: RNA sequencing using Ingenuity Pathway Analysis (IPA) compared HLM_2 cells to parent HuH6 cells. We queried the Ikeda (R2) gene database to compare histologic differentiation of hepatoblastoma and the level of retinoid X receptor-β (RXR-β) expression. Viability was assessed using alamarBlue assay. Cell motility was evaluated using monolayer wound healing (scratch) assay after treatment with increasing concentrations of UAB30. Data were reported as mean ± SEM, compared with two-tailed t-test, and p ≤ 0.05 considered significant.
Results: RNA sequencing showed significantly downregulated LXR/RXR pathway in HLM_2 compared to HuH6 cells (p = 3.3E-02) (Figure 1A). Ikeda database query of RXR-β expression in hepatoblastoma showed significantly decreased RXR-β expression (p = 0.026) in poorly differentiated tumors (Figure 1B). HLM_2 cells treated with UAB30 showed a significant decrease in viability at concentrations greater than 80 μM (p < 0.001); calculated LD50 ≈85 μM (Figure 1C). After treatment with 50 μM UAB30, HLM_2 cells had significantly decreased motility compared to control at 24 hours (p = 0.016) (Figure 1D). Representative photomicrographs demonstrating the change in wound healing area after 24 hours are included (Figure 1E).
Conclusion: We believe the downregulation of the LXR/RXR pathway might drive metastasis in hepatoblastoma and by activation of the RXR pathways specifically, we halt this malignant progression. We found that the RXR agonist, UAB30, significantly impacted metastatic hepatoblastoma cell viability and motility. These findings demonstrate the promising therapeutic potential rexinoid agonists hold in treating metastatic hepatoblastoma and validate the need for further investigation to translate these therapies to the clinical arena.
