Abstract 50: Anti angiogenesis tyrosine kinase inhibitor vandetanib as a radiosensitizer for hepatocellular carcinoma
Authors: Znati Sami 
Published: August 2019

Abstract
Background: The hypervascularity of Hepatocellular Carcinoma (HCC) has let anti-angiogenic therapies to be used clinically. Vandetanib is a selective inhibitor of VEGFR-II, -III and other pathways of angiogenesis. Previous investigators have suggested that vandetanib may be used as a radiosensitizer with radiotherapy to treat HCC; we evaluated the mechanism of this treatment effect.
Methods: A panel of 20 human HCC cell lines was treated with drug plus radiation to measure radiosensitization by 2-D clonogenic survival assays. A gap was created in confluent cells and gap-filling invasion was measured following vandetanib and radiation treatment. Three-dimensional-spheroids of HCC cells were grown alone or in co-culture with fibroblasts and treated with 5 or 10 μM vandetanib alone or in conjunction with 4 Gy radiation. Spheroid growth and invasion was measured daily following treatment and results compared to a control without treatment. A paired t-test was performed for all groups to measure significance between treatments and Coefficient of Drug Interaction (CDI) and two-factor ANOVA was calculated to measure interaction.
Results: In 2-D clonogenic survival assays, HCC cell lines showed inhibition when treated with vandetanib but no significant intrinsic radiosensitization was observed. 2-D migration assays showed a significant, dose-dependent reduction in migration after vandetanib treatment (p&lt;0.05) and additive reduction in cells treated with vandetanib plus radiation (p&lt;0.05). In 3-D spheroid assays, Hepa1-6 cells showed significant reduction in growth after 4 Gy radiation treatment versus controls (p&lt;0.05). When Hepa1-6 cells were grown in co-culture with NIH3T3 fibroblasts, growth compared with controls was significantly reduced after treatment with 4 Gy radiation, 5 and 10 μM vandetanib, and combinations thereof (p&lt;0.01). Similar results were demonstrated for Hep55.1-C grown in spheroids alone (p&lt;0.05) and in co-culture with NIH3T3 (p&lt;0.01). In human cell lines, 3-D spheroids of HLF cells treated with both vandetanib and radiation showed significant growth inhibition when compared to 4 Gy radiation (p&lt;0.005) and 5 µM vandetanib (p&lt;0.0001). In 3-D co-culture of HLF and NIH3T3 receiving combination treatment, invasion was significantly reduced over radiation (p&lt;0.05) and vandetanib (p&lt;0.0001) and in 3-D co-culture of JHH7 and LX2 cells, similar results were observed, with spheroid growth inhibited in combination treatment compared to 5 µM vandetanib (p&lt;0.05) and 4 Gy radiation (p&lt;0.005).
Conclusions: We have shown additive radiosensitization effects of vandetanib in 2-D migration assays and 3-D spheroid culture. Co-culture of HCC cells with fibroblasts showed significant inhibition among groups treated with both vandetanib and radiation therapy. Future studies will examine the role of immune cells in the mechanism of action of this novel combination therapy.
Citation Format: Sami Znati. Anti angiogenesis tyrosine kinase inhibitor vandetanib as a radiosensitizer for hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 50.