Vandetanib-eluting radiopaque beads for chemoembolization: physicochemical evaluation and biological activity of vandetanib in hypoxia.

Vandetanib-eluting radiopaque beads (VERB) have been developed for use in transarterial chemoembolization of liver tumours, with the goal of combining embolization with local delivery of antiangiogenic therapy. The objective of this study was to investigate how embolization-induced hypoxia may affect antitumoural activity of vandetanib, an inhibitor of vascular endothelial growth factor receptor (VEGFR) and epidermal growth factor receptor (EGFR), in the context of hepatocellular carcinoma (HCC) treatment. We studied the effect of vandetanib on proliferation, cell cycle and apoptosis of HCC cells, in hypoxic conditions, as well as the direct effects of the beads on 3D HCC spheroids. Vandetanib suppressed proliferation and induced apoptosis of HCC cells in vitro and was equipotent in hypoxic and normoxic conditions. High degrees of apoptosis were observed among cell lines in which vandetanib suppressed ERK1/2 phosphorylation and upregulated the proapoptotic protein Bim, but this did not appear essential for vandetanib-induced cell death in all cell lines. Vandetanib also suppressed the hypoxia-induced secretion of VEGF from HCC cells and inhibited proliferation of endothelial cells. Incubation of tumour spheroids with VERB led to sustained growth inhibition equivalent to the effect of free drug. We conclude that vandetanib has both antiangiogenic and direct anticancer activity against HCC cells even in hypoxic conditions, warranting the further evaluation of VERB as novel anticancer agents.

Radiosensitisation of Hepatocellular Carcinoma Cells by Vandetanib.

Hepatocellular Carcinoma (HCC) is increasing in incidence worldwide and requires new approaches to therapy. The combination of anti-angiogenic drug therapy and radiotherapy is one promising new approach. The anti-angiogenic drug vandetanib is a tyrosine kinase inhibitor of vascular endothelial growth factor receptor-2 (VEGFR-2) and RET proto-oncogene with radio-enhancement potential. To explore the benefit of combined vandetanib and radiotherapy treatment for HCC, we studied outcomes following combined treatment in pre-clinical models. METHODS: Vandetanib and radiation treatment were combined in HCC cell lines grown in vitro and in vivo. In addition to 2D migration and clonogenic assays, the combination was studied in 3D spheroids and a syngeneic mouse model of HCC. RESULTS: Vandetanib IC 50 s were measured in 20 cell lines and the drug was found to significantly enhance radiation cell kill and to inhibit both cell migration and invasion in vitro. In vivo, combination therapy significantly reduced cancer growth and improved overall survival, an effect that persisted for the duration of vandetanib treatment. CONCLUSION: In 2D and 3D studies in vitro and in a syngeneic model in vivo, the combination of vandetanib plus radiotherapy was more efficacious than either treatment alone. This new combination therapy for HCC merits evaluation in clinical trials.

Development and Implementation of an End-To-End Test for Absolute Dose Verification of Small Animal Preclinical Irradiation Research Platforms.

PURPOSE: Lack of standardization and inaccurate dosimetry assessment in preclinical research is hampering translational opportunities for new radiation therapy interventions. The aim of this work was to develop and implement an end-to-end dosimetry test for small animal radiation research platforms to monitor and help improve accuracy of dose delivery and standardization across institutions. METHODS AND MATERIALS: The test is based on a bespoke zoomorphic heterogeneous mouse and WT1 Petri dish phantoms with alanine as a reference detector. Alanine measurements within the mouse phantom were validated with Monte Carlo simulations at 0.5 mm Cu x-ray reference beam. Energy dependence of alanine in medium x-ray beam qualities was taken into consideration. For the end-to-end test, treatment plans considering tissue heterogeneities were created in Muriplan treatment planning systems (TPS) and delivered to the phantoms at 5 institutions using Xstrahl's small animal irradiation platforms. Mean calculated dose to the pellets were compared with alanine measured dose. RESULTS: Monte Carlo simulations and in phantom alanine measurements in NPL's reference beam were in excellent agreement, validating the experimental approach. At 1 institute, initial measurements showed a larger than 12% difference between calculated and measured dose caused by incorrect input data. The physics data used by the calculation engine were corrected, and the TPS was recommissioned. Subsequent end-to-end test measurements showed differences <5%. With an anterior field, 4 of the participating institutes delivered dose within 5% to both phantoms. CONCLUSIONS: An end-to-end dosimetry test was developed and implemented for dose evaluation in preclinical irradiation with small animal irradiation research platforms. The test was capable of detecting treatment planning commissioning errors and highlighted critical elements in dose calculation. Absolute dosimetry with alanine in relevant preclinical irradiation conditions showed reasonable levels of accuracy compared with TPS calculations. This work provides an independent and traceable dosimetric validation in preclinical research involving small animal irradiation.

Identification of anticancer drugs to radiosensitise BRAF-wild-type and mutant colorectal cancer.

OBJECTIVE: Patients with BRAF-mutant colorectal cancer (CRC) have a poor prognosis. Molecular status is not currently used to select which drug to use in combination with radiotherapy. Our aim was to identify drugs that radiosensitise CRC cells with known BRAF status. METHODS: We screened 298 oncological drugs with and without ionising radiation in colorectal cancer cells isogenic for BRAF. Hits from rank product analysis were validated in a 16-cell line panel of human CRC cell lines, using clonogenic survival assays and xenograft models in vivo. RESULTS: Most consistently identified hits were drugs targeting cell growth/proliferation or DNA damage repair. The most effective class of drugs that radiosensitised wild-type and mutant cell lines was PARP inhibitors. In clonogenic survival assays, talazoparib produced a radiation enhancement ratio of 1.9 in DLD1 (BRAF-wildtype) cells and 1.8 in RKO (BRAF V600E) cells. In DLD1 xenografts, talazoparib significantly increased the inhibitory effect of radiation on tumour growth (P ≤ 0.01). CONCLUSIONS: Our method for screening large drug libraries for radiosensitisation has identified PARP inhibitors as promising radiosensitisers of colorectal cancer cells with wild-type and mutant BRAF backgrounds.