Novel YAP inhibitor, CA3, demonstrates antitumoral activity in vitro and in vivo model of cholangiocarcinoma

Abstract

Presenter: Roberto Alva-Ruiz MD | Mayo Clinic, Rochester Background: Cholangiocarcinoma (CCA) is a highly aggressive form of liver cancer and is a major cause of cancer-related deaths. Despite its increasing incidence and lethality, treatment options for cholangiocarcinoma have largely remained unchanged, stressing the importance of developing new therapies. The Yes-associated protein (YAP)/Hippo pathway, important in tissue development and liver regeneration, is also implicated in the development of various malignancies. Previous work has shown that YAP overexpression promotes CCA tumorigenesis in vivo and in vitro. In this study, we sought to evaluate the efficacy of CA3, a novel YAP/TEAD inhibitor, using preclinical models including CCA cell lines and a patient-derived xenograft model. Methods: CCA cell lines (HuCCT1, KMCH, SB1, RBE, SNU 1079) were exposed to increasing concentrations of CA3. Cell viability was measured with CellTiter-Glo and subsequent IC50 curves developed. Caspase-3 and -7 activity was measured using Caspase-Glo 3/7 Assay in HuCCT1 and SB1 cell lines. Downstream YAP target genes (CTGF, ANKRD1, CYR61) were evaluated with RT-PCR after treatment with IC50 concentrations of CA3. PDX 283, a unique patient derived xenograft model of CCA was generated and treated with CA3 (1.5 mg/kg, 3x/weekly, I.P) and compared to vehicle group treated with DMSO/PBS. Tumor bearing mice were monitored for tumor progression. Results: IC50 concentrations for HuCCT1, KMCH, SB1, RBE, and SNU 1079 were consistent and biologically relevant at 0.766 uM, 0.572 uM, 1 uM, 0.573 uM, and 0.704 uM, respectively. There was a 4.45-fold and 2.29-fold increase in caspase-3 and -7 activity in HuCCT1 and SB1 cell lines exposed to CA3. In HuCCT1, KMCH, and RBE cell lines YAP target gene CYR61 demonstrated a 3, 1.6, and 1.7-fold decrease in activity, respectively following exposure to CA3. In vivo, CA3 arrested tumor growth as compared to vehicle over the course of the treatment study (p = 0.0002). Conclusion: In this study we show that CA3, a novel YAP/TEAD inhibitor, induces cell death in cholangiocarcinoma cell lines and demonstrates an inhibitory effect on YAP1 transcriptional activity. In addition, we demonstrate tumor growth arrest in a unique PDX model of CCA treated with CA3.