Abstract 5481: Therapy of human LN229 glioblastoma growing in the brain of nude mice by Macitentan, a dual endothelin receptor A and B antagonist, combined with Temozolomide.

Abstract Purpose: We determined whether the blockade of endothelin receptor pathways can reverse the chemoprotection mediated by astrocytes and produce therapy of Human LN 229 Glioblastoma cells growing in the brain of nude mice treated with the dual endothelin receptor antagonist, Macitentan and Temozolomide (TMZ). Materials and Methods: In the first set of experiments, murine astrocytes were cultured with tumor cells in the presence or absence of Macitentan and TMZ. For therapy studies the leuciferas labeled LN229 cells were implanted (stereotactically) into the brains of nude mice. The mice were ear tagged and imaged by IVIS spectrometer at multiple times. On day 24 the mice were randomized to receive vehicle, TMZ (p.o., 7.5mg/kg, one week on and two weeks off), Macitentan (p.o., 10mg/kg, daily) and Macitentan plus TMZ. Survival of mice was compared by Kaplan-Meyer curve (log-rank test) and immunohistochemical analyses were carried out for multiple markers. Results: Simultaneous blocking of endothelin receptor A and B pathways reversed the in culture protection induced by astrocytes against TMZ (p<0.05). Therapy with Macitentan and TMZ significantly prolonged the survival of mice (p<0.0001) .The blockade of endothelin receptor A and B significantly decreased the level of expression of phosphorylated AKT and MAPK, and down-regulated the expression of BCL2L1, TWIST1 and GSTA5 in LN 229 cells growing in the brain. Proliferation of tumor cells and tumor-associated endothelial cells was significantly decreased. Moreover the apoptosis of LN229 cells was significantly increased in the brain of the combination treatment group. Conclusion: Blockade of endothelin receptor A and B pathways by Macitentan combined with TMZ provides a new approach for the treatment of patients with Glioblastoma. Citation Format: Sun Jin Kim, Seung Wook Kim, Hyun Jin Choi, Ho Jeong Lee, Francois Lehembre, Junqin He, Urs Regenass, Charles A Conrad, W.K. Yung, Isaiah J. Fidler. Therapy of human LN229 glioblastoma growing in the brain of nude mice by Macitentan, a dual endothelin receptor A and B antagonist, combined with Temozolomide. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5481. doi:10.1158/1538-7445.AM2013-5481