MNGO-08: MENINGIOMA GROWTH INHIBITION AND RADIOSENSITIZATION BY THE SMALL MOLECULE YAP INHIBITOR VERTEPORFIN

Meningiomas frequently harbor inactivating mutations in the tumor suppressor protein Merlin (NF2), an upstream activator of the Hippo signaling pathway. This aberration drives tumor growth and aggressiveness through inactivation of this pathway and unchecked activation of its downstream effector, Yes-associated protein (YAP). The transcriptional coactivator YAP has been previously implicated in driving meningioma growth and malignant transformation of non-neoplastic arachnoid cells. YAP exerts its effect by direct binding to the TEAD family of transcription factors and transactivation of growth-related genes. However, the efficacy of pharmacologic modulation of this pathway in meningioma has yet to be explored. Verteporfin is a small molecule inhibitor of the porphyrin family, recently implicated as a direct inhibitor of YAP. Here, we report that Verteporfin modulates growth and radiation resistance in NF2 driven meningiomas through inhibition of the YAP-TEAD interaction. In particular, our data demonstrates that Verteporfin treatment in the NF2 mutant KT21MG1 human malignant meningioma cell line, results in a decreased activity of oncogenic YAP, resulting in decreased mRNA expression of YAP downstream targets (CTGF, Mcl-1 and ANKRD1) (p ≤ 0.05). Moreover, Verteporfin inhibits meningioma cell growth and proliferation in a dose dependent manner (MTT reduction and viable cell number) (p ≤ 0.05). Interestingly, pretreatment with Verteporfin results in increased sensitivity to irradiation in vitro (p ≤ 0.05). In addition, we explore the in vivo efficacy of Verteporfin treatment in a murine skull base xenograft model of human meningioma. Taken together, our results show that Verteporfin is a potent inhibitor of meningioma cell growth and radioresistance, making it an attractive drug candidate for treatment of this disease. Hence, this targeted therapy towards the NF2-YAP axis holds promising alternatives to current standard of care.