Preclinical evaluation of protein synthesis inhibitor omacetaxine in pediatric brainstem gliomas

Yongjuan Chen; Aaminah Khan; Christopher Katsinas; Filip Michniewicz; Jessie Goldberg; Laura Franshaw; Maria Tsoli; David S Ziegler

doi:10.1093/noajnl/vdae029

Preclinical evaluation of protein synthesis inhibitor omacetaxine in pediatric brainstem gliomas

Neurooncol Adv. 2024 Mar 16;6(1):vdae029. doi: 10.1093/noajnl/vdae029. eCollection 2024 Jan-Dec.

Authors

Yongjuan Chen¹, Aaminah Khan^{1

2}, Christopher Katsinas¹, Filip Michniewicz¹, Jessie Goldberg¹, Laura Franshaw¹, Maria Tsoli^{1

2}, David S Ziegler^{1

2

3}

Affiliations

¹ Children's Cancer Institute, Lowy Cancer Research Centre, UNSW Sydney, Kensington, New South Wales, Australia.
² School of Clinical Medicine, UNSW Medicine & Health, UNSW Sydney, Sydney, New South Wales, Australia.
³ Kids Cancer Centre, Sydney Children's Hospital, Randwick, New South Wales, Australia.

Abstract

Background: Diffuse intrinsic pontine gliomas (DIPGs) pose a significant challenge as a highly aggressive and currently incurable form of pediatric brain cancer, necessitating the development of novel therapeutic strategies. Omacetaxine, an FDA-approved protein synthesis inhibitor for treating certain hematological malignancies, was investigated for its potential antitumor effects against preclinical DIPG models.

Methods: We employed primary DIPG cultures to study omacetaxine's cytotoxicity and its impact on colony formation. Annexin V staining and flow cytometry assessed apoptosis. Wound healing assays evaluated migration, while western blotting determined inhibition of oncogenic proteins. We tested omacetaxine's therapeutic efficacy in an orthotopic DIPG model and assessed brain penetration using mass spectrometry.

Results: We found a pronounced cytotoxic activity of omacetaxine against DIPG neurospheres, with low IC₅₀ values of approximately 20 nM. Omacetaxine exerted its anti-proliferative effect by inhibiting protein synthesis and the induction of apoptotic pathways, evidenced by significant elevated levels of cleaved caspase 3 and cleaved PARP, both key markers of apoptosis. Omacetaxine effectively targeted oncogenic players such as PDGFRα and PI3K without additional effects on the mTOR signaling pathway. Furthermore, our study revealed the inhibitory effects of omacetaxine on cell migration, and a significant reduction in integrin/FAK signaling, which plays a crucial role in tumor progression and metastasis.

Conclusions: Despite these promising in vitro effects, omacetaxine's efficacy in an orthotopic DIPG model was limited due to inadequate penetration across the blood-brain barrier. As such, further research and advancements are crucial to improve the drug's brain penetration, thus enhancing its overall therapeutic potential.

Keywords: IPG; PDGFRα/PI3K; integrin signaling; omacetaxine; protein synthesis inhibitor.