Abstract 508: Determining the nuclear and cytoplasmic function of BMI-1 in diffuse intrinsic pontine glioma during M phase

Abstract

Abstract Diffuse Intrinsic Pontine Glioma (DIPG) represents one of the most aggressive malignancies of the central nervous system, predominantly affecting children. DIPG is a particularly poor prognosis brain tumor with a median overall survival of less than 1 year. Hence, there is an urgent need to develop novel therapies that not only improve outcome but mitigate long-term complications in children with DIPG. The protein BMI-1, a critical component of the Polycomb Repressive Complex 1 (PRC1), is a proto-oncogene implicated in development, stemness of normal and malignant cells, and self-renewal. BMI-1 has emerged as a potential therapeutic target in DIPG; however, its role in DIPG tumorigenesis and progression remains elusive. We have previously shown that PTC596, a potent BMI-1 modulator, induces chromosome scattering, M phase cell-cycle arrest, BMI-1 phosphorylation and translocation to the cytoplasm leading to the inhibition of its PRC1 canonical function and cell death. These findings imply the induction of the spindle assembly checkpoint (SAC), thereby preventing mitotic exit followed by BMI-1 phosphorylation, probably at multiple sites, suggesting a survival role of BMI-1 in M phase in DIPG. The objective of the present study is to delineate the molecular pathways governing BMI-1 function during M phase and to establish the temporal sequence of these biochemical events related to BMI-1. Our data demonstrated that following PTC596 treatment, BMI-1 is actively transported from the nucleus to the cytoplasm. Furthermore, we observed colocalization of BMI-1 with COX4 in the mitochondria during M phase. Moreover, using Alphafold prediction model, BMI-1 could interact with CRM1 transporter. These findings suggest a potential PRC1-independent role of BMI-1 during early M phase required for DIPG proliferation. We are currently investigating potential pathways involved in BMI-1 nuclear-cytosol translocation through bioinformatic analyses, protein-protein interaction simulations, and pharmacological inhibitor assays. Collectively, these studies aim to elucidate the molecular mechanisms underlying BMI-1 functions in DIPG, thereby potentially paving the way for the development of targeted therapeutic strategies related to M phase progression. Citation Format: Hao-Han Pang, Banlanjo Umaru, Shiva Senthil Kumar, Rachid Drissi. Determining the nuclear and cytoplasmic function of BMI-1 in diffuse intrinsic pontine glioma during M phase [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 508.