Diffuse intrinsic pontine glioma (DIPG) is a poor-prognosis pediatric brain tumor with a median survival of less than 1 year. No effective therapy is currently available, and no therapeutic advances have been made in several decades. We have previously identified BMI-1 as a potential therapeutic target in DIPG and have shown that BMI-1 is highly expressed in DIPG tumors regardless of histone 3 subtype. In the present study, we show that the modulation of BMI-1 leads to DNA damage, M phase cell-cycle arrest, chromosome scattering, and cell death. Interestingly, EZH2 inhibition did not alter these effects. Furthermore, modulation of BMI-1 sensitizes DIPG patient-derived stem-like cells to ionizing radiation (IR). Treatment of DIPG stem-like cells with PTC596, a BMI-1 modulator, and IR impairs the kinetics of DNA damage response (DDR). Both DDR foci formation and resolution were delayed, resulting in further reduction in cell viability compared with either treatment alone. In vivo, treatment of mice bearing DIPG xenografts with PTC596 leads to decreased tumor volume and growth kinetics, increased intratumoral apoptosis, and sustained animal survival benefit. Gene expression analysis indicates that BMI-1 expression correlates positively with DIPG stemness and BMI-1 signature. At the single-cell level, the analysis reveals that BMI-1 pathway is upregulated in undifferentiated cells and positively correlates with stemness in DIPG tumors. Implications: Together, our findings indicate that BMI-1 modulation is associated with mitotic abnormalities, impaired DDR, and cell death, supporting the combination of BMI-1 modulation and radiation as a promising novel therapy for children with DIPG.

中文翻译：

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弥漫性内源性脑桥胶质瘤细胞容易受到与 BMI-1 调节相关的有丝分裂异常的影响

弥漫性脑桥内源性胶质瘤 (DIPG) 是一种预后不良的小儿脑肿瘤，中位生存期不到 1 年。目前还没有有效的治疗方法，几十年来也没有取得任何治疗进展。我们之前已经将 BMI-1 确定为 DIPG 的潜在治疗靶点，并且已经表明，无论组蛋白 3 亚​​型如何，BMI-1 在 DIPG 肿瘤中都高度表达。在本研究中，我们表明 BMI-1 的调节导致 DNA 损伤、M 期细胞周期停滞、染色体散射和细胞死亡。有趣的是，抑制 EZH2 并没有改变这些效果。此外，BMI-1 的调节使 DIPG 患者来源的干细胞样细胞对电离辐射 (IR) 敏感。用 PTC596、BMI-1 调节剂和 IR 处理 DIPG 干细胞样细胞会损害 DNA 损伤反应 (DDR) 的动力学。DDR 病灶的形成和分辨率都被延迟，导致细胞活力与单独治疗相比进一步降低。在体内，用 PTC596 治疗携带 DIPG 异种移植物的小鼠会导致肿瘤体积和生长动力学减少，肿瘤内细胞凋亡增加，并持续改善动物存活率。基因表达分析表明 BMI-1 表达与 DIPG 干性和 BMI-1 特征呈正相关。在单细胞水平上，分析表明 BMI-1 通路在未分化细胞中上调，并与 DIPG 肿瘤的干性呈正相关。意义：我们的研究结果表明，BMI-1 调节与有丝分裂异常、DDR 受损和细胞死亡有关，