Department of Pediatric Oncology, Emory University School of Medicine, Atlanta, Georgia, USA.
Emory University Cancer Biology Graduate Program, Emory University, Atlanta, Georgia, USA.
Mol Cell Biol. 2019 Apr 2;39(8). doi: 10.1128/MCB.00268-18. Print 2019 Apr 15.
Cerebellar development is a highly regulated process involving numerous factors acting with high specificity, both temporally and by location. Part of this process involves extensive proliferation of cerebellar granule neuron precursors (CGNPs) induced by Sonic Hedgehog (SHH) signaling, but downstream effectors of mitogenic signaling are still being elucidated. Using primary CGNP cultures, a well-established model for SHH-driven proliferation, we show that SHH-treated CGNPs feature high levels of hypoxia-inducible factor 1α (HIF1α), which is known to promote glycolysis, stemness, and angiogenesis. In CGNPs cultured under normoxic conditions, HIF1α is posttranslationally stabilized in a manner dependent upon reactive oxygen species (ROS) and NADPH oxidase (NOX), both of which are also upregulated in these cells. Inhibition of NOX activity resulted in HIF1α destabilization and reduced levels of cyclin D2, a marker of CGNP proliferation. As CGNPs are the putative cells of origin for the SHH subtype of medulloblastoma and aberrant SHH signaling is implicated in other neoplasms, these studies may also have future relevance in the context of cancer. Taken together, our findings suggest that a better understanding of nonhypoxic HIF1α stabilization through NOX-induced ROS generation can provide insights into normal cell proliferation in cerebellar development and SHH-driven cell proliferation in cancers with aberrant SHH signaling.
小脑发育是一个高度受调控的过程，涉及许多因素，这些因素具有高度的特异性，无论是在时间上还是在位置上。这个过程的一部分涉及到小脑颗粒神经元前体（CGNPs）的广泛增殖，这是由 Sonic Hedgehog（SHH）信号诱导的，但促有丝分裂信号的下游效应物仍在阐明之中。使用原代 CGNP 培养物，这是一种用于 SHH 驱动增殖的成熟模型，我们表明，SHH 处理的 CGNPs 具有高水平的缺氧诱导因子 1α（HIF1α），HIF1α 已知可促进糖酵解、干细胞特性和血管生成。在 CGNPs 在常氧条件下培养时，HIF1α 通过依赖于活性氧（ROS）和 NADPH 氧化酶（NOX）的方式进行翻译后稳定，这两种酶在这些细胞中也被上调。NOX 活性的抑制导致 HIF1α 不稳定，并降低了 CGNP 增殖的标志物 cyclin D2 的水平。由于 CGNPs 是 SHH 型髓母细胞瘤的潜在起源细胞，并且异常的 SHH 信号在其他肿瘤中也有牵连，因此这些研究在癌症的背景下也可能具有未来的相关性。总之，我们的研究结果表明，通过 NOX 诱导的 ROS 生成更好地了解非缺氧性 HIF1α 稳定，可以深入了解小脑发育中的正常细胞增殖和异常 SHH 信号驱动的癌症中的细胞增殖。
