Anti-ZFX ChIP-seq in a human medulloblastoma cell line

The Hedgehog (Hh) signaling pathway regulates normal development and cell proliferation, whereas its aberrant activation causes tumor formation. Hh-induced tumors can arise from different tissues and can be indolent or highly aggressive, such as basal cell carcinoma (BCC) of the skin and neural progenitor-derived medulloblastoma (MB), respectively. Little is known about cell-intrinsic factors that control the development of such diverse Hh-dependent tumors. Transcription factor Zfx is required for the self-renewal of several stem cell types, whereas its role in malignant transformation remains controversial. We found that the deletion of Zfx prevented BCC formation and significantly delayed MB development caused by Hh activation in vivo. In contrast, Zfx was dispensable for the development of Hh-independent brain tumor glioblastoma. We used genome-wide expression and chromatin binding analysis in a human MB cell line to identify direct, evolutionarily conserved targets of Zfx. These targets included the Hh signal transducer Smoothened (Smo), suggesting that Zfx may directly control Hh pathway activation in tumors. Two additional targets of Zfx, Dis3L and Ube2j1, were also required for the growth of MB cells in vitro. These results identify a common cell-intrinsic regulator of diverse Hh-induced tumors, and suggest Zfx and Zfx-controlled genes as possible therapeutic targets in these malignancies.

刺猬因子（Hedgehog, Hh）信号通路可调控正常发育与细胞增殖，而其异常激活会引发肿瘤发生。Hh诱导的肿瘤可起源于多种组织，其表型可呈惰性或高侵袭性，分别对应皮肤基底细胞癌（basal cell carcinoma, BCC）与神经祖细胞来源的髓母细胞瘤（medulloblastoma, MB）。目前对于调控这类多样Hh依赖性肿瘤发生的细胞内在因子，学界尚缺乏深入了解。转录因子Zfx是多种干细胞自我更新过程所必需的，但其在恶性转化中的作用仍存在争议。本研究发现，体内敲除Zfx可阻止BCC的形成，并显著延迟Hh激活诱导的MB发生。与之相反，Zfx对于非Hh依赖性脑肿瘤胶质母细胞瘤（glioblastoma）的发育并非必需。我们通过人类MB细胞系的全基因组表达与染色质结合分析，鉴定出Zfx的直接且进化保守的靶基因。这些靶基因包括Hh信号转导分子Smoothened（Smo），提示Zfx可直接调控肿瘤中的Hh通路激活。另外两个Zfx靶基因Dis3L与Ube2j1，同样是体外MB细胞生长所必需的。本研究结果确定了一类可调控多样Hh诱导肿瘤的通用细胞内在调节因子，并提示Zfx及其调控的基因可作为这类恶性肿瘤的潜在治疗靶点。