Malaterre J, Pereira L, Putoczki T, Millen R, Paquet-Fifield S, Germann M, Liu J, Cheasley D, Sampurno S, Stacker S A, Achen M G, Ward R L, Waring P, Mantamadiotis T, Ernst M, Ramsay R G
Differentiation and Transcription Laboratory, Peter MacCallum Cancer Centre, Melbourne, Victoria, Australia.
Sir Peter MacCallum Department of Oncology, The University of Melbourne, Melbourne, Victoria, Australia.
Oncogene. 2016 May 12;35(19):2475-84. doi: 10.1038/onc.2015.305. Epub 2015 Aug 24.
Transcription factor Myb is overexpressed in most colorectal cancers (CRC). Patients with CRC expressing the highest Myb are more likely to relapse. We previously showed that mono-allelic loss of Myb in an Adenomatous polyposis coli (APC)-driven CRC mouse model (Apc(Min/+)) significantly improves survival. Here we directly investigated the association of Myb with poor prognosis and how Myb co-operates with tumor suppressor genes (TSGs) (Apc) and cell cycle regulator, p27. Here we generated the first intestinal-specific, inducible transgenic model; a MybER transgene encoding a tamoxifen-inducible fusion protein between Myb and the estrogen receptor-α ligand-binding domain driven by the intestinal-specific promoter, Gpa33. This was to mimic human CRC with constitutive Myb activity in a highly tractable mouse model. We confirmed that the transgene was faithfully expressed and inducible in intestinal stem cells (ISCs) before embarking on carcinogenesis studies. Activation of the MybER did not change colon homeostasis unless one p27 allele was lost. We then established that MybER activation during CRC initiation using a pro-carcinogen treatment, azoxymethane (AOM), augmented most measured aspects of ISC gene expression and function and accelerated tumorigenesis in mice. CRC-associated symptoms of patients including intestinal bleeding and anaemia were faithfully mimicked in AOM-treated MybER transgenic mice and implicated hypoxia and vessel leakage identifying an additional pathogenic role for Myb. Collectively, the results suggest that Myb expands the ISC pool within which CRC is initiated while co-operating with TSG loss. Myb further exacerbates CRC pathology partly explaining why high MYB is a predictor of worse patient outcome.
转录因子Myb在大多数结直肠癌（CRC）中过表达。表达最高水平Myb的CRC患者更易复发。我们之前表明，在一种由腺瘤性息肉病 coli（APC）驱动的CRC小鼠模型（Apc(Min/+)）中，Myb的单等位基因缺失显著提高了生存率。在此，我们直接研究了Myb与预后不良的关联，以及Myb如何与肿瘤抑制基因（TSG）（Apc）和细胞周期调节因子p27协同作用。在此，我们构建了首个肠道特异性、可诱导的转基因模型；一个MybER转基因，其编码由肠道特异性启动子Gpa33驱动的Myb与雌激素受体-α配体结合域之间的他莫昔芬诱导型融合蛋白。这是为了在一个高度易处理的小鼠模型中模拟具有组成型Myb活性的人类CRC。在开展致癌研究之前，我们证实该转基因在肠道干细胞（ISC）中能如实地表达且可诱导。除非一个p27等位基因缺失，MybER的激活不会改变结肠内环境稳态。然后我们证实，在使用致癌物前体处理氧化偶氮甲烷（AOM）启动CRC过程中激活MybER，增强了ISC基因表达和功能的大多数测量方面，并加速了小鼠的肿瘤发生。AOM处理的MybER转基因小鼠如实地模拟了CRC患者的相关症状，包括肠道出血和贫血，并提示缺氧和血管渗漏，确定了Myb的另一个致病作用。总体而言，结果表明Myb在与TSG缺失协同作用的同时，扩大了启动CRC的ISC池。Myb进一步加剧了CRC病理，部分解释了为何高MYB是患者预后较差的一个预测指标。
