Undifferentiated State Induced by Rb-p53 Double Inactivation in Mouse Thyroid Neuroendocrine Cells and Embryonic Fibroblasts
Undifferentiated State Induced by Rb-p53 Double Inactivation in Mouse Thyroid Neuroendocrine Cells and Embryonic Fibroblasts
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DOI：
10.1002/stem.1971
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发表时间：
2015-05-01
期刊：
影响因子：
5.2
通讯作者：
Takahashi, Chiaki
中科院分区：
文献类型：
--
作者：
Kitajima, Shunsuke;Kohno, Susumu;Takahashi, Chiaki
视网膜母细胞瘤肿瘤抑制蛋白（RB）在肿瘤进展期间比在肿瘤起始期间更频繁地失活。然而，其在控制与肿瘤进展相关的恶性特征中的确切作用知之甚少。我们建立了体内和体外模型来研究Rb失活诱导的未分化状态。Rb杂合子小鼠发生分化良好的甲状腺髓样癌。我们发现，额外的Trp 53缺失，没有改变谱系，这些Rb缺陷型肿瘤转化为低分化型与更高的自我更新活性。新鲜制备的Rb-/-; Trp 53（-/-）背景的小鼠胚胎成纤维细胞（MEFs）形成干细胞样球，其表达显著水平的胚胎基因，尽管缺乏在软琼脂上形成集落的能力或在免疫缺陷小鼠中的肿瘤。这表明Rb-p53双失活导致未分化状态，但没有致癌性转化。我们接下来建立了Rb-/-; N-ras（-/-）MEFs，其在Trp 53中具有自发致癌突变。这些细胞（RN 6）以Rb依赖的方式有效地产生表达非常高水平的胚胎基因的球体，并且似乎是致癌的。然后，我们筛选了FDA批准的药物库，以寻找抑制RN 6细胞球形活性的药物。数据显示，RN 6细胞对特异性药物敏感，包括对癌症干细胞有效的药物。综上所述，所有这些发现表明Rb和p53之间的遗传相互作用是正常和肿瘤细胞未分化状态的关键决定因素。
Retinoblastoma tumor suppressor protein (RB) is inactivated more frequently during tumor progression than during tumor initiation. However, its exact role in controlling the malignant features associated with tumor progression is poorly understood. We established in vivo and in vitro models to investigate the undifferentiated state induced by Rb inactivation. Rb heterozygous mice develop well-differentiated thyroid medullary carcinoma. We found that additional deletion of Trp53, without change in lineage, converted these Rb-deficient tumors to a poorly differentiated type associated with higher self-renewal activity. Freshly prepared mouse embryonic fibroblasts (MEFs) of Rb-/-; Trp53(-/-) background formed stem cell-like spheres that expressed significant levels of embryonic genes despite of lacking the ability to form colonies on soft agar or tumors in immune-deficient mice. This suggested that Rb-p53 double inactivation resulted in an undifferentiated status but without carcinogenic conversion. We next established Rb-/-; N-ras(-/-) MEFs that harbored a spontaneous carcinogenic mutation in Trp53. These cells (RN6), in an Rb-dependent manner, efficiently generated spheres that expressed very high levels of embryonic genes, and appeared to be carcinogenic. We then screened an FDA-approved drug library to search for agents that suppressed the spherogenic activity of RN6 cells. Data revealed that RN6 cells were sensitive to specific agents including ones those are effective against cancer stem cells. Taken together, all these findings suggest that the genetic interaction between Rb and p53 is a critical determinant of the undifferentiated state in normal and tumor cells.