Regulation of SLC7A11 by p53 in cancer metabolism

 描述(申请人提供)：尽管越来越多的证据表明，P53介导的细胞周期停滞、衰老和凋亡并不是其抑制肿瘤所必需的，但在缺乏典型功能的情况下，P53如何执行肿瘤抑制活性仍不清楚。在我们的初步研究中，我们发现半胱氨酸/谷氨酸逆向转运蛋白的组成部分SLC7A11是P53的转录靶标。通过抑制SLC7A11的表达，p53使细胞对铁下垂敏感，铁下垂是一种铁依赖的非凋亡性细胞死亡形式。值得注意的是，p533KR完全保留了调节SLC7A11表达和铁性下垂的能力。对突变小鼠的分析表明，P53介导的铁下垂与MDM2缺失相关的胚胎致死性有显著贡献。此外，SLC7A11在人类肿瘤中过表达，p53介导的SLC7A11和铁下垂调节癌细胞的存活。这里要检验的中心假设是，P53介导的SLC7A11表达和铁下垂是否作为一种独立的机制在肿瘤抑制中发挥作用，特别是当P53介导的细胞周期停滞、衰老和凋亡的途径不起作用时。拟议的研究包括以下两个具体目标。在目标1中，我们将剖析P53介导的SLC7A11在肿瘤代谢和癌细胞存活中的调节机制。为了研究P53在体内通过抑制SLC7A11的表达来调控肿瘤代谢途径的确切作用，我们将进一步研究P53-wt和p533KR在调节细胞摄取半胱氨酸以及其他代谢变化中的作用。此外，我们还将剖析肿瘤来源的点突变对P53/SLC7A11/铁下垂通路的潜在失调。我们将研究在不同类型的应激和非应激条件下，P53介导的铁下垂在正常细胞和癌细胞中是否都受到调控。最后，为了阐明P53介导的SLC7A11表达的机制，我们将确定在体内对SLC7A11表达至关重要的辅因子和信号转导。在目的2中，我们将评估p53介导的SLC7A11在体内的生物学意义。我们将首先考察抑制MDM2是否可以促进p53调节SLC7A11表达和激活铁下垂的能力，从而可能提高Nutlin-3诱导癌细胞死亡的效果。此外，由于SLC7A11在几种形式的人类癌症中都有过表达，很可能是P53介导的抑制在其介导的肿瘤抑制中起到了重要作用。我们将使用E-Myc/P53淋巴瘤模型来研究SLC7A11状态是否调节P53在Myc诱导的致瘤性中的作用。

 DESCRIPTION (provided by applicant): Although accumulating evidence suggests that p53-mediated cell cycle arrest, senescence and apoptosis are not absolutely required for its tumor suppression, it remains unclear how p53 executes the tumor suppression activity, in the absence of its canonical functions. In our preliminary study, we found that SLC7A11, a component of the cystine/glutamate antiporter, is a transcriptional target of p53. By suppressing SLC7A11 expression, p53 sensitizes cells to ferroptosis, an iron-dependent non-apoptotic form of cell death. Notably, p533KR fully retains the ability to regulate SLC7A11 expression and ferroptosis. Analysis of mutant mice shows that p53- mediated ferroptosis contributes significantly to the embryonic lethality associated with loss of Mdm2. Moreover, SLC7A11 is overexpressed in human tumors, and p53-mediated regulation of SLC7A11 and ferroptosis modulates cancer cell survival. The central hypothesis to be tested here is whether p53-mediated effects on SLC7A11 expression and ferroptosis act as an independent mechanism in tumor suppression, particularly when the p53-mediated pathways of cell-cycle arrest, senescence and apoptosis are inoperative. The proposed studies include the following two specific aims. In Aim 1, we will dissect the mechanisms of p53-mediated regulation of SLC7A11 in cancer metabolism and cancer cell survival. To investigate the precise role of p53 in modulating cancer metabolic pathways through suppressing SLC7A11 expression in vivo, we will further examine the roles of both p53-wt and p533KR in regulating cellular uptake of cystine as well as other metabolic changes. Moreover, we will dissect the potential dysregulation of the p53/SLC7A11/ferroptosis pathway by tumor-derived point mutants. We will investigate whether p53-mediated ferroptosis is regulated in both normal and cancer cells under different types of stressed and unstressed conditions. Finally, to elucidate the mechanism of p53-mediated SLC7A11 expression, we will identify cofactors and signaling that are critical for SLC7A11 expression in vivo. In Aim 2, we will evaluate the biological significance of p53-mediated regulation of SLC7A11 in vivo. We will first examine whether mdm2 inhibition can promote the ability of p53 in regulating SLC7A11 expression and activating ferroptosis, which may improve the efficacy of nutlin-3 in inducing cancer cell death. Moreover, since SLC7A11 overexpression is observed in several forms of human cancer, it is very likely that p53-mediated repression contributes significantly to its mediated tumor suppression. We will examine whether SLC7A11 status modulates the effect of p53 on Myc-induced tumorigenicity using the Eµ-Myc/ p53 lymphoma model.