Regulation of SLC7A11 by p53 in cancer metabolism

 描述（由申请人提供）：尽管越来越多的证据表明p53介导的细胞周期停滞、衰老和凋亡不是其肿瘤抑制所绝对需要的，但仍不清楚p53在缺乏其典型功能的情况下如何执行肿瘤抑制活性。在我们的初步研究中，我们发现，SLC 7A 11，胱氨酸/谷氨酸反向转运蛋白的组成部分，是p53的转录靶点。通过抑制SLC 7A 11表达，p53使细胞对铁凋亡敏感，铁依赖性非凋亡形式的细胞死亡。值得注意的是，p533 KR完全保留了调节SLC 7A 11表达和铁凋亡的能力。突变小鼠的分析表明，p53介导的铁凋亡显着有助于与Mdm 2的损失相关的胚胎致死。此外，SLC 7A 11在人类肿瘤中过表达，p53介导的SLC 7A 11调节和铁凋亡调节癌细胞存活。这里要检验的中心假设是p53介导的对SLC 7A 11表达和铁凋亡的作用是否作为肿瘤抑制的独立机制，特别是当p53介导的细胞周期停滞、衰老和凋亡途径被阻断时。拟议的研究包括以下两个具体目标。在目的1中，我们将剖析p53介导的调节SLC 7A 11在癌症代谢和癌细胞存活中的机制。为了研究p53在体内通过抑制SLC 7A 11表达调节癌症代谢途径中的确切作用，我们将进一步研究p53-wt和p533 KR在调节细胞摄取胱氨酸以及其他代谢变化中的作用。此外，我们将剖析潜在的失调p53/SLC 7A 11/ferroptosis途径的肿瘤衍生的点突变。我们将研究在不同类型的应激和非应激条件下，p53介导的铁凋亡是否在正常细胞和癌细胞中受到调节。最后，为了阐明p53介导的SLC 7A 11表达的机制，我们将鉴定对SLC 7A 11在体内表达至关重要的辅因子和信号传导。目的2：研究p53介导的SLC 7A 11基因表达调控的生物学意义。我们将首先检查mdm 2抑制是否可以促进p53调节SLC 7A 11表达和激活铁凋亡的能力，这可能提高nutlin-3诱导癌细胞死亡的功效。此外，由于在几种形式的人类癌症中观察到SLC 7A 11过表达，因此很可能p53介导的抑制对其介导的肿瘤抑制有显著贡献。我们将使用Eµ-Myc/ p53淋巴瘤模型检查SLC 7A 11状态是否调节p53对Myc诱导的致瘤性的作用。

 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.