Regulation Of P53 Signaling Research Articles

Rho family GTPase 1 (RND1), a novel regulator of p53, enhances ferroptosis in glioblastoma

BackgroundFerroptosis is an iron dependent cell death closely associated with p53 signaling pathway and is aberrantly regulated in glioblastoma (GBM), yet the underlying mechanism needs more exploration. Identifying new factors which regulate p53 and ferroptosis in GBM is essential for treatment.MethodsGlioma cell growth was evaluated by cell viability assays and colony formation assays. Lipid reactive oxygen species (ROS) assays, lipid peroxidation assays, glutathione assays, and transmission electron microscopy were used to assess the degree of cellular lipid peroxidation of GBM. The mechanisms of RND1 in regulation of p53 signaling were analyzed by RT-PCR, western blot, immunostaining, co-immunoprecipitation, ubiquitination assays and luciferase reporter assays. The GBM‐xenografted animal model was constructed and the tumor was captured by an In Vivo Imaging System (IVIS).ResultsFrom the The Cancer Genome Atlas (TCGA) database, we summarized that Rho family GTPase 1 (RND1) expression was downregulated in GBM and predicted a better prognosis of patients with GBM. We observed that RND1 influenced the glioma cell growth in a ferroptosis-dependent manner when GBM cell lines U87 and A172 were treated with Ferrostatin-1 or Erastin. Mechanistically, we found that RND1 interacted with p53 and led to the de-ubiquitination of p53 protein. Furthermore, the overexpression of RND1 promoted the activity of p53-SLC7A11 signaling pathway, therefore inducing the lipid peroxidation and ferroptosis of GBM.ConclusionsWe found that RND1, a novel controller of p53 protein and a positive regulator of p53 signaling pathway, enhanced the ferroptosis in GBM. This study may shed light on the understanding of ferroptosis in GBM cells and provide new therapeutic ideas for GBM.

Regulation of P53 signaling in breast cancer by the E3 ubiquitin ligase RNF187

The tumor suppressor P53 plays critical role in preventing cancer. P53 is rarely mutated and remains functional in luminal-type breast cancer(1). According to current knowledge, wild-type P53 function is tightly controlled by posttranslational modifications, such as ubiquitination. Several ubiquitin ligases have been shown to regulate P53 ubiquitination and protein stability. Here, we report that RNF187, a RING family ubiquitin ligase, facilitates breast cancer growth and inhibits apoptosis by modulating P53 signaling. RNF187 expression was elevated in breast cancer and correlated with breast cancer survival only in the P53 wild-type groups. Bioinformatic analysis showed that the expression of RNF187 was negatively correlated with the expression of P53 target genes, such as IGFBP3 and FAS, in breast cancer. RNF187 depletion inhibited breast cancer growth and facilitated cell death. RNA sequencing analysis indicated that RNF187 could be an important modulator of P53 signaling. Further experiments showed that RNF187 interacts with P53 and promotes its degradation by facilitating its polyubiquitination in breast cancer cells. Interestingly, the in vitro ubiquitin assay showed that RNF187 can directly ubiquitinate P53 in a manner independent of MDM2. These findings reveal a novel direct P53 regulator and a potential therapeutic target for breast cancer.

Abstract A25: Evaluation of Drug Disposition in Supratentorial Ependymoma

Abstract Introduction: The majority of pediatric supratentorial (ST) ependymomas (EPN) is driven by distinct gene fusions between C11orf95 and RELA. The resultant molecular group of ST-EPN-RELA tumors is characterized by constitutive activation of NF-κB signaling and deregulation of the p53 pathway. In contrast to surgery and radiotherapy, chemotherapy has failed to demonstrate significant benefit in the management of affected children. Alternative strategies including enhanced drug delivery, combination treatments, or application of new selective compounds are needed to tackle this disease. Material and Methods: RNAi and drug screening methods were applied to identify potential therapeutic approaches using ST-EPN-RELA cell lines. In order to identify optimal dosing strategies of selected drugs and to assess effects of combinatorial treatment approaches on blood-brain barrier (BBB) penetration, cerebral microdialysis combined with ultraperformance liquid chromatography and tandem mass spectrometry (UPLC-MS/MS) was applied. This approach allowed for exact, continuous, and time-dependent drug quantification in tumors or healthy tissue in freely moving experimental mice. Patient-derived xenograft models of ST-EPN-RELA were treated to investigate toxicity and outcome parameters. Results: Regulation of p53 signaling and nuclear protein shuttling were identified as promising therapeutic approaches. While low-dose dactinomycin could successfully reestablish p53 function in ST-EPN-RELA cells in vitro, penetration of the drug across the BBB was found to be very poor and did not result in a survival benefit of tumor-bearing mice. Preliminary results of alternative strategies such as combination with efflux pump inhibitors, liposomal packaging, and inhibition of XPO1 being the sole nuclear exporter of p53 hold promise to overcome these constraints. Conclusion: Oncogenic dependencies of ST-EPN-RELA are currently difficult to target. Preclinical evaluation of effective drug disposition combined with long-term treatment studies may help to better select promising compounds and thereby increase success rates of early clinical trials in patients with ST-EPN-RELA in the future. Citation Format: Julia Benzel, Max Sauter, Norman Mack, Abigail Davis, Johanna Weiss, Philipp Uhl, Jürgen Burhenne, Kendra K. Maass, Jens-Martin Hübner, Hendrik Witt, Anang Shelat, Amar Gajjar, Santhosh A. Upadhyaya, Aylin Camgoz, Frank Buchholz, Sina Oppermann, Marcel Kool, Daisuke Kawauchi, Olaf Witt, Walter E. Haefeli, Stefan M. Pfister, Clinton Stewart, Kristian W. Pajtler. Evaluation of Drug Disposition in Supratentorial Ependymoma [abstract]. In: Proceedings of the AACR Special Conference on the Advances in Pediatric Cancer Research; 2019 Sep 17-20; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Res 2020;80(14 Suppl):Abstract nr A25.

Iron Metabolism Regulates p53 Signaling through Direct Heme-p53 Interaction and Modulation of p53 Localization, Stability, and Function

SUMMARYIron excess is closely associated with tumorigenesis in multiple types of human cancers, with underlying mechanisms yet unclear. Recently, iron deprivation has emerged as a major strategy for chemotherapy, but it exerts tumor suppression only on select human malignancies. Here, we report that the tumor suppressor protein p53 is downregulated during iron excess. Strikingly, the iron polyporphyrin heme binds to p53 protein, interferes with p53-DNA interactions, and triggers both nuclear export and cytosolic degradation of p53. Moreover, in a tumorigenicity assay, iron deprivation suppressed wild-type p53-dependent tumor growth, suggesting that upregulation of wild-type p53 signaling underlies the selective efficacy of iron deprivation. Our findings thus identify a direct link between iron/heme homeostasis and the regulation of p53 signaling, which not only provides mechanistic insights into iron-excess-associated tumorigenesis but may also help predict and improve outcomes in iron-deprivation-based chemotherapy.