Inactivation Of P53 Research Articles

Cabozantinib selectively induces proteasomal degradation of p53 somatic mutant Y220C and impedes tumor growth.

Inactivation of p53 by mutations commonly occurs in human cancer. The mutated p53 proteins may escape proteolytic degradation and exhibit high expression in tumors and acquire gain-of-function activity that promotes tumor progression and chemo-resistance. Therefore, selectively targeting of the gain-of-function p53 mutants may serve as a promising therapeutic strategy for cancer prevention and treatment. In this study, we identified cabozantinib, a multikinase inhibitor currently used in the clinical treatment of several types of cancer, as a selective inducer of proteasomal degradation of the p53-Y220C mutant. We demonstrate that cabozantinib disrupts the interaction between p53Y220C and USP7, a deubiquitylating enzyme, resulting in the dissociation of p53Y220C protein from its binding with USP7 and subsequent ubiquitination and degradation mediated by CHIP (the carboxyl terminal of Hsp70-interacting protein). We also show that cabozantinib displays preferential cytotoxicity to p53Y220C-harboring cancer cells both invitro and invivo. This study demonstrates a novel, p53-Y220C mutant-targeted anticancer action and mechanism for cabozantinib and provides the rationale for use of this drug in the treatment of cancers that carry the p53-Y220C mutation.

Loss of Brcc3 in Zebrafish Embryos Increases Their Susceptibility to DNA Damage Stress.

DNA double-strand breaks (DSBs) represent one of the most severe forms of genetic damage in organisms, yet vertebrate models capable of monitoring DSBs in real-time remain scarce. BRCA1/BRCA2-containing complex subunit 3 (BRCC3), also known as BRCC36, functions within various multiprotein complexes to mediate diverse biological processes. However, the physiological role of BRCC3 in vertebrates, as well as the underlying mechanisms that govern its activity, are not well understood. To explore these questions, we generated brcc3-knockout zebrafish using CRISPR/Cas9 gene-editing technology. While brcc3 mutant zebrafish appear phenotypically normal and remain fertile, they exhibit significantly increased rates of mortality and deformity following exposure to DNA damage. Furthermore, embryos lacking Brcc3 display heightened p53 signaling, elevated γ-H2AX levels, and increased apoptosis in response to DNA-damaging agents such as ultraviolet (UV) light and Etoposide (ETO). Notably, genetic inactivation of p53 or pharmacological inhibition of Ataxia-telangiectasia mutated (ATM) activity rescues the hypersensitivity to UV and ETO observed in Brcc3-deficient embryos. These findings suggest that Brcc3 plays a critical role in DNA damage response (DDR), promoting cell survival during embryogenesis. Additionally, brcc3-null mutant zebrafish offer a promising vertebrate model for real-time monitoring of DSBs.

A novel ITGB8 transcript variant sustains ovarian cancer cell survival through genomic instability and altered ploidy on a mutant p53 background

BackgroundTranscript variants and protein isoforms are central to unique tissue functions and maintenance of homeostasis, in addition to being associated with aberrant states such as cancer, where their crosstalk with the mutated tumor suppressor p53 may contribute to genomic instability and chromosomal rearrangements. We previously identified several novel splice variants in ovarian cancer RNA-sequencing datasets; herein, we aimed to elucidate the biological effects of the Integrin Subunit Beta 8 variant (termed pITGB8-205).MethodsResolution of the full-length sequence of pITGB8-205 through rapid amplification of cDNA ends (RACE-PCR). Cell cycle analysis and karyotype studies were performed to further explore genomic instability. RNA-seq and proteomics analyses were used to identify the differential expression of the genes.ResultsThis full-length study revealed a unique 5’ sequence in pITGB8-205 that differed from the reported ITGB8-205 sequence, suggesting differential regulation of this novel transcript. Under a p53 mutant background, overexpression of pITGB8-205 triggered genetic instability reminiscent of oncogene-induced replicative stress with extensive abnormal mitoses and chromosomal and nuclear aberrations indicative of chromosomal instability, leading to near whole-genome duplication that imposes energy stress on cellular resources. Micronuclei and aneuploidy are striking features of pITGB8-205-overexpressing p53-mutant cells but are not enhanced in p53 wild-type (WT) cells. RNA-seq and proteomics analyses further suggested that p53 inactivation in ovarian cancer provides a permissive intracellular molecular niche for pITGB8-205 to mediate its effects on genomic instability. This observation is pivotal considering that most high-grade serous ovarian carcinoma (HGSC) tumors express mutant p53. The resulting aneuploid clones with enhanced self-renewal and survival capabilities disrupt clonal dominance under stress yet maintain a balance between replicative stress and prosurvival advantages.ConclusionpITGB8-205-overexpressing clones sustain ovarian tumor cell survival, achieve homeostasis and are formidable opponents of therapy.

Co-Regulation Mechanism of Host p53 and Fos in Transcriptional Activation of ILTV Immediate-Early Gene ICP4.

Infectious laryngotracheitis virus (ILTV) exhibits a cascade expression pattern of encoded genes, and ICP4 is the only immediate-early gene of ILTV, which plays a crucial role in initiating the subsequent viral genes. Therefore, studying the transcriptional regulation mechanism of ICP4 holds promise for effectively blocking ILTV infection and spread. Host transcriptional factors p53 and Fos are proven to regulate a variety of viral infections, and our previous studies have demonstrated their synergistic effects in regulating ILTV infection. In this study, we constructed eukaryotic expression vectors for p53 and Fos as well as their specific siRNAs and transfected them into a chicken hepatoma cell line. The results showed that knocking down p53 or Fos significantly inhibited ICP4 transcription, while overexpressing p53 or Fos had an opposite effect. A further CoIP and ChIP-qPCR assay suggested p53 and Fos physically interacted with each other, and jointly bound to the upstream transcriptional regulatory region of ICP4. To elucidate the specific mechanisms of p53 and Fos in regulating ICP4 transcription, we designed p53 and Fos protein mutants by mutating their DNA binding domains, which significantly reduced their binding ability to DNA without affecting their interaction. The results showed that Fos directly bound to the promoter region of ICP4 as a binding target of p53, and the p53-Fos protein complex acted as a transcriptional co-regulator of ICP4. Studying the transcriptional process and regulatory pattern of ICP4 is of great significance for understanding the molecular mechanism of ILTV infection, and thus for finding effective methods to control and prevent it.

Exploring the Impact of Molecular Hydrogen Therapy on Oxidative Stress in Bleomycin-Induced Idiopathic Pulmonary Fibrosis: A Research Protocol

Introduction: Idiopathic Pulmonary Fibrosis (IPF) is an intensifying respiratory disorder triggered by bleomycin in cancer patients, characterized by its lack of a definitive remedy. Bleomycin induces mitochondrial leakage and elevates Reactive Oxygen Species (ROS) in the pulmonary cavity, causing a reduction in glutathione (GSH), a vital lung antioxidant. This reduction in GSH levels, coupled with ROS's inactivation of the tumor suppressor gene p53, increases the chance of developing fibrosis. Although no antioxidant treatments that currently target these effects, Molecular Hydrogen Therapy (MHT) has proven effective in mitigating ROS in diseases like Chronic Obstructive Pulmonary Disease (COPD). This study aims to explore the impact of bleomycin-induced IPF on ROS and p53, investigating MHT as a potential treatment to alleviate oxidative stress in fibrosis. Methods: The experimental design includes four groups of mice, two receiving bleomycin injections and two receiving a control buffer solution. Within each subgroup, one group will undergo MHT, while the other will receive sterile air. Bronchoalveolar lavage will be used to measure GSH levels before and after MHT, and RNA sequencing will monitor p53 activity in all treatment and control groups. Results: Anticipated outcomes include elevated GSH levels in the MHT-treated bleomycin group, indicating an antioxidative effect. Consequently, improved p53 activity is expected compared to controls. Discussion: Anticipated results, based on existing literature, suggest that MHT enhances antioxidant defenses and modulates p53 activity, thereby reducing oxidative damage and fibrotic remodeling. These findings highlight the potential of MHT as a therapeutic intervention for IPF, with broader implications for managing other oxidative stress-mediated lung diseases. However, further research, including preclinical studies and clinical trials, is needed to validate these anticipated findings and ensure the long-term safety and efficacy of MHT in clinical practice. Conclusion: The study aims to replicate findings in human populations and proposes a paradigm shift in treating such diseases by addressing the root cause, ROS.

Interleukin-34-orchestrated tumor-associated macrophage reprogramming is required for tumor immune escape driven by p53 inactivation

As the most frequent genetic alteration in cancer, more than half of human cancers have p53 mutations that cause transcriptional inactivation. However, how p53 modulates the immune landscape to create a niche for immune escape remains elusive. We found that cancer stem cells (CSCs) established an interleukin-34 (IL-34)-orchestrated niche to promote tumorigenesis in p53-inactivated liver cancer. Mechanistically, we discovered that Il34 is a gene transcriptionally repressed by p53, and p53 loss resulted in IL-34 secretion by CSCs. IL-34 induced CD36-mediated elevations in fatty acid oxidative metabolism to drive M2-like polarization of foam-like tumor-associated macrophages (TAMs). These IL-34-orchestrated TAMs suppressed CD8+ Tcell-mediated antitumor immunity to promote immune escape. Blockade of the IL-34-CD36 axis elicited antitumor immunity and synergized with anti-PD-1 immunotherapy, leading to a complete response. Our findings reveal the underlying mechanism of p53 modulation of the tumor immune microenvironment and provide a potential target for immunotherapy of cancer with p53 inactivation.

PITAR, a DNA damage-inducible cancer/testis long noncoding RNA, inactivates p53 by binding and stabilizing TRIM28 mRNA.

In tumors with WT p53, alternate mechanisms of p53 inactivation are reported. Here, we have identified a long noncoding RNA, PITAR (p53 Inactivating TRIM28 Associated RNA), as an inhibitor of p53. PITAR is an oncogenic Cancer/testis lncRNA and is highly expressed in glioblastoma (GBM) and glioma stem-like cells (GSC). We establish that TRIM28 mRNA, which encodes a p53-specific E3 ubiquitin ligase, is a direct target of PITAR. PITAR interaction with TRIM28 RNA stabilized TRIM28 mRNA, which resulted in increased TRIM28 protein levels and reduced p53 steady-state levels due to enhanced p53 ubiquitination. DNA damage activated PITAR, in addition to p53, in a p53-independent manner, thus creating an incoherent feedforward loop to inhibit the DNA damage response by p53. While PITAR silencing inhibited the growth of WT p53 containing GSCs in vitro and reduced glioma tumor growth in vivo, its overexpression enhanced the tumor growth in a TRIM28-dependent manner and promoted resistance to Temozolomide. Thus, we establish an alternate way of p53 inactivation by PITAR, which maintains low p53 levels in normal cells and attenuates the DNA damage response by p53. Finally, we propose PITAR as a potential GBM therapeutic target.

Linked regulation of genome integrity and senescence-associated inflammation by p53.

Genomic instability and inflammation are distinct hallmarks of aging, but the connection between them is poorly understood. Understanding their interrelationship will help unravel new mechanisms and therapeutic targets of aging and age-associated diseases. Here we report a novel mechanism directly linking genomic instability and inflammation in senescent cells through a mitochondria-regulated molecular circuit driven by p53 and cytoplasmic chromatin fragments (CCF). We show, through activation or inactivation of p53 by genetic and pharmacologic approaches, that p53 suppresses CCF accumulation and the downstream inflammatory senescence-associated secretory phenotype (SASP), without affecting cell cycle arrest. p53 activation suppressed CCF formation by promoting DNA repair, and this is reflected in maintenance of genomic integrity, particularly in subtelomeric regions, as shown by single cell genome resequencing. Activation of p53 in aged mice by pharmacological inhibition of MDM2 reversed signatures of aging, including age- and senescence-associated transcriptomic signatures of inflammation and age-associated accumulation of monocytes and macrophages in liver. Remarkably, mitochondria in senescent cells suppressed p53 activity by promoting CCF formation and thereby restricting ATM-dependent nuclear DNA damage signaling. These data provide evidence for a mitochondria-regulated p53 signaling circuit in senescent cells that controls DNA repair, genome integrity, and senescence- and age-associated inflammation. This pathway is immunomodulatory in mice and a potential target for healthy aging interventions by small molecules already shown to activate p53.

SRBD1 Regulates the Cell Cycle, Apoptosis, and M2 Macrophage Polarization via the RPL11-MDM2-p53 Pathway in Glioma.

Low expression of certain ribosomal proteins leads to the inactivation of p53, which is mediated mainly by RPL5 or RPL11 (ribosomal protein L11). It is also unknown what mechanisms drive aberrant ribosomal proteins expression in tumor. SRBD1 (S1 RNA-binding domain 1), as a highly conserved RNA-binding protein, is lowly expressed in glioma tissues and correlated with glioma prognosis. In this study, we observed that SRBD1 was closely related to p53 signaling. The upregulation of SRBD1 elevated p53 levels, thereby activating the p53 signaling pathway. As an RNA bind protein, SRBD1 could bind to the 5'-UTR of target genes and regulate RNA translation. We further conducted RNA immunoprecipitation using anti-SRDB1 antibody and noticed 29 hub RNA, including RPL11. RPL11 could inhibit MDM2-mediated p53 ubiquitination. SRBD1 upregulation promoted RPL11 binding to MDM2 via elevating RPL11 protein levels, which in turn activated the p53 signaling. Disrupting the p53 signaling blocked SRBD1-induced glioma suppression. In mouse xenograft model, SRBD1 ectopic expression was effective in reducing the total M2 tumor-associated macrophages (TAMs) density and suppressed glioma tumor growth. In summary, these data show that SRBD1 has a critical role in inhibition of glioma tumor growth and M2 macrophage polarization, and targeting RPL11-MDM2-p53 signaling may be an effective strategy to improve therapy and survival for glioma patients.

A Boolean model explains phenotypic plasticity changes underlying hepatic cancer stem cells emergence

In several carcinomas, including hepatocellular carcinoma, it has been demonstrated that cancer stem cells (CSCs) have enhanced invasiveness and therapy resistance compared to differentiated cancer cells. Mathematical-computational tools could be valuable for integrating experimental results and understanding the phenotypic plasticity mechanisms for CSCs emergence. Based on the literature review, we constructed a Boolean model that recovers eight stable states (attractors) corresponding to the gene expression profile of hepatocytes and mesenchymal cells in senescent, quiescent, proliferative, and stem-like states. The epigenetic landscape associated with the regulatory network was analyzed. We observed that the loss of p53, p16, RB, or the constitutive activation of β-catenin and YAP1 increases the robustness of the proliferative stem-like phenotypes. Additionally, we found that p53 inactivation facilitates the transition of proliferative hepatocytes into stem-like mesenchymal phenotype. Thus, phenotypic plasticity may be altered, and stem-like phenotypes related to CSCs may be easier to attain following the mutation acquisition.

Gardenin B, A Natural Inhibitor for USP7: In vitro Evaluation and In silico Identification

Background: Ubiquitin-specific protease 7 (USP7) is one of the most widely studied deubiquitin enzymes (DUBs). The protein level of USP7 is highly expressed in a variety of malignant cancers, which suggests that it is a prognostic marker of cancers and a potential drug target for oncotherapy. Objective: The aim of this study was to identify natural and effective USP7 inhibitors, in order to understand the activation of the USP7/p53 pathway by natural inhibitors. Methods: In this study, USP7 enzyme activity screening assay system and p53 luciferase reporter assay system have been applied for the discovery of natural USP7 inhibitors targeting the catalytic active site. Molecular docking and molecular dynamics (MD) simulation revealed the combined mechanism between USP7 with gardenin B. Results: The gardenin B was screened from our home-lab natural products (160 flavonoids) and had cytotoxicity in HCT116 cells (IC50 = 46.28 ± 2.16 μM). Preliminary in vitro studies disclosed its antiproliferative activity and activated p53 signaling pathway in HCT116 cells. We found that the complex formed by gardenin B and 5vsk (Ledock score = -6.86, MM/GBSA score = -53.35) had the optimal binding conformation. Moreover, the MD simulation showed that the π-π interactions between gardenin B with His461 and Phe409, and the hydrogen bonds interaction between gardenin B with Leu406 played an important role in maintaining the close binding of the complexes. Conclusion: In conclusion, gardenin B could be used as a natural product inhibitor of USP7 for further optimized design and development potential.

Synthetic lethality of combined ULK1 defection and p53 restoration induce pyroptosis by directly upregulating GSDME transcription and cleavage activation through ROS/NLRP3 signaling

BackgroundHigh expression of ubiquitin ligase MDM2 is a primary cause of p53 inactivation in many tumors, making it a promising therapeutic target. However, MDM2 inhibitors have failed in clinical trials due to p53-induced feedback that enhances MDM2 expression. This underscores the urgent need to find an effective adaptive genotype or combination of targets.MethodsKinome-wide CRISPR/Cas9 knockout screen was performed to identify genes that modulate the response to MDM2 inhibitor using TP53 wild type cancer cells and found ULK1 as a candidate. The MTT cell viability assay, flow cytometry and LDH assay were conducted to evaluate the activation of pyroptosis and the synthetic lethality effects of combining ULK1 depletion with p53 activation. Dual-luciferase reporter assay and ChIP-qPCR were performed to confirm that p53 directly mediates the transcription of GSDME and to identify the binding region of p53 in the promoter of GSDME. ULK1 knockout / overexpression cells were constructed to investigate the functional role of ULK1 both in vitro and in vivo. The mechanism of ULK1 depletion to activate GSMDE was mainly investigated by qPCR, western blot and ELISA.ResultsBy using high-throughput screening, we identified ULK1 as a synthetic lethal gene for the MDM2 inhibitor APG115. It was determined that deletion of ULK1 significantly increased the sensitivity, with cells undergoing typical pyroptosis. Mechanistically, p53 promote pyroptosis initiation by directly mediating GSDME transcription that induce basal-level pyroptosis. Moreover, ULK1 depletion reduces mitophagy, resulting in the accumulation of damaged mitochondria and subsequent increasing of reactive oxygen species (ROS). This in turn cleaves and activates GSDME via the NLRP3-Caspase inflammatory signaling axis. The molecular cascade makes ULK1 act as a crucial regulator of pyroptosis initiation mediated by p53 activation cells. Besides, mitophagy is enhanced in platinum-resistant tumors, and ULK1 depletion/p53 activation has a synergistic lethal effect on these tumors, inducing pyroptosis through GSDME directly.ConclusionOur research demonstrates that ULK1 deficiency can synergize with MDM2 inhibitors to induce pyroptosis. p53 plays a direct role in activating GSDME transcription, while ULK1 deficiency triggers upregulation of the ROS-NLRP3 signaling pathway, leading to GSDME cleavage and activation. These findings underscore the pivotal role of p53 in determining pyroptosis and provide new avenues for the clinical application of p53 restoration therapies, as well as suggesting potential combination strategies.

Hdm2 disrupts HdmX-mediated nuclear export of p53 by sequestering it in nucleus

Dysfunction of the tumor suppressor p53 occurs in most human cancers, Hdm2 and HdmX play critical roles in p53 inactivation and degradation. Under unstressed conditions, HdmX binds to p53 like Hdm2, but HdmX cannot directly induce p53 degradation. Moreover, HdmX has been reported to stimulate Hdm2-mediated ubiquitination and degradation of p53. Here we reported that HdmX promoted the nuclear export of p53 independent of Hdm2 in living cells using FRET technology. Whereas, Hdm2 impeded HdmX-mediated nuclear export of p53 by sequestering it in nucleus. Interestingly, the C-terminal RING domain mutant Hdm2C464A formed heterooligomers with p53 in nucleus, which was inhibited by HdmX. The heterooligomers were located near PML-NBs. This study indicate that the nuclear Hdm2-HdmX interaction aborts the HdmX-mediated nuclear export of p53.

<i>Calendula officinalis</i> (Asteraceae) as a radiosensitizer in radiotherapy of tumors

The effect of aqueous-alcoholic tincture of Сalendula officinalis L. (Asteraceae) on tumor cells of different species and tissue origin was studied. Its potential as a radiosensitizer in combination with γ-radiation was determined. It has been established that C. officinalis tincture causes the death of tumor cells regardless of their p53 and p21 status. C. officinalis tincture has antioxidant properties, but for cells with active p21 it exhibits radiosensitizing rather than radioprotective properties. For cells lacking p21, C. officinalis tincture is a radioprotector, so the cell death is p21 mediated. A study of the radiosensitizing properties of C. officinalis was carried out on a mouse melanoma model in vivo. In combination with γ-radiation, it led to a significant inhibition of tumor growth (by 47%), as compared to irradiation only. The significant radiosensitizing effect and capability of overcoming the tumor cells resistance induced by p53 inactivation make C. officinalis tincture promising as an add-on to radiotherapy, allowing to reduce the effective radiation dose 1.7 times.

Anticancer activity of Aucklandia costus Falc. terpenes: Targeting MDM2 protein inhibition for therapeutic advancements

Context: Protein 53 (p53) is a well-known tumor suppressor protein, while murine double minute 2 (MDM2) acts as a negative regulator of p53, leading to p53 inactivation and cancer development. Aucklandia costus Falc. or Saussurea lappa contains bioactive compounds, particularly terpenoids, known for their anticancer activity against various cancer cells. Targeting the p53-MDM2 protein interaction and inhibiting MDM2 are crucial strategies in cancer therapy. Aims: To analyze the anticancer properties of A. costus terpenes against MDM2 protein. Methods: The compounds costunolide, dehydrocostus lactone, lappadilactone, and cynaropicrin were docked with MDM2 (PDB ID: 4HG7) using AutoDockTools 1.5.6. Additionally, the physicochemical, pharmacokinetic, and toxicity properties were predicted using pkCSM. Results: Lappadilactone exhibited the highest binding energy value, surpassing both the control and the native ligand. Following lappadilactone, cynaropicrin, costunolide, and dehydrocostus lactone displayed decreasing binding energies. When assessing ADMET properties with pkCSM, all compounds exhibited good permeability, suggesting their ability to penetrate intestinal cell membranes, and showed no signs of hepatotoxicity. Conclusions: Lappadilactone emerges as a promising candidate with high intestinal absorption, distinctive distribution characteristics, and a lack of mutagenic or hepatotoxic effects.

Structural basis of p53 inactivation by cavity-creating cancer mutations and its implications for the development of mutant p53 reactivators

SummaryThe cavity-creating p53 cancer mutation Y220C is an ideal paradigm for developing small-molecule drugs based on protein stabilization. Here, we have systematically analyzed the structural and stability effects of all oncogenic Tyr-to-Cys mutations (Y126C, Y163C, Y205C, Y220C, Y234C, and Y236C) in the p53 DNA-binding domain (DBD). They were all highly destabilizing, drastically lowering the melting temperature of the protein by 8–17 °C. In contrast, two non-cancerous mutations, Y103C and Y107C, had only a moderate effect on protein stability. Differential stabilization of the mutants upon treatment with the anticancer agent arsenic trioxide and stibogluconate revealed an interesting proximity effect. Crystallographic studies complemented by MD simulations showed that two of the mutations, Y234C and Y236C, create internal cavities of different size and shape, whereas the others induce unique surface lesions. The mutation-induced pockets in the Y126C and Y205C mutant were, however, relatively small compared with that of the already druggable Y220C mutant. Intriguingly, our structural studies suggest a pronounced plasticity of the mutation-induced pocket in the frequently occurring Y163C mutant, which may be exploited for the development of small-molecule stabilizers. We point out general principles for reactivating thermolabile cancer mutants and highlight special cases where mutant-specific drugs are needed for the pharmacological rescue of p53 function in tumors.

Therapeutic targeting of TP53 nonsense mutations in cancer.

Mutations in the TP53 tumor suppressor gene occur with high prevalence in a wide range of human tumors. A significant fraction of these mutations (around 10%) are nonsense mutations, creating a premature termination codon (PTC) that leads to the expression of truncated inactive p53 protein. Induction of translational readthrough across a PTC in nonsense mutant TP53 allows the production of full-length protein and potentially restoration of normal p53 function. Aminoglycoside antibiotics and a number of novel compounds have been shown to induce full-length p53 in tumor cells carrying various TP53 nonsense mutations. Full-length p53 protein generated by translational readthrough retains the capacity to transactivate p53 target genes and trigger tumor cell death. These findings raise hopes for efficient therapy of TP53 nonsense mutant tumors in the future.

SIRT-associated attenuation of cellular senescence in vascular wall

This review focuses on the vital function that SIRT1 and other sirtuins play in promoting cellular senescence in vascular smooth muscle cells, which is a key element in the pathogenesis of vascular aging and associated cardiovascular diseases. Vascular aging is a gradual process caused by the accumulation of senescent cells, which results in increased vascular remodeling, stiffness, and diminished angiogenic ability. Such physiological alterations are characterized by a complex interplay of environmental and genetic variables, including oxidative stress and telomere attrition, which affect gene expression patterns and trigger cell growth arrest. SIRT1 has been highlighted for its potential to reduce cellular senescence through modulation of multiple signaling cascades, particularly the endothelial nitric oxide (eNOS)/NO signaling pathway. It also modulates cell cycle through p53 inactivation and suppresses NF-κB mediated expression of adhesive molecules at the vascular level. The study also examines the therapeutic potential of sirtuin modulation in vascular health, identifying SIRT1 and its sirtuin counterparts as potential targets for reducing vascular aging. This study sheds light on the molecular basis of vascular aging and the beneficial effects of sirtuins, paving the way for the development of tailored therapies aimed at enhancing vascular health and prolonging life.

Abstract 1533: Characterizing tumor-immune surveillance in Li-Fraumeni syndrome

Abstract Li-Fraumeni Syndrome (LFS) is a cancer predisposition syndrome associated with germline TP53 mutations and increased lifetime risk of developing multiple cancers. p53, the protein encoded by TP53, plays a role in regulating various aspects of immune cell biology. Accordingly, inactivation of p53 in tumor cells shapes interactions with the immune system and influences the anti-tumor immune response. Mutation or deletion of p53 in immune cells also favors tumor development and progression. However, to date, a comprehensive study of immune cell populations and the anti-tumor immune response has not been undertaken in the context of LFS. We hypothesized that germline TP53 mutation carriers possess dysfunctional immune cells and/or immune responses, supporting LFS-associated tumor progression. Our preliminary data indicate a profound defect in tumor-immune surveillance in an LFS murine model. We observed that MC38 cancer cells develop significantly faster into tumors when injected into LFS mice (harboring a gain-of-function mutation Trp53R172H/WT) compared to wildtype (WT) control mice. Importantly, we identified significant alterations in immune cell compositions and phenotypes within the tumor microenvironment as well as immune organs using flow cytometry. We are currently using ex vivo proliferation assays and cytotoxicity assays to investigate the impact of mutant p53 on the tumor-killing ability of immune effector cells. Altogether, an improved understanding of anti-tumor immune dysfunction in the context of germline TP53 mutation may reveal the potential for innovative therapies to target different facets of the immune system to intercept cancer progression in LFS patients. Citation Format: Camilla Giovino, Nicholas Fischer, Noel Ong, Ashby Kissoondoyal, Ran Kafri, David Malkin. Characterizing tumor-immune surveillance in Li-Fraumeni syndrome [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1533.

Abstract 5959: Targeting TRIM11 is a potential therapeutic strategy for malignant gliomas

Abstract Background: TRIM11 (tripartite motif-containing protein 11) belongs to the TRIM/RBCC (the RING B-box coiled-coil) family of E3 ubiquitin ligases. Emerging evidence has demonstrated that TRIM11 is a novel target against cancer and neurodegenerative diseases as it plays vital role in cellular proliferation, differentiation, tumor progression, and apoptosis. Our previous work demonstrated that TRIM11 is over-expressed in high-grade gliomas and promotes proliferation, invasion, migration and tumor growth, suggesting that TRIM11 may be used as a target for malignant glioma treatment. The tumor suppressor p53 plays critical roles in tumor prevention, and deregulated p53 pathway has been found in a majority of glioblastomas (GBMs). Recent studies have shown that TRIM proteins are involved in the regulation of p53, and TRIM proteins are also regulated by p53. Methods: To evaluate the effect of TRIM11 on GBM progression in vivo, we intracranially implanted GBM cells over-expressing TRIM11 in immunocompromised mice, and the animal survival was monitored. We have synthesized a series of TRIM11 inhibitors and evaluated their anti-GBM potential in vitro. Furthermore, we tested the crosstalk between TRIM11 and p53 by knocking down TP53 through RNA interference. Results: Our in vivo data showed that the control group mice (GL261 parent line) survived longer than the mice bearing TRIM11 over-expressing GL261 tumors (p<0.05), suggesting TRIM11 enhances tumor progression in vivo. In vitro data showed that the oncogenic effect of TRIM11 may be related to its influence on the apoptosis pathway since a robust induction of poly (ADP-ribose) polymerase (PARP) was observed in TRIM11 over-expressing GBM cells. When treated with Temozolomide (TMZ), TRIM11 over-expressing cells were more resistant and showed a higher survival rate compared to parental cells. We screened a small library of TRIM11 inhibitors (~ 25 compounds), and identified several compounds which significantly inhibited the growth of both established and primary GBM cells in a dose-dependent manner, implicating that TRIM11 inhibitors may serve as novel agents for GBM treatment. We found that inactivation of p53 by siRNA increased the expression of TRIM11 and modulated the sensitivities of GBM cells to chemotherapy drugs. Conclusion: Despite remarkable advances in the prognosis and multidisciplinary treatment strategies, GBM is still the most lethal primary brain tumor, and there is a pressing need for newer anti-GBM agents with novel targets and mode of action. Our preclinical studies demonstrate a significant anti-tumor effect of TRIM11 inhibitors on malignant glioma cells. Our finding that TRIM11 may be modulated by p53 adds a new layer of regulation to this complicated signaling pathway. A better understanding of the crosstalk between p53 and TRIM11 will benefit the clinical application of targeting p53 and TRIM11 signaling pathways for therapeutical indications in GBM. Citation Format: Kaijun Di, Bhaskar C. Das, Daniela Alexandru Abrams, Daniela A. Bota. Targeting TRIM11 is a potential therapeutic strategy for malignant gliomas [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5959.