Wild-type P53 Research Articles

KRT20-/SATB2+/MCPyV+ Sinonasal Merkel Cell Carcinoma: A Detailed Immunohistochemical and In Situ Hybridization Study.

Merkel cell carcinoma (MCC) is an uncommon aggressive neoplasm, usually arising in sun-exposed skin of the head and neck. By immunohistochemistry, KRT20 and MCPyV positivity are found in about 90% and 80% of MCCs, respectively. Noteworthy, viral status in lip/oral cavity MCCs is poorly known. A 78-year-old male was referred presenting a tumor mass on the right maxilla four months ago. Computed tomography revealed an extensive osteolytic lesion in the right maxillary sinus extending into the orbit and nasal cavity and crossing the midline. Microscopy revealed large necrotic areas admixed by sheets of small, round cells with hyperchromatic nuclei exhibiting a '"salt and pepper" chromatin pattern, which showed immunopositivity for pan-KRT AE1/AE3, EMA, CD56, CD99 (weak), CD138, S100 (focal), vimentin (focal), synaptophysin, FLI1, INSM1, MCPyV, SATB2, and Ki-67 (MKI67 [40%]). Moreover, intact RB1 and wild-type p53 expression were observed. Relevantly, KRT20, KRT5/6, chromogranin A, p40, p63, HMB45, NF, TTF1, TDT (DNTT), PAX5, p16, KIT, as well as high-risk HPV and EBER1/2 (both by ISH), were negative. This report illustrates that a detailed immunohistochemical study, including STAB2 and MCPyV markers, as well as a careful clinical workup, are essential to adequately classify high-grade neuroendocrine carcinomas, especially KRT20-negative MCC.

High GRWD1 expression may predict clinically aggressive lower grade glioma, skin cutaneous melanoma, and kidney renal clear cell carcinoma carrying wild-type p53: a systematic study based on TCGA data analysis.

Glutamate-rich WD40 repeat containing 1 (GRWD1) is a novel oncogene/oncoprotein that downregulates the p53 tumor suppressor protein through several mechanisms. One important mechanism involves binding of GRWD1 to RPL11, which competitively inhibits the RPL11-MDM2 interaction and releases RPL11-mediated suppression of MDM2 ubiquitin ligase activity toward p53. Here, we mined the TCGA (The Cancer Genome Atlas) database to gain in-depth insight into the clinical relevance of GRWD1. We found that high expression of GRWD1 is associated with a poor prognosis for lower grade glioma (LGG) of the brain, skin cutaneous melanoma (SKCM), and kidney renal clear cell carcinoma (KIRC) carrying wild-type p53. Further investigations revealed that copy number alterations in the GRWD1 gene are one determinant of GRWD1 expression level. By contrast, even in patients with a diploid GRWD1 gene, high GRWD1 expression was associated with a poor prognosis for LGG, SKCM, and KIRC carrying wild-type p53. Additional studies suggest that some transcriptional factors may be involved in regulation of GRWD1 in cancers with a diploid GRWD1 gene. Taken together, the data presented herein suggest that high expression of GRWD1 may contribute to malignant behavior, and predict a clinically unfavorable prognosis for LGG, SKCM, and KIRC carrying wild-type p53.

INOS-Produced Nitric Oxide from Cancer Cells as an Intermediate of Stemness Regulation by PARP-1 in Colorectal Cancer

PARP-1 has been linked to the progression of several types of cancer. We have recently reported that PARP-1 influences tumor progression in CRC through the regulation of CSCs in a p53-dependent manner. In this study, we propose that nitric oxide (NO) produced by inducible nitric oxide synthase (iNOS) could act as a mediator. We evaluated the expression of iNOS in a cohort of patients previously used to analyze the effects of PARP-1 on CRC in relation to p53 status. We also developed an in vitro model in which PARP-1 was stably overexpressed. In CRC patients, iNOS expression correlated with the differentiation grade, and with a high expression of CSC markers, although only in wild-type p53 tumors, as previously found for PARP-1. In vitro, overexpression of PARP-1 induced increased growth and stemness in wild-type p53 cells, while exerting the opposite effect on mutated ones, as expected. Treatment with 1400W, a selective inhibitor of iNOS, or gene silencing of the gene counteracted the effects of PARP-1 in both p53 wild-type and p53 mutated cells. Given that the development of resistance has been demonstrated after treatment with PARP-1 inhibitors, iNOS could be considered a new therapeutic target in CRC, although only in patients with wild-type p53 tumors.

Orphan nuclear receptor NR2E3 is a new molecular vulnerability in solid tumors by activating p53

The orphan nuclear receptor NR2E3 has emerged as a potential tumor suppressor, yet its precise mechanisms in tumorigenesis require further investigation. Here, we demonstrate that the full-length protein isoform of NR2E3 instead of its short isoform activates wild-type p53 and is capable of rescuing certain p53 mutations in various cancer cell lines. Importantly, we observe a higher frequency of NR2E3 mutations in three solid tumors compared to the reference population, highlighting its potential significance in tumorigenesis. Specifically, we identify a cancer-associated NR2E3R97H mutation, which not only fails to activate p53 but also impedes NR2E3WT-mediated p53 acetylation. Moreover, we show that the small-molecule agonist of NR2E3, 11a, penetrates tumor mass of uterine cancer patients and increases p53 activation. Additionally, both NR2E3 and 11a exhibit similar multifaceted anti-cancer properties, underscoring NR2E3 as a novel molecular vulnerability in cancer cells. We further explore drug repurposing screens of FDA-approved anti-cancer drugs to develop NR2E3-targeted combinatorial treatments, such as the 11a-Romidepsin combination in HeLa cells. The underlying molecular mechanisms of these drug synergies include the activation of p53 pathway and inhibition of oncogenic pathway like MYC. Overall, our findings suggest that NR2E3 holds promise as a therapeutic target for cancer treatment, offering new avenues for effective anti-cancer strategies.

Small molecules that targeting p53 Y220C protein: mechanisms, structures, and clinical advances in anti-tumor therapy.

The p53 protein is regarded as the "Guardian of the Genome," but its mutation is tumor progression and present in more than half of malignant tumors. The pro-metastatic property of mutant p53 makes a strong argument for targeting mutant p53 with new therapeutic strategies. However, mutant p53 was considered as a challenging target for drug discovery due to the lack of small molecular binding pockets. Among them, mutant p53 Y220C creates a narrow crevice since the side chains dynamics on protein surface, which is suitable for designing small molecules to occupy the cavity and recovery the tumor suppressing function. Here, we describe the mechanism of p53 related signal pathway and how p53 Y220C regulate the tumorigenesis. We review the two types of p53 Y220C modulators including restoring the conformation of mutant p53 Y220C protein to wild-type p53 protein and recruiting histone acetyltransferase p300/CBP to acetylate p53 Y220C thus enables p53 Y220C dependent upregulation of apoptotic genes and downregulation of DNA damage response pathways. We also report clinical advances and challenges of these molecules in p53 Y220C medicated tumor therapy.

Theophylline alleviates cyclophosphamide-induced T cell senescence by downregulating acetylation of p53 at lysine 373.

Cyclophosphamide is a widely used immunosuppressive and chemotherapeutic agent in clinics. Previous studies have indicated that cyclophosphamide treatment induces cellular senescence in patients, although the underlying mechanisms remain elusive. Here, we reported that cyclophosphamide induced T cell senescence in the spleen of mice. Meanwhile, phosphoramide mustard cyclohexanamine (PM), an active metabolite of cyclophosphamide, triggered human T cell senescence. RNA sequencing analysis revealed that PM promoted senescence of primary human T cells through the activation of the p53 signaling pathway. Moreover, PM strongly increased the acetylation of p53 lysine 373 in T cells. Compared with the wild-type p53, mutating lysine 373 of p53 to arginine markedly reduced the p21 and p16 expression in PM treated Jurkat cells. Notably, we found that theophylline, an activator of histone deacetylase HDAC, ameliorated the senescence phenotype of both primary human T cells induced by PM and splenic T cells induced by cyclophosphamide in mice. Together, the results from current study could provide a potential strategy against cyclophosphamide-induced T cell senescence by inhibiting p53 acetylation.

S100A4 contributes to colorectal carcinoma aggressive behavior and to chemoradiotherapy resistance in locally advanced rectal carcinoma

To investigate the functional role of S100A4 in advanced colorectal carcinoma (Ad-CRC) and locally advanced rectal carcinoma (LAd-RC) receiving neoadjuvant chemoradiotherapy (NCRT). We analyzed histopathological and immunohistochemical sections from 150 patients with Ad-CRC and 177 LAd-RC patients treated with NCRT. S100A4 knockout (KO) HCT116 cells were also used. S100A4 expression was absent in normal mucosa but increased progressively from colorectal adenoma to carcinoma, suggesting that S100A4 regulation is an early event in colorectal carcinogenesis. In Ad-CRC, high S100A4 expression correlated with high tumor budding and nuclear β-catenin, deep invasion, lymph-vascular involvement, and unfavorable prognosis. In NCRT-treated LAd-RC, high S100A4 expression was associated with poor treatment response and short progression-free survival. S100A4 KO decreased the proliferation of HCT116 cells through activation of the p53/p21waf1 axis, and sensitized cells to adriamycin-induced apoptosis. Levels of the apoptotic marker, cleaved poly (ADP-ribose) polymerase 1, were significantly higher in samples with low S100A4 and wild type p53. Finally, we observed a direct interaction between S100A4 and p53. In conclusion, S100A4 expression engenders aggressive behavior in Ad-CRC through association with β-catenin-driven tumor buddings. S100A4 exerts anti-apoptotic and proliferative effects via inhibition of p53 in LAd-RC patients receiving NCRT, which leads to chemoradioresistance and poor prognosis.

Prognostic factors and survival outcomes of immunohistochemically detection based-molecular subtypes of endometrial cancer–analysis of 576 clinical cases

ObjectiveThe study aimed to identify distinct molecular subtypes of endometrial cancer (EC) by immunohistochemistry and to analyze their pathological characteristics, independent prognostic factors, and patient survival outcomes for potential clinical applications.Method576 patients with preoperative EC confined to the uterus were divided into three subgroups based on the immunohistochemical detection method: MMR-deficiency (MMRd), P53 wild type (P53wt) and P53 abnormal (P53abn). These subgroups were retrospectively analyzed, and their pathological characteristics, prognostic factors and survival outcomes were compared.ResultsWe identified 401 (69.6%), 123 (21.4%), and 52 (9%) cases of P53wt, MMRd, and P53abn subgroups, respectively. A significant difference was observed in the median age of onset, tumor stage, high-grade tumor differentiation, non-endometrioid carcinoma, myometrial invasion, lymphovascular invasion, the incidence of lymph node metastasis postoperative, and expression of ER and PR receptors among the three groups. Pathological type, lymphovascular invasion, ER and PR expression were identified as independent prognostic factors for disease-free survival (DFS). Additionally, pathological type, lymphovascular invasion, myometrial invasion, and PR expression were recognized as independent prognostic factors for overall survival (OS) in the study cohort. However, the survival outcome for P53abn was the worst, with lymphovascular invasion identified as an independent prognostic factor for DFS. Lymph node status, FIGO stage, and ER expression were identified as independent prognostic factors for OS.ConclusionThe study concludes that immunohistochemical detection-based subtyping of EC holds clinical practicality and can be employed to explore both pathological and clinical prognoses for EC patients.

Molecular Subtypes of Vulvar Squamous Cell Carcinoma: The Significance of HPV-Independent/p53 Wild Type.

Vulvar carcinoma is a rare disease, meeting the criteria for a "rare cancer", but its incidence is increasing, especially in women <60 years of age. Squamous cell carcinoma (VSCC) accounts for the overwhelming majority of vulvar carcinomas and is the focus of this review. As with many cancers, the increased understanding of molecular events during tumorigenesis has led to the emergence of the molecular subclassification of VSCC, which is subclassified into tumors that arise secondary to high-risk human papillomavirus infection (HPV-associated, or HPVa) and those that arise independently of HPV (HPVi), most commonly in the setting of a chronic inflammatory condition of the vulvar skin. This latter group of HPVi VSCC arises in most cases secondary to mutations in TP53, but recently, attention has focused on the uncommon TP53 wild-type HPVi VSCC. These three molecular subtypes of VSCC (HPVa, HPVi p53 abnormal, and HPVi p53 wild type), as well as their precursor lesions, cannot be diagnosed based on a routine histopathological examination or immunostaining for p53 and p16 as surrogate markers for TP53 mutation and high-risk HPV infection, respectively, are required. The molecular subtyping of VSCC shows high reproducibility and provides important prognostic information. HPVa VSCC has the most favorable prognosis, while HPVi VSCC with TP53 mutations (p53abn) has the worst prognosis, and HPVi VSCC with wild-type TP53 (p53wt) has an intermediate prognosis. In this review, we discuss the evidence supporting this molecular subclassification and its implications for the diagnosis and treatment of VSCC and its precursors.

Anticancer effects of aloe-emodin from Rheum undulatum L. through activation of the p53 pathway in human prostate cancer cells

Aloe-emodin, an anthraquinone compound naturally derived from Rheum undulatum L., has gained extensive research attention owing to its various pharmacological effects, including its potential as an anticancer, antivirus, anti-inflammatory, antibacterial, and anti-parasitic agent. It has demonstrated notable inhibitory effects against various types of cancer and cancer cells. Prostate cancer is among the most commonly identified cancers globally and remains a leading cause of cancer-associated deaths in men, often presenting challenges in early detection due to its asymptomatic nature during initial stages. The aim of present study was to determine the biological activity of aloe-emodin obtained from Rheum undulatum L. involving activation of the p53-dependent pathway in certain human prostate cancer cell lines. We explored the mechanisms underlying the anticancer effects of aloe-emodin using LNCaP cells, which include p53-wild type and phosphatase and tensin homolog-deficient mutated genes, a widely studied model in genomic research. Aloe-emodin induced apoptosis in LNCaP cells through several mechanisms, including upregulation of the cleavage of caspase-8 (a cross-linked promoter of cell death signals), phosphorylation of p53 at serine 15, DNA fragmentation, cleavage of poly [ADP-ribose] polymerase, and promotion of cell death. These findings strongly indicated that aloe-emodin's anticancer properties in human prostate cancer involve the activation of p53-induced cellular senescence. Conclusively, the findings of this study imply that aloe-emodin extracted from Rheum undulatum L. is a potential therapeutic compound for adjuvant chemotherapy that induces apoptosis and pyroptosis, an innate immune response, in preventing the progression of precancerous lesions in patients with prostate cancer.

P53 marker expression in epithelial ovarian tumours in a centre in Nigeria – a descriptive study

Backgroundp53 is a tumor suppressor gene. p53 expression in epithelial ovarian tumors (EOTs) is correlated with their biological behavior and predicts patient overall survival. However, there is a dearth of knowledge regarding p53 expression in these tumors among women from southwest Nigeria. Our study aimed to determine the patterns of p53 expression in various types of epithelial ovarian tumours.MethodsWe conducted a retrospective study of epithelial ovarian tumours. We retrieved formalin-fixed, paraffin-embedded (FFPE) tissue blocks of previously diagnosed epithelial tumors from the departmental archive. We performed immunohistochemical analysis using p53 antibodies. We scored the expression and staining intensity of p53 as follows: negative (0), focal/weakly positive (1 +), and diffuse/strongly positive (2 +) on the basis of the recommended Cytomation scoring system.ResultsThe spectrum of p53 expression in the 51 histologically diagnosed cases revealed that 29 cases had no expression, consisting of 21 benign EOTs, two borderline EOTs, and six malignant EOTs. Nine cases exhibited wild-type expression, including six serous carcinomas, two mucinous carcinomas, and one signet ring cell carcinoma. p53 overexpression was observed in 13 patients overall, with 12 having serous carcinomas and one having endometrioid carcinoma. Among the 21 serous carcinoma patients, 28.6% (6 patients) presented with wild-type p53 expression, 57.1% (12 patients) presented with p53 overexpression, and 14.3% (three patients) presented negative p53 expression. There was a significant association between p53 expression and the histological grade of serous carcinoma.ConclusionMost epithelial ovarian carcinomas in our hospital are high grade, with many serous carcinomas showing either p53 overexpression or loss of expression. This may contribute to the poor patient survival rate.

Dysregulation of the p53 pathway provides a therapeutic target in aggressive pediatric sarcomas with stem-like traits.

Pediatric sarcomas are bone and soft tissue tumors that often exhibit high metastatic potential and refractory stem-like phenotypes, resulting in poor outcomes. Aggressive sarcomas frequently harbor a disrupted p53 pathway. However, whether pediatric sarcoma stemness is associated with abrogated p53 function and might be attenuated via p53 reactivation remains unclear. We utilized a unique panel of pediatric sarcoma models and tumor tissue cohorts to investigate the correlation between the expression of stemness-related transcription factors, p53 pathway dysregulations, tumorigenicity in vivo, and clinicopathological features. TP53 mutation status was assessed by next-generation sequencing. Major findings were validated via shRNA-mediated silencing and functional assays. The p53 pathway-targeting drugs were used to explore the effects and selectivity of p53 reactivation against sarcoma cells with stem-like traits. We found that highly tumorigenic stem-like sarcoma cells exhibit dysregulated p53, making them vulnerable to drugs that restore wild-type p53 activity. Immunohistochemistry of mouse xenografts and human tumor tissues revealed that p53 dysregulations, together with enhanced expression of the stemness-related transcription factors SOX2 or KLF4, are crucial features in pediatric osteosarcoma, rhabdomyosarcoma, and Ewing's sarcoma development. p53 dysregulation appears to be an important step for sarcoma cells to acquire a fully stem-like phenotype, and p53-positive pediatric sarcomas exhibit a high frequency of early metastasis. Importantly, reactivating p53 signaling via MDM2/MDMX inhibition selectively induces apoptosis in aggressive, stem-like Ewing's sarcoma cells while sparing healthy fibroblasts. Our results indicate that restoring canonical p53 activity provides a promising strategy for developing improved therapies for pediatric sarcomas with unfavorable stem-like traits.

Inhibition of PSF activity overcomes resistance to treatment in cancers harboring mutant p53.

Mutations in the TP53 tumor suppressor genes are prevalent in aggressive cancers. Pharmacological reactivation of dysfunctional p53 due to mutations is a promising strategy for treating such cancers. Recently, a multifunctional proline- and glutamine-rich protein, PTB-associated splicing factor (PSF), was identified as a key driver of aggressive cancers. PSF promotes the expression of numerous oncogenes by modulating epigenetic and splicing mechanisms. We previously screened a small-molecule library and discovered compound No.10-3 as a potent PSF inhibitor. Here, we report the discovery of a No.10-3 analog, C-30, as a potent PSF inhibitor. Compared to No.10-3, C-30 treatment specifically suppressed the growth and induced apoptosis of mutant p53-bearing and therapy-resistant cancer cells. Interestingly, C-30 activated a set of p53-regulated genes in therapy-resistant cancer cells. A comprehensive analysis of PSF and p53 binding regions demonstrated a higher level of PSF-binding potential in mutant p53-expressing cancer cells around genomic regions identified as p53-binding peaks in p53-wild type cancer cells. Treatment of mutant p53-expressing cancer cells with C-30 decreases PSF binding around these sites, leading to activated histone acetylation. We further demonstrated that C-30 impaired tumor growth and increased the expression of p53-target genes in vivo. These results suggested that C-30 produces tumor-suppressive effects similar to the functional reactivation of p53, providing a rationale for the inhibition of PSF activity as a promising therapy against treatment-resistant cancer.

Prognostic effect of immunohistochemically determined molecular subtypes in gastric cancer

IntroductionGastric cancer is the fifth most common cancer worldwide and the fourth most common cause of cancer-related death. Two molecular subtyping classifications were recently introduced: The Cancer Genome Atlas (TCGA) and the Asian Cancer Research Group (ACRG) classifications.MethodsWe classified a cohort of 283 gastric cancer patients undergoing surgery at Helsinki University Hospital between 2000 and 2009. We constructed a tumour tissue microarray immunostained for the following markers: microsatellite instability (MSI) markers MSH2, MSH6, MLH1, and PMS2; p53; E-cadherin; and EBERISH.ResultsIn the univariate survival analysis for disease-specific survival, the Epstein–Barr virus (EBV) -positive subtype exhibited the worst prognosis with a hazard ratio (HR) of 2.49 (95% confidence interval [CI] 1.19–5.25, p = 0.016) compared with the most benign subtype, chromosomal instability (CIN). Using TCGA’s classification, the genetically stable (GS) and MSI subtypes exhibited a worse survival compared with CIN (HR 1.73 [95% CI 1.15–2.60], p = 0.009 and HR 1.74 [95% CI 1.06–2.84], p = 0.027, respectively). Using the ACRG classification, the p53 aberrant subtype exhibited the best prognosis, whereas wild-type p53, MSI, and the epithelial–mesenchymal transition (EMT) subtypes exhibited poorer prognoses (EMT: HR 1.90 [95% CI 1.30–2.77], p < 0.001) when compared with aberrant p53.ConclusionsImmunohistochemical analysis can identify prognostically different molecular subtypes of gastric cancer. The method is inexpensive and fast, yet reveals significant information for clinical decision-making. However, our study did not find that either molecular subtyping performed better than the other classification. Thus, further development of the most optimal grouping of different molecular subtypes is still needed.

Wild-Type p53 Regulates Apoptosis of Human Breast Cancer Cells.

The tumor suppressor wild-type p53 is known for its role in inducing apoptosis in tumor cells. This study investigated the relationship between wild-type p53 and protein phosphatase 1 (PP1) and caspase in promoting apoptosis of breast cancer cells. Human breast cancer cell lines MCF-7 and MDA-MB-231 obtained from the American Type Culture Collection were used in this study. Small interference RNAs (Si-RNA) and plasmids were used to regulate wild-type p53 expression in these two tumor cell lines through liposome-mediated transfection. GSK-2830371 (PP1 inhibitor) and zVAD (Caspase inhibitor) were employed to further verify the PP1 activating function of wild-type p53 in Caspase-dependent MCF-7 and MDA-MB-231 apoptosis. PP1 activity was quantitatively detected by phosphorus colorimetric assay. Co-immunoprecipitation (Co-IP), flow cytometry assay, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, Western blot, the real-time reverse transcriptase-polymerase chain reaction (RT-qPCR), and immunofluorescence staining were used to analyze cell apoptosis degree and marker protein expression. The expression level of PP1 in the breast cancer cells was successfully regulated by cell transfection. The phosphatase activity was increased, and obvious apoptotic cytological characteristics were observed in p53-overexpressed breast cancer cells. p53 knockdown/overexpression increased/decreased the level of B cell lymphoma 2 (Bcl-2), and decreased/increased levels of Caspase-3, cleaved Caspase-3, cleaved Caspase-8, Cytochrome C (Cyt-C), Truncated BID (tBid), Bcl-2-associated X (Bax), and cell apoptosis (p < 0.01). The promotion of proteins and apoptosis induced by p53 overexpression was reversed by GSK-2830371 or zVAD. Wild-type p53 might promote Caspase-dependent apoptosis of human breast cancer cells through PP1 activation.

P53 induces circFRMD4A to suppress cancer development through glycolytic reprogramming and cuproptosis.

Cuproptosis is a type of copper-induced cell death that mainly impacts cells relying on mitochondrial metabolism. Although p53 regulates glycolytic metabolism, its role in cuproptosis remains unclear. Here, we report that the circular RNA, circFRMD4A, is crucial for p53-mediated metabolic reprogramming and cuproptosis. CircFRMD4A originates from the transcript of FRMD4A, which is transcriptionally activated by p53, and the formation of circFRMD4A is facilitated by the RNA-binding protein EWSR1. CircFRMD4A functions as a tumor suppressor and enhances the sensitivity of cancer cells to elesclomol-induced cuproptosis. Mechanistic analysis reveals that circFRMD4A interacts with and inactivates the pyruvate kinase PKM2, leading to a decrease in lactate production and a redirection of glycolytic flux toward the tricarboxylic acid cycle. Finally, p53 agonists and elesclomol coordinately suppress the growth of cancer in a xenograft mouse model. Altogether, our study uncovers that p53 promotes glycolytic reprogramming and cuproptosis via circFRMD4A and suggests a potential combination strategy against cancers with wild-type p53.

Unraveling the Guardian: p53's Multifaceted Role in the DNA Damage Response and Tumor Treatment Strategies.

DNA damage can lead to mutations that can alter the function of oncogenes or tumor suppressor genes, thus promoting the development of cancer. p53 plays a multifaceted and complex role in the DNA damage response and cancer progression and is known as the 'guardian of the gene'. When DNA damage occurs, p53 is activated through a series of post-translational modifications, which stabilize the protein and enhance its function as a transcription factor. It regulates processes including cell cycle checkpoints, DNA repair and apoptosis, thereby preventing the spread of damaged DNA and maintaining genome integrity. On the one hand, p53 can initiate cell cycle arrest and induce cells to enter the G1/S and G2/M checkpoints, preventing cells with damaged DNA from continuing to proliferate and gaining time for DNA repair. At the same time, p53 can promote the activation of DNA repair pathways, including base excision repair, nucleotide excision repair and other repair pathways, to ensure the integrity of genetic material. If the damage is too severe to repair, p53 will trigger the apoptosis process to eliminate potential cancer risks in time. p53 also plays a pivotal role in cancer progression. Mutations in the p53 gene are frequently found in many cancers, and the mutated p53 not only loses its normal tumor suppressor function but may even acquire pro-cancer activity. Therefore, we also discuss therapeutic strategies targeting the p53 pathway, such as the use of small-molecule drugs to restore the function of wild-type p53, the inhibition of negative regulatory factors and synthetic lethality approaches for p53-deficient tumors. This review therefore highlights the important role of p53 in maintaining genomic stability and its potential in therapeutic strategies for cancer.

Resurrecting p53 by an Artificial Nano-Protein for Potent Photodynamic Retinoblastoma Therapy.

The treatment of retinoblastoma (RB), a formidable eye cancer that affects infants and children, is not only aimed at saving lives but at preserving ocular function, maintaining optimal visual acuity, and enhancing the overall quality of life. Photodynamic therapy has already been established as a secure and dependable therapeutic modality for the treatment of ocular diseases that effectively preserves ocular function; however, it fails to provide satisfactory outcomes against RB. To address this formidable challenge, groundbreaking advancement is aspired by delving into the genetic characteristics of RB, which initially involves the wild-type p53 pathway but is subsequently suppressed by MDM2 and MDMX. In this study, an artificial nanoprotein (ANP) is developed through the fusion of human serum albumin with a potent MDM2/MDMX degrading peptide and the porphyrin-photosensitizer verteporfin (VP). ANP effectively dismantles MDM2/MDMX proteins within the ubiquitin-proteasome degradation pathway and triggers VP-PDT-mediated cell death through mitochondrial impairment. Remarkably, ANP exhibited remarkable therapeutic efficacy in both subcutaneous and in situ RB mouse models, while maintaining a highly favorable biosafety profile. Collectively, ANP not only provides compelling evidence for sensitizing photodynamic RB therapy by reactivating p53, but also serves as an exceptionally potent photosensitizer with promising potential for clinical translation in RB treatment.

The Activation of p300 Enhances the Sensitivity of Pituitary Adenomas to Dopamine Agonist Treatment by Regulating the Transcription of DRD2.

Prolactinomas are commonly treated with dopamine receptor agonists (DAs), such as bromocriptine (BRC) and cabergoline (CAB). However, 10-30% of patients exhibit resistance to DA therapies. DA resistance is largely associated with reduced dopamine D2 receptor (DRD2) expression, potentially regulated by epigenetic modifications, though the underlying mechanisms are still unclear. Clinical samples were assessed for p300 expression. MMQ and AtT-20 cells were engineered to overexpress either wild-type p300 or a histone acetyltransferase (HAT) domain-mutant form of p300. Mechanistic studies included cell proliferation assays, flow cytometry, immunohistochemistry, immunofluorescence, co-immunoprecipitation, chromatin immunoprecipitation followed by quantitative PCR, reverse transcription quantitative PCR, and Western blotting. Additionally, an in vivo nude mouse xenograft model was used to confirm the in vitro findings. DAs downregulated p300 through the cAMP-PKA-CREB pathway. Activation of the HAT domain of p300 increased H3K18/27 acetylation, promoted DRD2 transcription, and worked synergistically with DA to exert anti-tumor effects both in vitro and in vivo. Tanshinone IIA (Tan IIA) upregulated p300 and DRD2, enhancing the therapeutic efficacy of BRC. These findings highlight the role of p300 in regulating DRD2 transcription in DA-resistant prolactinomas. Combining Tan IIA with BRC may offer a promising strategy to overcome DA resistance.

DDDR-02. NOVEL MDM4 INHIBITOR CEP-1347-BASED THERAPY FOR P53 WILD-TYPE MALIGNANT MENINGIOMA

Abstract BACKGROUND Although a significant proportion of meningiomas are clinically aggressive, there is currently no effective chemotherapy for them. An increasing number of studies have been conducted to develop targeted therapies, but none have focused on the p53 pathway as a potential target. In this study, we determined the in vitro and in vivo effects of CEP-1347, a novel small-molecule inhibitor of MDM4 with known safety in humans, on malignant meningioma cells, and also investigated the effects of CEP-1347 when combined with MDM2 inhibition. METHODS The effects of CEP-1347 and MDM4 knockdown on the p53 pathway in human meningioma cell lines with and without a p53 mutation were investigated using RT-PCR and Western blot analyses. The growth inhibitory effects of CEP-1347 were investigated in vitro and in a mouse xenograft model of meningioma. We also investigated the effects of CEP-1347 in combination with genetic or pharmacological inhibition of MDM2 in vitro. [Results] CEP-1347 at clinically relevant concentrations inhibited MDM4 expression, activated the p53 pathway in malignant meningioma cells with wild-type p53, and inhibited growth preferentially in cells expressing wild-type p53, which was mostly mimicked by MDM4 knockdown. CEP-1347 effectively inhibited the growth of malignant meningioma xenografts at a dose substantially lower than the maximum dose that could be safely administered to humans. The small-molecule MDM2 inhibitor RG7112 effectively cooperated with CEP-1347 to reduce MDM4 expression, activate the p53 pathway, and inhibit cell growth. [Conclusion] Our findings suggest that targeting the p53 pathway with CEP-1347 is a novel and viable approach to treating aggressive meningiomas, with even greater efficacy when combined with MDM2 inhibitors.