Mdm2-mediated ubiquitylation: p53 and beyond

Targeting EGFR/PI3K/AKT/mTOR and Bax/Bcl-2/caspase3 pathways with ivermectin mediates its anticancer effects against urethane-induced non-small cell lung cancer in BALB/c mice

Lung cancer's mortality is among the highest compared to other cancers globally. However, a recent study has shown that ivermectin, an antiparasitic drug, may have a promising anticancer effect on lung cancer. The present study aimed to investigate the impact of ivermectin on EGFR.3/PI3K4/AKT5/mTOR6 signaling pathway in NSCLC.7 Mice were divided into four groups; (1) normal; (2) oral ivermectin alone (5 mg/kg) daily; (3) NSCLC was induced by urethane (1.5 g/kg, i.p.) at days one and sixty; (4) NSCLC group treated with ivermectin. The effect of ivermectin on macroscopic, microscopic, and lung index was assessed. The antitumor and antiproliferative effects of ivermectin were investigated by CYFRA 21-1 level and Ki-67, respectively. IHC determined the molecular expression of EGFR8, while phosphorylated PI3K, AKT, and mTOR were quantified by Western blotting assay. ELISA assay of active caspase 3, Bcl-29, and BAX10 was used to assess the apoptotic effect of ivermectin. Finally, VEGF11 lung content was measured. Findings showed that ivermectin improved macro and microscopic pathological changes. Ivermectin induced cytotoxic effect as indicated by CYFRA 21-1 suppression besides enhancing BAX/Bcl-2 ratio and active caspase 3. The immunoexpression of Ki-67 and EGFR declined. Ivermectin remarkably reduced p-PI3K, p-AKT, p-mTOR, and VEGF expressions. Overall, the study proposes ivermectin as a promising drug for lung cancer through its orchestral regulation of EGFR/PI3K/AKT/mTOR/VEGF signaling.

PP2A adapter protein IER5 induces dephosphorylation and degradation of MDM2, thereby stabilizing p53

The tumor suppressor p53 activates transcription of the IER5 gene, which encodes an adapter protein of protein phosphatase PP2A. IER5 binds to both the B55 regulatory subunit of PP2A and PP2A's target proteins, facilitating PP2A/B55-catalyzed dephosphorylation of these proteins. Here, we show that IER5 functions as a positive regulator of p53 by inhibiting its ubiquitination, thereby increasing cellular p53 levels. Mechanistically, this effect of IER5 requires its nuclear localization and binding to both PP2A/B55 and the p53 ubiquitin E3 ligase MDM2. Importantly, IER5 fails to inhibit p53 ubiquitination in cells treated with the MDM2 inhibitor Nutlin-3. The IER5-PP2A/B55 complex dephosphorylates MDM2 at Ser166, leading to MDM2 ubiquitination and a reduction in nuclear MDM2. Altogether, our data provide evidence that IER5-PP2A/B55 regulates the nuclear balance between MDM2 and p53 via MDM2 dephosphorylation.

KT-253, a Novel MDM2 Degrader and p53 Stabilizer, Has Superior Potency and Efficacy than MDM2 Small-Molecule Inhibitors

Murine double minute 2 (MDM2) is an E3 ligase that inhibits the tumor suppressor protein p53. Clinical trials employing small-molecule MDM2/p53 interaction inhibitors have demonstrated limited activity, underscoring an unmet need for a better approach to target MDM2. KT-253 is a highly potent and selective heterobifunctional degrader that overcomes the MDM2 feedback loop seen with small-molecule MDM2/p53 interaction inhibitors and induces apoptosis in a range of hematologic and solid tumor lines. A single intravenous dose of KT-253 triggered rapid apoptosis and sustained tumor regression in p53 wild-type acute myeloid leukemia and acute lymphoblastic leukemia xenograft models. Additionally, a single intravenous dose of KT-253 in combination with standard-of-care venetoclax overcame venetoclax resistance in an acute myeloid leukemia xenograft model. The data herein define the therapeutic potential of KT-253 and support its clinical development in a range of hematologic and solid p53 wild-type malignancies, as a monotherapy and in combination with standard-of-care agents.

Advancing the Metabolic Dysfunction-Associated Steatotic Liver Disease Proteome: A Post-Translational Outlook

Metabolic dysfunction-associated steatotic liver disease (MASLD) is a prevalent liver disorder with limited treatment options. This review explores the role of post-translational modifications (PTMs) in MASLD pathogenesis, highlighting their potential as therapeutic targets. We discuss the impact of PTMs, including their phosphorylation, ubiquitylation, acetylation, and glycosylation, on key proteins involved in MASLD, drawing on studies that use both human subjects and animal models. These modifications influence various cellular processes, such as lipid metabolism, inflammation, and fibrosis, contributing to disease progression. Understanding the intricate PTM network in MASLD offers the potential for developing novel therapeutic strategies that target specific PTMs to modulate protein function and alleviate disease pathology. Further research is needed to fully elucidate the complexity of PTMs in MASLD and translate these findings into effective clinical applications.

Untangling the Role of MYC in Sarcomas and Its Potential as a Promising Therapeutic Target

MYC plays a pivotal role in the biology of various sarcoma subtypes, acting as a key regulator of tumor growth, proliferation, and metabolic reprogramming. This oncogene is frequently dysregulated across different sarcomas, where its expression is closely intertwined with the molecular features unique to each subtype. MYC interacts with critical pathways such as cell cycle regulation, apoptosis, and angiogenesis, amplifying tumor aggressiveness and resistance to standard therapies. Furthermore, MYC influences the tumor microenvironment by modulating cell-extracellular matrix interactions and immune evasion mechanisms, further complicating therapeutic management. Despite its well-established centrality in sarcoma pathogenesis, targeting MYC directly remains challenging due to its "undruggable" protein structure. However, emerging therapeutic strategies, including indirect MYC inhibition via epigenetic modulators, transcriptional machinery disruptors, and metabolic pathway inhibitors, offer new hope for sarcoma treatment. This review underscores the importance of understanding the intricate roles of MYC across sarcoma subtypes to guide the development of effective targeted therapies. Given MYC's central role in tumorigenesis and progression, innovative approaches aiming at MYC inhibition could transform the therapeutic landscape for sarcoma patients, providing a much-needed avenue to overcome therapeutic resistance and improve clinical outcomes.

USP38 functions as an oncoprotein by downregulating the p53 pathway through deubiquitination and stabilization of MDM2

Dysregulation of the MDM2-p53 pathway is a commonly observed phenomenon in cancer, where overexpression or amplification of MDM2 leads to increased degradation of p53. This results in reduced levels of p53, leading to the loss of its tumor-suppressive functions. The study focused on investigating the role of Ubiquitin-specific protease 38 (USP38) in cancer and its interaction with the MDM2-p53 axis. We revealed that USP38 positively correlates with MDM2 and negatively correlates with p53 expression. Mechanistically, USP38 directly binds to MDM2, functioning as a deubiquitinating enzyme (DUB) to stabilize MDM2 and suppress p53 expression. Knockout of USP38 hindered cancer cell proliferation, migration, and invasion, and enhanced apoptosis. Moreover, USP38 deficiency increased sensitivity to chemotherapy drugs and promoted ferroptosis in gastric and breast cancer cell lines. Importantly, these effects were found to be dependent on p53, as the downregulation of p53 reversed the phenotypic changes induced by USP38 knockout. These findings shed light on the oncogenic role of USP38 by modulating the MDM2-p53 axis, providing valuable insights into the molecular mechanisms of USP38 in cancer and potential therapeutic strategies for gastric and breast cancer.

Correlation between p53 immunoexpression and TP53 mutation status in extrapulmonary small cell neuroendocrine carcinomas and its association with patient survival

Extrapulmonary small cell neuroendocrine carcinoma (EP-SCNC) is a rare malignancy with a poor prognosis. Despite its morphological similarity to lung small cell carcinomas, its oncogenesis remains uncertain. One hundred and seventy-one EP-SCNC were enrolled in a multicenter study, and all tissue samples underwent an immunohistochemical p53 analysis. One hundred twenty-five samples were molecularly analyzed using next-generation sequencing (NGS), comprising DNA and RNA analysis. p53 normal/wild type expression was detected in 68 cases (39.8%), whereas aberrant expression was detected in 103 cases (60.2%). Molecular TP53 alteration was detected in 92 out of 125 tumors (73.6%). The TP53 mutation was shown to be prognostic and associated with shorter overall survival (p = 0.041). The multivariate analysis of p53 and TP53 mutational status found that it impacted overall survival relative to distinct sites of tumor locations (p = 0.004 and p = 0.001, respectively). Age did not influenced survival in the multivariate analysis of p53 and TP53 (p = 0.002; p < 0.001 resp.). Among tumors with paired immunohistochemical and molecular results, 108 exhibited concordance between the immunohistochemical and molecular analysis, whereas 17 were discordant. Accordingly, p53 aberrant expression was tightly associated with a TP53 mutation (p < 0.001). In discordant cases, molecular analysis revealed no alteration in three tumors with p53 overexpression. In contrast, in 14 tumors with wild-type p53 expression, TP53 genetic alteration was detected. Possible causes of discordance are discussed in this manuscript. Furthermore, the incidence of aberrant p53 expression / TP53 molecular alteration was noticeably lower in EP-SCNC than in small-cell lung carcinomas. Therefore, in EP-SCNC, other driver mutations should be sought since personalized therapy can improve patient prognosis.

Acral Melanoma: A Review of Its Pathogenesis, Progression, and Management

Acral melanoma is a distinct subtype of cutaneous malignant melanoma that uniquely occurs on ultraviolet (UV)-shielded, glabrous skin of the palms, soles, and nail beds. While acral melanoma only accounts for 2-3% of all melanomas, it represents the most common subtype among darker-skinned, non-Caucasian individuals. Unlike other cutaneous melanomas, acral melanoma does not arise from UV radiation exposure and is accordingly associated with a relatively low tumor mutational burden. Recent advances in genomic, transcriptomic, and epigenomic sequencing have revealed genetic alterations unique to acral melanoma, including novel driver genes, high copy number variations, and complex chromosomal rearrangements. This review synthesizes the current knowledge on the clinical features, epidemiology, and treatment approaches for acral melanoma, with a focus on the genetic pathogenesis that gives rise to its unique tumor landscape. These findings highlight a need to deepen our genetic and molecular understanding to better target this challenging subtype of melanoma.

Investigating the P53-dependent anti-cancer effect of ibutamoren in human cancer cell lines

The MDM2-p53 pathway plays a pivotal role in regulating cell cycle and apoptosis, with its dysfunction contributing to approximately 50% of human malignancies. MDM2, an E3 ubiquitin ligase, targets the tumour suppressor p53 for degradation, thereby promoting uncontrolled cell growth in cancers. Inhibiting the MDM2-p53 interaction represents a promising therapeutic strategy for reactivating p53's tumour-suppressive functions. This study explored the potential of ibutamoren (IBU) as a novel inhibitor of MDM2. In silico analyses utilizing molecular modelling revealed that IBU has a low IC50 for MDM2 inhibition and favourably binds to the p53-binding pocket of MDM2. In vitro experiments demonstrated that IBU treatment reduced the viability of immortalized cancer cell lines with a functional MDM2-p53 pathway but not in cell lines where this pathway harboured damaging mutations. This trend was further supported by RT-qPCR analysis, which showed differential expression of two p53 target genes upon IBU treatment in cell lines with wild MDM2-p53 pathways but not in those harbouring damaging mutations. These findings provide preliminary evidence supporting IBU's anticancer activity, plausibly through the MDM2-p53 pathway, and suggest that further studies are warranted to explore its mechanism of action and potential development as a lead compound in oncology research.

Unlocking the potential of LHPP: Inhibiting glioma growth and cell cycle via the MDM2/p53 pathway

The recurrence of glioma after treatment has remained an intractable problem for many years. Recently, numerous studies have explored the pivotal role of the mouse double minute 2 (MDM2)/p53 pathway in cancer treatment. Lysine phosphate phosphohistidine inorganic pyrophosphate phosphatase (LHPP), a newly discovered tumor suppressor, has been confirmed in numerous studies on tumors, but its role in glioma remains poorly understood. Expression matrices in The Cancer Genome Atlas (TCGA) and Chinese Glioma Genome Atlas (CGGA) databases were analyzed using gene set enrichment analysis (GSEA), revealing significant alterations in the p53 pathway among glioma patients with high LHPP expression. The overexpression of LHPP in glioma cells resulted in a reduction in cell proliferation, migration, and invasive ability, as well as an increase in apoptosis and alterations to the cell cycle. The present study has identified a novel inhibitory mechanism of LHPP against glioma, both in vivo and in vitro. The results demonstrate that LHPP exerts anti-glioma effects via the MDM2/p53 pathway. These findings may offer a new perspective for the treatment of glioma in the clinic.

Novel Therapeutics in Soft Tissue Sarcoma

There has been noteworthy progress in molecular characterisation and therapeutics in soft tissue sarcomas. Novel agents have gained regulatory approval by the FDA. Examples are the tyrosine kinase inhibitors avapritinib and ripretinib in gastrointestinal stromal tumours (GIST), the immune check point inhibitor atezolizumab in alveolar soft part tissue sarcoma, the γ-secretase inhibitor nirogacestat in desmoid tumours, the NTRK inhibitors larotrectinib and entrectinib in tumours with NTRK fusions, the mTOR inhibitor nab-sirolimus in PEComa, and the EZH-2 inhibitor tazemetostat in epithelioid sarcoma. The FDA has also recently granted accelerated approval for autologous T-cell therapy with afami-cel in patients with HLA-A*02 and MAGE-A4-expressing synovial sarcoma. There are other promising treatments that are still investigational, such as MDM2 and CDK4/6 inhibitors in well-/dedifferentiated liposarcoma, immune checkpoint inhibitors in the head and neck angiosarcoma and a subset of patients with undifferentiated pleomorphic sarcoma, and PARP inhibitors in leiomyosarcoma. The challenges in drug development in soft tissue sarcoma are due to the rarity and the molecular heterogeneity of the disease and the fact that many subtypes are associated with complex karyotypes or non-targetable molecular alterations. We believe that progress maybe possible with a better understanding of the complex biology, the development of novel compounds for difficult targets such as proteolysis targeting chimeras (Protacs), the utilisation of modern clinical trial designs, and enhanced collaboration of academia with industry to develop treatments with a strong biologic rationale.

Nucleo-cytoplasmic environment modulates spatiotemporal p53 phase separation

Liquid-liquid phase separation of various transcription factors into biomolecular condensates plays an essential role in gene regulation. Here, using cellular models and in vitro studies, we show the spatiotemporal formation and material properties of p53 condensates that might dictate its function. In particular, p53 forms liquid-like condensates in the nucleus of cells, which can bind to DNA and perform transcriptional activity. However, cancer-associated mutations promote misfolding and partially rigidify the p53 condensates with impaired DNA binding ability. Irrespective of wild-type and mutant forms, the partitioning of p53 into cytoplasm leads to the condensate formation, which subsequently undergoes rapid solidification. In vitro studies show that abundant nuclear components such as RNA and nonspecific DNA promote multicomponent phase separation of the p53 core domain and maintain their liquid-like property, whereas specific DNA promotes its dissolution into tetrameric functional p53. This work provides mechanistic insights into how the life cycle and DNA binding properties of p53 might be regulated by phase separation.

Targeting MDM2-mediated suppression of p53 with idasanutlin: a promising therapeutic approach for acute lymphoblastic leukemia

Despite available treatments for acute lymphoblastic leukemia (ALL), the disease's high clinical variability necessitates new therapeutic strategies, particularly for patients with high-risk features. The tumor suppressor protein p53, encoded by the TP53 gene and known as the guardian of the genome, plays a crucial role in preventing tumor development. Over 90% of ALL cases initially harbor wild-type TP53. Reactivation of p53, which is encoded from the wild type TP53 but lost its function for several reasons, is an attractive therapeutic approach in cancer treatment. p53 can be activated in a non-genotoxic manner by targeting its primary repressor, the MDM2 protein. Clinical trials involving MDM2 inhibitors are currently being conducted in a growing body of investigation, reflecting of the interest in incorporating these treatments into cancer treatment strategies. Early-phase clinical trials have demonstrated the promise of idasanutlin (RG7388), one of the developed compounds. It is a second-generation MDM2-p53 binding antagonist with enhanced potency, selectivity, and bioavailability. The aim of this study is to evaluate the efficacy of RG7388 as a therapeutic strategy for ALL and to investigate its potential impact on improving treatment outcomes for high-risk patients. RG7388 potently decreased the viability in five out of six ALL cell lines with diverse TP53 mutation profiles, whereas only one cell line exhibited high resistance. RG7388 induced a pro-apoptotic gene expression signature with upregulation of p53-target genes involved in the intrinsic and extrinsic pathways of apoptosis. Consequently, RG7388 led to a concentration-dependent increase in caspase-3/7 activity and cleaved poly (ADP-ribose) polymerase. In this research, RG7388 was investigated with pre-clinical methods in ALL cells as a novel treatment strategy. This study suggests further functional research and in-vivo evaluation, and it highlights the prospect of treating p53-functional ALL with MDM2 inhibitors.

Genetic alteration analysis of non-pediatric diffuse midline glioma, H3 K27-altered

Diffuse midline gliomas with H3 K27-alteration (DMGH3) are lethal and inoperable brain tumors. Although DMGH3s mainly occur in pediatric patients, they have also occurred in adult patients. This study aimed to analyze the clinicopathological significance of targetable genetic alterations in non-pediatric DMGH3. Next-generation sequencing (NGS) was conducted on 18 non-pediatric DMGH3 patients to analyze additional genetic alterations. The median age at diagnosis was 35 years, and the mean follow-up duration was 762 days. Fourteen cases involved the thalamus-hypothalamus (77.8%). Histologic high-grade features (WHO histologic grade ≥ 3) were observed in 11 (61.1%) patients. H3F3A (H3 K27 M) alterations were identified in all 18 patients using immunohistochemistry and NGS. TP53 mutations were found in 11 patients (61.1%), FGFR1 or PIK3CA in 3 (16.7%), ATRX in 6 (33.3%), NF1 in 4 (22.2%), and KRAS or ATM in 1 (5.6%). TP53 mutations were significantly correlated with high-grade histological features and worse overall survival (OS) (P < 0.05). Despite non-pediatric DMGH3 cases exhibiting superior OS compared to pediatric DMGH3 cases, TP53 mutations were associated with poorer OS outcomes. Notably, FGFR1 and PIK3CA mutations, which have been identified as potential targetable genes, were detected. In conclusion, non-pediatric DMGH3s showed predominant tumor localization within the thalamus and improved prognosis compared to those in pediatric cases, with TP53 alterations correlating with high-grade histology and shorter survival. Genetic profiling, particularly identifying targetable mutations like FGFR1 and PIK3CA, could inform personalized treatment strategies and improve patient outcomes.

Novel pharmacotherapies for the treatment of liposarcoma: a comprehensive update

INTRODUCTION

Liposarcomas are malignancies of adipocytic lineage and represent one of the most common types of soft tissue sarcomas. They encompass multiple histologies, each with unique molecular profiles. Treatment for localized disease includes resection, potentially with perioperative radiation or systemic therapy. Treatment for unresectable or metastatic disease revolves around palliative systemic therapy, for which improved therapies are urgently needed.

AREAS COVERED

We reviewed the literature on novel therapies in clinical development for liposarcomas within the past 5 years and discuss their potential impact on future treatment strategies.

EXPERT OPINION

Understanding of the molecular characteristics of liposarcoma subtypes has led to testing of several targeted therapies, including inhibitors of amplified gene products (CDK4 and MDM2) and upregulated proteins (XPO1). Immuno-oncology has played an increasing role in the treatment of liposarcomas, with checkpoint inhibition showing promise in dedifferentiated liposarcomas, and immune therapies targeting cancer testis antigens NY-ESO-1 and MAGE family proteins poised to become an option for myxoid/round cell liposarcomas. The search for novel agents from existing classes (tyrosine kinase inhibitors) with efficacy in liposarcoma also continues. Combination therapies as well as biomarker identification for patient selection of therapies warrant ongoing exploration.

MDM2 drives resistance to Osimertinib by contextually disrupting FBW7-mediated destruction of MCL-1 protein in EGFR mutant NSCLC

BACKGROUND

Overcoming resistance to Osimertinib in epidermal growth factor receptor (EGFR) mutant non-small cell lung cancer (NSCLC) is clinically challenging because the underlying mechanisms are not fully understood. The murine double minute 2 (MDM2) has been extensively described as a tumor promotor in various malignancies, mainly through a negative regulatory machinery on the p53 tumor suppressor. However, the significance of MDM2 on the sensitivity to Osimertinib has not been described.

METHODS

Osimertinib resistant cells were generated by standard dose escalation strategy and individual resistant clones were isolated for MDM2 testing. The MDM2 and its mutant constructs (ΔPBD, ΔRING, C464A) were introduced into PC-9, HCC827 and H1975 cells and evaluated for the sensitivity to Osimertinib by MTT assay, colony formation, EdU assay and TUNEL assay. MDM2 expression in resistant cells was manipulated by pharmacological and molecular approaches, respectively. Proteins that were implicated in PI3K/Akt, MAPK/Erk and apoptosis signaling were measured by Western blot analysis. Candidate proteins that interacted with MDM2 were captured by immunoprecipitation and probed with indicated antibodies.

RESULTS

In comparison with parental PC-9 cells, the PC-9 OR resistant cells expressed high level of MDM2. Ectopic expression of MDM2 in PC-9, HCC827 and H1975 sensitive cells generated an Osimertinib resistant phenotype, regardless of p53 status. MDM2 promoted resistance to Osimertinib through a PI3K/Akt and MAPK/Erk-independent machinery, in contrast, MDM2 selectively stabilized MCL-1 protein to arrest Osimertinib-induced cancer cell apoptosis. Mechanistically, MDM2 acted as a E3 ligase to ubiquitinate FBW7, a well-established E3 ligase for MCL-1, at Lys412 residue, which resulted in FBW7 destruction and MCL-1 stabilization. Targeting MDM2 to augment MCL-1 protein breakdown overcame resistance to Osimertinib in vitro and in vivo. Finally, the clinical relevance of MDM2-FBW7-MCL-1 regulatory axis was validated in mouse xenograft tumor model and in NSCLC specimen.

CONCLUSION

Overexpression of MDM2 is a novel resistant mechanism to Osimertinib in EGFR mutant NSCLC. MDM2 utilizes its E3 ligase activity to provoke FBW7 destruction and sequentially leads to MCL-1 stabilization. Cancer cells with aberrant MDM2 state are refractory to apoptosis induction and elicit a resistant phenotype to Osimertinib. Therefore, targeting MDM2 would be a feasible approach to overcome resistance to Osimertinib in EGFR mutant NSCLC.

Long-term breast cancer response to CDK4/6 inhibition defined by TP53-mediated geroconversion

Inhibition of CDK4/6 kinases has led to improved outcomes in breast cancer. Nevertheless, only a minority of patients experience long-term disease control. Using a large, clinically annotated cohort of patients with metastatic hormone receptor-positive (HR+) breast cancer, we identify TP53 loss (27.6%) and MDM2 amplification (6.4%) to be associated with lack of long-term disease control. Human breast cancer models reveal that p53 loss does not alter CDK4/6 activity or G1 blockade but instead promotes drug-insensitive p130 phosphorylation by CDK2. The persistence of phospho-p130 prevents DREAM complex assembly, enabling cell-cycle re-entry and tumor progression. Inhibitors of CDK2 can overcome p53 loss, leading to geroconversion and manifestation of senescence phenotypes. Complete inhibition of both CDK4/6 and CDK2 kinases appears to be necessary to facilitate long-term response across genomically diverse HR+ breast cancers.

Modulation of ATM enhances DNA repair in G2/M phase of cell cycle and averts senescence in Fuchs endothelial corneal dystrophy

Fuchs Endothelial Corneal Dystrophy (FECD) is an aging disorder characterized by expedited loss of corneal endothelial cells (CEnCs) and heightened DNA damage compared to normal CEnCs. We previously established that ultraviolet-A (UVA) light causes DNA damage and leads to FECD phenotype in a non-genetic mouse model. Here, we demonstrate that acute treatment with chemical stressor, menadione, or physiological stressors, UVA, and catechol estrogen (4-OHE2), results in an early and increased activation of ATM-mediated DNA damage response in FECD compared to normal CEnCs. Acute stress with UVA and 4OHE2 causes (i) greater cell-cycle arrest and DNA repair in G2/M phase, and (ii) greater cytoprotective senescence in NQO1-/- compared to NQO1+/+ cells, which was reversed upon ATM inhibition. Chronic stress with UVA and 4OHE2 results in ATM-driven cell-cycle arrest in G0/G1 phase, reduced DNA repair, and cytotoxic senescence, due to sustained damage. Likewise, UVA-induced cell-cycle reentry, gamma-H2AX foci, and senescence-associated heterochromatin were reduced in Atm-null mice. Remarkably, inhibiting ATM activation with KU-55933 restored DNA repair in G2/M phase and attenuated senescence in chronic cellular model of FECD lacking NQO1. This study provides insights into understanding the pivotal role of ATM in regulating cell-cycle, DNA repair, and senescence, in oxidative-stress disorders like FECD.

The Impact of Genetic Mutations on the Efficacy of Immunotherapies in Lung Cancer

Lung cancer is the leading cause of cancer-related mortality worldwide, primarily driven by genetic mutations. The most common genetic alterations implicated in lung cancer include mutations in TP53, KRAS, KEAP1, NF1, EGFR, NRF2, ATM, ALK, Rb1, BRAF, MET, and ERBB2. Targeted therapies have been developed to inhibit cancer growth by focusing on these specific genetic mutations. However, either the mutations are undruggable or the efficacy of these therapies is often compromised over time due to the emergence of drug resistance, which can occur through additional mutations in the targeted protein or alternative growth signaling pathways. In recent years, immunotherapy has emerged as a promising approach to enhance the effectiveness of cancer treatment by leveraging the body's immune system. Notable advancements include immune checkpoint inhibitors, monoclonal antibodies targeting cell surface receptors, antibody-drug conjugates, and bispecific antibodies. This review provides an overview of the mechanisms of FDA-approved immunotherapeutic drugs, offering an updated perspective on the current state and future developments in lung cancer therapy. More importantly, the factors that positively and negatively impact the immunotherapy's efficacy will also be discussed.

Perturbations in eIF3 subunit stoichiometry alter expression of ribosomal proteins and key components of the MAPK signaling pathways

Protein synthesis plays a major role in homeostasis and when dysregulated leads to various pathologies including cancer. To this end, imbalanced expression of eukaryotic translation initiation factors (eIFs) is not only a consequence but also a driver of neoplastic growth. eIF3 is the largest, multi-subunit translation initiation complex with a modular assembly, where aberrant expression of one subunit generates only partially functional subcomplexes. To comprehensively study the effects of eIF3 remodeling, we contrasted the impact of eIF3d, eIF3e or eIF3h depletion on the translatome of HeLa cells using Ribo-seq. Depletion of eIF3d or eIF3e, but not eIF3h reduced the levels of multiple components of the MAPK signaling pathways. Surprisingly, however, depletion of all three eIF3 subunits increased MAPK/ERK pathway activity. Depletion of eIF3e and partially eIF3d also increased translation of TOP mRNAs that encode mainly ribosomal proteins and other components of the translational machinery. Moreover, alterations in eIF3 subunit stoichiometry were often associated with changes in translation of mRNAs containing short uORFs, as in the case of the proto-oncogene MDM2 and the transcription factor ATF4. Collectively, perturbations in eIF3 subunit stoichiometry exert specific effect on the translatome comprising signaling and stress-related transcripts with complex 5' UTRs that are implicated in homeostatic adaptation to stress and cancer.

A metabolic crosstalk between liposarcoma and muscle sustains tumor growth

Dedifferentiated and Well-differentiated liposarcoma are characterized by a systematic amplification of the Murine Double Minute 2 (MDM2) oncogene. We demonstrate that p53-independent metabolic functions of chromatin-bound MDM2 are exacerbated in liposarcoma and mediate an addiction to serine metabolism to sustain tumor growth. However, the origin of exogenous serine remains unclear. Here, we show that elevated serine levels in mice harboring liposarcoma-patient derived xenograft, released by distant muscle is essential for liposarcoma cell survival. Repressing interleukine-6 expression, or treating liposarcoma cells with Food and Drugs Administration (FDA) approved anti-interleukine-6 monoclonal antibody, decreases de novo serine synthesis in muscle, impairs proliferation, and increases cell death in vitro and in vivo. This work reveals a metabolic crosstalk between muscle and liposarcoma tumor and identifies anti-interleukine-6 as a plausible treatment for liposarcoma patients.

The Role of Tumor Suppressor p53 Protein in HIV-Host Cell Interactions

The virus-host relationship is indispensable for executing successful viral infection. The pathogenesis of HIV is determined by an intricate interaction between the host and the virus for the regulation of HIV infection, thereby influencing various aspects, including the regulation of signaling pathways. High mutation rates and population heterogeneity characterize HIV with consequences for viral pathogenesis and the potential to escape the immune system and anti-viral inhibitors used in therapy. The origin of the high mutation rates exhibited by HIV may be attributed to a limited template-copied fidelity that likely operates in the cytoplasm. HIV-1 infection induces upregulation and activation of tumor suppressor p53 protein in the early stages of HIV-1 infection. p53 plays a multifaceted role in the context of HIV infection, thereby affecting viral replication. p53 is involved in maintaining genetic integrity, actively participating in various DNA repair processes through its various biochemical activities and via its ability to interact with components of the repair machinery. This report focuses on the impact of the p53 protein on the HIV-1 reverse transcription process while incorporating various incorrect and non-canonical nucleotides. The presence of functional host-coded p53 protein with proofreading-repair activities in the cytoplasm may lead to various biological outcomes.

Implications of p53 in mitochondrial dysfunction and Parkinson's disease

Purpose: To study the underlying molecular mechanisms of p53 in the mitochondrial dysfunction and the pathogenesis of Parkinson's disease (PD), and provide a potential therapeutic target for PD treatment.

Methods: We review the contributions of p53 to mitochondrial changes leading to apoptosis and the subsequent degeneration of dopaminergic neurons in PD.

Results: P53 is a multifunctional protein implicated in the regulation of diverse cellular processes via transcription-dependent and transcription-independent mechanisms. Mitochondria are vital subcellular organelles for that maintain cellular function, and mitochondrial defect and impairment are primary causes of dopaminergic neuron degeneration in PD. Increasing evidence has revealed that mitochondrial dysfunction-associated dopaminergic neuron degeneration is tightly regulated by p53 in PD pathogenesis. Neurodegenerative stress triggers p53 activation, which induces mitochondrial changes, including transmembrane permeability, reactive oxygen species production, Ca2+ overload, electron transport chain defects and other dynamic alterations, and these changes contribute to neurodegeneration and are linked closely with PD occurrence and development. P53 inhibition has been shown to attenuate mitochondrial dysfunction and protect dopaminergic neurons from degeneration under conditions of neurodegenerative stress.

Conclusions: p53 appears to be a potential target for neuroprotective therapy of PD.

P53: A key player in diverse cellular processes including nuclear stress and ribosome biogenesis, highlighting potential therapeutic compounds

The tumor suppressor proteins are key transcription factors involved in the regulation of various cellular processes, such as apoptosis, DNA repair, cell cycle, senescence, and metabolism. The tumor suppressor protein p53 responds to different type of stress signaling, such as hypoxia, DNA damage, nutrient deprivation, oncogene activation, by activating or repressing the expression of different genes that target processes mentioned earlier. p53 has the ability to modulate the activity of many other proteins and signaling pathway through protein-protein interaction, post-translational modifications, or non-coding RNAs. In many cancers the p53 is found to be mutated or inactivated, resulting in the loss of its tumor suppressor function and acquisition of new oncogenic properties. The tumor suppressor protein p53 also plays a role in the development of other metabolic disorders such as diabetes, obesity, and fatty liver disease. In this review, we will summarize the current data and knowledge on the molecular mechanisms and the functions of p53 in different pathways and processes at the cellular level and discuss the its implications for human health and disease.

Discovery of Novel p53-MDM2 Inhibitor (RG7388)-Conjugated PlatinumIV Complexes as Potent Antitumor Agents

While a number of p53-MDM2 inhibitors have progressed into clinical trials for the treatment of cancer, their progression has been hampered by a variety of problems, including acquired drug resistance, dose-dependent toxicity, and limited clinical efficiency. To make more progress, we integrated the advantages of MDM2 inhibitors and platinum drugs to construct novel PtIV-RG7388 (a selective MDM2 inhibitor) complexes. Most complexes, especially 5a and 5b, displayed greatly improved antiproliferative activity against both wild-type and mutated p53 cancer cells. Remarkably, 5a exhibited potent in vivo tumor growth inhibition in the A549 xenograft model (66.5%) without apparent toxicity. It arrested the cell cycle at both the S phase and the G2/M phase and efficiently induced apoptosis via the synergistic effects of RG7388 and cisplatin. Altogether, PtIV-RG7388 complex 5a exhibited excellent in vitro and in vivo antitumor activities, highlighting the therapeutic potential of PtIV-RG7388 complexes as antitumor agents.

P53 Gene as a Promising Biomarker and Potential Target for the Early Diagnosis of Reproductive Cancers

One of the crucial aspects of cancer research is diagnosis with specificity and accuracy. Early cancer detection mostly helps make appropriate decisions regarding treatment and metastasis. The well-studied transcription factor tumor suppressor protein p53 is essential for maintaining genetic integrity. p53 is a key tumor suppressor that recognizes the carcinogenic biological pathways and eradicates them by apoptosis. A wide range of carcinomas, especially gynecological such as ovarian, cervical, and endometrial cancers, frequently undergo TP53 gene mutations. This study evaluates the potential of the p53 gene as a biological marker for the diagnosis of reproductive system neoplasms. Immunohistochemistry of p53 is rapid, easy to accomplish, cost-effective, and preferred by pathologists as a surrogate for the analysis of TP53 mutation. Thus, this review lays a groundwork for future efforts to develop techniques using p53 for the early diagnosis of cancer.

Bioinformatics analysis and validation of CSRNP1 as a key prognostic gene in non-small cell lung cancer

Cysteine and serine-rich nuclear protein 1 (CSRNP1) has shown prognostic significance in various cancers, but its role in non-small cell lung cancer (NSCLC) remains elusive. We investigated CSRNP1 expression in NSCLC cases using bioinformatics tools from the GEO public repository and validated our findings through RT-qPCR in tumor and adjacent normal tissues. KEGG and GO enrichment analyses were employed to unveil the significant deregulation in signaling pathways. Additionally, clinical significance of CSRNP1 in NSCLC was determined through receiver operating curve (ROC) analysis, and its impact on survival was assessed using Kaplan-Meier analysis. To explore the functional impact of CSRNP1, we silenced its expression in NSCLC cells and assessed the effects on cell viability, migration, and invasion using MTT, Transwell, and wound-healing assays, respectively. Additionally, we investigated the influence of CSRNP1 silencing on the phosphorylation patterns of critical signaling proteins such as p53, p-Akt, and p-MDM2. Our results demonstrated significantly lower CSRNP1 expression in NSCLC tumor tissues (P < 0.01). ROC analysis indicated that NSCLC patients with high CSRNP1 expression exhibited extended overall survival and disease-free survival. Furthermore, CSRNP1 silencing promoted NSCLC cells viability, migration, and invasion (P < 0.05). Mechanistically, CSRNP1 silencing led to increased phosphorylation of AKT and MDM2, along with a concurrent reduction in p53 protein expression, suggesting its impact on NSCLC through deregulated cell cycle processes. In conclusion, our study underscores the significance of CSRNP1 in NSCLC pathogenesis, offering insights for targeted therapeutic interventions of NSCLC.

The p53-mediated cell cycle regulation is a potential mechanism for emodin-suppressing osteosarcoma cells

Background

As the most common primary bone cancer, the therapy of osteosarcoma requires further study. An anthraquinone derivative, emodin, has been found to have anticancer potential. We proposed that emodin suppresses osteosarcoma by cell cycle regulation mediated by p53.

Methods

This study determined the effect of emodin on viability and apoptosis of 6 osteosarcoma cell lines (p53 null cells MG63, G292, and A-673; p53 mutated cells HOS and SK-PN-DW; p53 expressing cells U2OS and 2 osteoblast cell lines), then knockdown p53 in U2OS, and observed the impacts of emodin on p53, p21, cyclin proteins, and cell cycle.

Results

High dose emodin (40-160 μM) induced cell death and apoptosis of all the cell lines; medium dose emodin (20 μM) preferentially inhibited osteosarcoma cells; low dose emodin (1-10 μM) preferentially inhibited p53 expressing osteosarcoma cells. Emodin dose-dependently inhibited p53 and p21 in U2OS. Emodin at 10 μM decreased the expression of Cdk2, E2F, and Cdk1; and increased RB but had no effects on cyclin E and cyclin B. The knockdown of p53 almost eliminated all the impacts of 10 μM emodin on cell cycle proteins.

Conclusions

Emodin suppresses U2OS by p53-mediated cell cycle regulation.

Identification of Novel, Selective Ataxia-Telangiectasia Mutated Kinase Inhibitors with the Ability to Penetrate the Blood-Brain Barrier: The Discovery of AZD1390

The inhibition of ataxia-telangiectasia mutated (ATM) has been shown to chemo- and radio-sensitize human glioma cells in vitro and therefore might provide an exciting new paradigm in the treatment of glioblastoma multiforme (GBM). The effective treatment of GBM will likely require a compound with the potential to efficiently cross the blood-brain barrier (BBB). Starting from clinical candidate AZD0156, 4, we investigated the imidazoquinolin-2-one scaffold with the goal of improving likely CNS exposure in humans. Strategies aimed at reducing hydrogen bonding, basicity, and flexibility of the molecule were explored alongside modulating lipophilicity. These studies identified compound 24 (AZD1390) as an exceptionally potent and selective inhibitor of ATM with a good preclinical pharmacokinetic profile. 24 showed an absence of human transporter efflux in MDCKII-MDR1-BCRP studies (efflux ratio <2), significant BBB penetrance in nonhuman primate PET studies (Kp,uu 0.33) and was deemed suitable for development as a clinical candidate to explore the radiosensitizing effects of ATM in intracranial malignancies.

The effect of p53 on the activity of NRF2 and NDRG2 genes through apoptotic pathway in IDH-wildtype glioblastoma

BACKGROUND

Tumor suppressor (p53) acts to integrate multiple stress signals into diverse antiproliferative responses. Its potential to transactivate or downregulate genes through apoptotic pathway in IDH-wildtype glioblastoma has never been explored.

METHODS

A group of twenty patients diagnosed with IDH-wildtype glioblastoma, were tested for p53 expression and NDRG2/NRF2 genes activity through protein and gene profiling assays. The connotation between these elements has been explored.

RESULTS

The mean patients' age was 64-years. All tumors were IDH-wildtype. p53 was expressed in 12 tumors and absent in 8 tumors. The activity of NDRG2 gene was downregulated in all cases. The activity of NRF2 gene was upregulated in 17 tumors and downregulated in 3 tumors. There was a significant statistical difference in PFS among tumors exhibiting different levels of p53 expression and NDRG2 gene activity [p-value= 0.025], in which 12 tumors with downregulated NDRG2 expression and positive p53 expression had earlier tumor recurrence. This statistical difference in PFS was insignificant when we compared p53 expression with NRF2 gene activity [p-value= 0.079].

CONCLUSIONS

During cell cycle arrest at G2 phase, p53 expression in IDH-wildtype glioblastoma in elderly individuals, coupled with the downregulation of NDRG2 gene activity, led to an aberrant increase in tumor cell proliferation and accelerated tumor recurrence. However, the influence of p53 on NRF2 gene activity was found to be insignificant.

A CANCER PERSISTENT DNA REPAIR CIRCUIT DRIVEN BY MDM2, MDM4 (MDMX), AND MUTANT P53 FOR RECRUITMENT OF MDC1 AND 53BP1 TO CHROMATIN

The influence of the metastasis promoting proteins mutant p53 (mtp53) and MDM2 on Cancer Persistent Repair (CPR) to promote cancer cell survival is understudied. Interactions between the DNA repair choice protein 53BP1 and wild type tumor suppressor protein p53 (wtp53) regulates cell cycle control. Cancer cells often express elevated levels of transcriptionally inactive missense mutant p53 (mtp53) that interacts with MDM2 and MDM4/MDMX (herein called MDMX). The ability of mtp53 to maintain a 53BP1 interaction while in the context of interactions with MDM2 and MDMX has not been described. We asked if MDM2 regulates chromatin-based phosphorylation events in the context of mtp53 by comparing the chromatin of T47D breast cancer cells with and without MDM2 in a phospho-peptide stable isotope labeling in cell culture (SILAC) screen. We found reduced phospho-53BP1 chromatin association, which we confirmed by chromatin fractionation and immunofluorescence in multiple breast cancer cell lines. We used the Proximity Ligation Assay (PLA) in breast cancer cell lines and detected 53BP1 in close proximity to mtp53, MDM2, and the DNA repair protein MDC1. Through disruption of the mtp53-MDM2 interaction, by either Nutlin 3a or a mtp53 R273H C-terminal deletion, we uncovered that mtp53 was required for MDM2-53BP1 interaction foci. Our data suggests that mtp53 works with MDM2 and 53BP1 to promote CPR and cell survival.

The mechanistic role of NAT10 in cancer: Unraveling the enigmatic web of oncogenic signaling

N-acetyltransferase 10 (NAT10), a versatile enzyme, has gained considerable attention as a significant player in the complex realm of cancer biology. Its enigmatic role in tumorigenesis extends across a wide array of cellular processes, impacting cell growth, differentiation, survival, and genomic stability. Within the intricate network of oncogenic signaling, NAT10 emerges as a crucial agent in multiple cancer types, such as breast, lung, colorectal, and leukemia. This compelling research addresses the intricate complexity of the mechanistic role of NAT10 in cancer development. By elucidating its active participation in essential physiological processes, we investigate the regulatory role of NAT10 in cell cycle checkpoints, coordination of chromatin remodeling, and detailed modulation of the delicate balance between apoptosis and cell survival. Perturbations in NAT10 expression and function have been linked to oncogenesis, metastasis, and drug resistance in a variety of cancer types. Furthermore, the bewildering interactions between NAT10 and key oncogenic factors, such as p53 and c-Myc, are deciphered, providing profound insights into the molecular underpinnings of cancer pathogenesis. Equally intriguing, the paradoxical role of NAT10 as a potential tumor suppressor or oncogene is influenced by context-dependent factors and the cellular microenvironment. This study explores the fascinating interplay of genetic changes, epigenetic changes, and post-translational modifications that shape the dual character of NAT10, revealing the delicate balance between cancer initiation and suppression. Taken together, this overview delves deeply into the enigmatic role of NAT10 in cancer, elucidating its multifaceted roles and its complex interplay with oncogenic networks.

Grass carp (Ctenopharyngodon idella) deacetylase SIRT1 targets p53 to suppress apoptosis in a KAT8 dependent or independent manner

Sirtuin1 (SIRT1) is known as a deacetylase to control various physiological processes. In mammals, SIRT1 inhibits apoptotic process, but the detailed mechanism is not very clear. Here, our study revealed that grass carp (Ctenopharyngodon idella) SIRT1 (CiSIRT1, MN125614.1) inhibits apoptosis through targeting p53 in a KAT8-dependent or a KAT8-independent manner. In CIK cells, CiSIRT1 over-expression results in significant decrease of some apoptotic gene expressions, including Bax/Bcl2, caspase3 and caspase9, whereas CiKAT8 or Cip53 facilitates the induction of apoptosis. Because CiSIRT1 separately interacted with CiKAT8 and Cip53, we speculated that CiSIRT1 blocked apoptosis may be by virtue of KAT8-p53 axis or directly by p53. In a KAT8-dependent manner, CiSIRT1 interacted with CiKAT8, then reduced the acetylation of CiKAT8 and subsequently promoted its degradation. Then, CiKAT8 acetylated p53 and induced p53-mediated apoptosis. MYST domain of CiKAT8 was critical in this pathway. In a KAT8-independent manner, CiSIRT1 also inhibited p53-induced apoptosis by directly deacetylating p53 and promoting the degradation of p53. Generally, these findings uncovered two pathways in which CiSIRT1 decreases the acetylation of p53 via a KAT8-dependent or a KAT8-independent manner.

Inhibition of human cervical cancer development through p53-dependent pathways induced by the specified triple helical β-glucan

This study demonstrates that the purified β-glucan (LNT) with a triple helix and relatively narrow molecular weight distribution, extracted and purified from artificially cultured Lentinus edodes, showed a significant cervical cancer inhibition with little cytotoxicity against normal cells in vitro and in vivo. From the in vitro data, the potential mechanism of anti-cervical cancer was preliminarily revealed as follows: LNT was firstly recognized by the human cervical cancer cell line of Hela and induced cell proliferation inhibition through p21 and apoptosis via a mitochondrion-dependent pathway by targeting the tumor suppressor of p53, indicated by an increase in reactive oxygen species (ROS) generation and a loss of mitochondrial membrane potential (Δψm), in a significant dosage-dependent manner. Meanwhile, LNT repressed tumor growth with an inhibition ratio of 61.2 % and induced tumor cell apoptosis through endogenous MDM2/p53/Bax/mitochondrion signal pathway by up-regulating the expression of p53, Bax, Cyt. c, caspase 9, and caspase 3, as well as down-regulating Bcl-2, MDM2, and PARP1 levels in Hela cells-transplanted BALB/c nude mice. This study provides a scientific basis for the clinical treatment of cervical cancer with LNT as a potential drug candidate characterized by the triple helix and specified molecular weight with a relatively narrow distribution.

Clinicopathological and genetic characteristics of gastric neuroendocrine tumour (NET) G3 and comparisons with neuroendocrine carcinoma and NET G2

AIMS

To characterise the clinicopathological and genetic characteristics of gastric neuroendocrine tumour G3 (gNET G3) and to compare them with those of gastric neuroendocrine carcinoma (gNEC) and gNET G2.

METHODS AND RESULTS

A total of 115 gastric neuroendocrine neoplasms (NENs) were included, of which gNET G3 was different from gNET G1/G2 in terms of tumour location (P = 0.029), number (P = 0.003), size (P = 0.010), the Ki67 index (P < 0.001), lymph node metastasis (P < 0.001) and TNM stage (P = 0.011), and different from gNEC/gastric mixed neuroendocrine-non-neuroendocrine neoplasm (gMiNEN) in terms of tumour size (P = 0.010) and the Ki67 index (P = 0.001). High-resolution copy number (CN) profiling and validation experiments showed CN gains and high expression of DLL3 in gNET G3. Hierarchical clustering analysis based on CN characteristics showed that gNET G3 was separated from gNEC but mixed with gNET G2. In gene set enrichment analysis, eight pathways were significantly enriched in gNEC when comparing gNET G3 and gNEC (P < 0.05), while no pathways were enriched when comparing gNET G3 and gNET G2. Whole-exome sequencing and validation experiments showed nonsense mutation of TP53 in one gNET G3, with wild-type staining for p53. In gNEC, TP53 mutations were detected in four of eight cases, and abnormal expression of p53 was detected in all cases.

CONCLUSION

Gastric NET G3 is a distinct entity with unique genetic characteristics, which are different from those of gNEC than gNET G2. Our results provide insight into some molecular alterations that may contribute to the development and progression of gNET G3 and serve as potential therapeutic targets.

USP13 regulates cell senescence through mediating MDM2 stability

AIMS

Lung aging results in altered lung function, reduced lung remodeling and regenerative capacity, and increased susceptibility to acute and chronic lung diseases. The molecular and physiological underlying mechanisms of lung aging remain unclear. Mounting evidence suggests that deubiquitinating enzymes (DUBs) play a critical role in tissue aging and diseases through regulation of cellular signaling pathways. Here we investigate the role of Ubiquitin-Specific Protease 13 (USP13) in cell senescence and lung aging and its underlying mechanisms.

MAIN METHODS

Protein levels of USP13 and MDM2 in lung tissues from aged and young mice were compared. Gene silencing and overexpression of USP13 in human cell lines were performed. MDM2 levels were examined by Quantitative Real-Time PCR and Western blotting analysis. The cell senescence levels of human cells were checked by the β-galactosidase staining.

KEY FINDINGS

Lung tissues from aged mice showed higher levels of USP13 compared to younger mice. We found a negative correlation between USP13 and MDM2 expression in lung tissues of aged mice. The increased protein levels of MDM2 were detected in lung tissues of USP13 deficient mice. Furthermore, overexpression of USP13 promoted cell senescence. Knockdown of USP13 increased MDM2 levels in lung cells, while overexpression of USP13 reduced it. The degradation of MDM2 caused by USP13 was prevented by the proteasome inhibitor MG132. Furthermore, we showed that USP13 targeted and reduced K63-linked polyubiquitination of MDM2. These results demonstrate that USP13 is involved in the aging signaling pathway in lungs through regulation of MDM2.

C9orf72 poly(PR) mediated neurodegeneration is associated with nucleolar stress

The ALS/FTD-linked intronic hexanucleotide repeat expansion in the C9orf72 gene is aberrantly translated in the sense and antisense directions into dipeptide repeat proteins, among which poly proline-arginine (PR) displays the most aggressive neurotoxicity in-vitro and in-vivo. PR partitions to the nucleus when heterologously expressed in neurons and other cell types. We show that by lessening the nuclear accumulation of PR, we can drastically reduce its neurotoxicity. PR strongly accumulates in the nucleolus, a nuclear structure critical in regulating the cell stress response. We determined that, in neurons, PR caused nucleolar stress and increased levels of the transcription factor p53. Downregulating p53 levels also prevented PR-mediated neurotoxicity both in in-vitro and in-vivo models. We investigated if PR could induce the senescence phenotype in neurons. However, we did not observe any indications of such an effect. Instead, we found evidence for the induction of programmed cell death via caspase-3 activation.

p53 amyloid pathology is correlated with higher cancer grade irrespective of the mutant or wild-type form

p53 (also known as TP53) mutation and amyloid formation are long associated with cancer pathogenesis; however, the direct demonstration of the link between p53 amyloid load and cancer progression is lacking. Using multi-disciplinary techniques and 59 tissues (53 oral and stomach cancer tumor tissue samples from Indian individuals with cancer and six non-cancer oral and stomach tissue samples), we showed that p53 amyloid load and cancer grades are highly correlated. Furthermore, next-generation sequencing (NGS) data suggest that not only mutant p53 (e.g. single-nucleotide variants, deletions, and insertions) but wild-type p53 also formed amyloids either in the nucleus (50%) and/or in the cytoplasm in most cancer tissues. Interestingly, in all these cancer tissues, p53 displays a loss of DNA-binding and transcriptional activities, suggesting that the level of amyloid load correlates with the degree of loss and an increase in cancer grades. The p53 amyloids also sequester higher amounts of the related p63 and p73 (also known as TP63 and TP73, respectively) protein in higher-grade tumor tissues. The data suggest p53 misfolding and/or aggregation, and subsequent amyloid formation, lead to loss of the tumor-suppressive function and the gain of oncogenic function, aggravation of which might determine the cancer grade.

MDM2- an indispensable player in tumorigenesis

Murine double minute 2 (MDM2) is a well-recognized molecule for its oncogenic potential. Since its identification, various cancer-promoting roles of MDM2 such as growth stimulation, sustained angiogenesis, metabolic reprogramming, apoptosis evasion, metastasis, and immunosuppression have been established. Alterations in the expression levels of MDM2 occur in multiple types of cancers resulting in uncontrolled proliferation. The cellular processes are modulated by MDM2 through transcription, post-translational modifications, protein degradation, binding to cofactors, and subcellular localization. In this review, we discuss the precise role of deregulated MDM2 levels in modulating cellular functions to promote cancer growth. Moreover, we also briefly discuss the role of MDM2 in inducing resistance against anti-cancerous therapies thus limiting the benefits of cancerous treatment.

Role of the SLIT-ROBO signaling pathway in renal pathophysiology and various renal diseases

SLIT ligand and its receptor ROBO were initially recognized for their role in axon guidance in central nervous system development. In recent years, as research has advanced, the role of the SLIT-ROBO signaling pathway has gradually expanded from axonal repulsion to cell migration, tumor development, angiogenesis, and bone metabolism. As a secreted protein, SLIT regulates various pathophysiological processes in the kidney, such as proinflammatory responses and fibrosis progression. Many studies have shown that SLIT-ROBO is extensively involved in various aspects of kidney development and maintenance of structure and function. The SLIT-ROBO signaling pathway also plays an important role in different types of kidney disease. This article reviews the advances in the study of the SLIT-ROBO pathway in various renal pathophysiological and kidney disorders and proposes new directions for further research in this field.

The Development of p53-Targeted Therapies for Human Cancers

p53 plays a critical role in tumor suppression and is the most frequently mutated gene in human cancers. Most p53 mutants (mutp53) are missense mutations and are thus expressed in human cancers. In human cancers that retain wtp53, the wtp53 activities are downregulated through multiple mechanisms. For example, the overexpression of the negative regulators of p53, MDM2/MDMX, can also efficiently destabilize and inactivate wtp53. Therefore, both wtp53 and mutp53 have become promising and intensively explored therapeutic targets for cancer treatment. Current efforts include the development of small molecule compounds to disrupt the interaction between wtp53 and MDM2/MDMX in human cancers expressing wtp53 and to restore wtp53-like activity to p53 mutants in human cancers expressing mutp53. In addition, a synthetic lethality approach has been applied to identify signaling pathways affected by p53 dysfunction, which, when targeted, can lead to cell death. While an intensive search for p53-targeted cancer therapy has produced potential candidates with encouraging preclinical efficacy data, it remains challenging to develop such drugs with good efficacy and safety profiles. A more in-depth understanding of the mechanisms of action of these p53-targeting drugs will help to overcome these challenges.

A small HDM2 antagonist peptide and a USP7 inhibitor synergistically inhibit the p53-HDM2-USP7 circuit

HDM2, an E3 ubiquitin ligase, is a crucial regulator of many proliferation-related pathways. It is also one of the primary regulators of p53. USP7, a deubiquitinase, also plays a key role in the regulation of both p53 and HDM2, thus forming a small regulatory network with them. This network has emerged as an important drug target. Development of a synergistic combination targeting both proteins is desirable and important for regulating this module. We have developed a small helically constrained peptide that potently inhibited p53-HDM2 interaction and exerted anti-proliferative effects on p53+/+ cells. A combination of this peptide-when attached to cell entry and nuclear localization tags-and a USP7 inhibitor showed synergistic anti-proliferative effects against cells harboring wild-type alleles of p53. Synergistic inhibition of two important drug targets may lead to novel therapeutic strategies.

DTX3L E3 ligase targets p53 for degradation at poly ADP-ribose polymerase-associated DNA damage sites

P53 is a master transcriptional regulator and effector of the DNA damage response (DDR) that localizes to DNA damage sites, in part, via an interaction with PARP1. However, the mechanisms that regulate p53 abundance and activity at PARP1-decorated DNA damage sites remain undefined. The PARP9 (BAL1) macrodomain-containing protein and its partner DTX3L (BBAP) E3 ligase are rapidly recruited to PARP1-PARylated DNA damage sites. During an initial DDR, we found that DTX3L rapidly colocalized with p53, polyubiquitylated its lysine-rich C-terminal domain, and targeted p53 for proteasomal degradation. DTX3L knockout significantly increased and prolonged p53 retention at PARP-decorated DNA damage sites. These findings reveal a non-redundant, PARP- and PARylation-dependent role for DTX3L in the spatiotemporal regulation of p53 during an initial DDR. Our studies suggest that targeted inhibition of DTX3L may augment the efficacy of certain DNA-damaging agents by increasing p53 abundance and activity.

Tissue specificity and spatio-temporal dynamics of the p53 transcriptional program

Transcription factors regulate hundreds of genes and p53 is no exception. As a stress responsive protein, p53 transactivates an array of downstream targets which define its role in maintaining physiological functions of cells/tissues. Despite decades of studies, our understanding of the p53 in vivo transcriptional program is still incomplete. Here we discuss some of the physiological stressors that activate p53, the pathological and physiological implications of p53 activation and the molecular profiling of the p53 transcriptional program in maintaining tissue homeostasis. We argue that the p53 transcriptional program is spatiotemporally regulated in a tissue-specific manner and define a p53 target signature that faithfully depicts p53 activity. We further emphasize that additional in vivo studies are needed to refine the p53 transactivation profile to harness it for therapeutic purposes.

Inclusion of Nitrofurantoin into the Realm of Cancer Chemotherapy via Biology-Oriented Synthesis and Drug Repurposing

Structural modifications of the antibacterial drug nitrofurantoin were envisioned, employing drug repurposing and biology-oriented drug synthesis, to serve as possible anticancer agents. Eleven compounds showed superior safety in non-cancerous human cells. Their antitumor efficacy was assessed on colorectal, breast, cervical, and liver cancer cells. Three compounds induced oxidative DNA damage in cancer cells with subsequent cellular apoptosis. They also upregulated the expression of Bax while downregulated that of Bcl-2 along with activating caspase 3/7. The DNA damage induced by these compounds, demonstrated by pATM nuclear shuttling, was comparable in both MCF7 and MDA-MB-231 (p53 mutant) cell lines. Mechanistic studies confirmed the dependence of these compounds on p53-mediated pathways as they suppressed the p53-MDM2 interaction. Indeed, exposure of radiosensitive prostatic cancer cells to low non-cytotoxic concentrations of compound 1 enhanced the cytotoxic response to radiation indicating a possible synergistic effect. In vivo antitumor activity was verified in an MCF7-xenograft animal model.

MDM2 for the practicing pathologist: a primer

The mouse double minute 2 (MDM2) gene is located on the long arm of chromosome 12 and is the primary negative regulator of p53. The MDM2 gene encodes an E3 ubiquitin-protein ligase that mediates the ubiquitination of p53, leading to its degradation. MDM2 enhances tumour formation by inactivating the p53 tumour suppressor protein. The MDM2 gene also has many p53-independent functions. Alterations of MDM2 may occur through various mechanisms and contribute to the pathogenesis of many human tumours and some non-neoplastic diseases. Detection of MDM2 amplification is used in the clinical practice setting to help diagnose multiple tumour types, including lipomatous neoplasms, low-grade osteosarcomas and intimal sarcoma, among others. It is generally a marker of adverse prognosis, and MDM2-targeted therapies are currently in clinical trials. This article provides a concise overview of the MDM2 gene and discusses practical diagnostic applications pertaining to human tumour biology.

Provocative non-canonical roles of p53 and AKT signaling: A role for Thymosin β4 in medulloblastoma

The PI3K/AKT and p53 pathways are key regulators of cancer cell survival and death, respectively. Contrary to their generally accepted roles, several lines of evidence, including ours in medulloblastoma, the most common childhood brain cancer, highlight non-canonical functions for both proteins and show a complex context-dependent dynamic behavior in determining cell fate. Interestingly, p53-mediated cell survival and AKT-mediated cell death can dominate in certain conditions, and these interchangeable physiological functions may potentially be manipulated for better clinical outcomes. This review article presents studies in which p53 and AKT behave contrary to their well-established functions. We discuss the factors and circumstances that may be involved in mediating these changes and the implications of these unique roles of p53 and AKT in devising therapeutic strategies. Lastly, based on our recent finding of Thymosin beta 4-mediated chemosensitivity via an AKT-p53 interaction in medulloblastoma cells, we also discuss the possible implications of Thymosin beta-4 in enhancing drug sensitivity in this deadly childhood disease.

Nucleolin mediates SARS-CoV-2 replication and viral-induced apoptosis of host cells

Host-oriented antiviral therapeutics are promising treatment options to combat COVID-19 and its emerging variants. However, relatively little is known about the cellular proteins hijacked by SARS-CoV-2 for its replication. Here we show that SARS-CoV-2 induces expression and cytoplasmic translocation of the nucleolar protein, nucleolin (NCL). NCL interacts with SARS-CoV-2 viral proteins and co-localizes with N-protein in the nucleolus and in stress granules. Knockdown of NCL decreases the stress granule component G3BP1, viral replication and improved survival of infected host cells. NCL mediates viral-induced apoptosis and stress response via p53. SARS-CoV-2 increases NCL expression and nucleolar size and number in lungs of infected hamsters. Inhibition of NCL with the aptamer AS-1411 decreases viral replication and apoptosis of infected cells. These results suggest nucleolin as a suitable target for anti-COVID therapies.

C9orf72 poly(PR) mediated neurodegeneration is associated with nucleolar stress

The ALS/FTD-linked intronic hexanucleotide repeat expansion in the C9orf72 gene is translated into dipeptide repeat proteins, among which poly-proline-arginine (PR) displays the most aggressive neurotoxicity in-vitro and in-vivo . PR partitions to the nucleus when expressed in neurons and other cell types. Using drosophila and primary rat cortical neurons as model systems, we show that by lessening the nuclear accumulation of PR, we can drastically reduce its neurotoxicity. PR accumulates in the nucleolus, a site of ribosome biogenesis that regulates the cell stress response. We examined the effect of nucleolar PR accumulation and its impact on nucleolar function and determined that PR caused nucleolar stress and increased levels of the transcription factor p53. Downregulating p53 levels, either genetically or by increasing its degradation, also prevented PR-mediated neurotoxic phenotypes both in in-vitro and in-vivo models. We also investigated whether PR could cause the senescence phenotype in neurons but observed none. Instead, we found induction of apoptosis via caspase-3 activation. In summary, we uncovered the central role of nucleolar dysfunction upon PR expression in the context of C9-ALS/FTD.

A Review of the Regulatory Mechanisms of N-Myc on Cell Cycle

Neuroblastoma has obvious heterogeneity. It is one of the few undifferentiated malignant tumors that can spontaneously degenerate into completely benign tumors. However, for its high-risk type, even with various intensive treatment options, the prognosis is still unsatisfactory. At the same time, a large number of research data show that the abnormal amplification and high-level expression of the MYCN gene are positively correlated with the malignant progression, poor prognosis, and mortality of neuroblastoma. In this context, this article explores the role of the N-Myc, MYCN gene expression product on its target genes related to the cell cycle and reveals its regulatory network in promoting tumor proliferation and malignant progression. We hope it can provide ideas and direction for the research and development of drugs targeting N-Myc and its downstream target genes.