The role of the MDM2/p53 axis in antitumor immune responses

OTUB1 promotes glioma progression by stabilizing TRAF4

BACKGROUND

Glioma is a highly heterogeneous brain tumor with poor prognosis. This study aims to investigate the functional role of OTUB1 in glioma and its impact on TRAF4 stability, seeking potential therapeutic targets.

METHODS

We mined single-cell sequencing data from 12 glioma patients to analyze the heterogeneity of 20,145 glioma cells. The expression of OTUB1 in glioma tissues and cell lines was assessed using Western blot and qPCR. Additionally, immunoprecipitation and ubiquitination assays were conducted to evaluate the effect of OTUB1 on TRAF4 and its role in regulating TRAF4 stability. In vitro assays were performed to assess the effects of OTUB1 on cell proliferation, migration, and clonogenicity, while in vivo experiments using xenograft models in nude mice validated the impact of OTUB1 on tumor growth.

RESULTS

OTUB1 was found to be significantly overexpressed in glioma tissues, correlating with poor patient outcomes. Knockdown of OTUB1 markedly inhibited the proliferation and migration of LN229 and U87MG cells while increasing apoptosis. Immunoprecipitation studies revealed that OTUB1 stabilizes TRAF4 by inhibiting its ubiquitination, thereby promoting glioma cell proliferation and invasion. In vivo, tumors with OTUB1 knockdown demonstrated significantly reduced growth rates.

CONCLUSION

OTUB1 plays a critical role in glioma progression and may serve as a novel therapeutic target. The development of inhibitors targeting OTUB1 could potentially improve outcomes for glioma patients.

TPI1 promotes p53 ubiquitination in bladder cancer by recruiting AKT to enhance MDM2 phosphorylation

Bladder cancer (BCa) is an aggressive malignancy with limited effective treatment options, and its poor outcomes largely result from delayed detection and therapeutic resistance. Triosephosphate isomerase 1 (TPI1) has been associated with tumor progression in various cancers, but its specific function in BCa remains poorly characterized. This study evaluated cancer-related markers and identified glycolysis as a key factor negatively impacting survival in BCa. Additionally, TPI1 was recognized as a potential prognostic marker, with its expression significantly elevated in BCa tissues compared to normal counterparts. Higher TPI1 levels were strongly linked to unfavorable clinical outcomes. Functional assays demonstrated that TPI1 overexpression significantly promoted BCa cell growth, migration, and invasive capabilities in vitro and in vivo. Mechanistically, TPI1 interacted with serine/threonine kinase B (AKT) and murine double minute 2 (MDM2) to form a protein complex, which enhanced the AKT-driven phosphorylation of MDM2 at serine 166 site, thereby promoting tumor protein p53 (p53) ubiquitination degradation. Furthermore, the truncated MDM2-F2 mutant (spanning 181-360) bound to TPI1, with amino acid 317 playing a critical role in this interaction. Notably, reducing AKT expression counteracted the p53 ubiquitination triggered by elevated TPI1.

Exploring the mechanisms of cinobufotalin in ovarian cancer treatment: An integrated approach combining network pharmacology, molecular docking and RNA Sequencing

Cinobufotalin (CINO), a bioactive compound derived from toad skin secretions, has demonstrated clinical efficacy in cancer treatment. However, its molecular mechanisms in ovarian cancer (OC) remain poorly characterized. This study systematically investigated the anti-OC mechanisms of CINO through an integrated strategy combining network pharmacology, molecular docking, and RNA sequencing. Potential CINO targets were predicted via Swiss Target Prediction, while OC-related genes were retrieved from GeneCards and OMIM. Intersecting targets were analyzed using PPI networks and functional enrichment (GO/KEGG). Molecular docking validated ligand-target interactions, and RNA-seq quantified differential gene expression in CINO-treated SKOV3 cells. Among 69 overlapping targets, 10 hub genes (EGFR, PTGS2, MDM2, MAPK1, MAPK3, MTOR, ESR1, PIK3CA, MMP9, and GSK3B) were identified. KEGG analysis highlighted the MAPK signaling and endocrine resistance pathways. RNA-seq revealed 1488 upregulated and 3253 downregulated DEGs, which were mainly enriched in axon development, axonogenesis, and primarily involved in the MAPK signaling pathway. CINO significantly suppressed EGFR, ESR1, MAPK1, MDM2, and mTOR expression (p < 0.05), aligning with pathway predictions. CINO exerts anti-OC effects by modulating endocrine resistance and MAPK signaling, providing a mechanistic foundation for its clinical application.

Genomics guiding personalized first-line immunotherapy response in lung and bladder tumors

BACKGROUND

Immune checkpoint inhibitors (ICI) have revolutionized cancer treatment, particularly in advanced non-small cell lung cancer (NSCLC) and muscle-invasive bladder cancer (MIBC). However, identifying reliable predictive biomarkers for ICI response remains a significant challenge. In this study, we analyzed real-world cohorts of advanced NSCLC and MIBC patients treated with ICI as first-line therapy.

METHODS

Tumor samples underwent Whole Genome Sequencing (WGS) to identify specific somatic variants and assess tumor mutational burden (TMB). Additionally, mutational signature extraction and pathway enrichment analyses were performed to uncover the underlying mechanisms of ICI response. We also characterized HLA-I haplotypes and investigated LINE-1 retrotransposition.

RESULTS

Distinct mutation patterns were identified in patients who responded to treatment, suggesting potential biomarkers for predicting ICI effectiveness. In NSCLC, tumor mutational burden (TMB) did not differ significantly between responders and non-responders, while in MIBC, higher TMB was linked to better responses. Specific mutational signatures and HLA haplotypes were associated with ICI response in both cancers. Pathway analysis showed that NSCLC responders had active inflammatory and immune pathways, while pathways enriched in non-responders related to FGFR3 and neural crest differentiation, associated to resistance mechanisms. In MIBC, responders had alterations in DNA repair, leading to more neoantigens and a stronger ICI response. Importantly, for the first time, we found that LINE-1 activation was positively linked to ICI response, especially in MIBC.

CONCLUSION

These findings reveal promising biomarkers and mechanistic insights, offering a new perspective on predicting ICI response and opening up exciting possibilities for more personalized immunotherapy strategies in NSCLC and MIBC.

Functions and mechanisms of non-histone post-translational modifications in cancer progression

Protein post-translational modifications (PTMs) refer to covalent and enzymatic alterations to folded or nascent proteins during or after protein biosynthesis to alter the properties and functions of proteins. PTMs are modified in a variety of types and affect almost all aspects of cell biology. PTMs have been reported to be involved in cancer progression by influencing multiple signaling pathways. The mechanism of action of histone PTMs in cancer has been extensively studied. Notably, evidence is mounting that PTMs of non-histone proteins also play a vital role in cancer progression. In this review, we provide a systematic description of main non-histone PTMs associated with cancer progression, including acetylation, lactylation, methylation, ubiquitination, phosphorylation, and SUMOylation, based on recent studies.

Harnessing p53 for targeted cancer therapy: new advances and future directions

The transcription factor p53 is the most frequently impaired tumor suppressor in human cancers. In response to various stress stimuli, p53 activates transcription of genes that mediate its tumor-suppressive functions. Distinctive characteristics of p53 outlined here enable a well-defined program of genes involved in cell cycle arrest, apoptosis, senescence, differentiation, metabolism, autophagy, DNA repair, anti-viral response, and anti-metastatic functions, as well as facilitating autoregulation within the p53 network. This versatile, anti-cancer network governed chiefly by a single protein represents an immense opportunity for targeted cancer treatment, since about half of human tumors retain unmutated p53. During the last two decades, numerous compounds have been developed to block the interaction of p53 with the main negative regulator MDM2. However, small molecule inhibitors of MDM2 only induce a therapeutically desirable apoptotic response in a limited number of cancer types. Moreover, clinical trials of the MDM2 inhibitors as monotherapies have not met expectations and have revealed hematological toxicity as a characteristic adverse effect across this drug class. Currently, combination treatments are the leading strategy for enhancing efficacy and reducing adverse effects of MDM2 inhibitors. This review summarizes efforts to identify and test therapeutics that work synergistically with MDM2 inhibitors. Two main types of drugs have emerged among compounds used in the following combination treatments: first, modulators of the p53-regulated transcriptome (including chromatin modifiers), translatome, and proteome, and second, drugs targeting the downstream pathways such as apoptosis, cell cycle arrest, DNA repair, metabolic stress response, immune response, ferroptosis, and growth factor signaling. Here, we review the current literature in this field, while also highlighting overarching principles that could guide target selection in future combination treatments.

OTUD7B is a new deubiquitinase targeting p53

Rationale: The tumor suppressor p53 safeguards against cellular transformation, with its expression regulated by diverse post-translational modifications (PTMs). While polyubiquitination by Mdm2 principally drives its proteasomal degradation, the identity of p53 deubiquitinases (DUBs) remains less well defined. This study investigates the role of the deubiquitinase enzyme OTUD7B in hepatocellular carcinoma (HCC), where it is notably downregulated and proposed to function as a tumor suppressor. Methods: Mass spectrometry screening of immunoprecipitates from HCC cells was used to identify OTUD7B-binding proteins. Co-immunoprecipitation assays with endogenous, ectopic, and mutant forms of OTUD7B and p53 assessed binding interactions and p53 polyubiquitination levels, respectively. Regulatory mechanisms were explored via luciferase reporter and chromatin immunoprecipitation (ChIP) assays. OTUD7B function was evaluated in vitro and in xenograft models using shRNA knockdown, overexpression, and CRISPR-Cas9 knockout. OTUD7B expression in normal and HCC tissues was analyzed by immunohistochemistry and immunoblotting. Results: We identified p53 as a binding partner of OTUD7B, confirming interactions with both wild-type and mutant p53 in HCC cells. OTUD7B was shown to remove lysine-linked polyubiquitin chains in p53, including those mediated by Mdm2, thereby stabilizing p53 by inhibiting its proteasomal degradation. Overexpression of OTUD7B suppressed growth in HCC cultures and xenografts through p53-dependent mitochondrial apoptosis, marked by PUMA and BAX induction. Conversely, OTUD7B knockdown promoted tumor growth. These effects were absent in p53-null or CRISPR-knockout cells, underscoring p53 as a key OTUD7B substrate. Additionally, OTUD7B expression was found to be transcriptionally repressed via p53-dependent mechanisms. Bioinformatics and ex vivo analysis revealed a positive correlation between OTUD7B and p53 protein levels in HCC tissues. Conclusion: OTUD7B plays a critical role in stabilizing both wild-type and mutant p53 in HCC cells, with its expression regulated through a mutual feedback loop involving p53. By inhibiting cell growth, OTUD7B exhibits tumor-suppressive properties, underscored by its atypical downregulation in patient tissues and its positive correlation with p53 expression. These findings highlight the clinical significance of OTUD7B and position it as a promising therapeutic target for modulating the p53 pathway in HCC.

Tackling Undruggable Targets with Designer Peptidomimetics and Synthetic Biologics

The development of potent, specific, and pharmacologically viable chemical probes and therapeutics is a central focus of chemical biology and therapeutic development. However, a significant portion of predicted disease-causal proteins have proven resistant to targeting by traditional small molecule and biologic modalities. Many of these so-called "undruggable" targets feature extended, dynamic protein-protein and protein-nucleic acid interfaces that are central to their roles in normal and diseased signaling pathways. Here, we discuss the development of synthetically stabilized peptide and protein mimetics as an ever-expanding and powerful region of chemical space to tackle undruggable targets. These molecules aim to combine the synthetic tunability and pharmacologic properties typically associated with small molecules with the binding footprints, affinities and specificities of biologics. In this review, we discuss the historical and emerging platforms and approaches to design, screen, select and optimize synthetic "designer" peptidomimetics and synthetic biologics. We examine the inspiration and design of different classes of designer peptidomimetics: (i) macrocyclic peptides, (ii) side chain stabilized peptides, (iii) non-natural peptidomimetics, and (iv) synthetic proteomimetics, and notable examples of their application to challenging biomolecules. Finally, we summarize key learnings and remaining challenges for these molecules to become useful chemical probes and therapeutics for historically undruggable targets.

Companion diagnostics and predictive biomarkers for PD-1/PD-L1 immune checkpoint inhibitors therapy in malignant melanoma

Programmed cell death receptor 1 (PD-1), when bound to the ligand programmed death-ligand 1 (PD-L1), can suppress cellular immunity and play a critical role in the initiation and development of cancer. Immune drugs targeting these two sites have been developed for different cancers, including malignant melanoma. The accompanying diagnostic method has been approved by the FDA to guide patient medication. However, the method of immunohistochemical staining, which varies widely due to the antibody and staining cut-off values, has certain limitations in application and does not benefit all patients. Increasing researches begin to focus on new biomarkers to improve objective response rates and survival in cancer patients. In this article, we enumerated three major groups, including tumour microenvironment, peripheral circulation, and gene mutation, which covered the current main research directions. In the future, we hope those biomarkers may be used to guide the treatment of patients with malignant melanoma.

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.

Comprehensive analysis of the relationship between ubiquitin-specific protease 21 (USP21) and prognosis, tumor microenvironment infiltration, and therapy response in colorectal cancer

BACKGROUND

Ubiquitin-specific proteases family is crucial to host immunity against pathogens. However, the correlations between USP21 and immunosurveillance and immunotherapy for colorectal cancer (CRC) have not been reported.

METHODS

The differential expression of USP21 between CRC tissues and normal tissues was analyzed using multiple public databases. Validation was carried out in clinical samples through qRT-PCR and IHC. The correlation between USP21 and the prognosis, as well as clinical pathological characteristics of CRC patients, was investigated. Moreover, cell models were established to assess the influence of USP21 on CRC growth and progression, employing CCK-8 assays, colony formation assays, and wound-healing assays. Subsequently, gene set variation analysis (GSVA) was used to explore the potential biological functions of USP21 in CRC. The study also examined the impact of USP21 on cytokine levels and immune cell infiltration in the tumor microenvironment (TME). Finally, the effect of USP21 on the response to immunotherapy and chemotherapy in CRC was analyzed.

RESULTS

The expression of USP21 was significantly upregulated in CRC. High USP21 is correlated with poor prognosis in CRC patients and facilitates the proliferation and migration capacities of CRC cells. GSVA indicated an association between low USP21 and immune activation. Moreover, low USP21 was linked to an immune-activated TME, characterized by high immune cell infiltration. Importantly, CRC with low USP21 exhibited higher tumor mutational burden, high PD-L1 expression, and better responsiveness to immunotherapy and chemotherapeutic drugs.

CONCLUSION

This study revealed the role of USP21 in TME, response to therapy, and clinical prognosis in CRC, which provided novel insights for the therapeutic application in CRC.

Targeting MDM2 in malignancies is a promising strategy for overcoming resistance to anticancer immunotherapy

MDM2 has been established as a biomarker indicating poor prognosis for individuals undergoing immune checkpoint inhibitor (ICI) treatment for different malignancies by various pancancer studies. Specifically, patients who have MDM2 amplification are vulnerable to the development of hyperprogressive disease (HPD) following anticancer immunotherapy, resulting in marked deleterious effects on survival rates. The mechanism of MDM2 involves its role as an oncogene during the development of malignancy, and MDM2 can promote both metastasis and tumor cell proliferation, which indirectly leads to disease progression. Moreover, MDM2 is vitally involved in modifying the tumor immune microenvironment (TIME) as well as in influencing immune cells, eventually facilitating immune evasion and tolerance. Encouragingly, various MDM2 inhibitors have exhibited efficacy in relieving the TIME suppression caused by MDM2. These results demonstrate the prospects for breakthroughs in combination therapy using MDM2 inhibitors and anticancer immunotherapy.