Integrated stress response (ISR) activation and apoptosis through HRI kinase by PG3 and other p53 pathway-restoring cancer therapeutics.

Restoration of the p53 pathway has been a long-term goal in the field of cancer research to treat tumors with mutated p53 and aggressive clinical behavior. p53 pathway restoration in p53-deficient cancers can be achieved by small molecules via p53-dependent or p53-independent processes. Hereafter p53-independent restoration of p53-pathway-signaling in p53-deficient/mutated tumors is referred to as 'restoration of the p53 pathway'. We compare activation of p53 target genes by novel compounds PG3 and PG3-Oc, that activate p53-target genes in a p53-independent manner, and four mutant p53-activating compounds while Nutlin-3a is used as negative control. PG3 and PG3-Oc upregulate p21, PUMA, and DR5 in five cancer cell lines with various p53 mutational statuses through ATF4 (Activating Transcriptional Factor 4) and integrated stress response (ISR) independent of p53. Mutant p53-targeting compounds induce expression of the 3 major downstream p53 target genes and ATF4 in a highly variable and cell-type-dependent manner. PG3 treatment activates ATF4 through ISR via kinase HRI (Heme-Regulated Inhibitor). ATF4 mediates upregulation of PUMA, p21, and NAG-1/GDF15 (Nonsteroidal anti-inflammatory drug-activated gene 1). We note that PUMA mediates apoptosis through activation of caspase-8 in HT29 cells and potentially caspase-10 in SW480 cells. We provide a novel mechanism engaged by PG3 to induce cell death via the HRI/ATF4/PUMA axis. Our results provide unique insights into the mechanism of action of PG3 as a novel cancer therapeutic targeting p53 pathway-like tumor suppression.

USP7 regulates growth and maintains the stemness of p53-mutant colorectal cancer cells via stabilizing of mutant p53.

Introduction: TP53 is one of the most frequently mutated genes among all cancers, and TP53 mutants occur more than 40% in colorectal cancers (CRCs). Accumulation of mutant p53 may augment colorectal cancer stem cells (CCSCs) phenotype and enhance colorectal tumorigenesis. Thus, reducing the level of mutant p53 protein is an attractive anticancer strategy. Methods: CSC-enriched cancer cells were obtained by tumor sphere formation assay. The effects of USP7 on the proliferation of cancer cells were determined by MTS and colony formation assays. Wound healing assay was used to test cell migratory abilities. qPCR and western blotting assays were performed to verify the mRNA and protein levels of CSC markers, USP7 and p53. Co-immunoprecipitation assay was used to test the interaction effects between USP7 and p53. Results: In this study, we found that USP7 and mutant p53 were dramatically elevated in CSC-enriched colorectal cancer cells and USP7 expression was positively associated with self-renewal and maintenance of CCSCs. USP7 regulated cell growth, stemness and migration of colorectal cancer cells. USP7 depletion significantly reduced proliferation of cancer cells and suppressed the self-renewal of CSC-enriched colorectal cancer cells. Further studies indicated that USP7 knockdown could significantly decrease mutant p53 protein levels both in CRCs and CSC-enriched colorectal cancer cells. Moreover, mutant p53 was stabilized by USP7 and they interacted with each other. Furthermore, USP7 inhibitor P5091 also diminished CCSCs self-renewal and reduced mutant p53 levels. Conclusion: Taken together, our findings demonstrated that USP7 involved in the modulation of CCSCs stemness, as well as a critical target for clinical treatment of cancers with different p53 mutations.

Therapeutic effects of focused ultrasound on vulvar squamous intraepithelial lesions in rat.

OBJECTIVE: In this study, we established a Sprague-Dawley rat model of vulvar squamous intraepithelial lesions and investigated the impact of focused ultrasound on the expression of hypoxia-inducible factor-1α (HIF-1α), vascular endothelial growth factor (VEGF) and mutant type p53 (mtp53) in the vulvar skin of rats with low-grade squamous intraepithelial lesions (LSIL). MATERIALS AND METHODS: The vulvar skin of 60 rats was treated with dimethylbenzanthracene (DMBA) and mechanical irritation three times a week for 14 weeks. Rats with LSIL were randomly allocated into the experimental group or the control group. The experimental group was treated with focused ultrasound, while the control group received sham treatment. RESULTS: After 14 weeks treatment of DMBA combined with mechanical irritation, LSIL were observed in 44 (73.33%) rats, and high-grade squamous intraepithelial lesions (HSIL) were observed in 14 (23.33%) rats. 90.91% (20/22) of rats showed normal pathology and 9.09% (2/22) of rats exhibited LSIL in the experimental group at four weeks after focused ultrasound treatment. 22.73% (5/22) of rats exhibited LSIL, 77.27% (17/22) of rats progressed to HSIL in the control group. Compared with the control-group rats, the levels of HIF-1α, VEGF and mtp53 were significantly decreased in experimental-group rats (p < 0.05). CONCLUSIONS: These results indicate that DMBA combined with mechanical irritation can induce vulvar squamous intraepithelial lesion in SD rats. Focused ultrasound can treat LSIL safely and effectively, prevent the progression of vulvar lesions, and improve the microenvironment of vulvar tissues by decreasing the localized expression of HIF-1α, VEGF, and mtp53 in rats.

Mutant p53 Exploits Enhancers to Elevate Immunosuppressive Chemokine Expression and Impair Immune Checkpoint Inhibitors in Pancreatic Cancer.

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive cancer without effective treatments. It is characterized by activating KRAS mutations and p53 alterations. However, how these mutations dysregulate cancer-cell-intrinsic gene programs to influence the immune landscape of the tumor microenvironment (TME) remains poorly understood. Here, we show that p53R172H establishes an immunosuppressive TME, diminishes the efficacy of immune checkpoint inhibitors (ICIs), and enhances tumor growth. Our findings reveal that the upregulation of the immunosuppressive chemokine Cxcl1 mediates these pro-tumorigenic functions of p53R172H. Mechanistically, we show that p53R172H associates with the distal enhancers of the Cxcl1 gene, increasing enhancer activity and Cxcl1 expression. p53R172H occupies these enhancers in an NF-κB-pathway-dependent manner, suggesting NF-κB's role in recruiting p53R172H to the Cxcl1 enhancers. Our work uncovers how a common mutation in a tumor-suppressor transcription factor appropriates enhancers, stimulating chemokine expression and establishing an immunosuppressive TME that diminishes ICI efficacy in PDAC.

Mutant P53 modulation by cryptolepine through cell cycle arrest and apoptosis in triple negative breast cancer.

BACKGROUND: Triple Negative Breast cancer is an aggressive breast cancer subtype. It has a more aggressive clinical course, an earlier age of onset, a larger propensity for metastasis, and worse clinical outcomes as evidenced by a higher risk of recurrence and a shorter survival rate. Currently, the primary options for TNBC treatment are surgery, radiation, and chemotherapy. These treatments however remain ineffective due to recurrence. However, given that p53 mutations have been identified in more than 60-88 % of TNBC, translating p53 into the clinical situation is particularly important in TNBC. In this study, we screened and evaluated the therapeutic potential of cryptolepine (CRP) in TNBC in-vitro models being an anti-malarial drug it could be repurposed as an anti-cancer therapeutic targeting TNBC. Moreover, the cytotoxicity activity of cryptolepine to TNBC cells and a detailed anti-tumor mechanism in mutant P53 has not been reported before. METHODS: MTT assays were used to examine the cytotoxicity and cell viability activity of Cryptolepine in TNBC, non-TNBC T47D and MCF-7 and non-malignant MCF10A cells. Scratch wound and clonogenic assay was used to evaluate the cryptolepine's effect on migration and colony forming ability of TNBC cells. Flow cytometry, MMP and DAPI was used to assess cell cycle arrest and cell apoptosis mechanism. The expression of proteins was detected by western blots. The differential expression of RNAs was evaluated by RT-PCR and the interaction between P53 and drug was evaluated computationally using in-silico approach and in-vitro using ChIP assay. RESULTS: In this study, we found that cryptolepine has more preferential cytotoxicity in TNBC than non-TNBC cells. Notably, our studies revealed the mechanism by which cryptolepine induces intrinsic apoptosis and inhibit migration, colony formation ability, induce cell cycle arrest by inducing conformational change in the mutant P53 thereby increasing its DNA binding ability, hence activating its tumor suppressing potential significantly. CONCLUSION: Our study revealed that CRP significantly reduced the proliferation, migration and colony forming ability of TNBC cells lines. Moreover, it was revealed that CRP induces cell cycle arrest and apoptosis by activating mutant P53 and enhancing its DNA binding ability to induce its tumor suppressing ability.

Pyrimidine Triones as Potential Activators of p53 Mutants.

p53 is a crucial tumor suppressor in vertebrates that is frequently mutated in human cancers. Most mutations are missense mutations that render p53 inactive in suppressing tumor initiation and progression. Developing small-molecule drugs to convert mutant p53 into an active, wild-type-like conformation is a significant focus for personalized cancer therapy. Prior research indicates that reactivating p53 suppresses cancer cell proliferation and tumor growth in animal models. Early clinical evidence with a compound selectively targeting p53 mutants with substitutions of tyrosine 220 suggests potential therapeutic benefits of reactivating p53 in patients. This study identifies and examines the UCI-1001 compound series as a potential corrector for several p53 mutations. The findings indicate that UCI-1001 treatment in p53 mutant cancer cell lines inhibits growth and reinstates wild-type p53 activities, including DNA binding, target gene activation, and induction of cell death. Cellular thermal shift assays, conformation-specific immunofluorescence staining, and differential scanning fluorometry suggest that UCI-1001 interacts with and alters the conformation of mutant p53 in cancer cells. These initial results identify pyrimidine trione derivatives of the UCI-1001 series as candidates for p53 corrector drug development.

Post-Translational Modifications (PTMs) of mutp53 and Epigenetic Changes Induced by mutp53.

Wild-type (wt) p53 and mutant forms (mutp53) play a key but opposite role in carcinogenesis. wtP53 acts as an oncosuppressor, preventing oncogenic transformation, while mutp53, which loses this property, may instead favor this process. This suggests that a better understanding of the mechanisms activating wtp53 while inhibiting mutp53 may help to design more effective anti-cancer treatments. In this review, we examine possible PTMs with which both wt- and mutp53 can be decorated and discuss how their manipulation could represent a possible strategy to control the stability and function of these proteins, focusing in particular on mutp53. The impact of ubiquitination, phosphorylation, acetylation, and methylation of p53, in the context of several solid and hematologic cancers, will be discussed. Finally, we will describe some of the recent studies reporting that wt- and mutp53 may influence the expression and activity of enzymes responsible for epigenetic changes such as acetylation, methylation, and microRNA regulation and the possible consequences of such changes.

Activating transcription factor 3 mediates apoptosis and cell cycle arrest in TP53-mutated anaplastic thyroid cancer cells.

BACKGROUND: It is believed that loss of p53 function plays a crucial role in the progression of well to poorly differentiated thyroid cancers including anaplastic thyroid carcinoma (ATC). Given the poor prognosis of ATC due to its strong therapeutic resistance, there is a need to establish new therapeutic targets to extend the survival of ATC patients. Activating transcription factor 3 (ATF3) can inhibit the oncogenic activity of mutant p53 and, as a result, contribute to tumor suppression in several TP53-mutated cancers. Herein, we demonstrate that the ectopic overexpression of ATF3 leads to the suppression of oncogenic mutant p53 activity in chemo-resistant 8305 C thyroid cancer cells harboring R273C p53 gene mutation. METHODS: The biological behavior of 8305 C cells was assessed pre- and post-transfection with pCMV6-ATF3 plasmid using MTT assay, fluorescent microscopy, cell cycle, and annexin V/PI flow cytometric analysis. The effect of ectopic ATF3 overexpression on the cellular level of p53 was examined by western blotting assay. The mRNA expression levels of TP53, TAp63, ΔNp63, and SHARP1 were evaluated in ectopic ATF3-expressing cells compared to controls. RESULTS: The overexpression of ATF3 in 8305 C thyroid cancer cells significantly decreased cell viability and induced apoptosis and cell cycle arrest in vitro. The immunoblotting of p53 protein revealed that ATF3 overexpression significantly increased the level of mutant p53 in 8305C cells compared to mock-transfected control cells. Additionally, elevated mRNA levels of TAp63 and SHARP1 and a decreased mRNA level of ΔNp63 were observed in PCMV6-AC-ATF3-transfected 8305 C cells with significant differences compared to the mock and untreated cells. CONCLUSION: In light of our findings, it is evident that therapeutic strategies aimed at increasing ATF3 expression or enhancing the interaction between ATF3 and mutant p53 can be a promising approach for the treatment of p53-mutated metastatic thyroid cancer.

Remodeling of anti-tumor immunity with antibodies targeting a p53 mutant.

BACKGROUND: p53, the most frequently mutated gene in cancer, lacks effective targeted drugs. METHODS: We developed monoclonal antibodies (mAbs) that target a p53 hotspot mutation E285K without cross-reactivity with wild-type p53. They were delivered using lipid nanoparticles (LNPs) that encapsulate DNA plasmids. Western blot, BLI, flow cytometry, single-cell sequencing (scRNA-seq), and other methods were employed to assess the function of mAbs in vitro and in vivo. RESULTS: These LNP-pE285K-mAbs in the IgG1 format exhibited a robust anti-tumor effect, facilitating the infiltration of immune cells, including CD8+ T, B, and NK cells. scRNA-seq revealed that IgG1 reduces immune inhibitory signaling, increases MHC signaling from B cells to CD8+ T cells, and enriches anti-tumor T cell and B cell receptor profiles. The E285K-mAbs were also produced in the dimeric IgA (dIgA) format, whose anti-tumor activity depended on the polymeric immunoglobulin receptor (PIGR), a membrane Ig receptor, whereas that of IgG1 relied on TRIM21, an intracellular IgG receptor. CONCLUSIONS: Targeting specific mutant epitopes using DNA-encoded and LNP-delivered mAbs represents a potential precision medicine strategy against p53 mutants in TRIM21- or PIGR-positive cancers.

Recent Advances on Mutant p53: Unveiling Novel Oncogenic Roles, Degradation Pathways, and Therapeutic Interventions.

The p53 protein is the master regulator of cellular integrity, primarily due to its tumor-suppressing functions. Approximately half of all human cancers carry mutations in the TP53 gene, which not only abrogate the tumor-suppressive functions but also confer p53 mutant proteins with oncogenic potential. The latter is achieved through so-called gain-of-function (GOF) mutations that promote cancer progression, metastasis, and therapy resistance by deregulating transcriptional networks, signaling pathways, metabolism, immune surveillance, and cellular compositions of the microenvironment. Despite recent progress in understanding the complexity of mutp53 in neoplastic development, the exact mechanisms of how mutp53 contributes to cancer development and how they escape proteasomal and lysosomal degradation remain only partially understood. In this review, we address recent findings in the field of oncogenic functions of mutp53 specifically regarding, but not limited to, its implications in metabolic pathways, the secretome of cancer cells, the cancer microenvironment, and the regulating scenarios of the aberrant proteasomal degradation. By analyzing proteasomal and lysosomal protein degradation, as well as its connection with autophagy, we propose new therapeutical approaches that aim to destabilize mutp53 proteins and deactivate its oncogenic functions, thereby providing a fundamental basis for further investigation and rational treatment approaches for TP53-mutated cancers.

Targeting mutant p53 with arsenic trioxide: A preclinical study focusing on triple negative breast cancer.

New treatments are urgently required for triple-negative breast cancer (TNBC). As TP53 is mutated in approximately 80% of TNBC, it is theoretically an attractive target for new drugs for this disease. Arsenic trioxide (ATO), which is used to treat promyelocytic leukaemia, was recently shown to reactivate mutant p53 and restore wild-type functionality. The aim of this study was to evaluate ATO as a potential new treatment for TNBC. Using a panel of 20 cell lines, we found that TNBC cell lines were more sensitive to ATO than non-TNBC cell lines (P = 0.045). Consistent with its ability to reactivate mutant p53, ATO was a more potent inhibitor of proliferation in cell lines with mutant TP53 than the wildtype TP53 (P = 0.027). Direct evidence of mutant p53 reactivation was the induction of multiple wild-type p53 canonical target genes such as CDKN1A, SLC7A11, BBC3, PMAIP1, SESN2, SRXN1 and TXNRD1. Our findings support the activation of mutant p53 by ATO and, furthermore, the possible repurposing of ATO to treat TP53-mutated TNBC.

Genome-wide CRISPR screens identify novel regulators of wild-type and mutant p53 stability.

Tumor suppressor p53 (TP53) is frequently mutated in cancer, often resulting not only in loss of its tumor-suppressive function but also acquisition of dominant-negative and even oncogenic gain-of-function traits. While wild-type p53 levels are tightly regulated, mutants are typically stabilized in tumors, which is crucial for their oncogenic properties. Here, we systematically profiled the factors that regulate protein stability of wild-type and mutant p53 using marker-based genome-wide CRISPR screens. Most regulators of wild-type p53 also regulate p53 mutants, except for p53 R337H regulators, which are largely private to this mutant. Mechanistically, FBXO42 emerged as a positive regulator for a subset of p53 mutants, working with CCDC6 to control USP28-mediated mutant p53 stabilization. Additionally, C16orf72/HAPSTR1 negatively regulates both wild-type p53 and all tested mutants. C16orf72/HAPSTR1 is commonly amplified in breast cancer, and its overexpression reduces p53 levels in mouse mammary epithelium leading to accelerated breast cancer. This study offers a network perspective on p53 stability regulation, potentially guiding strategies to reinforce wild-type p53 or target mutant p53 in cancer.

DNA-delivered monoclonal antibodies targeting the p53 R175H mutant epitope inhibit tumor development in mice.

The tumor suppressor p53 is the most common mutated gene in cancer, with the R175H as the most frequent p53 missense mutant. However, there are currently no approved targeted therapies or immunotherapies against mutant p53. Here, we characterized and investigated a monoclonal antibody (mAb) that recognizes the mutant p53-R175H for its affinity, specificity, and activity against tumor cells in vitro. We then delivered DNA plasmids expressing the anti-R175H mAb or a bispecific antibody (BsAb) into mice to evaluate their therapeutic effects. Our results showed that the anti-R175H mAb specifically bound to the p53-R175H antigen with a high affinity and recognized the human mutant p53-R175H antigen expressed on HEK293T or MC38 cells, with no cross-reactivity with wild-type p53. In cultured cells, the anti-R175H mAb showed higher cytotoxicity than the control but did not induce antibody-dependent cellular cytotoxicity. We made a recombinant MC38 mouse cell line (MC38-p53-R175H) that overexpressed the human p53-R175H after knocking out the endogenous mutant p53 alleles. In vivo, administration of the anti-R175H mAb plasmid elicited a robust anti-tumor effect against MC38-p53-R175H in mice. The administration of the anti-R175H BsAb plasmid showed no therapeutic effects, yet potent anti-tumor activity was observed in combination with the anti-PD-1 antibody. These results indicate that targeting specific mutant epitopes using DNA-delivered mAbs or BsAbs presents a form of improved natural immunity derived from tumor-infiltrating B cells and plasma cells against intracellular tumor antigens.

Proteasome inhibition paradoxically degrades gain-of-function mutant p53 R273H in NSCLC and could have therapeutic implications.

Lung cancer is the leading cause of cancer mortality. Despite therapeutic advances in recent years, new treatment strategies are needed to improve outcomes of lung cancer patients. Mutant p53 is prevalent in lung cancers and drives several hallmarks of cancer through a gain-of-function oncogenic program, and often predicts a poorer prognosis. The oncogenicity of mutant p53 is related to its stability and accumulation in cells by evading degradation by the proteasome. Therefore, destabilization of mutant p53 has been sought as a therapeutic strategy, but so far without clinical success. In this study, we report that proteasome inhibition results in degradation of mutant p53 in non-small cell lung cancer (NSCLC) cell lines bearing the R273H mutant protein and show evidence that this was mediated by hsp70. NSCLC cell lines with the mutant R273H allele demonstrated increased susceptibility and apoptosis to proteasome inhibitors. These data suggest that proteasome inhibitors could have therapeutic implications in some subsets of TP53 mutated NSCLC.

Novel oncogenic transcriptional targets of mutant p53 in esophageal squamous cell carcinoma.

Missense mutations in the DNA binding domain of p53 are observed frequently in esophageal squamous cell carcinoma (ESCC). Recent studies have revealed the potentially oncogenic transcriptional networks regulated by mutant p53 proteins. However, majority of these studies have focused on common "hotspot" p53 mutations while rarer mutations are poorly characterized. In this study, we report the characterization of rare, "non-hotspot" p53 mutations from ESCC. In vitro tumorigenic assays performed following ectopic-expression of certain "non-hotspot" mutant p53 proteins caused enhancement of oncogenic properties in squamous carcinoma cell lines. Genome-wide transcript profiling of ESCC tumor samples stratified for p53 status, revealed several genes exhibiting elevated transcript levels in tumors harboring mutant p53. Of these, ARF6, C1QBP, and TRIM23 were studied further. Reverse transcription-quantitative PCR (RT-qPCR) performed on RNA isolated from ESCC tumors revealed significant correlation of TP53 transcript levels with those of the three target genes. Ectopic expression of wild-type and several mutant p53 forms followed by RT-qPCR, chromatin affinity-purification (ChAP), and promoter-luciferase assays indicated the exclusive recruitment of p53 mutants-P190T and P278L, to the target genes leading to the activation of expression. Several functional assays following knockdown of the target genes revealed a significant suppression of tumorigenicity in squamous carcinoma cell lines. Rescue experiments confirmed the specificity of the knockdown. The tumorigenic effects of the genes were confirmed in nude mice xenograft assays. This study has therefore identified novel oncogenic targets of "non-hotspot" mutant p53 proteins relevant for ESCC besides validating the functional heterogeneity of the spectrum of tumor-specific p53 mutations.

Understanding the prion-like behavior of mutant p53 proteins in triple-negative breast cancer pathogenesis: The current therapeutic strategies and future directions.

Breast cancer (BC) is viewed as a significant public health issue and is the primary cause of cancer-related deaths among women worldwide. Triple-negative breast cancer (TNBC) is a particularly aggressive subtype that predominantly affects young premenopausal women. The tumor suppressor p53 playsa vital role in the cellular response to DNA damage, and its loss or mutations are commonly present in many cancers, including BC. Recent evidence suggests that mutant p53 proteins can aggregate and form prion-like structures, which may contribute to the pathogenesis of different types of malignancies, such as BC. This review provides an overview of BC molecular subtypes, the epidemiology of TNBC, and the role of p53 in BC development. We also discuss the potential implications of prion-like aggregation in BC and highlight future research directions. Moreover, a comprehensive analysis of the current therapeutic approaches targeting p53 aggregates in BC treatment is presented. Strategies including small molecules, chaperone inhibitors, immunotherapy, CRISPR-Cas9, and siRNA are discussed, along with their potential benefits and drawbacks. The use of these approaches to inhibit p53 aggregation and degradation represents a promising target for cancer therapy. Future investigations into the efficacy of these approaches against various p53 mutations or binding to non-p53 proteins should be conducted to develop more effective and personalized therapies for BC treatment.

Patient-derived tumor organoids with p53 mutations, and not wild-type p53, are sensitive to synergistic combination PARP inhibitor treatment.

Poly (ADP-ribose) polymerase inhibitors (PARPi) are used for patients with BRCA1/2 mutations, but patients with other mutations may benefit from PARPi treatment. Another mutation that is present in more cancers than BRCA1/2 is mutation to the TP53 gene. In 2D breast cancer cell lines, mutant p53 (mtp53) proteins tightly associate with replicating DNA and Poly (ADP-ribose) polymerase (PARP) protein. Combination drug treatment with the alkylating agent temozolomide and the PARPi talazoparib kills mtp53 expressing 2D grown breast cancer cell lines. We evaluated the sensitivity to the combination of temozolomide plus PARPi talazoparib treatment to breast and lung cancer patient-derived tumor organoids (PDTOs). The combination of the two drugs was synergistic for a cytotoxic response in PDTOs with mtp53 but not for PDTOs with wtp53. The combination of talazoparib and temozolomide induced more DNA double-strand breaks in mtp53 expressing organoids than in wild-type p53 expressing organoids as shown by increased γ-H2AX protein expression. Moreover, breast cancer tissue microarrays (TMAs) showed a positive correlation between stable p53 and high PARP1 expression in sub-groups of breast cancers, which may indicate sub-classes of breast cancers sensitive to PARPi therapy. These results suggest that mtp53 could be a biomarker to predict response to the combination of PARPi talazoparib-temozolomide treatment.

Nanoscale Metal-Organic Frameworks-Mediated Degradation of Mutant p53 Proteins and Activation of cGAS-STING Pathway for Enhanced Cancer Immunotherapy.

Activating cGAS-STING pathway has great potential to achieve effective antitumor immunotherapy. However, mutant p53 (mutp53), a commonly observed genetic alteration in over 50% of human cancer, will impede the therapeutic performance of the cGAS-STING pathway. Herein, multifunctional ZIF-8@MnO2 nanoparticles are constructed to degrade mutp53 and facilitate the cGAS-STING pathway. The synthesized ZIF-8@MnO2 can release Zn2+ and Mn2+ in cancer cells to induce oxidative stress and cytoplasmic leakage of fragmented mitochondrial double-stranded DNAs (dsDNAs). Importantly, the released Zn2+ induces variable degradation of multifarious p53 mutants through proteasome ubiquitination, which can alleviate the inhibitory effects of mutp53 on the cGAS-STING pathway. In addition, the released Mn2+ further increases the sensitivity of cGAS to dsDNAs as immunostimulatory signals. Both in vitro and in vivo results demonstrate that ZIF-8@MnO2 effectively promotes the cGAS-STING pathway and synergizes with PD-L1 checkpoint blockades, leading to remarkable regression of local tumors as well as distant metastases of breast cancer. This study proposes an inorganic metal ion-based nanoplatform to enhance the cGAS-STING-mediated antitumor immunotherapy, especially to those tumors with mutp53 expression.

microRNA-205 represses breast cancer metastasis by perturbing the rab coupling protein [RCP]-mediated integrin ß1 recycling on the membrane.

During cancer cell invasion, integrin undergoes constant endo/exocytic trafficking. It has been found that the recycling ability of integrin ß1 through Rab11-controlled long loop pathways is directly associated with cancer invasion. Previous studies showed that gain-of-function mutant p53 regulates the Rab-coupling protein [RCP]-mediated integrin ß1 recycling by inactivating tumor suppressor TAp63. So, we were interested to investigate the involvement of miR-205 in this process. In the current study first, we evaluated that the lower expression of miR-205 in MDA-MB-231 cell line is associated with high motility and invasiveness. Further investigation corroborated that miR-205 directly targets RCP resulting in attenuated RCP-mediated integrin ß1 recycling. Overexpression of TAp63 validates our in vitro findings. To appraise the anti-metastatic role of miR-205, we developed two in vivo experimental models- xenograft-chick embryo and xenograft-immunosuppressed BALB/c mice. Our in vivo results support the negative effect of miR-205 on metastasis. Therefore, these findings advocate the tumor suppressor activity of miR-205 in breast cancer cells and suggest that in the future development of miR-205-targeting RNAi therapeutics could be a smart alternative approach to prevent the metastatic fate of the disease.

Valproic acid increased the efficacy of EGFR TKIs on EGFR/TP53 co-mutated lung cancers and downregulated mutant-p53 levels.

The TP53 tumor suppressor is the most frequently mutated gene in human cancers. For p53-targeted therapy, one of the strategies was targeting mutant p53 for degradation. In EGFR-mutated lung cancer patients, concurrent TP53 mutation was associated with faster resistance to EGFR-TKIs. In this study, we discovered that valproic acid (VPA), a widely prescribed antiseizure medication, had a synergic effect on sensitive as well as acquired resistant lung cancers with EGFR/TP53 co-mutation in combination with EGFR-TKIs. In both in vitro and in vivo models, VPA greatly improved the efficacy of EGFR-TKIs, including forestalling the occurrence of acquired resistance and increasing the sensitivity to EGFR-TKIs. Mechanistically, VPA dramatically promoted degradation of mutant p53 in both sensitive and acquired resistant cells while inhibited mutant TP53 mRNA transcription only in sensitive cells. Together, this study suggested that VPA combination treatment could have beneficial effects on EGFR-mutant lung cancers with concurrent p53 mutation in both early and late stages, expanding the potential clinical applications for VPA.