P53 Stabilization Research Articles

Acetylation halts missense mutant p53 aggregation and rescues tumor suppression in non-small cell lung cancers

TP53 mutations are ubiquitous with tumorigenesis in non-small cell lung cancers (NSCLC). By analyzing the TCGA database, we reported that TP53 missense mutations are correlated with chromosomal instability and tumor mutation burden in NSCLC. The inability of wild-type nor mutant p53 expression can't predict survival in lung cancer cohorts, however, an examination of primary NSCLC tissues found that acetylated p53 did yield an association with improved survival outcomes. Molecularly, we demonstrated that acetylation drove the ubiquitination and degradation of mutant p53 but enhanced stability of wild-type p53. Moreover, acetylation of a missense p53 mutation prevented the gain of oncogenic function observed in typical TP53 mutant-expressing cells and enhanced tumor suppressor functions. Consequently, acetylation inducer targeting of missense mutant p53 may be a viable therapeutic goal for NSCLC treatment and may improve the accuracy of current efforts to utilize p53 mutations in a prognostic manner.

RPS27a and RPL40, Which Are Produced as Ubiquitin Fusion Proteins, Are Not Essential for p53 Signalling.

Two of the four human ubiquitin-encoding genes express ubiquitin as an N-terminal fusion precursor polypeptide, with either ribosomal protein (RP) RPS27a or RPL40 at the C-terminus. RPS27a and RPL40 have been proposed to be important for the induction of the tumour suppressor p53 in response to defects in ribosome biogenesis, suggesting that they may play a role in the coordination of ribosome production, ubiquitin levels and p53 signalling. Here, we report that RPS27a is cleaved from the ubiquitin-RP precursor in a process that appears independent of ribosome biogenesis. In contrast to other RPs, the knockdown of either RPS27a or RPL40 did not stabilise the tumour suppressor p53 in U2OS cells. Knockdown of neither protein blocked p53 stabilisation following inhibition of ribosome biogenesis by actinomycin D, indicating that they are not needed for p53 signalling in these cells. However, the knockdown of both RPS27a and RPL40 in MCF7 and LNCaP cells robustly induced p53, consistent with observations made with the majority of other RPs. Importantly, RPS27a and RPL40 are needed for rRNA production in all cell lines tested. Our data suggest that the role of RPS27a and RPL40 in p53 signalling, but not their importance in ribosome biogenesis, differs between cell types.

Butein inhibits cancer cell growth by rescuing the wild-type thermal stability of mutant p53

p53 is a transcription factor that activates the expression of various genes involved in the maintenance of genomic stability, and more than 50% of cancers harbor inactivating p53 mutations, which are indicative of highly aggressive cancer and poor prognosis. Pharmacological targeting of mutant p53 to restore the wild-type p53 tumor-suppressing function is a promising strategy for cancer therapy. In this study, we identified a small molecule, Butein, that reactivates mutant p53 activity in tumor cells harboring the R175H or R273H mutation. Butein restored wild-type-like conformation and DNA-binding ability in HT29 and SK-BR-3 cells harboring mutant p53-R175H and mutant p53-R273H, respectively. Moreover, Butein enabled the transactivation of p53 target genes and decreased the interactions of Hsp90 with mutant p53-R175H and mutant p53-R273H proteins, while Hsp90 overexpression reversed targeted p53 gene activation. In addition, Butein induced thermal stabilization of wild-type p53, mutant p53-R273H and mutant p53-R175H, as determined via CETSA. From docking study, we further proved that Butein binding to p53 stabilized the DNA-binding loop-sheet-helix motif of mutant p53-R175H and regulated its DNA-binding activity via an allosteric mechanism, conferring wild-type-like the DNA-binding activity of mutant p53. Collectively, the data suggest that Butein is a potential antitumor agent that restores p53 function in cancers harboring mutant p53-R273H or mutant p53-R175H. SignificanceButein restores the ability of mutant p53 to bind DNA by reversing its transition to the Loop3 (L3) state, endows p53 mutants with thermal stability and re-establishes their transcriptional activity to induce cancer cell death.

CDKN2A/p16 evaluation in cytology specimens.

CDKN2A/p16 evaluation in cytology specimens.

VprBP/DCAF1 regulates p53 function and stability through site-specific phosphorylation

VprBP (also known as DCAF1) is a recently identified kinase that is overexpressed in cancer cells and serves as a major determinant for epigenetic gene silencing and tumorigenesis. The role of VprBP in driving target gene inactivation has been largely attributed to its ability to mediate histone H2A phosphorylation. However, whether VprBP also phosphorylates non-histone proteins and whether these phosphorylation events drive oncogenic signaling pathways have not been explored. Here we report that serine 367 phosphorylation (S367p) of p53 by VprBP is a key player in attenuating p53 transcriptional and growth suppressive activities. VprBP catalyzes p53S367p through a direct interaction with the C-terminal domain of p53. Mechanistically, VprBP-mediated S367p inhibits p53 function in the wake of promoting p53 proteasomal degradation, because blocking p53S367p increases p53 protein levels, thereby enhancing p53 transactivation. Furthermore, abrogation of VprBP-p53 interaction by p53 acetylation is critical for preventing p53S367p and potentiating p53 function in response to DNA damage. Together, our findings establish VprBP-mediated S367p as a negative regulator of p53 function and identify a previously uncharacterized mechanism by which S367p modulates p53 stability.

Targeting USP2 regulation of VPRBP-mediated degradation of p53 and PD-L1 for cancer therapy

Since Mdm2 (Mouse double minute 2) inhibitors show serious toxicity in clinic studies, different approaches to achieve therapeutic reactivation of p53-mediated tumor suppression in cancers need to be explored. Here, we identify the USP2 (ubiquitin specific peptidase 2)-VPRBP (viral protein R binding protein) axis as an important pathway for p53 regulation. Like Mdm2, VPRBP is a potent repressor of p53 but VPRBP stability is controlled by USP2. Interestingly, the USP2-VPRBP axis also regulates PD-L1 (programmed death-ligand 1) expression. Strikingly, the combination of a small-molecule USP2 inhibitor and anti-PD1 monoclonal antibody leads to complete regression of the tumors expressing wild-type p53. In contrast to Mdm2, knockout of Usp2 in mice has no obvious effect in normal tissues. Moreover, no obvious toxicity is observed upon the USP2 inhibitor treatment in vivo as Mdm2-mediated regulation of p53 remains intact. Our study reveals a promising strategy for p53-based therapy by circumventing the toxicity issue.

GINS4 suppresses ferroptosis by antagonizing p53 acetylation with Snail

Ferroptosis is an iron-dependent oxidative, nonapoptotic form of regulated cell death caused by the destruction of redox homeostasis. Recent studies have uncovered complex cellular networks that regulate ferroptosis. GINS4 is a promoter of eukaryotic G1/S-cell cycle as a regulator of initiation and elongation of DNA replication, but little is known about its impact on ferroptosis. Here, we found that GINS4 was involved in the regulation of ferroptosis in lung adenocarcinoma (LUAD). CRISPR/Cas9-mediated GINS4 KO facilitated ferroptosis. Interestingly, depletion of GINS4 could effectively induce G1, G1/S, S, and G2/M cells to ferroptosis, especially for G2/M cells. Mechanistically, GINS4 suppressed p53 stability through activating Snail that antagonized the acetylation of p53, and p53 lysine residue 351 (K351 for human p53) was the key site for GINS4-suppressed p53-mediated ferroptosis. Together, our data demonstrate that GINS4 is a potential oncogene in LUAD that functions to destabilize p53 and then inhibits ferroptosis, providing a potential therapeutic target for LUAD.

Abstract 5289: Proteomic profile of breast carcinomas with unbalanced levels of progesterone receptor isoforms

Abstract Preclinical studies indicate that progesterone receptors (PR) play a relevant role in breast carcinogenesis. Even more, a misbalanced expression of PR isoforms A (PRA) and B (PRB) differentially affect breast cancer progression and only tumors with higher levels of PRA than PRB (PRA-H) respond to an antiprogestin treatment. There are controversial results regarding the prognosis of PRA-H luminal tumors compared with those with the opposite ratio (PRB-H tumors) highlighting the necessity to further understand the role of PR isoforms in tumor progression and to develop novel methods to discriminate these tumors without performing western blot studies. Along this line we have previously studied the transcriptome of PRA-H or PRB-H breast cancer samples, thus our aim is to expand these results and compare the proteome profile of PRA-H and PRB-H samples obtained from postmenopausal breast cancer patients. Nuclear (Nuc) and cytosolic (Cyt) protein fractions were obtained from 18 breast cancer samples classified as PRA-H or PRB-H and they were studied by LC-MS/MS (UltiMate 3000 LC system - Q Exactive HF-X mass spectrometer - Thermo). We observed 289 differentially deregulated proteins in Cyt (164 down and 125 up) and 301 in Nuc extracts (131 down and 170 up; logFC > 1, pval < 0.05). Gene set enrichment analysis of the Nuc fractions showed biological processes related to Cell junction organization (pval = 8,87e-05), Collagen formation (pval = 0,0005), and Cell-Cell communication processes (pval = 0,0035) in PRB-H tumors; while in PRA-H tumors, pathways related to Innate Immune System (pval = 8,8e-05), Class I MHC mediated antigen processing & presentation (pval = 8e-05) and Stabilization of p53 (pval = 0,0051) processes were enriched. Similar trends were observed in Cyt fractions. Individual candidates that were overrepresented in both fractions in PRB-H tumors are BAG3 and GH3, related to cell proliferation, and VWF, related to the activation of the Akt pathway. Overrepresented proteins in both fractions of PRA-H tumors are BST2, IFT27 related to invasion, and MIF associated with poor prognosis. As we were interested in looking for differential expressed proteins that could be tested in plasma samples to discriminate both tumor types, using the Vertebrate Secretome Database we focused on those that might be secreted. Noteworthy is CBP1 which was overrepresented in the PRB-H tumors and this was in agreement with the RNA-Seq data and with results obtained using preclinical models, repurposing this protein as one candidate of concern in the search for biomarkers. Other secretory proteins of interest are SFRP2 and SERPIND1, both highly expressed in PRA-H Cyt fractions. In conclusion, this study underscores the biological differences between PRA-H and PRB-H breast carcinomas and provides candidates that deserve to be tested as surrogate markers in plasma to discriminate patients that may benefit from an antiprogestin treatment. Citation Format: Andres M. Elia, Jana Sanchez, Rui Vitorino, Leo Saldain, Paula Martinez Vazquez, Javier Burruchaga, Eunice Spengler, Javier Muñoz, Paola Rojas, Luisa Helguero, Claudia Lanari. Proteomic profile of breast carcinomas with unbalanced levels of progesterone receptor isoforms. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5289.

Abstract 4875: The anti-tumor effects of GSK-3β inhibitor (9-1NG-41) in ETMR and ATRT pediatric brain tumors

Abstract Purpose Embryonal brain tumors (EBTs): ETMR (embryonal tumor with multilayered rosettes) and ATRT (atypical teratoid rhabdoid tumor) are aggressive malignancies with poor prognosis necessitating alternative strategies. GSK-3β is a serine threonine kinase often overexpressed in solid tumors and a positive regulator of NF-κB which promotes tumor growth and chemotherapy resistance. 9-ING-41 is a maleimide-based small molecule that crosses the blood brain barrier and selectively inhibits GSK-3β. Previously we demonstrated that 9-ING-41 decreases ETMR and ATRT cell viability through apoptosis and increases p53 signaling, however the exact mechanism leading to its activation is unknown. This study aims to determine the optimal dosing for 9-ING-41 and describe the phenotypic response of these cell lines to 9-ING-41 using cell viability assay, western blotting and neurosphere assay. This information will help further elucidate the mechanism of action for this drug. Methods ATRT cell lines ATRT 2141, ATRT-787199, ATRT 803499, LCH-091-07 and the ETMR cell line BT-183 were grown for 24hrs prior to 9-ING-41 treatment in DMEM and Neurocult medium, respectively. Cell viability was assessed after 72hrs of treatment using Cell Titer Glo 2.0. Western blots were analyzed for XIAP, cleaved caspase-3, p53, MDM2 after 24 and 48 hours at 200nM, 400nM and 600nM. Neurosphere assays were done by seeding two cells per well in a 96-well plate followed by treatment with 9-ING-41. Neurosphere frequency and size was monitored weekly for up to 4 weeks using Incucyte® S3 software. Pearson’s correlation graph was generated to determine the relationship between GSK-3β expression and sensitivity to 9-ING-41. Graph Pad Prism was used for statistical analysis and level of significance set to p=0.05. Results The IC50s of 9-ING-41 in cell lines ATRT 2141, ATRT-787199, ATRT 803499 and LCH-091-07 were 194nM, 558nM, 730nM & 5353nM, respectively. We observed decreased expression of NF-κB mediated anti-apoptotic marker XIAP and an increase in expression of apoptotic marker cleaved caspase-3 and tumor suppressor p53 in response to 9-ING-41. MDM2, a negative regulator of p53 had a significant increase in expression indicating it is not responsible for p53 increase which may suggest ATM pathway could be responsible for regulating p53 increase. GSK-3β expression in vitro, correlated with sensitivity to 9-ING-41. There was a dose dependent decrease in frequency and size of neurospheres in response to 9-ING-41. Conclusion 9-ING-41 decreases cell viability and neurosphere formation in ETMR and ATRT cell lines within clinically relevant doses. p53 stabilization is not mediated by MDM2 and may be downstream of the ATM pathway. Further studies are underway to demonstrate its efficacy in mouse models. Citation Format: Divya Gandra, Lauren Difabio, Kaitlyn H. Smith, Kimberly Q. McKinney, Giselle S. Sholler. The anti-tumor effects of GSK-3β inhibitor (9-1NG-41) in ETMR and ATRT pediatric brain tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4875.

Abstract 4950: Discovery of potent and selective CK1α molecular degrader with a favorable safety profile for acute myeloid leukemia and solid tumors

Abstract CK1α, an isoform of casein kinase 1 (CK1), promotes tumor growth by enhancing negative effects of MDM2 and MDMX on p53. Unlike other cancer types, the frequency of TP53 mutations is relatively low (< 20%) in acute myeloid leukemia (AML). Therefore, promoting apoptosis by activation of p53 pathway has been a promising strategy for treatment of AML with wild-type (WT) TP53. However, preclinical activities of p53 activators have not been fully translated into clinic, partly due to their on-target hematological toxicities. We hypothesized that inhibition of CK1α can be an alternative strategy. To develop a small molecule targeting CK1α, we identified a novel CK1α-selective molecular glue degrader (MGD), PIN-A1 through screening of compounds hijacking cereblon (CRBN) E3 ligase. Here, we report its robust pharmacological activities in various preclinical AML models as a single agent or in combination with other targeted therapies along with its superior safety profile to MDM2 inhibitors. First, we demonstrated PIN-A1 can form a ternary complex with CK1α and CRBN using TR-FRET assay. Selective degradation of CK1α by PIN-A1 was also confirmed by global proteomics analysis. PIN-A1 induced rapid degradation of CK1α in human AML MV-4-11 cells harboring WT TP53, followed by increasing the level of p53 protein and its downstream target genes, ultimately leading to apoptotic cell death. Consistent with these results, preferential sensitivity of AML cells with WT TP53 to the CK1α degrader was demonstrated in screening assay of broad panel of liquid cancer cell lines. When combined with other targeted therapies agents used for AML, PIN-A1 displayed strong synergistic effects in cell killing. To evaluate its pharmacological activity in vivo, PIN-A1 was tested in a xenograft model engrafted with MV-4-11 and a dissemination model of MOLM-14, respectively. Systemic administration of PIN-A1 alone resulted in robust antitumor activity consistent with > 90% CK1α degradation in tumor tissues, comparably achieved at a much lower dose in combo treatments. Importantly, animals remained tumor-free (5/8) in the MV-4-11 model or prolonged survival in the disseminated model even after they were no longer on the combination treatment of PIN-A1 with a targeted agent X. Lastly, while PIN-A1 had negligible effects on the viability of human PBMC with minimal activation of the p53 pathway at an efficacious dose range for MV-4-11 (Therapeutic index= 8,333), agent X induced p53 pathway and enhanced anti-leukemic activity to a similar extent in two cell types (Therapeutic index=4). Also, we found that the combination treatment of PIN-A1 with agent X had a substantial effect on several solid tumors driven by enhancing the stability and activity of p53. In summary, these results suggest that a CK1α MGD with its favorable safety profile has a potential to become an effective treatment option for advanced AML and solid tumors. Citation Format: Jinuk Kong, Jisu Park, Heekyu Lee, Hyunseok Kang, Deokjae Lee, Hyunsun Jo. Discovery of potent and selective CK1α molecular degrader with a favorable safety profile for acute myeloid leukemia and solid tumors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4950.

Abstract 3929: MDMX overexpression in cancer cells confers significant resistance to MDMX inhibitor XI-006 and may modulate chemosensitivity through suppressing p53 activation of pro-apoptotic factors

Abstract MDM2 inhibition has gained popularity in recent years as a therapeutic strategy in targeting both solid tumors and hematological malignancies, and several small molecule inhibitors of the p53-MDM2 binding interface have progressed into clinical trials in recent years. Alongside direct stabilization of p53, MDM2 has further been identified to have immune implications in terms of CD8+ T-cell mediated anti-tumor immunity and checkpoint-blockade therapies. However, little work has been done to explore the therapeutic targeting potential of related protein MDMX (MDM4). Pan-cancer analyses conducted by our lab (in part presented at the ASCO 2022 Annual Meeting) identify an important role of MDMX in several tumor types. Particularly, MDMX amplification is associated with a higher risk of brain and liver metastasis, and MDMX amplification itself also presents with significant frequency (10%) in glioblastoma multiforme (GBM). Notably, MDMX amplification also served as a better predictor of reduced overall survival in NSCLC following checkpoint-blockade. We have also previously reported on associations between MDMX amplification and CDKN2A deep deletions in melanoma, a predictor of favorable response to checkpoint blockade. Such findings establish the need for further exploration to be done and the role of MDMX both in cell phenotype and potential immune regulation to be better characterized. Preliminary data acquired from transient overexpression experiments using lipofection of MDMX cDNA and MDMX inhibitor XI-006 (NSC207895) alone and in combination with chemotherapy further supports the viability of MDMX-inhibition as a therapeutic strategy in several cell lines. Overexpression of MDMX in HCT116 p53WT cells demonstrably confers remarkable resistance to MDMX inhibitor XI-006 at a 72-hour timepoint (IC50 of 104.75 uM in overexpressing cells versus 29.03 uM in WT), and treatment with oxaliplatin reveals both reduced basal and post-treatment expression of p53-upregulated modulator of apoptosis (PUMA). Further mechanistic workup of this phenomenon is underway, particularly with an emphasis on immuno-oncological therapeutic translations. Altogether, initial findings ultimately establish the need for further investigation into the mechanistic basis of MDMX-correlated clinical outcomes and the therapeutic potential of MDMX inhibition. Citation Format: Andrew George, Arielle De La Cruz, Shengliang Zhang, Ilyas Sahin, Praveen Srinivasan, Maximilian Schwermann, Morgan Turcotte, Taylor Arnoff, Wafik S. El-Deiry. MDMX overexpression in cancer cells confers significant resistance to MDMX inhibitor XI-006 and may modulate chemosensitivity through suppressing p53 activation of pro-apoptotic factors. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3929.

Abstract 3719: Targeting the eIF6 and 60S ribosomal subunit interaction interface in cancers

Abstract Translational control is integral to cancer initiation and progression. A subset of translation initiation factors are deregulated in cancers to facilitate their rampant growth and proliferation. Eukaryotic translation initiation factor 6 (eIF6) is one such factor that is over expressed in many cancers including lung, colon, ovarian and breast cancers, and deregulation of eIF6 is correlated with a poor cancer prognosis. Association of eIF6 with 60S is critical for 60S assembly. However, eIF6 must be released from 60S prior to translation to permit inter subunit interactions between 60S and 40S and to facilitate the formation of translationally proficient 80S complex. Release of eIF6 is deregulated in the ribosomopathy- Shwachman Diamond Syndrome that is predisposed to leukemias. Also, loss of eIF6 markedly delays tumorigenesis without affecting normal growth, which presents eIF6 as a viable therapeutic target. A potential therapeutic strategy is to target the eIF6 and 60S ribosomal interaction interface. Through extensive biophysical analyses, we had identified residues that are critical for the interaction between eIF6 and 60S ribosomal subunit. We show that targeting these key residues in the eIF6-60S interaction interface markedly delays colonic cancer growth and inhibits protein synthesis. Interestingly, targeting eIF6 leads to an upregulation of p53 independent of the DNA damage response, suggesting that ribosomal stress contributes to the stabilization of p53. Future studies will determine the mRNA targets that are translationally deregulated by inactivation of eIF6. We will also determine the effect of targeting eIF6 function in inhibiting tumor growth and progression in vivo. Citation Format: Kavya Meena Harish, Aparna Biswas, Poonam Roshan, Sofia Origanti. Targeting the eIF6 and 60S ribosomal subunit interaction interface in cancers. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3719.

LIM domain-containing protein Ajuba inhibits chemotherapy-induced apoptosis by negatively regulating p53 stability in colorectal cancer cells.

LIM protein-domain containing protein Ajuba (encoded by AJUBA) functions as a scaffold protein to regulate protein-protein interactions, signalling transduction and genes transcription. AJUBA expression is higher in colorectal cancer (CRC) tissues than normal tissues, but its specific molecular function in CRC progression is still not very clear. Here, we found that, in CRC cancer cell lines, overexpression of AJUBA decreased p53 levels, whereas knock-down of AJUBA significantly increased p53 levels. Although the presence of Ajuba did not influence p53 transcription, it formed a complex with p53 and MDM2 to promote the degradation of p53. AJUBA overexpression reduced the sensitivity of cancer cells to chemotherapeutic drugs and vice versa. In addition, chemotherapeutic drugs significantly induced AJUBA expression, which was largely dependent on the presence of p53. Therefore, Ajuba formed a negative feedback loop to regulate p53 expression and activity. In conclusion, as a novel p53-negative regulator, Ajuba inhibits the apoptosis of CRC cells induced by chemotherapeutic drugs and it may be a new therapeutic target for CRC treatment.

Mitochondrial Ca2+ overload due to altered proteostasis amplifies apoptosis in C2C12 myoblasts under hypoxia: Protective role of nanocurcumin formulation.

Severe hypoxia triggers apoptosis leads to myofibers loss and is attributable to impaired intracellular calcium (iCa2+ ) homeostasis, resulting in reduced muscle activity. Hypoxia increases intracellular Ca2+ by activating the release of Ca2+ from iCa2+ stores, however, the effect of increased [iCa2+ ] on the mitochondria of muscle cells at high-altitude hypoxia is largely unexplored. This study examined mitochondrial Ca2+ overload due to altered expression of mitochondrial calcium uptake 1 (MICU1), that is, a gatekeeper of the mitochondrial Ca2+ uniporter, impaired mitochondrial membrane potential (ΔΨm). p53 stabilization and its translocation to the mitochondria were observed following disrupted mitochondrial membrane integrity in myoblasts under hypoxia. Furthermore, the downstream effects of p53 led to the upregulation of proapoptotic proteins (Bax, Caspase-3, and cytochrome C) in myoblasts under hypoxia. Nanocurcumin-pyrroloquinoline quinone formulation (NCF; Indian patent no. 302877), developed to address hypoxia-induced consequences, was found to be beneficial in maintaining mitochondrial Ca2+ homeostasis and limiting p53 translocation into mitochondria under hypoxia in muscle myoblasts. NCF treatment also modulates heat shock proteins and apoptosis-regulating protein expression in myoblasts. Conclusively, we proposed that mitochondrial Ca2+ overload due to altered MICU1 expression intensifies apoptosis and mitochondrial dysfunctionality. The study also reported that NCF could improve mitochondrial [Ca2+ ] homeostasis and antiapoptotic ability in C2C12 myoblasts under hypoxia.

Proteasome inhibitor bortezomib stabilizes and activates p53 in hematopoietic stem/progenitors and double-negative T cells in vivo

We have previously shown that proteasome inhibitor bortezomib stabilizes p53 in stem and progenitor cells within gastrointestinal tissues. Here, we characterize the effect of bortezomib treatment on primary and secondary lymphoid tissues in mice. We find that bortezomib stabilizes p53 in significant fractions of hematopoietic stem and progenitor cells in the bone marrow, including common lymphoid and myeloid progenitors, granulocyte-monocyte progenitors, and dendritic cell progenitors. The stabilization of p53 is also observed in multipotent progenitors and hematopoietic stem cells, albeit at lower frequencies. In the thymus, bortezomib stabilizes p53 in CD4-CD8- T cells. Although there is less p53 stabilization in secondary lymphoid organs, cells in the germinal center of the spleen and Peyer's patch accumulate p53 in response to bortezomib. Bortezomib induces the upregulation of p53 target genes and p53 dependent/independent apoptosis in the bone marrow and thymus, suggesting that cells in these organs are robustly affected by proteasome inhibition. Comparative analysis of cell percentages in the bone marrow indicates expanded stem and multipotent progenitor pools in p53R172H mutant mice compared with p53 wild-type mice, suggesting a critical role for p53 in regulating the development and maturation of hematopoietic cells in the bone marrow. We propose that progenitors along the hematopoietic differentiation pathway express relatively high levels of p53 protein, which under steady-state conditions is constantly degraded by Mdm2 E3 ligase; however, these cells rapidly respond to stress to regulate stem cell renewal and consequently maintain the genomic integrity of hematopoietic stem/progenitor cell populations.

Benzo(a)pyrene and Cerium Dioxide Nanoparticles in Co-Exposure Impair Human Trophoblast Cell Stress Signaling

Human placenta is a multifunctional interface between maternal and fetal blood. Studying the impact of pollutants on this organ is crucial because many xenobiotics in maternal blood can accumulate in placental cells or pass into the fetal circulation. Benzo(a)pyrene (BaP) and cerium dioxide nanoparticles (CeO2 NP), which share the same emission sources, are found in ambient air pollution and also in maternal blood. The aim of the study was to depict the main signaling pathways modulated after exposure to BaP or CeO2 NP vs. co-exposure on both chorionic villi explants and villous cytotrophoblasts isolated from human term placenta. At nontoxic doses of pollutants, BaP is bioactivated by AhR xenobiotic metabolizing enzymes, leading to DNA damage with an increase in γ-H2AX, the stabilization of stress transcription factor p53, and the induction of its target p21. These effects are reproduced in co-exposure with CeO2 NP, except for the increase in γ-H2AX, which suggests a modulation of the genotoxic effect of BaP by CeO2 NP. Moreover, CeO2 NP in individual and co-exposure lead to a decrease in Prx-SO3, suggesting an antioxidant effect. This study is the first to identify the signaling pathways modulated after co-exposure to these two pollutants, which are common in the environment.

HCINAP alleviates senescence by regulating MDM2 via p14ARF and the HDAC1/CoREST complex.

Cellular senescence is a major process affected by multiple signals and coordinated by a complex signal response network. Identification of novel regulators of cellular senescence and elucidation of their molecular mechanisms will aid the discovery of new treatment strategies for aging-related diseases. In the present study, we identified human coilin-interacting nuclear ATPase protein (hCINAP) as a negative regulator of aging. Depletion of cCINAP significantly shortened the lifespan of Caenorhabditis elegans and accelerated primary cell aging. Moreover, mCINAP deletion markedly promoted organismal aging and stimulated senescence-associated secretory phenotype in the skeletal muscle and liver from mouse models of radiation-induced senescence. Mechanistically, hCINAP functions through regulating MDM2 status by distinct mechanisms. On one hand, hCINAP decreases p53 stability by attenuating the interaction between p14ARF and MDM2; on the other hand, hCINAP promotes MDM2 transcription via inhibiting the deacetylation of H3K9ac in the MDM2 promoter by hindering HDAC1/CoREST complex integrity. Collectively, our data demonstrate that hCINAP is a negative regulator of aging and provide insight into the molecular mechanisms underlying the aging process.

Mechanism of Action p53

P53 is a 393 residue protein in humans made up of five proposed domains, with which the central DNA binding domain with 100-300 sequences very important for the direct binding of p53 in the promoters of its target genes to specific response elements. P53 is a tumor suppressor gene with cellular stress like oxygen deficiency, oxidative stress, radiation and carcinogens substances, is stimulated has major roles in translational regulation and feedback processes. A wide variety of damage signals that relate to the stability, post-translational alteration and recruitment of p53 to binding sites in chromatin which activate the p53 pathway. As a transcriptional activation, p53 mediates transcriptional changes which facilitate cell death, senescence or reversing and protective arrest of the cell cycle. P53 is a protein under intense investigation because it is necessary to prevent tumor, in human tumors have been found to deregulation of p53 activity. On this article study focuses the mechanism of suppressive p53 effects in the response to any stress and correlation of the mutation p53 with different tumor.

The role of ubiquitin pathway-mediated regulation of immune checkpoints in cancer immunotherapy.

With the continuous cognition of the relationship between tumor cells and tumor immune microenvironment, immunotherapy based on the immune checkpoint blockade has achieved great breakthroughs, led to improved clinical outcomes, and prolonged survival for cancer patients in recent years. Nevertheless, the de novo or acquired resistance to immunotherapy has greatly counteracted the efficacy, leading to a 20%-40% overall response rate. Thus, further in-depth understanding of the regulation of the tumor microenvironment and antitumor immunity is urgently warranted. Ubiquitination-mediated protein degradation plays vital roles in protein stabilization, activation, and dynamics as well as in cellular homeostasis modulation. The dysregulated ubiquitination and deubiquitination are closely related to the changes in physiological and pathological processes, which subsequently result in a variety of diseases including cancer. In this review, the authors first summarize the current knowledge about the involvement of the ubiquitin-proteasome system in tumor development with the ubiquitin conjugation-regulated stability of p53, phosphatase and tensin homolog, and Myc protein as examples, then dissect the potential implications of ubiquitination-mediated immune checkpoints degradation in tumor microenvironment and immune responses, and finally discuss the effects of therapeutically targeting the ubiquitin-proteasome pathway on immunotherapy, with the goal of providing deep insights into the exploitation of more precise and effective combinational therapy against cancer.

Tumor suppressor p53 regulates heat shock factor 1 protein degradation in Huntington’s disease

p53 and HSF1 are two major transcription factors involved in cell proliferation and apoptosis, whose dysregulation contributes to cancer and neurodegeneration. Contrary to most cancers, p53 is increased in Huntington's disease (HD) and other neurodegenerative diseases, while HSF1 is decreased. p53 and HSF1 reciprocal regulation has been shown in different contexts, but their connection in neurodegeneration remains understudied. Using cellular and animal models of HD, we show that mutant HTT stabilized p53 by abrogating the interaction between p53 and E3 ligase MDM2. Stabilized p53 promotes protein kinase CK2 alpha prime and E3 ligase FBXW7 transcription, both of which are responsible for HSF1 degradation. Consequently, p53 deletion in striatal neurons of zQ175 HD mice restores HSF1 abundance and decrease HTT aggregation and striatal pathology. Our work shows the mechanism connecting p53 stabilization with HSF1 degradation and pathophysiology in HD and sheds light on the broader molecular differences and commonalities between cancer and neurodegeneration.