MDM2 Inhibitor Research Articles

Design, Synthesis and Preliminary In‐Vitro Activity of 6‐Hydroxyalkyl β‐Carboline Derivatives for the Development of Drug Conjugates Targeting MDM2

AbstractThe mouse‐double‐minute‐2 (MDM2) protein, the main downregulator of the tumor suppressor p53 protein, represents a promising target for the development of novel anticancer therapies. However, the lack of selectivity and poor effectiveness in tumors bearing mutated‐p53 impaired the approval of several MDM2 inhibitors for the market. In this context, the possibility of generating drug‐conjugates within a MDM2 inhibitor is a growing research area aimed to overcome these drawbacks. Considering the promising MDM2 inhibition by the β‐carboline‐based 1, in this work we explored the introduction of a new functionalization on it for a future conjugation while preserving its anticancer properties. Based on preliminary docking studies, we synthesized derivatives 2 a–d having linear hydroxyalkyl chains with different lengths at the 6‐position of the β‐carboline core, which effectively preserved the submicromolar IC50 on wild‐type‐p53‐U87MG glioblastoma cell line observed with 1. Candidates 2 a, d showed the functionalization was tolerated with respect of bioactivity also on mutated‐p53‐U138MG glioblastoma cell line, and their hydroxyl groups proved to be easily accessible when coupled to 4‐pentynoic‐N,N’‐dimethylethylenediamine affording derivatives 10 a, d with high yields. In summary, our results led to generating novel 6‐hydroxyalkyl‐β‐carboline compounds displaying a suitable hydroxyl‐site useful to improve the efficacy and/or the tumor specificity of 1 through conjugation strategies.

Exploration of marine natural compounds as promising MDM2 inhibitors for treating triple-negative breast cancer: insights from molecular docking, ADME/T studies, molecular dynamics simulation and MM-PBSA binding free energy calculations

Triple-negative breast cancer (TNBC), the most aggressive form of breast cancer, presents a significant mortality risk owing to its elevated potential for metastasis. The overexpression of Murine Double Minute 2 homolog (MDM2) protein, a key suppressor of tumour suppressor p53, in TNBC amplifies its growth, advancement, and invasiveness. Thus, inhibiting MDM2 protein emerges as a compelling strategy to enhance the efficacy of TNBC treatment. We aimed to identify novel potential MDM2 inhibitors from natural marine compounds, known for their distinctive chemical structures and heightened anticancer activities, utilizing molecular docking, ADME/T analysis, molecular dynamics (MD) simulations, MM-PBSA calculations, and in silico PASS predictions. A marine compound library was constructed for initial screening purpose and the molecular docking analysis revealed that two marine compounds, namely 10,11-dihydrosodwanone B and sodwanone T, exhibited significantly higher binding affinity (− 9.6 kcal/mol and − 9.1 kcal/mol, respectively) compared to the established inhibitor nutlin-3a (− 8.4 kcal/mol). ADME/T investigations were conducted to ensure the drug-likeness properties and safety of these compounds. Additionally, in silico PASS tool predicted that both compounds possess a heightened potential for anticancer activities. Molecular dynamics simulations (100 ns) and MM-PBSA calculations indicated that sodwanone T formed a relatively more stable complex and had a higher binding-free energy with MDM2, respectively. In conclusion, this research suggests sodwanone T as a promising candidate for further testing and development as an MDM2 inhibitor for potential therapeutic applications against TNBC. Nevertheless, substantial experimental and clinical investigations are necessary to enhance its applicability in clinical settings.Graphical abstract

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

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

TMOD-19. GERMLINEELP1 DEFICIENCY SENSITIZES CEREBELLAR GRANULE NEURON PROGENITORS TO SHH MEDULLOBLASTOMA

Abstract Germline loss-of-function (LOF) variants in Elongator complex protein 1 (ELP1) are the most prevalent predisposing genetic events observed in medulloblastoma (MB), accounting for 30% of the Sonic Hedgehog 3 subtype (SHH-3). Molecularly, ELP1-associated SHH-MBs acquire somatic PTCH1 mutations in >80% of cases, and universal loss-of-heterozygosity of the wild-type ELP1 and PTCH1 alleles through loss of chromosome-arm 9q, resulting in their biallelic inactivation. Notably, germline ELP1 LOF occurs mutually exclusive with somatic/germline TP53 mutations in the SHH-3 subtype, suggesting that genetic perturbation of either ELP1 or TP53 may promote similar downstream oncogenic consequences in cerebellar granule neuron progenitors (GNPs), the accepted cellular origin of SHH-MB. Despite these findings, the molecular, biochemical, and cellular mechanism(s) by which ELP1-deficiency provokes malignant pathogenesis remain unknown. In this study, we sought to close this knowledge gap and functionally determine why children harboring pathogenic ELP1 germline variants are at an increased risk of developing SHH-MB. Mice were genetically engineered to mimic heterozygous Elp1 LOF (Elp1HET). We studied the effect of loss of ELP1 in GNPs using a combination of molecular profiling, immunophenotyping, and cellular assays. GNPs from Elp1HET exhibited a spectrum of molecular and biochemical hallmarks of malignant transformation including increased DNA replication stress, DNA damage, accelerated cell cycle progression, and stalled differentiation. Orthotopic transplantation of Elp1HET GNPs engineered to harbor somatic Ptch1 inactivation yielded SHH-MB-like tumors with compromised p53 signaling, providing an explanation for the specificity of ELP1-associated tumors in SHH-3, and their exclusivity with TP53-mutant tumors. Treatment of ELP1-mutant patient-derived xenografts with an FDA-approved MDM2 inhibitor reactivated p53-dependent apoptosis and extended survival. Collectively, our findings functionally substantiate the role of ELP1 deficiency in predisposition to SHH-3 MB and nominate therapeutic strategies to overcome p53 inhibition as a rational treatment option.

Role of AhR-Hsp90-MDM2-mediated VDR ubiquitination in PM2.5-induced renal toxicity

Background and objectivesThe kidney is a primary target for the accumulation of particulate matter (PM2.5). This study aimed to investigate PM2.5-induced renal toxicity mechanisms, focusing on the aryl hydrocarbon receptor (AhR)-Hsp90-MDM2 axis and its impact on vitamin D receptor (VDR) ubiquitination. MethodsPM2.5's role in activating the AhR and its downstream pathways was investigated using in vitro and in vivo models. Renal damage and therapeutic effects in PM2.5-exposed and paricalcitol-treated mice were evaluated using weight measurements, histopathology, and scanning electron microscopy. AhR, Hsp90, and VDR localization and expression in renal cells were assessed using FISH and Western blot. Protein interactions were examined using co-immunoprecipitation. Differentially expressed gene (DEG) analysis of GEO datasets was used to identify related proteins and genes. ResultsPM2.5 exposure caused significant renal damage in mice, including increased serum creatinine, albuminuria, and histopathological deterioration, which were alleviated by paricalcitol. PM2.5 induced the nuclear translocation of AhR and Hsp90 and reduced nuclear VDR expression; paricalcitol reversed these effects. Immunohistochemistry confirmed these findings. PM2.5 upregulated the NLRP3/caspase-1/IL-1β/IL-18 axis, which was reversed by paricalcitol treatment. Inhibition of Hsp90 increased nuclear VDR expression through MDM2 mediation. DEG analysis identified VDR-regulated genes; PM2.5 increased the mRNA levels of IL-6, IL-2, and CXCL8, which were downregulated by Hsp90 and MDM2 inhibitors, with VDR agonists further decreasing these levels. ConclusionThis study reveals a novel mechanism of PM2.5-induced renal toxicity through the AhR-Hsp90-MDM2 axis, promoting VDR ubiquitination and degradation and increasing inflammation. These findings provide a foundation for future studies and lay the groundwork for developing targeted interventions to mitigate the public health impact of PM2.5 exposure.

Enhanced Anti-Melanoma Activity of Nutlin-3a Delivered via Ethosomes: Targeting p53-Mediated Apoptosis in HT144 Cells.

This study evaluated ethosomes as a novel nanodelivery system for nutlin-3a, a known MDM2 inhibitor and activator of the p53 pathway, to improve nutlin-3a's poor solubility, limiting its bio-distribution and therapeutic efficacy. The potential of nutlin-3a-loaded ethosomes was investigated on two in vitro models of melanoma: the HT144 cell line p53wild-type and the SK-MEL-28 cell line p53mutated. Nutlin-3a-loaded ethosomes were characterized for their physicochemical properties and used to treat melanoma cells at different concentrations, considering nutlin-3a solution and empty ethosomes as controls. The biological effects on cells were evaluated 24 and 48 h after treatment by analyzing the cell morphology and viability, cell cycle, and apoptosis rate using flow cytometry and the p53 pathway's activation via Western blotting. The results indicate that ethosomes are delivery systems able to maintain nutlin-3a's functionality and specific biological action, as evidenced by the molecular activation of the p53 pathway and the biological events leading to cell cycle block and apoptosis in p53wild-type cells. Nutlin-3a-loaded ethosomes induced morphological changes in the HT144 cell line, with evident apoptotic cells and a reduction in the number of viable cells of over 80%. Furthermore, nutlin-3a-loaded ethosomes successfully modulated two p53-regulated proteins involved in survival/apoptosis, with up to a 2.5-fold increase in membrane TRAIL-R2 and up to an 8.2-fold decrease in Notch-1 (Notch intracellular domain, NICD) protein expression. The expression of these molecules is known to be altered or dysfunctional in a large percentage of melanoma tumors. Notably, ethosomes, regardless of their nutlin-3a loading, exhibited the ability to reduce HT144 melanoma cellular migration, as assessed in real time using xCELLigence, likely due to the modification of lipid rafts, suggesting their potential antimetastatic properties. Overall, nutlin-3a delivery using ethosomes appears to be a significantly effective means for upregulating the p53 pathway and downregulating active Notch-1, while also taking advantage of their unexpected ability to reduce cellular migration. The findings of this study could pave the way for the development of specific nutlin-3a-loaded ethosome-based medicinal products for cutaneous use.

MDM2 inhibition is associated with the emergence of TP53-altered clonal hematopoiesis

MDM2 inhibition is associated with the emergence of TP53-altered clonal hematopoiesis

Introducing Chemoselective Peptide Conjugation via N-Alkylation of Pyridyl-alanine: Solution and Solid Phase Applications.

A novel chemoselective peptide conjugation via late-stage N-alkylation of pyridyl-alanine (PAL) in the solution and solid phase, namely, NAP, is demonstrated. The method constructs functionally diverse and highly stable N-alkylated conjugates with various peptides. Notably, conjugations in the solid phase offered a more economical process. The method can provide the opportunity for dual labeling along with a cysteine handle in a peptide chain. Finally, we showcased that the antiproliferative activities of the p53 peptide (MDM2 inhibitor) could be 2-fold enhanced via NAP conjugation with the RGD peptide (selective integrin binder).

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.

Linked regulation of genome integrity and senescence-associated inflammation by p53.

Genomic instability and inflammation are distinct hallmarks of aging, but the connection between them is poorly understood. Understanding their interrelationship will help unravel new mechanisms and therapeutic targets of aging and age-associated diseases. Here we report a novel mechanism directly linking genomic instability and inflammation in senescent cells through a mitochondria-regulated molecular circuit driven by p53 and cytoplasmic chromatin fragments (CCF). We show, through activation or inactivation of p53 by genetic and pharmacologic approaches, that p53 suppresses CCF accumulation and the downstream inflammatory senescence-associated secretory phenotype (SASP), without affecting cell cycle arrest. p53 activation suppressed CCF formation by promoting DNA repair, and this is reflected in maintenance of genomic integrity, particularly in subtelomeric regions, as shown by single cell genome resequencing. Activation of p53 in aged mice by pharmacological inhibition of MDM2 reversed signatures of aging, including age- and senescence-associated transcriptomic signatures of inflammation and age-associated accumulation of monocytes and macrophages in liver. Remarkably, mitochondria in senescent cells suppressed p53 activity by promoting CCF formation and thereby restricting ATM-dependent nuclear DNA damage signaling. These data provide evidence for a mitochondria-regulated p53 signaling circuit in senescent cells that controls DNA repair, genome integrity, and senescence- and age-associated inflammation. This pathway is immunomodulatory in mice and a potential target for healthy aging interventions by small molecules already shown to activate p53.

Long-term Tolerance to Islet Transplantation via Targeted Reduction of beta cell-specific T cells.

Activated beta-cell reactive CD4 + and CD8 + T effector cells undergo a profound DNA-damage response which is targetable by small molecule inhibitors of the p53 and cell cycle pathways that lead to apoptosis. The use of a combination of MDM2 and WEE1 inhibitors, which termed "p53 potentiation with checkpoint abrogation" (PPCA), conferred significant therapeutic efficacy in treating mouse models of new onset T1D. Specific targeting of these T effector cells by PPCA results in a loss of inflammatory T cell subsets, notably proliferation CD4 + Th0 and Th1 subsets and CD8 + T effector memory cells, as determined by single cell RNA-seq studies with the preservation of T regulatory cells. When autologous islet grafts are given to established diabetic NOD mice, a single course of PPCA results in long-term islet graft acceptance, restoration of normoglycemia and loss of beta cell specific CD4 + and CD8 + T cells. PPCA shows promise as a potential means of estimating islet graft tolerance in T1D recipients of islet graft transplantation.

BH3-mimetics or DNA-damaging agents in combination with RG7388 overcome p53 mutation-induced resistance to MDM2 inhibition

The development of drug resistance reduces the efficacy of cancer therapy. Tumor cells can acquire resistance to MDM2 inhibitors, which are currently under clinical evaluation. We generated RG7388-resistant neuroblastoma cells, which became more proliferative and metabolically active and were less sensitive to DNA-damaging agents in vitro and in vivo, compared with wild-type cells. The resistance was associated with a mutation of the p53 protein (His193Arg). This mutation abated its transcriptional activity via destabilization of the tetrameric p53-DNA complex and was observed in many cancer types. Finally, we found that Cisplatin and various BH3-mimetics could enhance RG7388-mediated apoptosis in RG7388-resistant neuroblastoma cells, thereby partially overcoming resistance to MDM2 inhibition.

Combination of MDM2 and Targeted Kinase Inhibitors Results in Prolonged Tumor Control in Lung Adenocarcinomas With Oncogenic Tyrosine Kinase Drivers and MDM2 Amplification.

MDM2, a negative regulator of the TP53 tumor suppressor, is oncogenic when amplified. MDM2 amplification (MDM2amp) is mutually exclusive with TP53 mutation and is seen in 6% of patients with lung adenocarcinoma (LUAD), with significant enrichment in subsets with receptor tyrosine kinase (RTK) driver alterations. Recent studies have shown synergistic activity of MDM2 and MEK inhibition in patient-derived LUAD models with MDM2amp and RTK driver alterations. However, the combination of MDM2 and RTK inhibitors in LUAD has not been studied. We evaluated the combination of MDM2 and RTK inhibition in patient-derived models of LUAD. In a RET-fusion LUAD patient-derived model with MDM2amp, MDM2 inhibition with either milademetan or AMG232 combined with selpercatinib resulted in long-term in vivo tumor control markedly superior to either agent alone. Similarly, in an EGFR-mutated model with MDM2amp, combining either milademetan or AMG232 with osimertinib resulted in long-term in vivo tumor control, which was strikingly superior to either agent alone. These preclinical in vivo data provide a rationale for further clinical development of this combinatorial targeted therapy approach.

Synthetic lethality of combined ULK1 defection and p53 restoration induce pyroptosis by directly upregulating GSDME transcription and cleavage activation through ROS/NLRP3 signaling

BackgroundHigh expression of ubiquitin ligase MDM2 is a primary cause of p53 inactivation in many tumors, making it a promising therapeutic target. However, MDM2 inhibitors have failed in clinical trials due to p53-induced feedback that enhances MDM2 expression. This underscores the urgent need to find an effective adaptive genotype or combination of targets.MethodsKinome-wide CRISPR/Cas9 knockout screen was performed to identify genes that modulate the response to MDM2 inhibitor using TP53 wild type cancer cells and found ULK1 as a candidate. The MTT cell viability assay, flow cytometry and LDH assay were conducted to evaluate the activation of pyroptosis and the synthetic lethality effects of combining ULK1 depletion with p53 activation. Dual-luciferase reporter assay and ChIP-qPCR were performed to confirm that p53 directly mediates the transcription of GSDME and to identify the binding region of p53 in the promoter of GSDME. ULK1 knockout / overexpression cells were constructed to investigate the functional role of ULK1 both in vitro and in vivo. The mechanism of ULK1 depletion to activate GSMDE was mainly investigated by qPCR, western blot and ELISA.ResultsBy using high-throughput screening, we identified ULK1 as a synthetic lethal gene for the MDM2 inhibitor APG115. It was determined that deletion of ULK1 significantly increased the sensitivity, with cells undergoing typical pyroptosis. Mechanistically, p53 promote pyroptosis initiation by directly mediating GSDME transcription that induce basal-level pyroptosis. Moreover, ULK1 depletion reduces mitophagy, resulting in the accumulation of damaged mitochondria and subsequent increasing of reactive oxygen species (ROS). This in turn cleaves and activates GSDME via the NLRP3-Caspase inflammatory signaling axis. The molecular cascade makes ULK1 act as a crucial regulator of pyroptosis initiation mediated by p53 activation cells. Besides, mitophagy is enhanced in platinum-resistant tumors, and ULK1 depletion/p53 activation has a synergistic lethal effect on these tumors, inducing pyroptosis through GSDME directly.ConclusionOur research demonstrates that ULK1 deficiency can synergize with MDM2 inhibitors to induce pyroptosis. p53 plays a direct role in activating GSDME transcription, while ULK1 deficiency triggers upregulation of the ROS-NLRP3 signaling pathway, leading to GSDME cleavage and activation. These findings underscore the pivotal role of p53 in determining pyroptosis and provide new avenues for the clinical application of p53 restoration therapies, as well as suggesting potential combination strategies.

616: Targeting PSMA7 in combination with RT and MDM2 inhibition enhances cell death in p53 wild-type GBM

616: Targeting PSMA7 in combination with RT and MDM2 inhibition enhances cell death in p53 wild-type GBM

Astilbin Induces Apoptosis in Oral Squamous Cell Carcinoma through p53 Reactivation and Mdm-2 Inhibition.

Oral squamous cell carcinoma (OSCC) is a frequently occurring malignancy in the head and neck region. The most commonly mutated gene in OSCC is the tumor suppressor gene p53 (TP53), linked to lower survival and treatment resistance in OSCC patients. Astilbin is a flavonoid amongst several herbal treatments with a variety of pharmacological actions mainly including antioxidant, anti-inflammatory, and anti-cancer characteristics. This study evaluated the effects of astilbin on proliferation of OSCC cell lines SCC90 and SCC4 (bearing a p53 mutation) in relevance to p53 and Mdm-2 pathways. Astilbin inhibited the proliferation of SCC4 and SCC90 cells in a dose- and time-dependent manner. The IC50 values for both the cell lines were about 75 μM for astilbin. A p53 activator (RITA) was used to determine the effects of astilbin on p53 activity, and the results demonstrated synergistic reduction in cell growth. However, when combined with pifithrin-α (a p53 inhibitor), astilbin demonstrated a strong inhibition of its response. Astilbin reduced the mitochondrial membrane potential in SCC4 cells, which is a sign of apoptotic activity. Astilbin decreased the amounts of Mdm-2 (negative regulator of p53) and increased the expression of the p53 gene and protein. In a p53-dependent manner, astilbin suppressed the ability of SCC4 cells to form colonies and heal wounds. This was followed by the induction of mitochondrial intrinsic apoptosis via the activation of caspases 9 and 3, cleavage of PARP, and the suppression of pro-apoptotic Bid. Astilbin-induced p53-mediated apoptosis in OSCC cells as herbal medicinal ingredients.

Tandem mass tag-based quantitative proteomic analysis of metformin's inhibitory effects on ovarian cancer cells.

Metformin (MET), a type 2 diabetes treatment, has attracted increased attention for its potential antitumor properties; however, the precise mechanism underlying this activity remains unclear. Our previous in vivo and in vitro studies revealed MET's inhibitory effect on ovarian cancer, with the synergistic effects of MET and the MDM2 inhibitor RG7388 contributing to ovarian cancer treatment. This study further explores the mechanism underlying MET's inhibition of ovarian cancer. Following MET treatment, we analyzed the differentially expressed proteins in ovarian cancer cells using a tandem mass tag (TMT)-based proteomic approach coupled with bioinformatics. Using A2780 and SKOV3 ovarian cancer cells, we identified six upregulated and two downregulated proteins after MET treatment. Bioinformatics analysis revealed that these proteins predominately affect ovarian cancer cells by regulating iron ion transport, iron ion homeostasis, and mitochondrial and ribosomal functions. Validation via western blot confirmed MET-induced elevation of hydroxybutyrate dehydrogenase type 2 (BDH2) protein expression levels in A2780 and SKOV3 cells. Overall, our findings suggest that combining MET with other metabolic drugs, such as iron-chelating agents and mitochondrial inhibitors, may result in synergistic antitumor effects, thereby offering novel avenues for ovarian cancer treatment development.

MDM2 inhibitor APG-115 synergizes with ABT-199 to induce cell apoptosis in chronic lymphocytic leukemia.

Although clinical outcomes in chronic lymphocytic leukemia (CLL) have greatly improved with several approved small molecular inhibitors, acquired resistance does occur, leading to disease progression and eventual death. Thus, the effort to explore novel inhibitors and combination therapeutic regimens is needed. The inhibition of MDM2-p53 interaction to restore p53 function has been regarded as a potential strategy for treating different cancers. We investigated the effects of novel MDM2 inhibitor APG-115 in CLL. We found that APG-115 treatment upregulated the expression of p53, MDM2, and p21 at the mRNA and protein level. APG-115 inhibited cell proliferation, induced apoptosis, and arrested the cell cycle at G0/G1 stage. Moreover, APG-115 inhibited the expression of BCL-2, BCL-xL, and MCL-1, and suppressed the activation of AKT and ERK signaling pathways. APG-115 combined with the BCL2 inhibitor, ABT-199 (venetoclax), led to further inhibition of the expression of BCL-2 family anti-apoptotic proteins and consequently enhanced cell death. Collectively, this study demonstrates that APG-115 activates p53 and thus inhibits multiple pro-survival mechanisms, which provides a rational explanation for APG-115 efficiency in inducing cell apoptosis in CLL. The synergistic effect of APG-115 with ABT-199 suggested a potential combination application in CLL therapy.

Oscillatory Dynamics and Regulatory Mechanisms of the p53-Per2 Network in DNA-Damaged Cells.

Circadian rhythm disruptions are linked to increased cancer risk and unfavorable prognosis in patients with cancer, highlighting the critical role of the interplay between the circadian rhythm factor Per2 and the tumor suppressor p53. This brief presents, for the first time, a mathematical model to capture the dynamics of the p53-Per2 network in DNA-damaged cells. The model accurately describes the different stages of the process from unstressed cells to cellular repair and finally to apoptosis as the degree of DNA damage increases. Furthermore, it is found that increasing the inhibition of Per2 by p53 leads to the phase advance of Per2 oscillations, whereas by modulating the inhibition of Mdm2 by Per2, an independent amplitude modulation of active p53 can be achieved, with the range of modulation increasing with the strength of the inhibition. Moreover, the effects of time delays inherent in the transcription, translation, and nuclear translocation of Per2 on the circadian rhythm of DNA-damaged cells are quantitatively investigated by theoretical analyses. It is found that time delays can induce stable oscillations through a supercritical Hopf bifurcation, thereby maintaining the circadian function of DNA-damaged cells and enhancing their DNA-damage repair capacity. This study proposes new insights into cancer prevention and treatment strategies.

Induction of the Mdm2 gene and protein by kinase signaling pathways is repressed by the pVHL tumor suppressor

The tumor suppressor von Hippel-Lindau, pVHL, is a multifaceted protein. One function is to dock to the hypoxia-inducible transcription factor (HIF) and recruit a larger protein complex that destabilizes HIF via ubiquitination, preventing angiogenesis and tumor development. pVHL also binds to the tumor suppressor p53 to activate specific p53 target genes. The oncogene Mdm2 impairs the formation of the p53-pVHL complex and activation of downstream genes by conjugating nedd8 to pVHL. While Mdm2 can impact p53 and pVHL, how pVHL may impact Mdm2 is unclear. Like p53 somatic mutations, point mutations are evident in pVHL that are common in renal clear cell carcinomas (RCC). In patients with RCC, Mdm2 levels are elevated, and we examined whether there was a relationship between Mdm2 and pVHL. TCGA and DepMap analysis revealed that mdm2 gene expression was elevated in RCC with vhl point mutations or copy number loss. In pVHL reconstituted or deleted isogenetically match RCC or MEF cell lines, Mdm2 was decreased in the presence of pVHL. Furthermore, through analysis using genetic and pharmacological approaches, we show that pVHL represses Mdm2 gene expression by blocking the MAPK-Ets signaling pathway and blocks Akt-mediated phosphorylation and stabilization of Mdm2. Mdm2 inhibition results in an increase in the p53-p21 pathway to impede cell growth. This finding shows how pVHL can indirectly impact the function of Mdm2 by regulating signaling pathways to restrict cell growth.