MDM2 Protein Expression Research Articles

Prognostic Importance of PTEN, p53, and MDM2 Expressions in Endometrioid and Serous-Type Endometrial Carcinomas

Aim: Endometrial carcinomas (ECs) are neoplasms with the highest rate of change in the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway. In this study, the relationship among PTEN, MDM2, and p53 protein expression in the PI3K/AKT/mTOR pathway with clinicopathological data in endometrioid endometrial carcinomas (EECs) and serous-type endometrial carcinomas (SECs) was evaluated. Material and Method: A hundred and twenty cases of patients who underwent hysterectomy for EC between 2009 and 2021 were included in the study. Thirty cases of SEC and 90 cases of EEC were evaluated. EEC cases consist of grades 1-3 tumors, and each group includes 30 patients. p53 was examined in two groups as normal/wild type and abnormal/mutant type. PTEN and MDM2 were examined in two groups: positive and negative. The relationship among p53, PTEN, and MDM2 immunohistochemical expression status with histological grade, myometrial invasion, cervical invasion, lymphovascular invasion (LVI), metastatic lymph nodes, presence of tumor in peritoneal fluid, tumor stage, and overall and progression-free survival was evaluated. Results: Loss of PTEN was associated with EEC compared to SEC (p

The role of MDM2 in angiogenesis: implications for endothelial tip cell formation.

In the present study, we examined the role of MDM2 in the angiogenesis process and its potential association with the sprouting of endothelial tip cells. To address this, we performed hypoxia-treated gastric cancer cells (HGC-27) to quantitative RT-PCR and Western blot analysis to measure the levels of MDM2 and VEGF-A mRNA and protein expression. Subsequently, we employed siRNA to disrupt MDM2 expression, followed by hypoxia treatment. The expression levels of MDM2 and VEGF-A mRNA and protein were subsequently reassessed. Additionally, ELISA was utilized to quantify the secretion levels of VEGF-A in each experimental group. A conditioned medium derived from HGC-27 cells treated with different agents was employed to assess its influence on the formation of EA.hy926 endothelial tip cells, using various techniques including Transwell plates migration assays, wound healing experiments, vascular formation assays, scanning electron microscopy, and immunofluorescence staining. These findings demonstrated that the in vitro knockdown of MDM2 in the conditioned medium exhibited significant inhibitory effects on endothelial cell migration, wound healing, and vascular formation. Additionally, the intervention led to a reduction in the presence of CD34+ tip cells and the formation of filopodia in endothelial cells, while partially restoring the integrity of tight junctions. Subsequent examination utilizing RNA-seq revealed that the suppression of MDM2 in HGC-27 cells resulted in the downregulation of the PI3K/AKT signaling pathway. Consequently, this downregulation led to an elevation in angiogenic effects induced by hypoxia.

An MDM2 degrader shows potent cytotoxicity to MDM2-overexpressing acute lymphoblastic leukemia cells with minimal toxicity to normal cells/tissues

The MDM2 oncogene is amplified and/or overexpressed in various human cancers and elevated expression of MDM2 protein acts as a survival factor promoting cancer progression through both p53-dependent and -independent pathways. Here, we report a novel small-molecule chemical compound (MX69-102) that we identified to induce MDM2 protein degradation, resulting in reactivation of p53, inhibition of XIAP, and potent cell growth inhibition and apoptosis in MDM2-overexpressing acute lymphoblastic leukemia (ALL) in vitro and in vivo. We have previously identified a compound (MX69) that binds to the MDM2 C-terminal RING domain and induces MDM2 protein degradation. In the present study, we performed structural modifications of MX69 and selected analog MX69-102, showing increased MDM2-targeting activity. MX69-102 exhibited significantly enhanced inhibitory and apoptotic effects on a group of MDM2-overexpressing ALL cell lines in vitro with IC50 values of about 0.2 μM, representing an approximately 38-fold increase in activity compared to MX69. MX69-102 also showed effective inhibition on xenografted human MDM2-overexpressing ALL in SCID mice. Importantly, MX69-102 had minimal or no inhibitory effect on normal human hematopoiesis in vitro and was very well tolerated in vivo in animal models. Based on the strong inhibitory and apoptotic activity against MDM2-overexpressing ALL, along with minimal or no toxicity to normal cells/tissues, MX69-102 is a candidate for further development as a novel MDM2-targeted therapeutic drug for refractory/MDM2-overexpressing ALL.

Association of MDM2 Overexpression in Ameloblastomas with MDM2 Amplification and BRAFV600E Expression.

Ameloblastoma is a rare tumor but represents the most common odontogenic neoplasm. It is localized in the jaws and, although it is a benign, slow-growing tumor, it has an aggressive local behavior and high recurrence rate. Therefore, alternative treatment options or complementary to surgery have been evaluated, with the most promising one among them being a targeted therapy with the v-Raf murine sarcoma viral oncogene homologue B (BRAF), as in ameloblastoma the activating mutation V600E in BRAF is common. Studies in other tumors have shown that the synchronous inhibition of BRAF and human murine double minute 2 homologue (MDM2 or HDM2) protein is more effective than BRAF monotherapy, particularly in the presence of wild type p53 (WTp53). To investigate the MDM2 protein expression and gene amplification in ameloblastoma, in association with BRAFV600E and p53 expression. Forty-four cases of ameloblastoma fixed in 10% buffered formalin and embedded in paraffin were examined for MDM2 overexpression and BRAFV600E and p53 expression by immunohistochemistry, and for MDM2 ploidy with fluorescence in situ hybridization. Sixteen of forty-four (36.36%) cases of ameloblastoma showed MDM2 overexpression. Seven of sixteen MDM2-positive ameloblastomas (43.75%) were BRAFV600E positive and fifteen of sixteen MDM2-positive ameloblastomas (93.75%) were p53 negative. All MDM2 overexpressing tumors did not show copy number alterations for MDM2. Overexpression of MDM2 in ameloblastomas is not associated with MDM2 amplification, but most probably with MAPK activation and WTp53 expression. Further verification of those findings could form the basis for the use of MDM2 expression as a marker of MAPK activation in ameloblastomas and the trial of dual BRAF/MDM2 inhibition in the management of MDM2-overexpressing/BRAFV600E-positive/WTp53 ameloblastomas.

Comparison of three-dimensional cell culture techniques of dedifferentiated liposarcoma and their integration with future research.

Background: Dedifferentiated liposarcoma is a formidable sarcoma subtype due to its high local recurrence rate and resistance to medical treatment. While 2D cell cultures are still commonly used, 3D cell culture systems have emerged as a promising alternative, particularly scaffold-based techniques that enable the creation of 3D models with more accurate cell-stroma interactions. Objective: To investigate how 3D structures with or without the scaffold existence would affect liposarcoma cell lines growth morphologically and biologically. Methods: Lipo246 and Lipo863 cell lines were cultured in 3D using four different methods; Matrigel® ECM scaffold method, Collagen ECM scaffold method, ULA plate method and Hanging drop method, in addition to conventional 2D cell culture methods. All samples were processed for histopathological analysis (HE, IHC and DNAscope™), Western blot, and qPCR; moreover, 3D collagen-based models were treated with different doses of SAR405838, a well-known inhibitor of MDM2, and cell viability was assessed in comparison to 2D model drug response. Results: Regarding morphology, cell lines behaved differently comparing the scaffold-based and scaffold-free methods. Lipo863 formed spheroids in Matrigel® but not in collagen, while Lipo246 did not form spheroids in either collagen or Matrigel®. On the other hand, both cell lines formed spheroids using scaffold-free methods. All samples retained liposarcoma characteristic, such as high level of MDM2 protein expression and MDM2 DNA amplification after being cultivated in 3D. 3D collagen samples showed higher cell viability after SAR40538 treatment than 2D models, while cells sensitive to the drug died by apoptosis or necrosis. Conclusion: Our results prompt us to extend our investigation by applying our 3D models to further oncological relevant applications, which may help address unresolved questions about dedifferentiated liposarcoma biology.

The Antiproliferative and Proapoptotic Effects of Cucurbitacin B on BPH-1 Cells via the p53/MDM2 Axis.

Cucurbitacin B (Cu B), a triterpenoid compound, has anti-inflammatory and antioxidant activities. Most studies only focus on the hepatoprotective activity of Cu B, and little effort has been geared toward exploring the effect of Cu B on the prostate. Our study identified that Cu B inhibited the proliferation of the benign prostatic hyperplasia epithelial cell line (BPH-1). At the molecular level, Cu B upregulated MDM2 and thrombospondin 1 (THBS1) mRNA levels. Immunocytochemistry results revealed that the protein expressions of p53 and MDM2 were upregulated in BPH-1 cells. Furthermore, Cu B upregulated THBS1 expression and downregulated COX-2 expression in the BPH-1 cell supernatant. Altogether, Cu B may inhibit prostate cell proliferation by activating the p53/MDM2 signaling cascade and downregulating the COX-2 expression.

10014-CBMS-2 CONCURRENT TARGETING OF MDM4 AND MDM2 USING CEP-1347 AS AN EFFECTIVE THERAPEUTIC STRATEGY FOR P53 WILD-TYPE MALIGNANT BRAIN TUMORS

Abstract The development of MDM4 inhibitors as an approach to reactivating p53 in human cancer is attracting increasing attention; however, whether they affect the function of MDM2 and how they interact with MDM2 inhibitors remain unknown. We addressed this question in the present study using CEP-1347, an inhibitor of MDM4 protein expression. The effects of CEP-1347, the genetic and/or pharmacological inhibition of MDM2, and their combination on the p53 pathway in malignant brain tumor cell lines expressing wild-type p53 were investigated by RT-PCR and Western blot analyses. The growth inhibitory effects of CEP-1347 alone or in combination with MDM2 inhibition were examined by dye exclusion and/or colony formation assays. The treatment of malignant brain tumor cell lines with CEP-1347 markedly increased MDM2 protein expression, while blocking CEP-1347-induced MDM2 overexpression by genetic knockdown augmented the effects of CEP-1347 on the p53 pathway and cell growth. Blocking the MDM2-p53 interaction using the small molecule MDM2 inhibitor RG7112, but not MDM2 knockdown, reduced MDM4 expression. Consequently, RG7112 effectively cooperated with CEP-1347 to reduce MDM4 expression, activate the p53 pathway, and inhibit cell growth. The present results suggest CEP-1347-induced MDM2 overexpression combined with the selective inhibition of MDM2's interaction with p53, while preserving its ability to inhibit MDM4 expression, as a novel and rational strategy to effectively reactivate p53 in wild-type p53 cancer cells.

MDM2 amplification is rare in gastric cancer

The MDM2 proto-oncogene (MDM2) is a primary negative regulator of p53. The latter is frequently mutated in gastric cancer (GC). In the present study, we aimed to validate gene amplification, protein expression, and the putative tumor biological function of MDM2 in a well-characterized Western GC cohort. MDM2 amplification and protein expression were studied in a cohort of 327 GCs by fluorescence in situ hybridization (FISH) and immunohistochemistry. Gene amplification and protein expression were correlated with diverse clinicopathological patient characteristics including patient outcome. Immunohistochemically, 97 GCs (29.7%) were categorized as MDM2 positive and 230 GCs (70.3%) as negative. An amplification of MDM2 was found in 11 (3.4%) cases without evidence of intratumoral heterogeneity. Nine of these eleven (81.8%) cases showed MDM2 protein expression. MDM2 amplification correlated significantly with MDM2 protein expression (p < 0.001). On a case-by-case analysis, MDM2-amplified cases showed varied histological phenotypes and were most commonly microsatellite stable; EBV, HER2, and MET negative; and FGFR2 positive. A single case harbored both, MDM2 amplification and TP53 mutation. MDM2 amplification and MDM2 expression, respectively, did not correlate with overall or tumor-specific survival. Our targeted analysis of MDM2 in a well-characterized cohort of GC patients showed that MDM2 amplification is rare, of no specific histological phenotype, and may not be always mutually exclusive with TP53 mutations. Given the low number of cases, currently, no diagnostic or therapeutic recommendation related to MDM2 amplification can be given for GC of Western origin.

Antagonizing MDM2 Overexpression Induced by MDM4 Inhibitor CEP-1347 Effectively Reactivates Wild-Type p53 in Malignant Brain Tumor Cells.

The development of MDM4 inhibitors as an approach to reactivating p53 in human cancer is attracting increasing attention; however, whether they affect the function of MDM2 and how they interact with MDM2 inhibitors remain unknown. We addressed this question in the present study using CEP-1347, an inhibitor of MDM4 protein expression. The effects of CEP-1347, the genetic and/or pharmacological inhibition of MDM2, and their combination on the p53 pathway in malignant brain tumor cell lines expressing wild-type p53 were investigated by RT-PCR and Western blot analyses. The growth inhibitory effects of CEP-1347 alone or in combination with MDM2 on inhibition were examined by dye exclusion and/or colony formation assays. The treatment of malignant brain tumor cell lines with CEP-1347 markedly increased MDM2 protein expression, while blocking CEP-1347-induced MDM2 overexpression by genetic knockdown augmented the effects of CEP-1347 on the p53 pathway and cell growth. Blocking the MDM2-p53 interaction using the small molecule MDM2 inhibitor RG7112, but not MDM2 knockdown, reduced MDM4 expression. Consequently, RG7112 effectively cooperated with CEP-1347 to reduce MDM4 expression, activate the p53 pathway, and inhibit cell growth. The present results suggest the combination of CEP-1347-induced MDM2 overexpression with the selective inhibition of MDM2's interaction with p53, while preserving its ability to inhibit MDM4 expression, as a novel and rational strategy to effectively reactivate p53 in wild-type p53 cancer cells.

Autologous blood transfusion promotes autophagy and inhibits hepatocellular carcinoma progression through HIF-1α signalling pathway.

To explore the molecular mechanism of autologous blood transfusion promoting autophagy of hepatocellular carcinoma (HCC) cells and inhibiting the HCC progression through HIF-1α signalling pathway. This is a research paper. Rat hepatocellular carcinoma model and HepG2 cell model were built. The rats with HCC were conducted a surgery, and their blood was collected for detection to detect the recurrence and metastasis of the rats. Western blot was used to analysed the expression of HIF-1α, TP53, MDM2, ATG5 and ATG14 protein. The apoptosis rate of HepG2 cells was detected by flow cytometry, and autophagosomes were observed by transmission electron microscopy. HIF-1α expression was measured by immunofluorescence assay. The expressions of HIF-1α, TP53, MDM2, ATG5 and ATG14 protein were highest in model + autoblood group compared with the model group. HIF-1α content of model group was higher, but content of TP53, MDM2, ATG5 and ATG14 in the model group is the second. The highest apoptosis rate was found in HepG2 + autoblood group. The number of autophagosomes in HepG2 + autoblood was obviously larger than that of HepG2 + autoblood + inhibitor. HIF-1α expression of immunofluorescence assay showed that high expression of HIF-1α was clearly observed in HepG2 and HepG2 + autoblood group from confocal observation. However, there was no HIF-1α protein expression in HepG2 + autoblood + inhibitor group. The migration rate in HepG2 group, HepG2 + autoblood group and HepG2 + autoblood + inhibitor group was 85.71 ± 7.38%, 14.36 ± 6.54% and 61.25 ± 5.39%, respectively. Autologous blood transfusion promotes autophagy of HCC cells through HIF-1α signalling pathway, which further inhibits HCC migration and erosion.

Identification of p53-target genes in human papillomavirus-associated head and neck cancer by integrative bioinformatics analysis.

Head and neck cancer (HNC) is a highly prevalent and heterogeneous malignancy. Although extensive efforts have been made to advance its treatment, the prognosis remained poor with increased mortality. Human papillomaviruses (HPV) have been associated with high risk in HNC. TP53, a tumor suppressor, is the most frequently altered gene in HNC, therefore, investigating its target genes for the identification of novel biomarkers or therapeutic targets in HPV-related HNC progression is highly recommended. Transcriptomic profiles from three independent gene expression omnibus (GEO) datasets, including 44 HPV+ and 70 HPV- HNC patients, were subjected to integrative statistical and Bioinformatics analyses. For the top-selected marker, further in-silico validation in TCGA and GTEx databases and experimental validation in 65 (51 HPV- and 14 HPV+) subjects with histologically confirmed head and neck squamous cell carcinoma (HNSCC) have been performed. A total of 498 differentially expressed genes (DEGs) were identified including 291 up-regulated genes and 207 down-regulated genes in HPV+ compared to HPV- HNSCC patients. Functional annotations and gene set enrichment analysis (GSEA) showed that the up-regulated genes were significantly involved in p53-related pathways. The integrative analysis between the Hub-genes identified in the complex protein-protein network and the top frequent genes resulting from GSEA showed an intriguing correlation with five biomarkers which are EZH2, MDM2, PCNA, STAT5A and TYMS. Importantly, the MDM2 gene showed the highest gene expression difference between HPV+ and HPV- HNSCC (Average log2FC = 1.89). Further in-silico validation in a large HNSCC cohort from TCGA and GTEx databases confirmed the over-expression of MDM2 in HPV+ compared to HPV- HNSCC patients (p = 2.39E-05). IHC scoring showed that MDM2 protein expression was significantly higher in HPV+ compared to HPV- HNSCC patients (p = 0.031). Our findings showed evidence that over-expression of MDM2, proto-oncogene, may affect the occurrence and proliferation of HPV-associated HNSCC by disturbing the p53-target genes and consequently the p53-related pathways.

Abstract 470: A MDM2 degrader inhibits cell proliferation and growth of MDM2-overexpressing acute lymphoblastic leukemia in SCID mice

Abstract The MDM2 oncogene is amplified and/or overexpressed in various human cancers and elevated expression of MDM2 protein acts as a survival factor promoting cancer progression mainly through inhibition of the tumor suppressor p53. Here, we report a novel small-molecule chemical compound (MX69-114b) that we identified to induce MDM2 protein degradation resulting in reactivation of p53 and potent cell growth inhibition and apoptosis in MDM2-overexpressing acute lymphoblastic leukemia (ALL). We have previously identified a compound (MX69) that binds to the MDM2 C-terminal RING domain and induces MDM2 protein degradation. In the present study, we performed structural modification of MX69 and selected analog MX69-114b showing increased MDM2-targeting activity. MX69-114b exhibited significantly enhanced inhibitory and apoptotic effects on a group of MDM2-overexpressing ALL cell lines in vitro with IC50 values of 0.08-0.14 µM, representing a &amp;gt;80-100-fold increase in activity compared to MX69. MX69-114b also showed inhibitory effects on xenografted human MDM2-overexpressing ALL in SCID mice at a much lower dose than did MX69. Importantly, MX69-114b had minimal or no inhibitory effect on normal human hematopoiesis in vitro and was very well tolerated in vivo in animal models. Based on the strong inhibitory and apoptotic activity against MDM2-overexpressing ALL, along with minimal or no toxicity to normal cells/tissues, MX69-114b is a candidate for further development as a novel MDM2-targeted therapeutic drug for refractory ALL. Citation Format: tao Liu, Lubing Gu, Anna Mui, Zhongzhi Wu, Wei Li, Muxiang Zhou. A MDM2 degrader inhibits cell proliferation and growth of MDM2-overexpressing acute lymphoblastic leukemia in SCID mice [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 470.

462 RNA-Based Therapeutics Targeting the Oncogenic Splicing Factor TRA2β Rewire Glioblastoma Cell Transcriptomes and Inhibit Their Proliferation

INTRODUCTION: Glioblastomas are an aggressive brain tumor that, despite current treatment paradigms, carry a poor prognosis. Novel therapies aimed at specific glioblastoma alterations are needed. Alternative RNA splicing is a critical step in gene expression that allows a single gene to encode multiple RNA and subsequently protein isoforms. Alternative splicing becomes dysregulated in human tumors, including glioblastoma, through alterations in upstream regulatory splicing factor proteins such as TRA2β, an oncogene that enhances glioma cell proliferation. Despite these known alterations, targeting alternative splicing in glioblastomas has not been leveraged therapeutically. METHODS: U87MG glioblastoma cells were treated with splice-switching antisense oligonucleotides (ASOs) targeting the TRA2β transcript (ASO-1570) or non-targeting control (ASO-CTL). Cancer-relevant phenotypes, including proliferation and apoptosis, were measured using high-content imaging. Transcriptomic splicing signatures were defined using high-depth RNA-sequencing with computational tools that quantify percent splicing event inclusion (PSI) and validated using RT-PCR and western blotting. RESULTS: ASO-1570 treatment increased inclusion of a poison-exon in TRA2β leading to decreased coding transcripts and subsequent reductions in TRA2β protein expression compared to ASO-CTL. ASO-1570 significantly decreased cell proliferation and increased apoptosis. Mechanistically, ASO-1570 treated cells exhibited significant differences in alternatively spliced events, impacting genes involved in cancer-relevant pathways such as p53 and mTOR signaling. For example, ASO-1570 led to increased exon skipping in MDM2 leading to decreased MDM2 protein expression and increased p53 wild-type expression. ASO-1570 treatment also impacted growth of U87MG 3D-neurospheres, suggesting efficacy in advanced models that better capture in vivo conditions. CONCLUSIONS: Glioblastoma cells are sensitive to ASO-mediated TRA2β knockdown, which mechanistically induced transcriptome wide changes that impact cancer-related pathways. Further testing of this ASO in vivo may open novel avenues for its use as a targeted glioblastoma therapeutic.

Ginkgo Biflavones Cause p53 Wild-Type Dependent Cell Death in a Transcription-Independent Manner of p53

Ginkgo biloba, as a medicinal plant in both traditional and western medicine, emerged as a potential therapeutic agent for the management of a variety of diseases, but ginkgo biflavones (bilobetin, isoginkgetin, and ginkgetin) application in cancer therapy and underlying mechanisms of action remained elusive. In the present study, we identified ginkgo biflavones as potential p53 activators that could enhance p53 protein expression level by inhibiting MDM2 protein expression. At the same time, they induced cell death independent of p53 transcriptional activity. Moreover, ginkgetin was a standout among ginkgo biflavones that reduced the survival of HCT-116 cells by induction of apoptosis and G2/M phase arrest. Furthermore, ginkgo biflavones induced ROS generation significantly, which resulted in ferroptosis. Finally, we provide evidence that ginkgetin strengthened the antitumor effect of fluorouracil (5-FU) in the HCT-116 colon cancer xenograft model. To sum up, ginkgo biflavones represent a new class of p53 activator that depends on the p53 wild-type status and warrants further exploration as potential anticancer agents.

Reduced MDM2 and MDM4 Protein, but Not mRNA, Expression Is Associated with More Severe Disease in Acute Myeloid Leukemia (AML), Myelodysplastic Syndromes (MDS), and Chronic Myelomoncytic Leukemia (CMML)

Background: Following studies suggesting overexpression of MDM2 and MDM4 in AML, clinical trials were conducted in AML with MDM2 inhibitors, generally combined with chemotherapy, with so far relatively limited results. On the other hand , in those studies, MDM2 and 4 expressionwas mainly assessed on mRNA and the indirect estimation of protein expression using immunohistochemistry on mononuclear cells (MNCs). In addition, results were often conflicting, based in particular on different cells studied and techniques used. We analyzed MDM2 and MDM4 expressioin AML, MDS and CMML, analyzing both mRNA and protein levels, the latter by flow cytometry. Methods: Bone marrow samples from 113 (53 AML, 17 of them in complete remission (CR) after treatment, 50 MDS or 10 CMML) adult patients (classified according to WHO2016) seen at Hôpital Saint-Louis, Paris, were collected between 2018 and 2021 . Bone marrow samples collected from hip surgery of 17 elderly aged-matched donors without hematological disorder were used as controls. For the mRNA Human,CD34+ cells were purified from MNCs and total mRNA purified. RT-qPCR was performed and expression of each mRNA was analyzed in the CD34+ population. MDM2, MDM4 and p53 protein expression was determined in all samples with monoclonal antibody staining and flow cytometry analysis. In controls and in MDS and CMML patients without excess of marrow blasts (<5%), protein expression was assessed in the CD34+/CD45low population In patients with excess of marrow blasts (5% or greater,), because of the heterogeneity of CD34 expression on blast cells, protein expression was assessed on the CD45low/SSC blast population. Data were acquired using a BD FACS Canto II. Results: For protein expression, In CD34+/CD45low cells from MDS/CMML patients without excess of blasts, MFI was 795.7 for MDM2, 2555 for MDM4 and 500.6 for p53, with no significant differences with controls for p53 (p=0.3620) but lower levels in patients for MDM2 (p=0.0123) and MDM4 (p=0.0337). In the blast population of patients with excess of blasts, MDM2, MDM4 and p53 protein expression were drastically decreased in MDS (MFI: MDM2=320.8, p<0.0001; MDM4=1017, p<0.0001; p53=137.5, p<0.0001), AML (MFI: MDM2=233.2, p<0.0001; MDM4=833.8, p<0.0001; p53=111.8, p<0.0001) and CMML (MFI: MDM2=262.2, p=0.0001; MDM4=851.7, p<0.0001; p53=113.3, p=0.0007) (Fiigure A) compared with control CD34+/CD45low cells. Comparison between CD34+/CD45low bone marrow cells from patients without excess of blasts and CD45low/SSC blasts of patients with excess of blasts (AML, MDS, CMML) showed in the latter group lower expression of each protein for MDS (MFI: MDM2 p<0.0001; MDM4 p=0.0005; p53 p=0.0007), AML (MFI: MDM2 p<0.0001; MDM4 p<0.0001; p53 p<0.0001) and CMML (MFI: MDM2 p=0.005; MDM4 p=0.0165; p53 p=0.0268). We found a negative correlation for MDM2 (r=-0.3191, p=0.0018), MDM4 (r=-0.3925, p<0.0001), p53 (r =0.3195, p=0.0018) between protein expression levels and marrow blast percentage. Expression of CD34+/CD45low cells from patients in CR (MFI: MDM2= 1797; MDM4 =2993; p53=971) showed no significant differences with the control CD34+/CD45low cells (MFI:MDM2 p=0,4533; MDM4 p=0.1420; p53 p=0.2891). For MDM2 and MDM4 proteins, patients whose expression value was lower than the median had significant poorer survival than those with a higher value (MDM2 p=0.0209; MDM4 p= 0.1025; p53 p=0.0304) (Figure B). In MDS, however, protein expression had no significant impact on the probability of progression to AML (MDM2 p=0.5636; MDM4 p= 0.1488; p53p=0.7816). No significant differences in mRNA expression were found between CD34+ cells from healthy donors and patients without excess blast or patients with excess blast. We observed no correlation between the mRNA and protein expression levels Conclusions: We found in AML, MDS and CMML a discrepancy between mRNA levels and protein levels for MDM2, MDM4 and p53, and overall low MDM2 and MDM4 protein expression, which might explain the relatively low efficacy of MDM2 inhibitors observed so far in clinical trials . The relatively high MDM2 and p53 levels observed in control bone marrows possibly also explains, at least in part, the reported toxicity of these drugs on myeloid cells in clinical trials. Figure 1View largeDownload PPTFigure 1View largeDownload PPT Close modal

Novel ginsenoside derivatives induce apoptosis in HepG-2 cells via the MDM2-p53 signaling pathway

In this study, 6-aryl-5-cyanopyrimidines and quinazolinones were introduced into panaxadiol (PD) to synthesize 25 new panaxadiol derivatives. The cytotoxicity of these compounds against three cancer cells and one normal cell was examined by methylthiazoletetrazolium (MTT) cytotoxicity experiment. The findings demonstrated that PD cyanopyrimidine derivatives have superior anti-proliferative effects over quinazoline derivatives. Among them, PM14 had the strongest inhibitory activity on the proliferation of human hepatoma cell lines (HepG-2), the IC50 value was 2.13 ± 0.20 μM. 4′,6-diamidino-2-phenyl-indole (DAPI) staining showed that PM14 made HepG-2 nucleus shrink and had obvious apoptosis. Mechanistic studies confirmed that the derivative PM14 activates p53 signaling pathway by reducing the expression of MDM2 protein, and further induces an increase in the intracellular Bax/Bcl-2 ratio, down-regulated the expression of Caspase-3, up-regulated Cl-Caspase-3 expression, eventually leading to cell apoptosis. This lays the foundation for subsequent development of derivatives with stronger anti-proliferative activity.

4′,7-Di-O-methylnaringenin (DMNG), a naringenin derivative, activates p53 signal pathway through down-regulating MDM2

• DMNG is a potential p53 signaling activator. • DMNG inhibits HCT-116 cells proliferation via arresting the progression of G2/M cell cycle and inducing apoptosis. • DMNG is unable to cause DNA damage, and also cannot induce ROS stress. • DMNG activates p53 signal pathway through down-regulating MDM2. Naringenin, a citrus flavonoid that possessed various biological activities, had emerged as a potential therapeutic agent for the management of a variety of diseases, but naringenin derivatives’ application in cancer therapy and underlying mechanisms of action were not fully understood. Our recent work had shown that 4′,7-Di-O-methylnaringenin (DMNG) exerted its anti-colon cancer activity and the underlying mechanisms of action. We reported that DMNG could activate p53 signal pathway, dependent of p53 wild type status. We observed that DMNG decreased the survival of HCT-116 cells by induction of apoptosis and G2/M phase arrest. We further demonstrated that, in a dose- and time-dependent manner, DMNG effectively downregulated the MDM2 protein expression at protein translation level. Hence, our study unearthed that DMNG was a potential therapeutic and anti-metastatic agent for human colon cancer through down-regulating MDM2 and activating p53 pathway.

Molecular mechanism of GANT61 combined with doxorubicin in the treatment of gliomas based on network pharmacology

Gliomas are common malignant intracranial tumors. Efficacious targeted therapy against gliomas is lacking. GANT61 combined with the chemotherapy drug doxorubicin for treatment of glioma (LN-229) cells, and the effect of their combination, was tested. The molecular mechanism was explored by target prediction, along with functional analysis using the Gene Ontology (GO) database, enrichment analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG) database, construction of protein–protein interaction (PPI) networks, and protein expression. Combination of GANT61 plus doxorubicin could inhibit the growth of LN-229 cells effectively. Wound-healing data and expression of migration proteins related to epithelial-to-mesenchymal transition showed that this combination could inhibit the migration of LN-229 cells. Sixty-one targets of drug and disease intersected. Functional analysis revealed negative regulation of apoptosis, positive regulation of cell proliferation, and other biological processes related to apoptosis and proliferation. Pathway-enrichment analysis showed drug combination to be related to the cyclic adenosine monophosphate signaling pathway, pathways in cancer, and Hedgehog signaling pathway. Measurement of expression of several proteins related to these pathways revealed expression of BIRC5, GLi1 and GLi2, MMP3 and MMP9 proteins to decrease, and expression of MDM2 and P53 proteins to decrease and increase, respectively. This study provides a: (a) new direction for targeted therapy of gliomas; (b) theoretical basis for drug research and molecular-mechanism research on gliomas. How to cite: Chen J, Zhang Q, Zhang G et al. Molecular mechanism of GANT61 combined with doxorubicin in the treatment of gliomas based on network pharmacology. Electron J Biotechnol 2022;55. https://doi.org/10.1016/j.ejbt.2021.11.001.

The ubiquitin‐proteasomal pathway in glaucomatous lamina cribrosa cells

AbstractPurposePrimary open‐angle glaucoma (POAG) is an age‐related fibrotic condition and a leading cause of blindness worldwide. POAG‐related damage is initiated within the lamina cribrosa (LC) region of the optic nerve head, driven by the pathological activation of resident LC cells. LC cells bear striking similarities to proliferative, apoptotic‐resistant myofibroblasts known to be responsible for organ fibrosis. Myofibroblast dysregulation is linked to targeted proteasomal degradation of p53 by the E3 ubiquitin‐protein ligase MDM2 (mouse‐double‐minute‐2) thus negating p53’s important regulatory role in cell‐cycle/apoptosis. This project aims to evaluate the role of p53, MDM2, and the ubiquitin‐proteasomal pathway in glaucomatous LC cells.MethodsPrimary human normal LC (NLC) and glaucoma LC (GLC) cells (n = 3 donors) were cultured under standard conditions and treated for 48 hours with RG‐7112 (p53‐MDM2 interaction inhibitor, Abcam). The p53‐MDM2 ubiquitin‐proteasomal pathway was analysed by real‐time polymerase chain reaction (qRT‐PCR) for gene expression and protein levels via western blotting.ResultsMDM2 gene expression levels were significantly elevated (p = 0.006) in GLC cells (1.00 ± 0.12) versus NLC cells (0.89 ± 0.08). p53‐MDM2 inhibitor RG‐7112 treatment caused a further significant (p = 0.001) increase in MDM2 transcription levels in GLC cells (1.17 ± 0.04). p53 transcription levels were equivocal between GLC cells (0.88 ± 0.09) and NLC cells (0.87 ± 0.08), with RG‐7112 treatment leading to a significant increase (p = 0.028) in p53 transcription levels in GLC cells (0.95 ± 0.06). Western blot analysis showed significant decreased protein expression levels of p53 (0.76 ± 0.09)(p = 0.047) and increased protein expression of MDM2 (1.57 ± 0.33)(p = 0.042) in GLC cells compared to NLC. Interestingly, p53‐MDM2 inhibitor RG‐7112 treatment increased p53 (1.14 ± 0.43)(p = 0.267) and decreased MDM2 protein expression levels (0.92 ± 0.25)(p = 0.06) in GLC cells.ConclusionsOur data suggest the ubiquitin‐proteasomal pathway is significantly dysregulated in GLC cells with MDM2 led p53 protein degradation negatively impacting its key role as “guardian of the genome”. Targeting the p53 ubiquitin‐proteasomal pathway in lamina cribrosa fibrosis may lead to future novel therapeutic interventions.

Effect of RITA on TP53 Mutant Human Mantle Cell Lymphoma Cell Line and Its Mechanism

To investigate the effect of RITA on TP53 mutant human mantle cell lymphoma (MCL) cell line Mino and its possible mechanism. Mino cells were cultured in RPMI-1640 and treated with RITA at a concentration of 0-16 μmol/L for 24,48,72 hours. Cell viability was assessed by CCK-8 assay. The cells were treated by RITA (0-8 μmol/L) for 48 h, the cell apoptosis induced by RITA was detected by annexin V/PI flow cytometry. Western blot was performed to evaluate the expression of protein BCL-2, Caspase-3, Cleaved Caspase-3, PARP, MDM2, and P53 in Mino cells. After treatment with 0.5, 1, 2, 4, 8, and 16 μmol/L RITA for 48 h, the proliferation inhibition rate of Mino cells was (1.2±5.6)%, (14.9±4.9)%, (41.7±5.0)%, (61.8±2.4)%, (70.2±2.8)%, and (70.8±2.4)%, respectively. RITA could inhibit the proliferation of Mino cells significantly, and statistical analysis showed that the inhibition rate was increased with the increasing of RITA concentration (r=0.767). After the cells were treated by 4 μmol/L RITA for 24, 48, and 72 h, the proliferation inhibition rate was (25.2±3.8)%, (61.8±2.4)%, and (87.0±0.7)%, respectively. Satistical analysis showed that the inhibition rate was also increased with the increasing of treatment time (r=0.978). The apoptosis rate of Mino cells treated by 0, 2, 4, and 8 μmol/L RITA for 48 h was (5.4±0.4)%, (15.3±0.6)%, (38.7±1.7)%, and (50.8±1.1)%, respectively, and it showed dose-dependent manner (r=0.961). Western blot showed that with the increasing of RITA concentration, the BCL-2 protein expression was decreased in a dose-dependent manner (r=0.932), moreover, PARP cleavage and Caspase-3 activation were found, while the protein expression of MDM2 and P53 showed no change. RITA can inhibit the proliferation and induce the apoptosis of Mino cells significantly. The mechanism may be dependent on the Caspase pathway, but independent on the P53 pathway.