Mdm2 in growth signaling and cancer

EVA1A reverses lenvatinib resistance in hepatocellular carcinoma through regulating PI3K/AKT/p53 signaling axis

Lenvatinib is a commonly used first-line drug for the treatment of advanced hepatocellular carcinoma (HCC). However, its clinical efficacy is limited due to the drug resistance. EVA1A was a newly identified tumor suppressor, nevertheless, the impact of EVA1A on resistance to lenvatinib treatment in HCC and the potential molecular mechanisms remain unknown. In this study, the expression of EVA1A in HCC lenvatinib-resistant cells is decreased and its low expression was associated with a poor prognosis of HCC. Overexpression of EVA1A reversed lenvatinib resistance in vitro and in vivo, as demonstrated by its ability to promote cell apoptosis and inhibit cell proliferation, invasion, migration, EMT, and tumor growth. Silencing EVA1A in lenvatinib-sensitive parental HCC cells exerted the opposite effect and induced resistance to lenvatinib. Mechanistically, upregulated EVA1A inhibited the PI3K/AKT/MDM2 signaling pathway, resulting in a reduced interaction between MDM2 and p53, thereby stabilizing p53 and enhancing its antitumor activity. In addition, upregulated EVA1A suppressed the PI3K/AKT/mTOR signaling pathway and promoted autophagy, leading to the degradation of mutant p53 and attenuating its oncogenic impact. On the contrary, loss of EVA1A activated the PI3K/AKT/MDM2 signaling pathway and inhibited autophagy, promoting p53 proteasomal degradation and mutant p53 accumulation respectively. These findings establish a crucial role of EVA1A loss in driving lenvatinib resistance involving a mechanism of modulating PI3K/AKT/p53 signaling axis and suggest that upregulating EVA1A is a promising therapeutic strategy for alleviating resistance to lenvatinib, thereby improving the efficacy of HCC treatment.

The roles of ERIANIN in tumor and innate immunity and its' perspectives in immunotherapy

Traditional Chinese medicine has been used in China for thousands of years. In 2022, the 14th Five-Year Plan for the Development of Traditional Chinese Medicine was released, aiming to enhance traditional Chinese medicine health services and improve policies and systems for high-quality traditional Chinese medicinal development by 2025. ERIANIN, the main component of the traditional Chinese medicine Dendrobium, plays an important role in anti-inflammatory, antiviral, antitumor, antiangiogenic, and other pharmacological effects. ERIANIN has broad-spectrum antitumor effects, and its tumor-suppressive effects have been confirmed in the study of various diseases, such as precancerous lesions of the stomach, gastric cancer, liver cancer, lung cancer, prostate cancer, bladder cancer, breast cancer, cervical cancer, osteosarcoma, colorectal cancer, leukaemia, nasopharyngeal cancer and melanoma through the multiple signaling pathways. Thus, the aim of this review was to systematically summarise the research on ERIANIN with the aim of serving as a reference for future research on this compound and briefly discuss some future perspectives development of ERIANIN in combined immunotherapy.

Comprehensive review on signaling pathways of dietary saponins in cancer cells suppression

Nutrigenomics utilizes high-throughput genomic technologies to reveal changes in gene and protein levels. Excitingly, ever-growing body of scientific findings has provided sufficient evidence about the interplay between diet and genes. Cutting-edge research and advancements in genomics, epigenetics and metabolomics have deepened our understanding on the role of dietary factors in the inhibition of carcinogenesis and metastasis. Dietary saponins, a type of triterpene glycosides, are generally found in Platycodon grandifloras, Dioscorea oppositifolia, asparagus, legumes, and sea cucumber. Wealth of information has started to shed light on pleiotropic mechanistic roles of dietary saponins in cancer prevention and inhibition. In this review, we have attempted to summarize the in vitro research of dietary saponins in the last two decades by searching common databases such as Google Scholar, PubMed, Scopus, and Web of Science. The results showed that dietary saponins exerted anti-cancer activities via regulation of apoptosis, autophagy, arrest cell cycle, anti-proliferation, anti-metastasis, and anti-angiogenesis, by regulation of several critical signaling pathways, including MAPK, PI3K/Akt/mTOR, NF-κB, and VEGF/VEGFR. However, there is no data about the dosage of dietary saponins for practical anti-cancer effects in human bodies. Extensive clinical studies are needed to confirm the effectiveness of dietary saponins for further commercial and medical applications.

Novel Therapies in Myeloproliferative Neoplasms: Beyond JAK Inhibitor Monotherapy

Myeloproliferative neoplasms (MPNs) are clonal hematopoietic disorders that consist classically of polycythemia vera (PV), essential thrombocythemia (ET), and myelofibrosis (MF). Janus kinase (JAK) inhibitors have become the standard of therapy in treating patients with intermediate- to higher-risk MF. However, JAK inhibitor (JAKi) treatment can be associated with development of resistance, suboptimal response, relapse, or treatment-related adverse effects. With no approved therapies beyond the JAKi class, the estimated median survival, post JAKi failure, is approximately two years or less; therefore, novel therapies are urgently needed in the MF field. In this review, we discuss ruxolitinib use in MPNs as well as causes of ruxolitinib failure or discontinuation. In addition, we review novel therapies being investigated alone or in combination with JAKi administration. We summarize concepts and mechanisms behind emerging novel therapies being studied for MPNs. This review of emerging novel therapies outlines several novel mechanisms of agents, including via promotion of apoptosis, alteration of the microenvironment, activation or inactivation of various pathways, targeting fibrosis, and telomerase inhibition.

Alteration of MDM2 by the Small Molecule YF438 Exerts Antitumor Effects in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) exhibits a high mortality rate and is the most aggressive subtype of breast cancer. As previous studies have shown that histone deacetylases (HDAC) may represent molecular targets for TNBC treatment, we screened a small library of synthetic molecules and identified a potent HDAC inhibitor (HDACi), YF438, which exerts effective anti-TNBC activity both in vitro and in vivo. Proteomic and biochemical studies revealed that YF438 significantly downregulated mouse double minute 2 homolog (MDM2) expression. In parallel, loss of MDM2 expression or blocking MDM2 E3 ligase activity rendered TNBC cells less sensitive to YF438 treatment, revealing an essential role of MDM2 E3 ligase activity in YF438-induced inhibition of TNBC. Mechanistically, YF438 disturbed the interaction between HDAC1 and MDM2, induced the dissociation of MDM2-MDMX, and subsequently increased MDM2 self-ubiquitination to accelerate its degradation, which ultimately inhibited growth and metastasis of TNBC cells. In addition, analysis of clinical tissue samples demonstrated high expression levels of MDM2 in TNBC, and MDM2 protein levels closely correlated with TNBC progression and metastasis. Collectively, these findings show that MDM2 plays an essential role in TNBC progression and targeting the HDAC1-MDM2-MDMX signaling axis with YF438 may provide a promising therapeutic option for TNBC. Furthermore, this novel underlying mechanism of a hydroxamate-based HDACi in altering MDM2 highlights the need for further development of HDACi for TNBC treatment. SIGNIFICANCE: This study uncovers the essential role of MDM2 in TNBC progression and suggests that targeting the HDAC1-MDM2-MDMX axis with a hydroxamate-based HDACi could be a promising therapeutic strategy for TNBC.

Association between MDM2 SNP309 and endometrial cancer risk: A PRISMA-compliant meta-analysis

BACKGROUND

Murine double minute 2 homolog (MDM2) plays an important role in the downregulation of P53 tumor suppressor gene. MDM2 inhibits P53 transcriptional activity and thereby results in accelerated tumor formation. Overexpression of MDM2 has been found in several cancer types including endometrial cancer. SNP309 is located in the promoter region of MDM2 and contributes to the overexpression of MDM2. The association between MDM2 SNP309 polymorphism and endometrial cancer risk has been investigated in several studies; however, the conclusion remains controversial.

OBJECTIVES

We performed the present meta-analysis to give a comprehensive conclusion of the association between MDM2 SNP309 polymorphism and endometrial cancer susceptibility.

METHODS

We conducted a literature research on PubMed, Embase, Cochrane Library, OVID, Web of Science, Wan Fang, CNKI, and CQVIP databases up to July 31, 2018. Newcastle-Ottawa scale was used to assess the quality of studies. We evaluated the strength of association by combining odds ratios (ORs) and 95% confidence intervals (CIs) in 5 different genetic models under a fixed-effect model or random-effect model. We further conducted subgroup analysis by ethnicity, source of control, histological type, clinical type, grade, and stage of tumor. Sensitivity analysis and publication bias were also performed.

RESULTS

Nine eligible studies were finally included in our meta-analysis. We found MDM2 SNP309 polymorphism increased the risk of endometrial cancer under allele model (OR: 1.23, 95% CI: 1.06-1.41, P = .005), homozygote model (OR: 1.43, 95% CI: 1.13-1.81, P = .003) and recessive model (OR: 1.55, 95% CI: 1.17-2.04, P = .002). Subgroup analysis suggested a similar elevated risk in both Asians and Caucasians. We identified a strong association of enhanced susceptibility to endometrial cancer in endometrioid group (OR: 2.13, 95% CI: 1.28-3.54, P = .004) and Type I group (OR: 1.89, 95% CI: 1.25-2.86, P = .002) under dominant model. We identified no significant publication bias according to Egger's test.

CONCLUSIONS

Our meta-analysis suggested that MDM2 SNP309 polymorphism increased the risk of endometrial cancer significantly, especially in endometrioid and Type I endometrial cancer, indicating MDM2 could serve as a potential diagnostic factor marker for endometrial cancer.

Association between positive murine double minute 2 expression and clinicopathological characteristics of esophageal squamous cell carcinoma: a meta-analysis

The correlations of murine double minute 2 (MDM2) T309G and esophageal cancer were elucidated because the association between MDM2 expression states and clinicopathological parameters of esophageal squamous cell carcinoma (ESCC) is controversial. We conducted a meta-analysis on studies screened from PubMed, Web of Science, Embase, the Cochrane Library, and the Chinese Biomedical Literature Databases that were published before October 2014. All studies describing the association between MDM2 and ESCC were traced. Meta-analysis was performed using the STATA software (Stata Corp., College Station, TX, USA). A total of 9 studies with 707 cases and 324 controls were included. MDM2 expression was higher in ESCC than in normal esophageal epithelium (odds ratio [OR] 10.38, 95% confidence interval [CI] 6.42-16.78, P < 0.001). High MDM2 expression was associated with early primary tumor stage (T1/T2 vs. T3/T4, OR 0.59, 95% CI 0.38-0.92, P = 0.018) and increased risk of regional lymph node metastasis (N0 vs. N1, OR 1.66, 95% CI 1.03-2.67, P = 0.039). However, no relationship was observed between MDM2 expression and the risk of distant metastasis (OR = 2.09, 95% CI 1.00-4.36, P = 0.050), and MDM2 was not significantly correlated with TP53 expression (OR 1.22, 95% CI 0.53-2.77, P = 0.643). Our analysis suggests that MDM2 acts as a potent marker of early primary tumor stage but higher risk of regional lymph node metastasis in ESCC. However, because of the limited number of studies included, the result should be further clarified by well-designed prospective studies.

The effect of Metformin on endometrial tumor-regulatory genes and systemic metabolic parameters in polycystic ovarian syndrome--a proof-of-concept study

The aim of this proof-of-concept study was to determine the effects of three-month Metformin therapy on the expression of tumor-regulatory genes (p53, cyclin D2 and BCL-2) in the endometrium of women with polycystic ovary syndrome (PCOS). A total of 40 women, aged between 21 and 45 years with PCOS (Rotterdam criteria) were recruited. The participants were assessed at pre- and 3-month-post-Metformin therapy for the menstrual regularities, weight reduction, Ferriman Galway scores, fasting blood glucose (FBG), total cholesterol, LDL, HDL and p53, BCL-2 and cyclin D2 gene expression. Five participants conceived spontaneously after the initial recruitment. Majority (68%) resumed regular menstrual cycles after Metformin. There were significant reduction in BMI (p = 0.001), weight (p = 0.001) and Ferriman Galway scores (p = 0.001). A significant improvement was seen in mean FBG (p = 0.002), total cholesterol (p = 0.001), LDL (p = 0.003) and HDL cholesterol levels (p = 0.015). Tumor suppressor gene (p53) was significantly up-regulated after Metformin (10 out of 14 women), with p value 0.016. BCL-2 and cyclin D2 (oncogenes) were slightly up-regulated without significant difference (p = 0.119 and 0.155, respectively). In conclusion, Metformin therapy improved clinical and metabolic parameters in women with PCOS and up-regulated p53 tumor suppressor gene significantly. Further studies are however required to independently validate our findings.

Quantitative high content imaging of cellular adaptive stress response pathways in toxicity for chemical safety assessment

Over the past decade, major leaps forward have been made on the mechanistic understanding and identification of adaptive stress response landscapes underlying toxic insult using transcriptomics approaches. However, for predictive purposes of adverse outcome several major limitations in these approaches exist. First, the limited number of samples that can be analyzed reduces the in depth analysis of concentration-time course relationships for toxic stress responses. Second these transcriptomics analysis have been based on the whole cell population, thereby inevitably preventing single cell analysis. Third, transcriptomics is based on the transcript level, totally ignoring (post)translational regulation. We believe these limitations are circumvented with the application of high content analysis of relevant toxicant-induced adaptive stress signaling pathways using bacterial artificial chromosome (BAC) green fluorescent protein (GFP) reporter cell-based assays. The goal is to establish a platform that incorporates all adaptive stress pathways that are relevant for toxicity, with a focus on drug-induced liver injury. In addition, cellular stress responses typically follow cell perturbations at the subcellular organelle level. Therefore, we complement our reporter line panel with reporters for specific organelle morphometry and function. Here, we review the approaches of high content imaging of cellular adaptive stress responses to chemicals and the application in the mechanistic understanding and prediction of chemical toxicity at a systems toxicology level.

The p53-Mdm2 loop: a critical juncture of stress response

The presence of a functional p53 protein is a key factor for the proper suppression of cancer development. A loss of p53 activity, by mutations or inhibition, is often associated with human malignancies. The p53 protein integrates various stress signals into a growth restrictive cellular response. In this way, p53 eliminates cells with a potential to become cancerous. Being a powerful decision maker, it is imperative that p53 will be activated properly, efficiently and temporarily in response to stress. Equally important is that p53 activation will be extinguished upon recovery from stress, and that improper activation of p53 will be avoided. Failure to achieve these aims is likely to have catastrophic consequences for the organism. The machinery that governs this tight regulation is largely based on the major inhibitor of p53, Mdm2, which both blocks p53 activities and promotes its destabilization. The interplay between p53 and Mdm2 involves a complex network of positive and negative feedback loops. Relief from Mdm2 suppression is required for p53 to be stabilized and activated in response to stress. Protection from Mdm2 entails a concerted action of modifying enzymes and partner proteins. The association of p53 with the PML-nuclear bodies may provide an infrastructure in which this complex regulatory network can be orchestrated. In this chapter we use examples to illustrate the regulatory machinery that drives this network.

Investigation of genetic polymorphisms related to the outcome of radiotherapy for prostate cancer patients

The purpose of this study was to evaluate the association between ATM, TP53 and MDM2 polymorphisms in prostate cancer patients and morbidity after radiotherapy. The presence of ATM (rs1801516), TP53 (rs1042522, rs1800371, rs17878362, rs17883323, and rs35117667), and MDM2 (rs2279744) polymorphisms was assessed by direct sequencing of PCR fragments from 48 patients with histologically proven prostate adenocarcinoma and treated with external beam radiation. The side effects were classified according to the Radiation Therapy Oncology Group (RTOG) score. The results showed no association between clinical characteristics and the development of radiation toxicities (P > 0.05). The C>T transition in the position 16273 (intron 3) of TP53 (rs35117667) was significantly associated with the risk of acute skin toxicity (OR: 0.0072, 95% CI 0.0002–0.227, P = 0.003). The intronic TP53 polymorphism at position 16250 (rs17883323) was associated with chronic urinary toxicity (OR: 0.071, 95%CI 0.006–0.784, P = 0.032). No significant associations were found for the remaining polymorphisms (P > 0.05). The results show that clinical characteristics were not determinant on the developing of radiation sensitivity in prostate cancer patients, and intronic TP53 polymorphisms would be associated with increased acute and chronic radiation toxicities. These observations corroborate the importance of investigating the genetic profile to predict adverse side effects in patients undergoing radiotherapy.

MDM2 SNP309 polymorphism contributes to endometrial cancer susceptibility: evidence from a meta-analysis

OBJECTIVE

The SNP309 polymorphism (T-G) in the promoter of MDM2 gene has been reported to be associated with enhanced MDM2 expression and tumor development. Studies investigating the association between MDM2 SNP309 polymorphism and endometrial cancer risk reported conflicting results. We performed a meta-analysis of all available studies to explore this association.

METHODS

All studies published up to August 2013 on the association between MDM2 SNP309 polymorphism and endometrial cancer risk were identified by searching electronic databases PubMed, Web of Science, EMBASE, and Chinese Biomedical Literature database (CBM). The association between the MDM2 SNP309 polymorphism and endometrial cancer risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs).

RESULTS

Eight case-control studies with 2069 endometrial cancer cases and 4546 controls were identified. Overall, significant increase of endometrial cancer risk was found when all studies were pooled in the meta-analysis (GG vs. TT: OR = 1.464, 95% CI 1.246-1.721, P < 0.001; GG vs. TG + TT: OR = 1.726, 95% CI 1.251-2.380, P = 0.001; GG + TG vs. TT: OR = 1.169, 95% CI 1.048-1.304, P = 0.005). In subgroup analysis by ethnicity and HWE in controls, significant increase of endometrial cancer risks were observed in Caucasians and studies consistent with HWE. In subgroup analysis according to study quality, significant associations were observed in both high quality studies and low quality studies.

CONCLUSIONS

This meta-analysis suggests that MDM2 SNP309 polymorphism contributes to endometrial cancer susceptibility, especially in Caucasian populations. Further large and well-designed studies are needed to confirm this association.

Metallothionein 1G functions as a tumor suppressor in thyroid cancer through modulating the PI3K/Akt signaling pathway

BACKGROUND

MT1G inactivation mediated by promoter methylation has been reported in thyroid cancer. However, the role of MT1G in thyroid carcinogenesis remains unclear. The aim of this study is to examine the biological functions and related molecular mechanisms of MT1G in thyroid cancer.

METHODS

Methylation-specific PCR (MSP) was performed to analyze promoter methylation of MT1G and its relationship with clinicopathological characteristics of papillary thyroid cancer (PTC) patients. Conventional and real-time quantitative RT-PCR assays were used to evaluate mRNA expression. The functions of ectopic MT1G expression were determined by cell proliferation and colony formation, cell cycle and apoptosis, as well as cell migration and invasion assays.

RESULTS

MT1G expression was frequently silenced or down-regulated in thyroid cancer cell lines, and was also significantly decreased in primary thyroid cancer tissues compared with non-malignant thyroid tissues. Promoter methylation, along with histone modification, contributes to MT1G inactivation in thyroid tumorigenesis. Moreover, our data showed that MT1G hypermethylation was significantly positively associated with lymph node metastasis in PTC patients. Importantly, restoring MT1G expression in thyroid cancer cells dramatically suppressed cell growth and invasiveness, and induced cell cycle arrest and apoptosis through inhibiting phosphorylation of Akt and Rb.

CONCLUSIONS

We have for the first time revealed that MT1G appears to be functional tumor suppressor involved in thyroid carcinogenesis mainly through modulating the phosphatidylinositol-3-kinase (PI3K)/Akt pathway and partially through regulating the activity of Rb/E2F pathway in this study.

An updated meta-analysis on the association of MDM2 SNP309 polymorphism with colorectal cancer risk

BACKGROUND

The mouse double minute 2 (MDM2) gene encodes a phosphoprotein that interacts with P53 and negatively regulates its activity. The SNP309 polymorphism (T-G) in the promoter of MDM2 gene has been reported to be associated with enhanced MDM2 expression and tumor development. Studies investigating the association between MDM2 SNP309 polymorphism and colorectal cancer (CRC) risk reported conflicting results. We performed a meta-analysis of all available studies to explore the association of this polymorphism with CRC risk.

METHODS

All studies published up to July 2013 on the association between MDM2 SNP309 polymorphism and CRC risk were identified by searching electronic databases PubMed, EMBASE, and Chinese Biomedical Literature database (CBM) databases. The association between the MDM2 SNP309 polymorphism and CRC risk was assessed by odds ratios (ORs) together with their 95% confidence intervals (CIs).

RESULTS

A total of 14 case-control studies including 4460 CRC cases and 4828 controls were identified. We did not find a significant association between the MDM2 SNP309 polymorphism and CRC risk in all genetic models in overall population. However, in subgroup analysis by ethnicity, significant associations were found in Asians (TG vs. TT: OR = 1.197, 95% CI = 1.055-1.358, P=0.005; GG+TG vs. TT: OR = 1.246, 95% CI = 1.106-1.404, P=0.000) and Africans. When stratified by HWE in controls, significantly increased risk was also found among the studies consistent with HWE (TG vs. TT: OR = 1.166, 95% CI = 1.037-1.311, P= 0.010). In subgroup analysis according to p53 mutation status, and gender, no any significant association was detected.

CONCLUSIONS

The present meta-analysis suggests that the MDM2 is a candidate gene for CRC susceptibility. The MDM2 SNP309 polymorphism may be a risk factor for CRC in Asians.

Do CDKN2 p16 540 C>G, CDKN2 p16 580 C>T, and MDM2 SNP309 T>G gene variants act on colorectal cancer development or progression?

CDNK2 p16 plays a pivotal role in G1/S transition by regulating the p53 pathway, which was regulated by a nuclear oncoprotein, mouse double minute 2 (MDM2). Overexpression of the MDM2 gene has been shown in a number of tumor types, its gene amplification is found to associate with accelerated tumor development and failure to treatment in both hereditary and sporadic cancers. Although genetic association studies have revealed the relationship between certain genetic polymorphisms and genes that play important roles in the development and progression of colorectal cancer (CRC), it is still unknown. Therefore, the polymorphisms of p16 540 C>G, 580 C>T, and MDM2 SNP309 T>G designed to investigate the risk of CRC development and progression in a Turkish population. We enrolled 87 patients with CRC and 75 healthy controls into the study. Genotypings were determined using polymerase chain reaction-restriction fragment length polymorphism techniques. Genotype distributions of p16 540 C>G and 580 C>T were found in agreement with the Hardy-Weinberg equilibrium in patients and controls. MDM2 SNP309 T>G was found in agreement with the Hardy-Weinberg equilibrium in controls, but not in patients. The results of our study, the G allele of p16 540 C>G and GG genotype of MDM2 SNP309 T>G were found significantly lower in patients compared with controls (p<0.001, p<0.05, respectively). Haplotype analyses have shown that the C allele of both the CDKN2 p16 540 C>G and 580 C>T variants together indicate a risk haplotype for the patient group; besides, carrying the G allele of p16 540 and G allele of MDM2 also seems a risk haplotype for the patient group. Our study is the first study that investigates the relationship among variants of CDKN2 p16 540 C>G, 580 C>T, and MDM2 SNP309 T>G risk of CRC and the development and progression in the Turkish population.

Association of MDM2 SNP309 and TP53 Arg72Pro polymorphisms with risk of endometrial cancer

The incidence of endometrial cancer, a common gynecological malignancy, is increasing in Japan. We have previously shown that the ER/MDM2/p53/p21 pathway plays an important role in endometrial carcinogenesis. In the present study, we investigated the effects of germline single nucleotide polymorphisms in murine double minute 2 (MDM2) SNP309, TP53 Arg72Pro, ESR1 PvuII and XbaI, and p21 codon 31 on endometrial cancer risk. We evaluated these polymorphisms in DNA samples from 125 endometrial cancer cases and 200 controls using polymerase chain reaction-based restriction fragment length polymorphism. The association of each genetic polymorphism with endometrial cancer was examined by the odds ratio and 95% confidence interval, which were obtained using logistic regression analysis. The SNP309 GG genotype non-significantly increased the risk of endometrial cancer. The 95% confidence interval for the GG genotype vs. the TT genotype of MDM2 SNP309 was 1.76 (0.93–3.30). Endometrial cancer was not associated with tested SNP genotypes for TP53, ESR1 and p21. The combination of SNP309 GG + TG and TP53 codon 72 Arg/Arg significantly increased endometrial cancer risk. The adjusted OR was 2.53 (95% confidence interval, 1.03–6.21) and P for the interaction was 0.04. This result was supported by in vitro data showing that endometrial cancer cell lines with the SNP309 G allele failed to show growth inhibition by treatment with RITA, which reduces p53-MDM2 binding. The presence of the SNP309 G allele and TP53 codon 72 Arg/Arg genotype is associated with an increased risk of endometrial cancer in Japanese women.

MDM2 regulates estrogen receptor α and estrogen responsiveness in breast cancer cells

Murine double minute clone 2 (MDM2) is a multifunctional protein, which modulates nuclear receptor-mediated transactivation. In this study, we show that MDM2 significantly enhanced estrogen receptor α (ERα) and ERα/specificity protein-mediated transactivation in MCF-7 and ZR-75 breast cancer cells. This was demonstrated by both MDM2 overexpression and knockdown experiments by RNA interference. ERα interacted with wild-type MDM2 and deletion mutants of MDM2 containing amino acids 1-342 (C-terminal deletion) and 134-490 (N-terminal deletion), but not 134-342. In contrast, only wild-type but not mutant MDM2 enhanced ERα-mediated transactivation. Protein-protein interactions in vitro were 17β-estradiol (E(2)) independent, whereas fluorescent resonance energy transfer experiments in living cells showed that E(2) enhanced ERα-MDM2 interactions. Subsequent RNA interference and mammalian two-hybrid experiments suggested that MDM2 did not directly interact with endogenous coactivators such as the steroid receptor coactivators but played a role in enhancing ERα-mediating gene expression and estrogen responsiveness through interactions with ERα.

Melatonin and vitamin D3 synergistically down-regulate Akt and MDM2 leading to TGFβ-1-dependent growth inhibition of breast cancer cells

Melatonin and vitamin D3 inhibit breast cancer cell growth and induce apoptosis, but they have never been combined as a breast cancer treatment. Therefore, we investigated whether their association could lead to an enhanced anticancer activity. In MCF-7 breast cancer cells, melatonin together with vitamin D3, induced a synergistic proliferative inhibition, with an almost complete cell growth arrest at 144 hr. Cell growth blockade is associated to an activation of the TGFβ-1 pathway, leading to increased TGFβ-1, Smad4 and phosphorylated-Smad3 levels. Concomitantly, melatonin and D3, alone or in combination, caused a significant reduction in Akt phosphorylation and MDM2 values, with a consequent increase of p53/MDM2 ratio. These effects were completely suppressed by adding a monoclonal anti-TGFβ-1 antibody to the culture medium. Taken together, these results indicate that cytostatic effects triggered by melatonin and D3 are likely related to a complex TGFβ-1-dependent mechanism, involving down-regulation of both MDM2 and Akt-phosphorylation.

Enigma negatively regulates p53 through MDM2 and promotes tumor cell survival in mice

The human E3 ubiquitin ligase murine double minute 2 (MDM2) targets the tumor suppressor p53 for ubiquitination and degradation but also promotes its own ubiquitination and subsequent degradation. As the balance between MDM2 and p53 levels plays a crucial role in regulating cell proliferation and apoptosis, we sought to identify factors selectively inhibiting MDM2 self-ubiquitination. Here we have shown that the LIM domain protein Enigma directly interacts with MDM2 to form a ternary complex with p53 in vitro and in human hepatoma and colon carcinoma cell lines and mouse embryonic fibroblasts. We found that Enigma elicited p53 degradation by inhibiting MDM2 self-ubiquitination and increasing its ubiquitin ligase activity toward p53 in cells. Moreover, mitogenic stimuli such as serum, FGF, and HGF increased Enigma transcription via induction of serum response factor (SRF), leading to MDM2 stabilization and subsequent p53 degradation. We observed similar results in the livers of mice treated with HGF. In humans, we found SRF and Enigma coexpressed with MDM2 but not p53 in several liver and stomach tumors. Finally, we showed that Enigma promoted cell survival and chemoresistance by suppressing p53-mediated apoptosis in both cell lines and a mouse xenograft model. Our findings suggest a role for Enigma in tumorigenesis and uncover a mechanism whereby mitogens attenuate p53 antiproliferative activity through an SRF/Enigma/MDM2 pathway.

Low-dose mithramycin exerts its anticancer effect via the p53 signaling pathway and synergizes with nutlin-3 in gynecologic cancers

MDM2 is a direct negative regulator of p53. The p53-independent mdm2-P1 and p53-dependent mdm2-P2 promoters have been recently shown to harbor Sp1 binding sites. Mithramycin, an inhibitor of Sp1 DNA binding, has been used clinically to treat hypercalcemia and some types of neoplastic disorders. In this study, we investigated the mechanisms behind the anticancer effect of mithramycin. In gynecologic cancer cells expressing wild-type p53, mithramycin stabilized p53 and increased the expression of the p53 downstream target genes PUMA and p21, arrested the cell cycle, and induced apoptosis. This activation of the p53 signaling pathway was a specific effect of MTH at concentrations <50 nm. Mithramycin temporally decreased transcription of both the mdm2-P1 and -P2 promoters. This was followed by a subsequent increase of mdm2-P2 promoter activity by activated p53. Up-regulated MDM2 was in its active form, and consequently attenuated p53 activity. Although mithramycin activated p53 and suppressed the growth of human gynecologic cancer cell xenografts in mice, this was accompanied with a secondary up-regulation of MDM2. Combined treatment with mithramycin and nutlin-3, a drug that inhibits MDM2-p53 interaction, overcame a secondary up-regulation of MDM2 and synergistically inhibited cancer cell growth by inducing apoptosis through activation of the p53 signaling pathway. These observations provide a better understanding of the mechanisms of mithramycin activity, and suggest a potential role for combining mithramycin and nutlin-3 as a chemotherapeutic treatment for gynecologic cancers.

Nutlin-3a induces cytoskeletal rearrangement and inhibits the migration and invasion capacity of p53 wild-type cancer cells

MDM2 is an E3 ubiquitin ligase that binds and ubiquitinates the tumor suppressor protein p53, leading to its proteasomal degradation. Nutlin-3a (Nutlin) is a preclinical drug that binds MDM2 and prevents the interaction between MDM2 and p53, leading to p53 stabilization and activation of p53 signaling events. Previous studies have reported that Nutlin promotes growth arrest and/or apoptosis in cancer cells that express wild-type p53. In the current study, Nutlin treatment caused a cytoskeletal rearrangement in p53 wild-type human cancer cells from multiple etiologies. Specifically, Nutlin decreased actin stress fibers and reduced the size and number of focal adhesions in treated cells. This process was dependent on p53 expression but was independent of p21 expression and growth arrest. Consistent with this, Nutlin-treated cells failed to form filamentous actin-based motility structures (lamellipodia) and displayed significantly decreased directional persistence in response to migratory cues. Finally, chemotactic assays showed a p53-dependent/p21-independent decrease in migratory and invasive capacity of Nutlin-treated cells. Taken together, these findings reveal that Nutlin treatment can inhibit the migration and invasion capacity of p53 wild-type cells, adding to the potential therapeutic benefit of Nutlin and other small molecule MDM2 inhibitors. Mol Cancer Ther; 9(4); 895-905. (c)2010 AACR.

Mdm2-mediated ubiquitylation: p53 and beyond

The really interesting genes (RING)-finger-containing oncoprotein, Mdm2, is a promising drug target for cancer therapy. A key Mdm2 function is to promote ubiquitylation and proteasomal-dependent degradation of the tumor suppressor protein p53. Recent reports provide novel important insights into Mdm2-mediated regulation of p53 and how the physical and functional interactions between these two proteins are regulated. Moreover, a p53-independent role of Mdm2 has recently been confirmed by genetic data. These advances and their potential implications for the development of new cancer therapeutic strategies form the focus of this review.

Chemotherapy induces NEDP1-mediated destabilization of MDM2

MDM2 is an E3 ligase that promotes ubiquitin-mediated destruction of p53. Cellular stresses such as DNA damage can lead to p53 activation due in part to MDM2 destabilization. Here, we show that the stability of MDM2 is regulated by an ubiquitin-like NEDD8 pathway and identify NEDP1 as a chemotherapy-induced isopeptidase that deneddylates MDM2, resulting in MDM2 destabilization concomitant with p53 activation. Concordantly, RNAi-mediated knockdown of endogenous NEDP1 blocked diminution of MDM2 levels and increased chemoresistance of tumor cells. These findings unveil the regulation of MDM2 stability through NEDP1 as a common molecular determinant governing chemotherapy-induced p53-dependent cell death.

MI-63: a novel small-molecule inhibitor targets MDM2 and induces apoptosis in embryonal and alveolar rhabdomyosarcoma cells with wild-type p53

Background:

Interruption of the role of p53s as a tumour suppressor by MDM2 may be one of the mechanisms by which cancer cells evade current therapy. Blocking the inhibition of wild-type p53 by MDM2 in cancer cells should reactivate p53's tumour suppressor functions and enhance current cancer treatments. MI-63 is a novel non-peptide small molecule that has shown strong binding affinity (K_i=3 nM) for MDM2; however, its effects on paediatric cancer cells and the specific mechanism of tumour suppressor reactivation have not been evaluated.

Methods:

Rhabdomyosarcoma (RMS), the most common childhood soft tissue sarcoma, expresses either wild-type or mutant p53 protein. We examined the inhibitory effects of MI-63 in embryonal RMS (ERMS) and alveolar RMS (ARMS) cell lines expressing wild-type or mutated p53.

Results:

Treatment with MI-63 reduced cell viability by 13.4% and by <1%, respectively, at 72 h in both RH36 and RH18 cell lines expressing wild-type p53. In contrast, RH30 and RD2 cells expressing p53 mutants are resistant to MI-63 treatment. An increased expression of p53, p21^WAF1, and Bax protein was observed after treatment with MI-63 in RMS cells with wild-type p53, and apoptosis was confirmed by cleaved PARP and caspase-3 expression. However, RD2 and RH30 RMS cells, as well as human normal skeletal muscle cells, showed a minimal increase in p53 signalling and no induction of cleaved PARP and caspase-3. MI-63 was compared with Nutlin-3, a known MDM2 inhibitor, and was found to be more potent in the inhibition of cell proliferation/viability. Further, synergy was observed when MI-63 was used in combination with doxorubicin.

Conclusion:

These results indicate that MI-63 is a potent therapeutic agent for RMS cells expressing wild-type p53 protein.

MDM2, P53, P21WAF1 and pAKT protein levels in genesis and behaviour of adenoid cystic carcinoma

BACKGROUND

MDM2, P53, P21(WAF1) and pAKT are proteins associated with the balance between cell death and survival. There are many hypotheses regarding the role of these proteins in salivary gland tumours. However, many molecular events that activate or inactivate regulatory genes remain unknown. The aim of this study was to evaluate and to correlate MDM2, P53, P21(WAF1) and pAKT protein expressions in adenoid cystic carcinomas (ACC).

METHODS

Twenty-two cases of ACC were evaluated by immunohistochemistry and one cell line derived from ACC was analyzed by Western Blotting and immunofluorescence techniques.

RESULTS

Strong MDM2 and pAKT, variable P53 and null P21 expressions were found in the cases analyzed, but no statistical correlation was established when comparing MDM2 and pAKT expressions in the 3 different ACC subtypes. The ACC cell line showed intense nuclear and cytoplasmatic MDM2 and pAKT expressions and null P53 and P21 expressions.

CONCLUSIONS

Results indicate that MDM2 and pAKT are related to the tumorigenesis of ACC, but they might not be directly connected to tumour progression. We also demonstrate that the pAKT pathway is active in ACC and it seems to be activating the MDM2 shuttle from the cytoplasm to the nucleus, where it phosphorylates P53 and carries it to the cytoplasm for degradation.

Targeting Mdm2 and Mdmx in cancer therapy: better living through medicinal chemistry?

Genomic and proteomic profiling of human tumor samples and tumor-derived cell lines are essential for the realization of personalized therapy in oncology. Identification of the changes required for tumor initiation or maintenance will likely provide new targets for small-molecule and biological therapeutics. For example, inactivation of the p53 tumor suppressor pathway occurs in most human cancers. Although this can be due to frank p53 gene mutation, almost half of all cancers retain the wild-type p53 allele, indicating that the pathway is disabled by other means. Alternate mechanisms include deletion or epigenetic inactivation of the p53-positive regulator arf, methylation of the p53 promoter, or elevated expression of the p53 regulators Mdm2 and Mdmx. This review discusses current models of p53 regulation by Mdm2 and Mdmx and presents the rationale for design of future Mdmx-specific therapeutics based on our knowledge of its structure and biological functions.

Effects of the single nucleotide polymorphism at MDM2 309 on breast cancer patients with/without BRCA1/2 mutations

BACKGROUND

A germ line single nucleotide polymorphism (SNP) in the first intron of the gene encoding MDM2 at position 309, an important modulator of p53, has been described. BRCA1/2 mutation have been associated with increased rates of breast cancers with mutated P53. It was shown that the presence of MDM2 309 SNP correlated with younger cancer onset age in individuals with a p53 mutations. The differential effects of this SNP were also linked to estrogen receptor activation. Here we report on our study of 453 Ashkenazi breast cancer patients of whom 180 were positive for the known Ashkenazi BRCA1/2 mutations

METHODS

DNA from breast cancer patients was obtained for analysis of one of the three common BRCA1/2 mutations and MDM2 SNP309. Data regarding cancer onset and death ages was obtained from our database and Statistical analysis was performed using the SPSS statistical package (SPCC Inc., Chicago, IL), and JMP software (SAS Institute, Cary, NC).

RESULTS

The percentage of MDM2 SNP309 in control and BRCA 1/2 population which is similar to that reported for other Jewish Ashkenazi populations at 52.2% for the heterozygotes and 25.0% for MDM2SNP309G/G and 22.8% for MDM2SNP309T/T.There was not a statistical significant difference in median age of disease onset in the different MDM2 SNP309 subgroups of the BRCA1/2 carriers. When we further divided the group into under and above 51 years old ( presumed menopause age) in the BRCA1 positive subset we found that there were less patients of the MDM2SNP309 G/G versus the MDM2SNP309 T/T in the over 51 patient group (p = 0.049). This result has been obtained in a relatively small subgroup and is of borderline statistical significance. Interestingly, in the BRCA1/2 mutation carriers, we found a survival advantage for patients harboring the SNP309 G/G genotype (p = 0.0086) but not for the 272 patients not harbouring this mutations.

CONCLUSION

MDM2SNP309G/G main effect on BRCA1/2 positive mutation carriers is linked to its effect on patients survival. Further research is needed in order to understand the reason for this difference.

Regulation of peroxisome proliferator-activated receptor-alpha by MDM2

Peroxisome proliferator-activated receptor-alpha (PPARalpha) belongs to the nuclear receptor (NR) family of transcription factors and regulates lipid and glucose metabolism. Like other NRs, the regulation of gene expression by PPARalpha depends on cofactor recruitment to the transcription complex and multiple protein-protein interactions. In this study, Murine Double Minute 2 (MDM2), an E3 ubiquitin ligase, is identified as a PPARalpha-interacting protein that regulates PPARalpha transcriptional activity. MDM2 modulated the transcriptional activity of PPARalpha and PPARbeta/delta, but not PPARgamma in reporter assays. Knockdown of MDM2 by small interfering RNA in rat hepatoma cells inhibited ligand-induced mRNA levels of several PPARalpha target genes involved in lipid metabolism. MDM2 associated with PPARalpha on target gene promoters, and this association increased in response to Wy14,643 treatment. MDM2 interacted with PPARalpha and this interaction occurred with the A/B domain of PPARalpha. Coexpression of MDM2 increased PPARalpha ubiquitination and the E3 ubiquitin ligase activity of MDM2 affected PPARalpha protein expression and transcriptional activity. MDM2 expression was decreased in response to clofibrate in wild-type (WT), but not in PPARalpha null mice, indicating a PPARalpha-dependent regulation. These studies identify a role for MDM2 in regulating PPARalpha-mediated pathways of lipid metabolism.

Cell transformation and proteome alteration in QSG7701 cells transfected with hepatitis C virus non-structural protein 3

Persistent hepatitis C virus (HCV) infection can cause liver cirrhosis and hepatocellular carcinoma. Non-structural protein 3 (NS3), an important part of HCV, has been implicated in the life cycle of the virus and interacts with host cellular proteins. In this study, we investigated the effect of NS3 protein on cell tranformation and related protein alteration in human hepatocyte QSG7701 cells. The results indicated that stable expression of the NS3 protein in QSG7701 cells induced transformed characters with reduced population doubling time, anchorage-independent growth and tumor development. Fifteen differentially-expressed proteins were separated and identified using 2-D electrophoresis and matrix-assisted laser desorption ionization-time of flight mass spectrometry. Western blot analysis confirmed that the increase of phospho-p44/42 and phospho-p38 proteins was associated with transformed cells. These results supported the view that HCV NS3 protein plays a transforming role and provided some clues to elucidate the carcinogenesis mechanism of HCV-related hepatocellular carcinoma.

A proteomics analysis of cell signaling alterations in colorectal cancer

To gain further insight into alterations in cellular pathways, tumor profiling, and marker discovery in colorectal cancer (CRC) we used a new antibody microarray specific for cell signaling. Soluble protein extracts were prepared from paired tumor/normal biopsies of 11 patients diagnosed with colorectal carcinoma at different stages; four liver carcinomas were used as a reference. Antibody microarray analysis identified 46 proteins that were differentially expressed between normal colorectal epithelium and adenocarcinoma. These proteins gave a specific signature for CRC, different from other tumors, as well as a panel of novel markers and potential targets for CRC. Twenty-four proteins were validated by using a specific colorectal cancer tissue microarray and immunoblotting analysis. Together with some previously well known deregulated proteins in CRC (beta-catenin, c-MYC, or p63), we found new potential markers preferentially expressed in CRC tumors: cytokeratin 13, calcineurin, CHK1, clathrin light chain, MAPK3, phospho-PTK2/focal adhesion kinase (Ser-910), and MDM2. CHK1 antibodies were particularly effective in discriminating between tumoral and normal mucosa in CRC. Moreover a global picture of alterations in signaling pathways in CRC was observed, including a significant up-regulation of different components of the epidermal growth factor receptor and Wnt/beta-catenin pathways and the down-regulation of p14(ARF). The experimental approach described here should be applicable to other pathologies and neoplastic processes.

Analysis of signaling pathways in 90 cancer cell lines by protein lysate array

Multiple signal transduction pathways play a crucial role in cancer development, progression, and response to different therapies. An important issue is whether common signal transduction pathways are ubiquitously altered in all cancer types and some unique pathways are involved in different cancer types. Another important issue is whether and how transduction signaling molecules are heterogeneously expressed and activated in different cancer cells within and between cancer cell types.

METHODS

To gain insight into these issues, we assembled a protein lysate array with 90 different cell lines of 12 different cell types. Each sample is diluted 2-fold six times, and samples from the dilution series were printed three times on the array. We then measured the expression levels and phosphorylation status of 52 different signaling proteins with specific antibodies and carried out statistical hierarchical clustering analysis.

RESULTS

The most significant finding based on the cluster analysis was that the cell lines did not group based on tumor types, suggesting that the signaling pathways studied were commonly activated in most of the tumor types cultured in vitro. As expected, related proteins associated with specific signaling pathways clustered together, and analysis of the 30 most differentially expressed proteins revealed the PI3-K signaling pathway was upregulated in several different tumor types and the VEGF-angiogenesis pathway was downregulated in hematopoetic cancers. Another important observation, with clinical implications was that EGFR was the most heterogeneous among all the cell lines. We also observed signaling pathways unique to specific types of cancers such as the inverse relationship between p16ink and Rb, and the EGFR mediated pathway activation characteristic of pancreatic cancers.

CONCLUSIONS

Using reverse phase lysate array analysis in this study, we were able to determine potential relationships and signaling pathways, both common and unique, to different types of cancer using cell lines in vitro. This data could be utilized for mining information related to an individual cancer of interest and combined with morphological and genomic profiles would help in creating a combination of expression markers and/or functional signaling maps for specific cancer diagnosis and therapy.

An inhibitory effect on cell proliferation by blockage of the MAPK/estrogen receptor/MDM2 signal pathway in gynecologic cancer

OBJECTIVE

We previously demonstrated that that the Ras/ER/MDM2 pathway was critical for NIH3T3 cell transformation. In this study, we examined the effect of blocking this pathway on cell growth in gynecologic cancer cells.

METHODS

(1) The levels of MDM2, ER, p53 and p21 in endometrial or ovarian cancer cell lines were investigated and compared with that in normal cells by Western blots. (2) The effects of MEK-inhibitor and/or anti-estrogen, and siRNA of MDM2 on cell growth, tumorigenicity in nude mice were examined.

RESULTS

The MDM2 level was enhanced in cancer cells compared with normal cells. Treatment with MEK inhibitor(U0126) resulted in a reduced MDM2 level, enhanced p53 and p21 levels and inhibited cell growth by the induction of premature senescence. The effect of MEK inhibitor on cell growth was affected by ER levels and functions. Treatment with low-dose MEK inhibitor in combination with anti-estrogen (ICI182,780) had a more inhibitory effect on cell growth compared to treatment with MEK inhibitor or anti-estrogen alone in cancer cells. Down-regulation of the MDM2 level by siRNA resulted in the inhibition of growth in cancer cells.

CONCLUSION

The blockage of the MAPK/ER/MDM2 pathway suppress cell proliferation and it is supposed as a new molecular target therapy in estrogen-dependent gynecologic cancers, such as endometrial or ovarian cancer.

AKT-1 Regulates DNA-Damage-Induced Germline Apoptosis in C. elegans

The cellular response to genotoxic stress involves the integration of multiple prosurvival and proapoptotic signals that dictate whether a cell lives or dies. In mammals, AKT/PKB regulates cell survival by modulating the activity of several apoptotic proteins, including p53. In Caenorhabditis elegans, akt-1 and akt-2 regulate development in response to environmental cues by controlling the FOXO transcription factor daf-16, but the role of these genes in regulating p53-dependent apoptosis is not known. In this study, we show that akt-1 and akt-2 negatively regulate DNA-damage-induced apoptosis in the C. elegans germline. The antiapoptotic activity of akt-1 is independent of its target gene daf-16 but dependent on cep-1/p53. Although only akt-1 regulates the apoptotic activity of cep-1, both akt-1 and akt-2 modulate the intensity of the apoptotic response independently of the transcriptional activity of CEP-1. Finally, we show that AKT-1 regulates apoptosis but not cell-cycle progression downstream of the HUS-1/MRT-2 branch of the DNA damage checkpoint.

Targets and strategies for T-cell based vaccines in patients with B-cell chronic lymphocytic leukemia

T-cell based immunotherapies might be a novel option for the treatment of B-cell chronic lymphocytic leukemia (B-CLL), a disease characterized by a prolonged natural course. Different strategies of active immunotherapy have been tested in vitro to enhance a specific T-cell response against tumor cells and an anti-leukemic effect has been observed in B-CLL patients after allogenic stem cell transplantation. Several antigens have been characterized as tumor/leukemia associated antigens (T/LAAs) in B-CLL with the potential to elicit specific anti-tumor response encompassing idiotype immunoglobulin, oncofetal antigen-immature laminin receptor protein (OFAiLRP), survivin, as well as fibromodulin, the receptor for hyaluronic acid mediated motility (RHAMM/CD168) and the murine double-minute 2 oncoprotein (MDM2). This study presents an overview of possible targets and genetherapeutical maneuvers for future immunotherapies of B-CLL patients and summarizes recent clinical vaccination trials with dendritic cells (DCs) for B-CLL.