Murine Double Minute 2 Protein Expression Research Articles

Reduced murine double minute 2 and 4 protein, but not messenger RNA, expression is associated with more severe disease in myelodysplastic syndromes and acute myeloblastic leukaemia.

The human homologues of murine double minute 2 (MDM2) and 4 (MDM4) negatively regulate p53 tumour suppressor activity and are reported to be frequently overexpressed in human malignancies, prompting clinical trials with drugs that prevent interactions between MDM2/MDM4 and p53. Bone marrow samples from 111 patients with acute myeloblastic leukaemia, myelodysplastic syndrome or chronic myelomonocytic leukaemia were examined for protein (fluorescence-activated cell sorting) and messenger RNA (mRNA) expression (quantitative polymerase chain reaction) of MDM2, MDM4 and tumour protein p53 (TP53). Low protein expression of MDM2 and MDM4 was observed in immature cells from patients with excess of marrow blasts (>5%) compared with CD34+ /CD45low cells from healthy donors and patients without excess of marrow blasts (<5%). The mRNA levels were indistinguishable in all samples examined regardless of disease status or blast levels. Low MDM2 and MDM4 protein expression were correlated with poor survival. These data show a poor correlation between mRNA and protein expression levels, suggesting that quantitative flow cytometry analysis of protein expression levels should be used to predict and validate the efficacy of MDM2 and MDM4 inhibitors. These findings show that advanced disease is associated with reduced MDM2 and MDM4 protein expression and indicate that the utility of MDM2 and MDM4 inhibitors may have to be reconsidered in the treatment of advanced myeloid malignancies.

Nuclear Receptor PXR Confers Irradiation Resistance by Promoting DNA Damage Response Through Stabilization of ATF3.

Low response rate to radiotherapy remains a problem for liver and colorectal cancer patients due to inappropriate DNA damage response in tumors. Here, we report that pregnane X receptor (PXR) contributes to irradiation (IR) resistance by promoting activating transcription factor 3 (ATF3)-mediated ataxia-telangiectasia-mutated protein (ATM) activation. PXR stabilized ATF3 protein by blocking its ubiquitination. PXR–ATF3 interaction is required for regulating ATF3, as one mutant of lysine (K) 42R of ATF3 lost binding with PXR and abolished PXR-reduced ubiquitination of ATF3. On the other hand, threonine (T) 432A of PXR lost binding with ATF3 and further compromised ATM activation. Moreover, the PXR–ATF3 interaction increases ATF3 stabilization through disrupting ATF3–murine double minute 2 (MDM2) interaction and negatively regulating MDM2 protein expression. PXR enhanced MDM2 auto-ubiquitination and shortened its half-life, therefore compromising the MDM2-mediated degradation of ATF3 protein. Structurally, both ATF3 and PXR bind to the RING domain of MDM2, and on the other hand, MDM2 binds with PXR on the DNA-binding domain (DBD), which contains zinc finger sequence. Zinc finger sequence is well known for nuclear receptor peroxisome proliferator-activated receptor-γ (PPARγ) playing E3 ligase activity to degrade nuclear factor κB (NFκB)/p65. However, whether zinc-RING sequence grants E3 ligase activity to PXR remains elusive. Taken together, these results provide a novel mechanism that PXR contributes to IR resistance by promoting ATF3-mediated ATM activation through stabilization of ATF3. Our result suggests that targeting PXR may sensitize liver and colon cancer cells to IR therapy.

1199-P: The Oncogene MDM2 Induces M1 Macrophage Polarization and Adipose Tissue Inflammation in Obesity

Obesity is characterized by chronic low-grade inflammation that contributes to the pathogenesis of type 2 diabetes. Adipose tissue macrophages predominantly switch to a pro-inflammatory phenotype known as M1 during obesity. The accumulation of pro-inflammatory M macrophages in obese adipose tissue results in the secretion of a cluster of pro-inflammatory cytokines that instigate adipose tissue inflammation and insulin resistance. Here we discovered that expression of oncoprotein murine double minute 2 (MDM2) was elevated in obese white adipose tissues. Also, MDM2 protein expression was drastically induced in macrophages activated with lipopolysaccharide (LPS) and interferon-γ (IFNγ). Mice with myeloid cells-specific MDM2 haploinsufficiency (Mye-MDM2 KO mice) were generated and subjected to high-fat-diet (HFD) feeding. After 16 weeks of HFD feeding, obesity-induced glucose intolerance and insulin resistance were alleviated in Mye-MDM2 KO mice with reference to their wild type (WT) controls. Systemic inflammation induced by LPS injection was also reduced in Mye-MDM2 KO mice. In vitro, expression of M1 genes induced by LPS and IFNγ were inhibited in bone marrow-derived macrophages with haplodeficiency of MDM2. Similarly, pharmacological inhibition of MDM2 with the small molecule inhibitor Nutlin-3a attenuates pro-inflammatory cytokines secretion by macrophages. Mechanistically, haplodeletion of MDM2 led to decreased expression of glycolytic genes in BMDM during M1 activation. Taken together, we demonstrated a novel role of MDM2 in regulating glycolysis and M1 macrophage activation in addition to its role as a negative regulator of p53 tumour suppressor protein, suggesting it as a potential therapeutic target for treating type 2 diabetes. Disclosure K. Cheng: None. Funding Hong Kong General Research Fund (17100717)

Restoration of miR-193a-5p and miR-146 a-5p Expression Induces G1 Arrest in Colorectal Cancer through Targeting of MDM2/p53.

Purpose: Colorectal cancer (CRC) remains a universal and lethal cancer owing to metastatic and relapsing disease. Currently, the role of microRNAs has been checked in tumorigeneses. Numerous studies have revealed that between the tumor suppressor miRNAs, the reduced expression of miR-146a-5p and -193a-5p in several cancers including CRC tissues are related with tumor progression and poor prognosis of patients. The purpose of this study is to examine the role of miR-146 a-5p and -193 a-5p in CRC cell cycle progression. Methods: The miR-193a-5p and -146 a-5p mimics were transfected into HT-29 CRC cells via jetPEI transfection reagent and their impact was assessed on p53, cyclin B, and NF-kB gene expression. The inhibitory effect of these miRNAs on cell cycle was assessed by flow cytometry. The consequence of miR-193a-5p and miR-146 a-5p on the protein expression level of Murine double minute 2 (MDM2) was assessed by western blotting. Results: miR193a-5p and -146a-5p regulated the expression of MDM2 protein and p53, cyclin B, and NF-kB gene expression in CRC cells. Treatment of HT-29 cells with miRNA-146a-5p and -193a-5p induced G1 cell cycle arrest. Conclusion: The findings of our study suggest that miR146a-5p and -193a-5p may act as a potential tumor suppressor by their influence on cell cycle progression in CRC cells. Thus, miRNA-146a-5p and -193a-5p restoration may be recommended as a potential therapeutic goal in the treatment of CRC patients.

An Open-Label, Phase 2 Study of KRT-232, a First-in-Class, Oral Small Molecule Inhibitor of MDM2, for the Treatment of Patients with Myelofibrosis (MF) Who Have Previously Received Treatment with a JAK Inhibitor

An Open-Label, Phase 2 Study of KRT-232, a First-in-Class, Oral Small Molecule Inhibitor of MDM2, for the Treatment of Patients with Myelofibrosis (MF) Who Have Previously Received Treatment with a JAK Inhibitor

Extracellular matrix differences in glioblastoma patients with different prognoses.

Glioblastoma is the most common malignant central nervous system tumor. Patient outcome remains poor despite the development of therapy and increased understanding of the disease in the past decades. Glioma cells invade the peritumoral brain, which results in inevitable tumor recurrence. Previous studies have demonstrated that the extracellular matrix (ECM) is altered in gliomas and serves a major role in glioma invasion. The present study focuses on differences in the ECM composition of tumors in patients with poor and improved prognosis. The mRNA and protein expression of 16 invasion-associated ECM molecules was determined using reverse trascription-quantitiative polymerase chain reaction and immunohistochemistry, respectively. Clinical factors of patients with different prognoses was also analyzed. It was determined that age and postoperative Karnofsky performance score were associated with patient survival. Furthermore, Fms-related tyrosine kinase 4/vascular endothelial growth factor receptor 3 (FLT4/VEGFR3), murine double minute 2 (MDM2) and matrix metallopeptidase 2 (MMP2) mRNA levels were significantly different between the two prognostic groups. Additionally, brevican, cluster of differentiation 44, hyaluronan mediated motility receptor, integrin-αV and -β1, and MDM2 protein expression were indicated to be significantly different in immunohistochemistry slides. Using the expression profile, including the invasion spectrum of the samples, it was possible to identify the prognostic group of the sample with high efficacy, particularly in cases with poor prognosis. In conclusion, it was determined that ECM components exhibit different expression levels in tumors with different prognoses and thus the invasion spectrum can be used as a prognostic factor in glioblastoma.

Single-Nucleotide Polymorphism 309T>G in the MDM2 Promoter Determines Functional Outcome After Stroke.

Background and Purpose- The E3 ubiquitin ligase MDM2 (murine double minute 2) is the main negative regulator of the p53 protein-a key player in neuronal apoptosis after ischemia. A functional single-nucleotide polymorphism in the human MDM2 gene promoter (rs2279744) regulates MDM2 protein expression. We investigated whether the MDM2 SNP309, by controlling p53-mediated apoptosis, determines functional outcome after stroke. Methods- Primary cortical neurons were subjected to oxygen and glucose deprivation. Mice were subjected to ischemic (transient middle cerebral artery occlusion) or hemorrhagic (collagenase injection) stroke models. Protein and mRNA levels of MDM2 and p53 were measured in both neuronal and brain extracts. The interaction of MDM2 with p53 was disrupted by neuronal treatment with nutlin-3a. siRNA was used to knockdown MDM2 expression. We analyzed the link between the MDM2 SNP309 and functional outcome, measured by the modified Rankin Scale scores, in 2 independent hospital-based stroke cohorts: ischemic stroke cohort (408 patients) and intracerebral hemorrhage cohort (128 patients). Results- Experimental stroke and oxygen and glucose deprivation induced the expression of MDM2 in the brain and neurons, respectively. Moreover, oxygen and glucose deprivation promoted MDM2 binding with p53 in neurons. Disruption of the MDM2-p53 interaction with nutlin-3a, or MDM2 knockdown by siRNA, triggered p53 accumulation, which increased neuronal susceptibility to oxygen and glucose deprivation-induced apoptosis. Finally, we showed that patients harboring the G allele in the MDM2 promoter had higher MDM2 protein levels and showed better functional outcome after stroke than those harboring the T/T genotype. The T/T genotype was also associated with large infarct volume in ischemic stroke and increased lesion volume in patients with intracerebral hemorrhage. Conclusions- Our results reveal a novel role for the MDM2-p53 interaction in neuronal apoptosis after ischemia and show that the MDM2 SNP309 determines the functional outcome of patients after stroke.

MDM2 promotes rheumatoid arthritis via activation of MAPK and NF-κB

Murine double minute-2 (MDM2) has pleiotropic roles in immune activation and regulation. However, the role of MDM2 in rheumatoid arthritis (RA) remains unknown. We undertook this study to investigate the role of MDM2 in rheumatoid arthritis (RA). Fibroblast-like synoviocytes (FLS) were isolated from 25 patients with active RA and 25 patients with osteoarthritis (OA). FLS were stimulated in the presence or absence of IL-1β in vitro. Mice with collagen-induced arthritis (CIA) were treated with Nutlin-3a (100mg/kg) or vehicle twice daily for 2weeks. MDM2 expression was determined by Western blot. MDM2 was down-regulated by specific gene silencing. The concentrations of pro-inflammatory cytokines and matrix metalloproteinases (MMPs) were analyzed using enzyme-linked immunosorbent assay (ELISA). The pathways of mitogen-activated protein kinase (MAPK) and nuclear factor-kappa B (NF-κB) were investigated by Western blot. Arthritis scoring and histological analysis were conducted. MDM2 expression was significantly higher in RA-FLS than in OA-FLS. MDM2 protein expression was positively correlated with disease activity of RA. MDM2 promoted the production of TNF-α, IL-6, MMP1 and MMP13 through MAPK and NF-κB pathways in RA-FLS. Nutlin-3a treatment decreased the arthritis severity and joint damage in CIA. Nutlin-3a also inhibited the activation of MAPK and NF-κB in arthritic joints. In conclusion, MDM2 inhibition exhibits anti-inflammatory activity and MDM2 might be a new therapeutic target for RA.

Relationship Between MDM2 and p53 Alterations in Colorectal Cancer and Their Involvement and Prognostic Value in the Tunisian Population

The prevalence of p53 mutations in colorectal cancer could reach 90%. The most important regulator of this protein that was identified originally was the Murine Double Minute2 (MDM2) oncoprotein, by which the levels of p53 were fixed through an autoregulatory feedback loop. In cancer cases, the overexpression of MDM2 deregulates this feedback, and the signaling pathway between MDM2 and p53 is blocked. We genotyped 167 patients and 167 healthy blood donors to determinate the mutational status of MDM2 and p53. Immunohistochemical analysis was performed on tumor and normal mucosa. The MDM2 polymorphism study showed a higher distribution of MDM2 SNP309 in tumors compared with healthy controls. At the same time, the majority of samples with SNP309 indicated a positive expression of MDM2 protein in the tumor. In this case, we found a first significant association between p53 expression and the single-strand conformational polymorphism analysis and a second association between the MDM2 polymorphism and p53 mutation. Moreover, the nuclear overexpression of MDM2 and SNP309 was significantly related to a higher mortality rate. In this work we wanted to highlight the role, which is becoming increasingly important, of MDM2. In fact, we conclude that the effects of MDM2 SNP309 may be considered a valuable prognostic marker to predict poor outcome for Tunisian patients with colorectal cancer.

MDM2 SNP309T&gt;G polymorphism increases susceptibility to hepatitis B virus‐related hepatocellular carcinoma in a northeast Han Chinese population

The murine double minute 2 (MDM2) gene encodes a negative regulator of the tumour protein p53. A single nucleotide polymorphism (SNP) in MDM2 promoter, SNP309 T > G, has been showed to influence MDM2 protein expression and accelerate tumour formation. To investigate further the role of this locus, we examined the association of the SNP with hepatitis B virus (HBV)-related hepatocellular carcinoma (HCC) in a northeast Han Chinese population. MDM2 SNP309 was genotyped in 310 HBV-related HCC patients, 314 non-HCC subjects with HBV infection and 480 healthy controls by using a PCR-RFLP method. Significant differences of MDM2 SNP309 were detected between HBV-related HCC patients and healthy controls (OR 1.729, 95%CI 1.369-2.183, P < 0.0001) or non-HCC subjects with HBV infection (OR 1.351, 95% CI 1.060-1.722, P = 0.015) by a logistic regression analysis. Our data also revealed that subjects with the G allele had higher HBV-related HCC susceptibility than those with the T allele in various genetic models. In a meta-analysis, where we pooled our data with other published studies, the association between this loci and the disease was further confirmed (pooled OR 1.54, 95% CI 1.37-1.72, P < 0.0001). These results suggested that the MDM2 SNP309 might influence the risk of developing HBV-related HCC in a northeast Han Chinese population.

Evaluation of immunohistochemical expression of MDM2 protein in comparison with MDM2 gene amplification in diagnosing lipomatous tumors

ObjectiveOur goal was to compare the immunohistochemical detection of murine double minute 2 (MDM2) protein and MDM2 gene amplification in diagnosing adipose tissue tumors.Materials and methodsMDM2 protein expression was examined by immunohistochemistry in formalin-fixed paraffin-embedded tissue sam

Expression of p53, MDM2, p21, heat shock protein 70, and HPV 16/18 E6 proteins in oral verrucous carcinoma and oral verrucous hyperplasia

Oral verrucous hyperplasia is a precancerous lesion of oral verrucous carcinoma. This study used immunohistochemistry to examine the expression of p53, murine double minute 2 (MDM2), p21, heat shock protein 70 (HSP 70), and human papillomavirus (HPV) 16/18 E6 proteins in 48 oral verrucous carcinoma and 30 oral verrucous hyperplasia samples. The mean labeling indices of p53, MDM2, p21, HSP 70, and HPV 16/18 E6 proteins in oral verrucous carcinoma samples were 21%, 31%, 7%, 17%, and 0.5%, respectively, and those in oral verrucous hyperplasia samples were 19%, 35%, 11%, 14%, and 0.3%, respectively. Immunohistochemistry with the above-cited 5 biomarkers could not help differentiate oral verrucous hyperplasia from oral verrucous carcinoma. The low expression of p21 may partially explain abnormal epithelial overgrowth in both verrucous lesions. The pathogenesis of both verrucous lesions may be at least partially attributed to the overexpression of MDM2 protein and moderate expression of HSP 70 protein in both lesions.

MDM2 SNP309T>G Polymorphism with Hepatocellular Carcinoma Risk: A Meta-analysis

The murine double minute 2 (MDM2) gene encodes a negative regulator of the tumor protein p53. A single nucleotide polymorphism (SNP) in MDM2 promoter, SNP309 T>G, has been reported to alter MDM2 protein expression and accelerate tumor formation in humans. Studies investigating the association between the polymorphism and human hepatocellular carcinoma (HCC) risk reported conflicting results. We performed a meta-analysis to explore the association of this polymorphism and HCC risk. All eligible studies published were searched for in PubMed. Crude odds ratios (ORs) with 95% confidence intervals (CIs) were assessed for the association using fixed- and random-effects models. We identified five case-control studies including 738 cases and 1014 controls for the present meta-analysis. In studies with limited data, we detected significant associations for all genetic models in the overall analysis (OR = 2.51, 95% CI = 1.88-3.36 for GG vs. TT, p <0.001, P(het) = 0.666; OR = 1.71, 95% CI = 1.35-2.18 for TG vs. TT, p <0.001, P(het) = 0.925; OR = 1.94, 95% CI = 1.54-2.43 for dominant model TG + GG vs. TT, p <0.001, P(het) = 0.772; OR = 1.74, 95% CI = 1.39-2.20 for recessive model GG vs. TT + TG, p <0.001, P(het) = 0.656). Moreover, in the subgroup analysis based on Hardy-Weinberg equilibrium (HWE) in controls, sample size, and ethnicity, significant associations were observed in most genetic models. This meta-analysis suggests that the MDM2 309 G allele probably acts as an important HCC risk factor. To further confirm our findings, well-designed studies with large sample sizes and representing different ethnicities are required.

MDM2 gene amplification and protein expressions in colon carcinoma: is targeting MDM2 a new therapeutic option?

The aim of this study was to investigate murine double minute-2 (MDM2) gene copy number changes in colon carcinoma and to correlate these findings with an immunohistochemical analysis of MDM2 protein expression and histopathologic prognostic indicators of the tumors. The study included 80 cases of sporadic colon carcinomas. MDM2 protein expression was assessed by immunohistochemistry, and MDM2 gene status by fluorescence in situ hybridization. MDM2 gene amplification was detected in 18% of the 80 cases examined. A strong correlation was found between MDM2 gene amplification and the presence, intensity, and staining proportion of cytoplasmic MDM2 protein expression (p = 0.01). No correlation was found between MDM2 gene amplification and the well-established histopathologic prognostic factors. Given the correlation with gene amplification, we clearly demonstrated that cytoplasmic expression of MDM2 protein is true and relevant and that this finding has to be taken into account when immunohistochemistry would be used as a screening for MDM2 gene amplification in the near future. Targeting MDM2 could be a new approach in colon cancer therapy. The amplification status could be a predictive factor of the response to MDM2-targeted therapy.

Prognostic Factors and Expression of MDM2 in Patients with Primary Extremity Liposarcoma

The objective of this study was to investigate MDM2 (murine double minute 2) protein expression and evaluate its relationship with some anatomical and pathological aspects, aiming also to identify prognostic factors concerning local recurrence-free survival, metastasis-free survival and overall survival in patients with primary liposarcomas of the extremities. Of 50 patients with primary liposarcomas of the extremities admitted to a Reference Service, between 1968 and 2004, 25 were enrolled in the study, following eligibility and exclusion criteria. The adverse factors that influenced the risk for local recurrence in the univariant analysis included male sex (P = 0.023), pleomorphic histological subtype (P = 0.027), and high histological grade (P = 0.007). Concerning metastasis-free survival, age less than 50 years (P = 0.040), male sex (P = 0.040), pleomorphic subtype (P < 0.001), and high histological grade (P = 0.003) had a worse prognosis. Adverse factors for overall survival were age under 50 years (P = 0.040), male sex (P = 0.040), pleomorphic subtype (P < 0.001), and high histological grade (P = 0.003). There was no correlation between immunohistochemically observed MDM2 protein expressions and the anatomical and pathological variables studied. The immunohistochemical expression of MDM2 protein was not considered to have a prognostic value for any of the surviving patients in this study (local recurrence-free survival, metastasis-free survival, or overall survival). The immunoexpression of MDM2 protein was a frequent event in the different subtypes of liposarcomas.

Effect of a Single Nucleotide Polymorphism in the Murine Double Minute 2 Promoter (SNP309) on the Sensitivity to Topoisomerase II–Targeting Drugs

A single nucleotide polymorphism (SNP) SNP309 (T-->G) in the murine double minute 2 (MDM2) promoter creates a high-affinity Sp1 binding site and increases the expression of MDM2 mRNA and protein. Approximately 40% of the populations harbor at least one variant allele and 12% to 17% are homozygous G/G at codon 309. This MDM2 SNP increases susceptibility to cancer and decreases the response of cancer cells to certain forms of treatment, such as radiation therapy and DNA-damaging drugs. Topoisomerase II (TopoII)-targeting agents are commonly used chemotherapeutic drugs with a broad spectrum of activity. However, resistance to TopoII poisons limits their effectiveness. We show that MDM2 SNP309 rendered a panel of cancer cell lines that are homozygous for SNP309 selectively resistant (approximately 10-fold) to certain TopoII-targeting chemotherapeutic drugs (etoposide, mitoxantrone, amsacrine, and ellipticine). The mechanism underlying this observation was Mdm2-mediated down-regulation of TopoII; on drug exposure, MDM2 bound to TopoII and resulted in decreased cellular enzyme content. Knockdown of MDM2 by RNA interference stabilized TopoIIalpha and decreased resistance to TopoII-targeting drugs. Thus, MDM2 SNP309 (T-->G) may represent a relatively common, previously unappreciated determinant of drug sensitivity. Given the frequency of SNP309 in the general population (40% in heterozygous T/G and 12% in homozygous G/G condition), our observation may have important implications for the individualization of cancer chemotherapy.

Lung Cancer Pathogenesis Associated With Wood Smoke Exposure

Tobacco is considered the most important cause of lung cancer, but other factors could also be involved in its pathogenesis. The aim of the present work was to establish an association between wood smoke exposure and lung cancer pathogenesis, and to analyze the effects of wood smoke on p53 and murine double minute 2 (MDM2) protein expression. Blood samples were obtained from 62 lung cancer patients, 9 COPD patients, and 9 control subjects. Of the 62 lung cancer patients, 23 were tobacco smokers (lung cancer associated with tobacco [LCT] group), 24 were exposed to wood smoke (lung cancer associated with wood smoke [LCW] group), and 15 could not be included in these groups. Western blot assays were performed to identify the presence of p53, phospho-p53, and murine double minute 2 (MDM2) isoforms in plasma samples. Densitometric analysis was used to determine the intensity of p53, phospho-p53, and MDM2 bands. Approximately 38.7% of the lung cancer patients examined had an association with wood smoke exposure, most of them women living in rural areas. Adenocarcinoma was present in 46.7% of these patients. The p53 and phospho-p53 proteins were significantly increased in LCW samples (56,536.8 +/- 4,629 densitometry units [DU] and 58,244.8 +/- 7,492 DU, respectively [+/- SD]), in comparison with the other groups. The 57-kD MDM2 isoform plasma concentration was very high in LCW and LCT samples (75,696.4 +/- 11,979 DU and 78,551.7 +/- 11,548 DU, respectively). MDM2-p53 complexes were present in a high concentration in control and COPD subjects. This allows p53 degradation and explains the low concentrations of p53 found in these groups. MDM2-phospho-p53 complexes were observed in COPD but not in the other samples. This correlates with the low concentration of p53 observed in the COPD group (13,657 +/- 2,012 DU), and could explain the different clinic evolution of this smoker population in comparison with the LCT subjects. This study suggests that there is a possible association of lung cancer with wood smoke exposure. Likewise, our findings demonstrate that wood smoke could produce similar effects on p53, phospho-p53, and MDM2 protein expression as tobacco.

Expression of MDM2 protein and mRNA in condyloma acuminata.

In order to investigate the role of murine double minute 2 (MDM2) in cell proliferation and carcinogenesis in condyloma acuminatum (CA), immunohistochemistry and in situ hybridization were used to detect the expression of MDM2 protein and mRNA in normal skin and skin lesions of CA of vulva. PCR was also used to detect HPV types. The results showed that in 32 observed CA specimens, the expression of MDM2 protein and mRNA was detected in 18 (56.25%) and 22 (68.75%) respectively, while the co-expression of MDM2 protein and mRNA was found in 14. PCR results revealed that HPV6/11 and HPV16/18 subtypes were shown in 28(87.5%) and 4 (12.5%) respectively out of 32 CA specimens. Out of the 18 positive specimens expressing MDM2 protein, HPV6/11 subtypes were shown in 15 and HPV16/18 subtypes in 3. In 22 positive specimens expressing MDM2 mRNA, HPV6/11 subtypes were shown in 18 and HPV16/18 subtypes in 4. No expression of MDM2 protein and MDM2 mRNA was observed in normal skin. Our study indicated that the overexpression of MDM2 might be involved in malignant proliferation and carcinogenesis of CA.

The expression of murine double minute 2 is a favorable prognostic marker in esophageal squamous cell carcinoma without p53 protein accumulation.

Murine double minute 2 (MDM2) is an oncoprotein that inhibits the function of p53 tumor-suppressor protein. Although there have been a few reports on MDM2 gene abnormalities, there has been no investigation into expression of the product of this gene in esophageal squamous cell carcinoma. Thus, the clinicopathological and prognostic significance of the product of the MDM2 gene is as yet unknown. MDM2 protein expression status was analyzed in surgically resected materials by immunohistochemical procedures. The expression of MDM2 significantly correlated inversely with tumor size, depth of invasion, lymph node metastasis, lymphatic vessel invasion, and stage of disease. However, the expression of MDM2 correlated with neither p53 protein accumulation status nor Ki-67 labeling index. The prognosis with MDM2-positive status was significantly better than that with MDM2-negative status for patients with p53-negative tumors, but not in those with p53-positive tumors. Moreover, multivariate analysis showed that the expression of MDM2 was an independent prognostic factor in patients with p53-negative tumors. These findings indicate that MDM2 immunohistochemical analysis may provide useful information concerning the prognosis in esophageal squamous cell carcinoma patients with p53-negative tumors.