The murine double minute 2 (MDM2) oncogene exerts major oncogenic activities in human cancers; it is not only the best‐documented negative regulator of the p53 tumor suppressor, but also exerts ...p53‐independent activities. There is an increasing interest in developing MDM2‐based targeted therapies. Several classes of MDM2 inhibitors have been evaluated in preclinical models, with a few entering clinical trials, mainly for cancer therapy. However, noncarcinogenic roles for MDM2 have also been identified, demonstrating that MDM2 is involved in many chronic diseases and conditions such as inflammation and autoimmune diseases, dementia and neurodegenerative diseases, heart failure and cardiovascular diseases, nephropathy, diabetes, obesity, and sterility. MDM2 inhibitors have been shown to have promising therapeutic efficacy for treating inflammation and other nonmalignant diseases in preclinical evaluations. Therefore, targeting MDM2 may represent a promising approach for treating and preventing these nonmalignant diseases. In addition, a better understanding of how MDM2 works in nonmalignant diseases may provide new biomarkers for their diagnosis, prognostic prediction, and monitoring of therapeutic outcome. In this review article, we pay special attention to the recent findings related to the roles of MDM2 in the pathogenesis of several nonmalignant diseases, the therapeutic potential of its downregulation or inhibition, and its use as a biomarker.
The tumor suppressor p53 is believed to be the mostly studied molecule in modern biomedical research. Although p53 interacts with hundreds of molecules to exert its biological functions, there are ...only a few modulators regulating its expression and function, with murine double minute 2 (MDM2) playing a key role in this regard. MDM2 also contributes to malignant transformation and cancer development through p53-dependent and -independent mechanisms. There is an increasing interest in developing MDM2 inhibitors for cancer prevention and therapy. We recently demonstrated that the nuclear factor of activated T cells 1 (NFAT1) activates MDM2 expression. NFAT1 regulates several cellular functions in cancer cells, such as cell proliferation, migration, invasion, angiogenesis, and drug resistance. Both NFAT isoforms and MDM2 are activated and overexpressed in several cancer subtypes. In addition, a positive correlation exists between NFAT1 and MDM2 in tumor tissues. Our recent clinical study has demonstrated that high expression levels of NFAT1 and MDM2 are independent predictors of a poor prognosis in patients with hepatocellular carcinoma. Thus, inhibition of the NFAT1-MDM2 pathway appears to be a novel potential therapeutic strategy for cancer. In this review, we summarize the potential oncogenic roles of MDM2 and NFAT1 in cancer cells and discuss the efforts of discovery and the development of several newly identified MDM2 and NFAT1 inhibitors, focusing on their potent in vitro and in vivo anticancer activities. This review also highlights strategies and future directions, including the need to focus on the development of more specific and effective NFAT1-MDM2 dual inhibitors for cancer therapy.
Neuroblastoma is an aggressive pediatric solid tumor with an overall survival rate of <50% for patients with high-risk disease. The majority (>98%) of pathologically-diagnosed neuroblastomas have ...wild-type p53 with intact functional activity. However, the mouse double minute 2 (MDM2) homolog, an E3 ubiquitin ligase, is overexpressed in neuroblastoma and leads to inhibition of p53. MDM2 also exerts p53-independent oncogenic functions. Thus, MDM2 seems to be an attractive target for the reactivation of p53 and attenuation of oncogenic activity in neuroblastoma.
In this study, we evaluated the anticancer activities and underlying mechanisms of action of SP141, a first-in-class MDM2 inhibitor, in neuroblastoma cell lines with different p53 backgrounds. The findings were confirmed in mouse xenograft models of neuroblastoma.
We demonstrate that SP141 reduces neuroblastoma cell viability, induces apoptosis, arrests cells at the G2/M phase, and prevents cell migration, independent of p53. In addition, in neuroblastoma xenograft models, SP141 inhibited MDM2 expression and suppressed tumor growth without any host toxicity at the effective dose.
MDM2 inhibition by SP141 results in the inhibition of neuroblastoma growth and metastasis, regardless of the p53 status of the cells and tumors. These findings provide proof-of-concept that SP141 represents a novel treatment option for both p53 wild-type and p53 null neuroblastoma.
There is a desperate need for novel and efficacious chemotherapeutic strategies for human brain cancers. There are abundant molecular alterations along the p53 and MDM2 pathways in human glioma, ...which play critical roles in drug resistance. The present study was designed to evaluate the in vitro and in vivo antitumor activity of a novel brain-penetrating small molecule MDM2 degrader, termed SP-141. In a panel of nine human glioblastoma and medulloblastoma cell lines, SP-141, as a single agent, potently killed the brain tumor-derived cell lines with IC
values ranging from 35.8 to 688.8 nM. Treatment with SP-141 resulted in diminished MDM2 and increased p53 and p21
levels, G2/M cell cycle arrest, and marked apoptosis. In intracranial xenograft models of U87MG glioblastoma (wt p53) and DAOY medulloblastoma (mutant p53) expressing luciferase, treatment with SP-141 caused a significant 4- to 9-fold decrease in tumor growth in the absence of discernible toxicity. Further, combination treatment with a low dose of SP-141 (IC
) and temozolomide, a standard anti-glioma drug, led to synergistic cell killing (1.3- to 31-fold) in glioma cell lines, suggesting a novel means for overcoming temozolomide resistance. Considering that SP-141 can be taken up by the brain without the need for any special delivery, our results suggest that SP-141 should be further explored for the treatment of tumors of the central nervous system, regardless of the p53 status of the tumor.
► VNTR polymorphism in the promoter region of XRCC5 (rs6147172) has been reported. ► The aim of this study is to introduce a novel allele for the XRCC5 VNTR polymorphism. ► In the current study, we ...identified a new allele (named the 3R allele). ► Promoter of XRCC5 contains several copies of Sp1 recognition cis regulatory elements. ► The novel 3R allele could expand the number of cis regulatory elements to eight.
Polymorphism of variable number of tandem repeats (VNTR) in the promoter region of X-ray repair cross-complementing 5 (XRCC5; MIM: 194364, rs6147172) has been reported. The main aim of the present study is to introduce a novel allele for the VNTR polymorphism in the promoter region of XRCC5. The participants of the present study were of 535 (140 males, 395 females), unrelated, adult, healthy Iranian blood donors (Caucasians/Muslims). Genotypes of XRCC5 VNTR were determined by a high resolution melting analysis, and confirmed by DNA sequencing. Based on the sequencing of new bands upper than the 2R allele band, a novel allele was introduced (named 3R allele). The promoter region of XRCC5 contains several copies of Sp1 recognition cis regulatory elements. The novel 3R allele is capable of expanding the number of cis regulatory elements to eight. The prevalence of the 0R, 1R, 2R and 3R alleles in our sample was 0.0645, 0.5439, 0.3794 and 0.0122, respectively. The study group was at the Hardy–Weinberg equilibrium for the genotypic frequencies (χ2=3.95, df=6, P=0.73). It is suggested that the prevalence of the novel allele (3R allele) among European populations may be higher than its prevalence among Iranians.
► VNTR polymorphism in the promoter region of XRCC5 (rs6147172) has been reported. ► This polymorphism has four alleles: 3R, 2R, 1R and 0R. ► This study is investigating the influence of this ...polymorphism on XRCC5 mRNA levels. ► The mRNA level of XRCC5 decreased as function of number of tandem repeats. ► The 3R allele dramatically decreases the gene expression of XRCC5.
Polymorphism of variable number of tandem repeats (VNTR) in the promoter region of X-ray repair cross-complementing 5 (MIM: 194364, XRCC5; rs6147172) was reported. The aim of the present study is to evaluate the influence of this polymorphism on XRCC5 mRNA levels. Genotypes of XRCC5 VNTR were determined by high resolution of melting analysis (HRMA). The quantitative XRCC5 mRNA expression (compared to ß-actin expression) among 0R/1R, 1R/2R, and 1R/3R genotypes was investigated. There was a negative correlation between the overall number of tandem repeats and XRCC5 expression (r=−0.965, df=7, P<0.001). The mRNA level of XRCC5 decreased as function of number of tandem repeats. The 3R allele of the VNTR polymorphism in the XRCC5 promoter region dramatically decreases the gene expression.
In heart failure, signaling downstream the β2-adrenergic receptor is critical. Sympathetic stimulation of β2-adrenergic receptor alters cAMP (cyclic adenosine 3',5'-monophosphate) and triggers PKA ...(protein kinase A)-dependent phosphorylation of proteins that regulate cardiac function. cAMP levels are regulated in part by PDEs (phosphodiesterases). Several AKAPs (A kinase anchoring proteins) regulate cardiac function and are proposed as targets for precise pharmacology. AKAP12 is expressed in the heart and has been reported to directly bind β2-adrenergic receptor, PKA, and PDE4D. However, its roles in cardiac function are unclear.
cAMP accumulation in real time downstream of the β2-adrenergic receptor was detected for 60 minutes in live cells using the luciferase-based biosensor (GloSensor) in AC16 human-derived cardiomyocyte cell lines overexpressing AKAP12 versus controls. Cardiomyocyte intracellular calcium and contractility were studied in adult primary cardiomyocytes from male and female mice overexpressing cardiac AKAP12 (AKAP12
) and wild-type littermates post acute treatment with 100-nM isoproterenol (ISO). Systolic cardiac function was assessed in mice after 14 days of subcutaneous ISO administration (60 mg/kg per day). AKAP12 gene and protein expression levels were evaluated in left ventricular samples from patients with end-stage heart failure.
AKAP12 upregulation significantly reduced total intracellular cAMP levels in AC16 cells through PDE8. Adult primary cardiomyocytes from AKAP12
mice had significantly reduced contractility and impaired calcium handling in response to ISO, which was reversed in the presence of the selective PDE8 inhibitor (PF-04957325). AKAP12
mice had deteriorated systolic cardiac function and enlarged left ventricles. Patients with end-stage heart failure had upregulated gene and protein levels of AKAP12.
AKAP12 upregulation in cardiac tissue is associated with accelerated cardiac dysfunction through the AKAP12-PDE8 axis.
► High resolution melting analysis (HRMA) is a recent development method for genotyping. ► This study introduces the HRMA method for genotyping of the XRCC5 VNTR polymorphism. ► All genotypes of the ...XRCC5 VNTR polymorphism could be accurately detected by HRMA.
Several polymorphisms in the XRCC5 (X-ray repair cross-complementing 5; OMIM: 194364) were reported. Polymorphism of variable number of tandem repeats (VNTR) in the promoter region of XRCC5 (rs6147172) was reported. The main aim of the present study is to introduce the high resolution melting analysis (HRMA) method for genotyping of the polymorphism of XRCC5 VNTR. Genotypes of XRCC5 VNTR were determined by HRMA and conventional PCR method, and confirmed by DNA sequencing. The results for genotyping using HRMA and conventional PCR showed 100% concordance. All genotypes of the XRCC5 VNTR polymorphism could be accurately detected by HRMA.
Variation in DNA repair genes is one of the mechanisms that may lead to variation in DNA repair capacity. Ku, a heterodimeric DNA-binding complex, is directly involved in repair of DNA double-strand ...breaks. Ku consists of two subunits, Ku70 and Ku80, which are encoded by the
XRCC6
and
XRCC5
genes, respectively. In the present study, we investigated whether common genetic variant in variable number of tandem repeats (VNTR)
XRCC5
and T-991C
XRCC6
was associated with an altered risk of breast cancer. The present study included 407 females with breast cancer and 395 age frequency-matched controls which were randomly selected from the healthy female blood donors. The
XRCC5
and
XRCC6
polymorphisms were determined using PCR-based methods. For
XRCC5
polymorphism, in comparison with the 1R/1R genotype, the 0R/0R genotype increased breast cancer risk (OR 9.55, 95 %CI 1.19–76.64,
P
= 0.034). The 1R/3R genotype compared with 1R/1R genotype decreased the risk of breast cancer (Fisher’s exact test
P
= 0.015). There was no association between T-991C polymorphism of
XRCC6
and breast cancer risk. Mean of age at diagnosis of breast cancer for 0, 1, 2, 3, and >4 repeat in
XRCC5
were 39.2, 41.9, 44.3, 45.8, and 47.3 years, respectively. The Kaplan–Meier survival analysis revealed that the number of repeat was associated with age at diagnosis of breast cancer (log rank statistic = 13.90,
df
= 4,
P
= 0.008). The findings of the present study revealed that either breast cancer risk or age at diagnosis of breast cancer was associated with the VNTR polymorphism at promoter region of
XRCC5
.
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