A genetic variant within MDM4 3'UTR miRNA binding site is associated with HPV16-positive tumors and survival of oropharyngeal cancer

Cellular, Structural Basis, and Recent Progress for Targeting Murine Double Minute X (MDMX) in Tumors

Murine double minute X (MDMX) is an oncoprotein that mainly has a negative regulatory effect on the tumor suppressor p53 to induce tumorigenesis. As MDMX is highly expressed in various types of tumor cells, targeting and inhibiting MDMX are becoming a promising strategy for treating cancers. However, the high degree of structural homology between MDMX and its homologous protein murine double minute 2 (MDM2) is a great challenge for the development of MDMX-targeted therapies. This review introduces the structure, distribution, and regulation of the MDMX, summarizes the structural features and structure-activity relationships (SARs) of MDMX ligands, and focuses on the differences between MDMX and MDM2 in these aspects. Our purpose of this work is to propose potential strategies to achieve the specific targeting of MDMX.

Posttranscriptional regulation of FAN1 by miR-124-3p at rs3512 underlies onset-delaying genetic modification in Huntington's disease

Many Mendelian disorders, such as Huntington's disease (HD) and spinocerebellar ataxias, arise from expansions of CAG trinucleotide repeats. Despite the clear genetic causes, additional genetic factors may influence the rate of those monogenic disorders. Notably, genome-wide association studies discovered somewhat expected modifiers, particularly mismatch repair genes involved in the CAG repeat instability, impacting age at onset of HD. Strikingly, FAN1, previously unrelated to repeat instability, produced the strongest HD modification signals. Diverse FAN1 haplotypes independently modify HD, with rare genetic variants diminishing DNA binding or nuclease activity of the FAN1 protein, hastening HD onset. However, the mechanism behind the frequent and the most significant onset-delaying FAN1 haplotype lacking missense variations has remained elusive. Here, we illustrated that a microRNA acting on 3'-UTR (untranslated region) SNP rs3512, rather than transcriptional regulation, is responsible for the significant FAN1 expression quantitative trait loci signal and allelic imbalance in FAN1 messenger ribonucleic acid (mRNA), accounting for the most significant and frequent onset-delaying modifier haplotype in HD. Specifically, miR-124-3p selectively targets the reference allele at rs3512, diminishing the stability of FAN1 mRNA harboring that allele and consequently reducing its levels. Subsequent validation analyses, including the use of antagomir and 3'-UTR reporter vectors with swapped alleles, confirmed the specificity of miR-124-3p at rs3512. Together, these findings indicate that the alternative allele at rs3512 renders the FAN1 mRNA less susceptible to miR-124-3p-mediated posttranscriptional regulation, resulting in increased FAN1 levels and a subsequent delay in HD onset by mitigating CAG repeat instability.

MDM4: What do we know about the association between its polymorphisms and cancer?

MDM4 is an important p53-negative regulator, consequently, it is involved in cell proliferation, DNA repair, and apoptosis regulation. MDM4 overexpression and amplification are described to lead to cancer formation, metastasis, and poor disease prognosis. Several MDM4 SNPs are in non-coding regions, and some affect the MDM4 regulation by disrupting the micro RNA binding site in 3'UTR (untranslated region). Here, we gathered several association studies with different MDM4 SNPs and populations to understand the relationship between its SNPs and solid tumor risk. Many studies failed to replicate their results regarding different populations, cancer types, and risk genotypes, leading to conflicting conclusions. We suggested that distinct haplotype patterns in different populations might affect the association between MDM4 SNPs and cancer risk. Thus, we propose to investigate some linkage SNPs in specific haplotypes to provide informative MDM4 markers for association studies with cancer.

MDM4 polymorphisms associated with the risk but not the prognosis of esophageal cancer in Cixian high-incidence region from northern China

AIM

The mouse double minute 4 (MDM4) may contribute to tumorgenesis by inhibiting p53 tumor suppressor activity. This study was designed to investigate whether MDM4 polymorphisms could affect susceptibility to esophageal squamous cell carcinoma (ESCC) and the survival of ESCC patients in a population from Cixian high-incidence region of northern China, which has not been explored.

METHODS

MDM4 rs1380576 and rs4245739 were genotyped by polymerase chain reaction-ligase detection reaction (PCR-LDR) in 568 ESCC patients and 578 controls.

RESULTS

Compared to rs1380576 C/C genotype, C/G genotype was associated with decreased risk of ESCC (odds ratio [OR] = 0.761, 95% confidence interval [CI] = 0.595-0.973). Compared to rs4245739 A/A genotype, A/C or C/C genotype was related to increased susceptibility to ESCC (OR = 1.551, 95% CI = 1.001-2.402). Individuals with GC haplotype had significantly higher risk of ESCC than those with CA or GA haplotype (OR = 1.598, 95% CI = 1.048-2.438). Neither rs1380576 nor rs4245739 influenced the survival of ESCC patients.

CONCLUSION

rs1380576 and rs4245739 may be used to predict susceptibility to ESCC for population in Cixian high-incidence region.

MDM4 alternative splicing and implication in MDM4 targeted cancer therapies

The oncogenic MDM4, initially named MDMX, has been identified as a p53-interacting protein and a key upstream negative regulator of the tumor suppressor p53. Accumulating evidence indicates that MDM4 plays critical roles in the initiation and progression of multiple human cancers. MDM4 is frequently amplified and upregulated in human cancers, contributing to overgrowth and apoptosis inhibition by blocking the expression of downstream target genes of p53 pathway. Disruptors for MDM4-p53 interaction have been shown to restore the anti-tumor activity of p53 in cancer cells. MDM4 possesses multiple splicing isoforms whose expressions are driven by the presence of oncogenes in cancer cells. Some of the MDM4 splicing isoforms lack p53 binding domain and may exhibit p53-independent oncogenic functions. These features render MDM4 to be an attractive therapeutic target for cancer therapy. In the present review, we primarily focus on the detailed molecular structure of MDM4 splicing isoforms, candidate regulators for initiating MDM4 splicing, deregulation of MDM4 isoforms in cancer and potential therapy strategies by targeting splicing isoforms of MDM4.

The role of miRNAs in MDMX-p53 interplay

MicroRNAs (miRNAs) are endogenous noncoding RNAs of 19-24 nucleotides in length and are tightly related to tumorigenesis and progression. Recent studies have demonstrated that the tumor suppressor p53 and its negative controller MDMX are regulated by miRNAs in different ways. Some miRNAs directly target p53 and regulate its expression and function, whereas some miRNAs target MDMX and regulate p53's activity indirectly. The overexpression of several miRNAs can restore the activity of p53 by negatively regulating MDMX in cancer cells. Therefore, a better understanding of the miRNAs-MDMX-p53 network will put forward potential research directions for developing anticancer therapeutics. In the present review, we mainly focus on the regulatory effects of miRNAs on the MDMX-p53 interplay as well as the role of the miRNAs-MDMX-p53 network in human cancer.

Association of MDM4 Gene rs4245739 Polymorphism with the Risk and Clinical Characteristics of Colorectal Cancer in a Chinese Han Population

Background

Studies show that MDM4 may play a pivotal role in colorectal cancer (CRC). Recently, a host of studies suggest that MDM4 gene rs4245739 polymorphism may modify the risk of different cancers.

Methods

In this study, we were interested whether MDM4 gene rs4245739 polymorphism correlated with the risk and clinical characteristics of CRC. Logistic regression was adopted to estimate the association of rs4245739 polymorphism and CRC risk.

Results

We enrolled 444 CRC patients and 530 controls and found MDM4 gene rs4245739 polymorphism may decrease the risk of CRC. Stratified analyses uncovered that this variant was connected to a less risk of CRC in females, non-drinkers, non-smokers, and people under 60 years old. Additionally, rs4245739 polymorphism was related to TNM staging, pathological type, tumor size, and location of CRC. Furthermore, this polymorphism was significantly linked with the survival of CRC.

Conclusion

Totally, this study suggests that MDM4 rs4245739 polymorphism is linked with the risk and clinical characteristics of CRC.