MYCN gene polymorphisms and Wilms tumor susceptibility in Chinese children

N-Myc transcriptionally activates Skp2 to suppress p27 expression in small cell lung cancer

BACKGROUND

Small cell lung cancer (SCLC) is characterized by a high proliferative rate, a strong predilection for early metastasis and poor prognosis. Novel SCLC biomarkers are urgently required to improve current diagnostic and treatment modalities. MYCN encodes the proto-oncogene N-Myc that is overexpressed in SCLC, but its downstream effectors are poorly characterized. Here, we investigated the role of the N-Myc/Skp2/p27 axis during SCLC progression.

METHODS

Immunohistochemistry (IHC) and western blotting were performed to evaluate N-Myc/Skp2/p27 expression. SCLC cell apoptosis was investigated through TUNEL staining. Wound healing and transwell assays were performed to detect the migratory and invasive potential of SCLC cells. N-Myc and Skp2 binding was confirmed through luciferase reporter and ChIP assays. Xenograft models were developed to investigate the function of Skp2 during SCLC tumor growth in vivo.

RESULTS

N-Myc and Skp2 were overexpressed in SCLC, whilst p27 expression was suppressed. Skp2 facilitated SCLC progression by protecting cells from apoptosis and facilitating cell migration and invasion. N-Myc was found to bind to the promoter region of Skp2 to enhance its expression. Skp2 enhanced tumor growth in vivo through the suppression of p27. Skp2 silencing reversed the pro-oncogenic effects of N-myc in SCLC tumors.

CONCLUSION

We show that N-Myc enhances Skp2 to regulate p27 expression during SCLC progression. We therefore highlight the N-Myc/Skp2/p27 axis as a novel diagnostic and much-needed therapeutic target in SCLC.

Mycn deficiency underlies the development of orofacial clefts in mice and humans

Non-syndromic cleft lip with or without cleft palate (NSCL/P) is the most common subphenotype of non-syndromic orofacial clefts (NSOFCs) arising from genetic and/or environmental perturbations during embryonic development. We previously identified 2p24.2 as a risk locus associated with NSCL/P in the Chinese Han population, and MYCN is a candidate risk gene in this region. To understand the potential function of MYCN in craniofacial development, we generated Wnt1-Cre;Mycnflox/flox mice that exhibited cleft palate, microglossia, and micrognathia, resembling the Pierre Robin sequence (PRS) in humans. Further analyses indicated that the cleft palate was secondary to the delayed elevation of palatal shelves caused by micrognathia. The micrognathia resulted from impaired chondrogenic differentiation in Merkel's cartilage, which limited tongue development, leading to microglossia. In terms of mechanism, Mycn deficiency in cranial neural crest cells (CNCCs) downregulated Sox9 expression by inhibiting Wnt5a in a CNCC-derived chondrogenic lineage in Merkel's cartilage. To investigate whether MYCN deficiency contributed to NSCL/P, we performed direct sequencing targeting all exons and exon-intron boundaries of MYCN in 104 multiplex families with mendelian NSCL/P and identified a novel pathogenic variant in MYCN. Taken together, our data indicate that ablation of Mycn in mouse CNCCs could resemble PRS by suppressing the Wnt5a-Sox9 signaling pathway in Merkel's cartilage and that mutations in MYCN may be novel potential causes of NSCL/P.

The association of miR34b/c and TP53 gene polymorphisms with Wilms tumor risk in Chinese children

Wilms tumor is the most common pediatric malignancy in the kidney. The miR34b/c is a downstream target gene of the transcription factor p53. The important role of TP53 mutations, the methylation of miR34b/c, and the interaction between these two molecules in tumorigenesis have been well documented. Due to the biological connection between p53 and miR34b/c, in the present study, we investigated the association between polymorphisms in these two molecules and Wilms tumor susceptibility through genotyping two important functional polymorphisms (miR34b/c rs4938723 T>C and TP53 rs1042522 C>G) in 183 cases and 603 controls. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) derived from the logistic regression analysis were used to assess the correlation of miR34b/c rs4938723 and TP53 rs1042522 polymorphisms with Wilms tumor risk. Our results indicated that the association of miR34b/c rs4938723 and TP53 rs1042522 polymorphisms with Wilms tumor susceptibility was not statistically significant. Stratified analysis by age, gender, and clinical stage, as well as combined effect analysis were also performed, yet, no significant association was found. In conclusion, our study indicated a lack of association between the two selected polymorphisms and Wilms tumor susceptibility. Our findings need to be verified in studies with larger sample size in the future.

HMGA2 Polymorphisms and Hepatoblastoma Susceptibility: A Five-Center Case-Control Study

BACKGROUND

Hepatoblastoma is a rare disease. Its etiology remains obscure. No epidemiological reports have assessed the relationship of High Mobility Group A2 (HMGA2) single nucleotide polymorphisms (SNPs) with hepatoblastoma risk. This case-control study leads as a pioneer to explore whether HMGA2 SNPs (rs6581658 A>G, rs8756 A>C, rs968697 T>C) could impact hepatoblastoma risk.

METHODS

We acquired samples from 275 hepatoblastoma cases and 1018 controls who visited one of five independent hospitals located in the different regions of China. The genotyping of HMGA2 SNPs was implemented using the PCR-based TaqMan method, and the risk estimates were quantified by odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

In the main analysis, we identified that rs968697 T>C polymorphism was significantly related to hepatoblastoma risk in the additive model (adjusted OR=0.73, 95% CI=0.54-0.98, P=0.035). Notably, participants carrying 2-3 favorable genotypes had reduced hepatoblastoma risk (adjusted OR=0.71, 95% CI=0.52-0.96, P=0.028) in contrast to those carrying 0-1 favorable genotypes. Furthermore, stratification analysis revealed a significant correlation between rs968697 TC/CC and hepatoblastoma risk for males and clinical stage I+II. The existence of 2-3 protective genotypes was correlated with decreased hepatoblastoma susceptibility in children ≥17 months old, males, and clinical stage I+II cases, when compared to 0-1 protective genotype.

CONCLUSION

To summarize, these results indicated that the HMGA2 gene SNPs exert a weak influence on hepatoblastoma susceptibility. Further validation of the current conclusion with a larger sample size covering multi-ethnic groups is warranted.

MYCN gene polymorphisms and Wilms tumor susceptibility in Chinese children

BACKGROUND

Wilms tumor, derived from embryonic cells, accounts for a large proportion of pediatric renal tumors. MYCN encoded by MYCN proto-oncogene, a member of the MYC family, is a BHLH transcription factor. It plays a critical role in tumorigenesis and predicts poor clinical outcomes in various types of cancer. However, the role of MYCN remained unclarified in Wilms tumor. In this study, we investigated the association between MYCN gene polymorphisms and Wilms tumor susceptibility.

METHODS

Four MYCN gene polymorphisms (rs57961569 G > A, rs9653226 T > C, rs13034994 A > G, and rs60226897 G > A) were genotyped in 183 cases and 603 controls. Adjusted odds ratios (AORs) and 95% confidence intervals (CIs) were calculated to evaluate the association between MYCN gene polymorphisms and Wilms tumor susceptibility.

RESULTS

Overall, no significant association was found for any of the four MYCN gene polymorphisms. Interestingly, in the stratification analysis, the rs57961569 was found to be associated with decreased Wilms tumor susceptibility in the children older than 18 months (AOR = 0.65, 95% CI = 0.42-1.00, P = .050). Moreover, older children carrying 2-4 risk genotypes were at increased risk of Wilms tumor (OR = 1.55, 95% CI = 1.001-2.40, P = .0497). Haplotype GCAA was shown to significantly increased Wilms tumor risk (AOR = 2.40, 95% CI = 1.12-5.14, P = .024).

CONCLUSION

Our study demonstrated that these MYCN gene polymorphisms might be low penetrant variants in Wilms tumor.