MYCN gene polymorphisms and Wilms tumor susceptibility in Chinese children

Abstract 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.


| INTRODUC TI ON
Wilms tumor is a classic embryonal tumor in the developing kidney, with a 90% cure rate. [1][2][3] Despite the high cure rate in patients with low-risk Wilms tumor, patients with poor histologic and molecular characteristics, bilateral lesions, and recurrent disease have a much lower survival rate and deserve more attentions. 4 Moreover, approximately 24% of Wilms tumor survivors are at a higher risk of other diseases, including second primary cancers, infertility, and cardiac disease. 5,6 In the clinical, although Wilms tumor patients have a high cure rate, high-risk patients still have a very poor prognosis. Therefore, we must fully understand the polymorphisms in Wilms tumor patients to find more effective, cheaper, and safer treatment.
At the same time, understanding the genetic inheritance of Wilms tumor is also an important premise to improve the prognosis of patients.

Some causal gene mutations have been reported in Wilms
tumor. For instance, individuals with WT1 mutations have an enormous risk of Wilms tumor. 7,8 A study by Ciceri et al suggested that constitutional anomalies of CHEK2 play an important role in the development of Wilms tumor. 9 Moreover, a series of genetic alterations were identified associate with Wilms tumor susceptibility, including WTX, 10 CITED1, 11 SIX1, 12 SIX2, 13 TP53, 14,15 HACE1,16 LIN28B, 17 and KRAS. 18

| Study subjects
In this hospital-based epidemiological study, we recruited 183 pa-

| SNP selection and genotyping
Four polymorphisms (rs57961569 G > A, rs9653226 T > C, rs13034994 A > G, and rs60226897 G > A) in the MYCN gene were selected in this study as we described previously. 25 Specific criteria of SNPs selection and genotyping methods have been described in our previous study. [26][27][28] All the above four polymorphisms are located at the binding sites of transcription factors, which have potential effects on the binding ability of transcription factors. In addition, they all have a minor allele frequency greater than 5% in the Chinese population.

| Statistical analysis
Hardy-Weinberg equilibrium (HWE) among controls was calculated using goodness-of-fit chi-squared test. And the differences in demographic variables and SNPs frequencies between cases and controls were tested using two-sided chi-squared test. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were adopted to appraise the association of MYCN gene SNPs with Wilms tumor risk.
Difference between groups was deemed to be effective significant when P < .05. All of the statistical analyses were processed with the

| Characteristics of study population
The characteristics of subjects from Wenzhou and Guangzhou are summarized in Table S1. All the participants were under the age of 15 years, and the mean age was 29.64 months (±25.71, range = 1-144 months) for cases and 29.00 months (±24.00, range = 0.07-156 months) for controls, respectively. The discrepancy in age and gender between the cases and controls was not statistically significant (P = .486 for age and P = .997 for gender). In the case group, 6.56% of the patients were in clinical stage I, 30.05% were in II, 31.69% were in III, 21.86% were in IV, and 9.84% were not available (NA).

| Correlation of MYCN gene polymorphisms with Wilms tumor risk
The detailed results are presented in Table 1. None of the four selected polymorphisms showed obvious deviation from the HWE in the control groups (P = .582 for the rs57961569 G > A polymorphism, P = .719 for the rs9653226 T > C polymorphism, P = .581 for the rs13034994 A > G polymorphism, P = .377 for the rs60226897 G > A polymorphism). Overall, no significant association was found between MYCN gene polymorphisms and Wilms tumor risk. No significant results were observed for the combined effect of risk genotypes either.

| Stratification analysis
Stratification analysis was performed according to age, sex, and clinical stages (

| D ISCUSS I ON
We performed the current study to investigate the association of  MYCN not only is related to the development of neuroblastoma, but also is one of the most powerful prognostic markers of neuroblastoma. We have delved the association between MYCN gene SNPs and neuroblastoma susceptibility before, and we found that SNP rs57961569 G > A was significantly associated with neuroblastoma risk. 25 MYCN also regulated the regulatory circuits of genes involved in the progression of neuroblastoma through TFAP4. 43  In conclusion, no significant association was found between MYCN gene polymorphisms and Wilms tumor risk in overall analysis, but stratification and haplotype analyses suggested that MYCN gene polymorphisms might be low penetrant variants in Wilms tumor susceptibility. Studies with larger sample size are need to verify our finding.

ACK N OWLED G M ENTS
This study was funded by grants from the Pearl River S&T Nova

CO N FLI C T S O F I NTE R E S T
The authors declare that there are no conflicts of interest.