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Single Nucleotide Polymorphisms in the Wilms' Tumour Gene 1 in Clear Cell Renal Cell Carcinoma
Umeå University, Faculty of Medicine, Department of Medical Biosciences, Clinical chemistry.
Umeå University, Faculty of Medicine, Department of Medical Biosciences, Clinical chemistry.
Umeå University, Faculty of Medicine, Department of Surgical and Perioperative Sciences, Urology and Andrology.
Umeå University, Faculty of Medicine, Department of Medical Biosciences, Clinical chemistry. Umeå University, Faculty of Medicine, Department of Medical Biosciences, Pathology.
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2013 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 3, e58396Article in journal (Refereed) Published
Abstract [en]

The Wilms' tumour gene 1 (WT1) single nucleotide polymorphism (SNP) rs16754 has recently been described as an independent prognostic factor in acute myeloid leukaemia (AML) patients. It is of great interest to test whether WT1 SNPs can be used as a molecular marker in other cancer types in order to improve risk and treatment stratification. We performed sequencing analysis on all 10 exons of the WT1 gene in a total of 182 patients with clear cell renal cell carcinoma (ccRCC). Six different SNPs were identified, in descending order for minor allele frequency: rs2234582, rs16754, rs1799925, rs5030315, rs2234583, and rs2234581. At least one minor allele for WT1 SNP was identified in 61% of ccRCC patients. In the entire study population, only 6% carried two copies of the minor allele. The genotypes of WT1 SNPs in 78 tumour-free kidney tissue specimens were found to be in 95% concordance with corresponding tumour samples. No correlation was observed between WT1 SNP genotypes and RNA expression level. WT1 SNP genotypes did not associate with clinical and pathological characteristics. We found favourable outcomes associated with the homozygous minor allele for WT1 SNP. However, SNP genotypes did not show to be of prognostic significance when comparing wild-type versus homozygous or heterozygous for the minor allele in the entire cohort. None of the previously reported WT1 mutations in AML was found in the present study. A novel WT1 missense mutation was identified in only one patient. Our data suggest that common WT1 mutations are not involved in ccRCC. Due to too few cases harbouring the homozygous minor allele, the prognostic impact needs to be verified in larger study populations.

Place, publisher, year, edition, pages
2013. Vol. 8, no 3, e58396
National Category
Cancer and Oncology
Identifiers
URN: urn:nbn:se:umu:diva-70351DOI: 10.1371/journal.pone.0058396ISI: 000316936100116OAI: oai:DiVA.org:umu-70351DiVA: diva2:621658
Available from: 2013-05-16 Created: 2013-05-14 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Wilms' tumor gene 1 in different types of cancer
Open this publication in new window or tab >>Wilms' tumor gene 1 in different types of cancer
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The Wilms’ tumor gene 1 (WT1) was first reported as a tumor suppressor gene in Wilms’ tumor. However, later studies have shown the oncogenic properties of WT1 in a variety of tumors. It was recently proposed that WT1 was a chameleon gene, due to its dual functions in tumorigenesis. We aimed to investigate the clinical significance of WT1 as biomarker in acute myeloid leukemia (AML) and clear cell renal cell carcinoma (ccRCC) and to elucidate the function of WT1 as an oncogene in squamous cell carcinoma of head and neck (SCCHN).

In AML, it was suggested that WT1 expression was an applicable marker of minimal residual disease (MRD). In adult patients with AML, we found a good correlation between WT1 expression levels normalized to two control genes, β-actin and ABL. Outcome could be predicted by a reduction in WT1 expression in bone marrow (≥ 1-log) detected less than 1 month after diagnosis, when β-actin was used as control. Also, irrespective of the control gene used, outcome could be predicted by a reduction in WT1 expression in peripheral blood (≥ 2-log) detected between 1 and 6 months after treatment initiation.

Previous studies in RCC demonstrated that WT1 acted as a tumor suppressor. Thus, we tested whether single nucleotide polymorphisms (SNPs) or mutations in WT1 might be associated with WT1 expression and clinical outcome in patients with ccRCC. We performed sequencing analysis on 10 exons of the WT1 gene in a total of 182 patient samples, and we identified six different SNPs in the WT1 gene. We found that at least one or two copies of the minor allele were present in 61% of ccRCC tumor samples. However, no correlation was observed between WT1 SNP genotypes and RNA expression levels. Moreover, none of the previously reported WT1 mutations were found in ccRCC. Nevertheless, we found that a favorable outcome was associated the homozygous minor allele for WT1 SNP. We then further investigated whether WT1 methylation was related to WT1 expression and its clinical significance. Methylation array and pyrosequencing analyses showed that the WT1 promoter region CpG site, cg22975913, was the most frequently hypermethylated CpG site. We found a trend that showed nearly significant correlation between WT1 mRNA levels and hypermethylation in the 5’-untranslated region. Hypermethylation in the WT1 CpG site, cg22975913, was found to be associated with patient age and a worse prognosis.

One previous study reported that WT1 was overexpressed in SCCHN. That finding suggested that WT1 might play a role in oncogenesis. We found that both WT1 and p63 could promote cell proliferation. A positive correlation between WT1 and p63 expression was observed, and we identified p63 as a WT1 target gene. Furthermore, several known WT1 and p63 target genes were affected by knocking down WT1. Also, co-immunoprecipitation analyses demonstrated a protein interaction between WT1 and p53.

In summary, WT1 gene expression can provide useful information for MRD detection during treatment of patients with AML. In RCC, our results suggested that the prognostic impact of WT1 SNPs was limited to the subgroup of patients that were homozygous for the minor allele, and that WT1 promoter hypermethylation could be used as a prognostic biomarker. In SCCHN, WT1 and p63 acted as oncogenes by affecting multiple genes involved in cancer cell growth.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. 59 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1717
Keyword
WT1, AML, MRD, ccRCC, SNPs, DNA methylation, SCCHN, p63
National Category
Cancer and Oncology
Research subject
Clinical Chemistry
Identifiers
urn:nbn:se:umu:diva-103389 (URN)978-91-7601-263-5 (ISBN)
Public defence
2015-06-12, Hörsal Betula, 6M, Norrlands universitetssjukhus, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2015-05-22 Created: 2015-05-21 Last updated: 2015-09-02Bibliographically approved
2. Significance of Wilms’ tumor gene 1 as a biomarker in acute leukemia and solid tumors
Open this publication in new window or tab >>Significance of Wilms’ tumor gene 1 as a biomarker in acute leukemia and solid tumors
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Wilms’ tumor gene 1 (WT1) is a zinc finger transcriptional regulator with crucial functions in embryonic development. Originally WT1 was described as a tumor suppressor gene, but later studies have shown oncogenic properties of WT1 in a variety of tumors. Because of its dual functions in tumorigenesis, WT1 has been described as a chameleon gene. In this thesis, the significance of WT1 as a biomarker was investigated in acute myeloid leukemia (AML), clear cell renal cell carcinoma (ccRCC), ovarian carcinoma (OC) and childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL).

Previous studies have suggested that expression of WT1 is a potential marker for detection of minimal residual disease (MRD) in AML. We aimed to define expression of WT1 as an MRD marker in AML. In adult AML patients, we found that a reduction of WT1 expression in bone marrow (≥ 1-log) detected less than 1 month after diagnosis was associated with an improved overall survival (OS) and freedom from relapse (FFR). In peripheral blood, a reduction of WT1 expression (≥ 2-log) detected between 1 and 6 months after treatment initiation was associated with an improved OS and FFR.

WT1 harbor pathogenic genetic variants in a considerable proportion of AML and T-lymphoblastic leukemia (T-ALL), but mutations have not been reported in BCP-ALL. We aimed to evaluate the clinical impact of WT1 mutations and single nucleotide polymorphisms (SNPs) in BCP-ALL. Pathogenic mutations in the WT1 gene were rarely seen in childhood BCP-ALL. However, five WT1 SNPs were identified. In survival analyses, WT1 SNP rs1799925 was found to be associated with worse OS, indicating that WT1 SNP rs1799925 may be a useful marker for clinical outcome in childhood BCP-ALL. We also explored whether WT1 mutations and SNPs in ccRCC could be used as biomarkers for risk and treatment stratification. We therefore examined whether SNPs or mutations in WT1 were associated with WT1 expression and clinical outcome. Sequencing analysis revealed that none of the previously reported WT1 mutations were found in ccRCC; however, we identified six different WT1 SNPs. Our data suggest that pathogenic WT1 mutations are not involved in ccRCC, and the prognostic significance of WT1 SNPs in ccRCC is considerably weak. However, a favorable OS and disease-specific survival were found in the few cases harboring the homozygous minor allele.

OC has a poor prognosis, and early effective screening markers are lacking. Serous OCs are known to express the WT1 protein. Overexpressed oncogenic proteins can be considered potential candidate antigens for cancer vaccines and T-cell therapy. It was therefore of great interest to investigate whether anti-WT1 IgG antibody (Ab) measurements in plasma could serve as biomarkers of anti-OC response. We found limited prognostic impact, but the results indicated that anti-WT1 IgG Ab measurements in plasma and WT1 staining in tissue specimens could be potential biomarkers for patient outcome in the high-risk subtypes of OCs.

In conclusion, the results of this thesis indicate that WT1 gene expression can provide information about MRD of patients with AML, and WT1 SNP rs1799925 may be used as a biomarker for predicting clinical outcome in childhood BCP-ALL. In ccRCC, the prognostic significance of WT1 SNPs is weak and limited to the subgroup of patients that are homozygous for the minor allele. In OCs anti-WT1 IgG Ab measurement in plasma and WT1 staining in tissue specimens could possibly be used as biomarkers for predicting patient outcome in the high-risk subtypes of OCs.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2016. 67 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1799
Keyword
Wilms’ tumor gene 1, biomarker, leukemia, renal cell carcinoma, ovarian carcinoma
National Category
Clinical Laboratory Medicine
Research subject
Clinical Chemistry; Pathology
Identifiers
urn:nbn:se:umu:diva-120912 (URN)978-91-7601-458-5 (ISBN)
Public defence
2016-06-15, Sal D, 9 tr., Tandläkarhögskolan, Norrlands universitetssjukhus (NUS), Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2016-05-25 Created: 2016-05-23 Last updated: 2016-05-26Bibliographically approved

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