WT1

Primary Author(s)*

Paul De Fazio, MSc, Monash Health

Synonyms

Wilms Tumor 1, Wilms Tumor Protein

Genomic Location

Cytoband: 11p13

Genomic Coordinates:

chr11:32,409,321-32,457,176 [hg19]

chr11:32,387,775-32,435,630 [hg38]

Cancer Category/Type

• Wilms’ Tumor

• Acute Myeloid Leukaemia (AML)

Gene Overview

Structure and Function

Wilms’ Tumor 1 (WT1) was originally cloned in 1990 as a tumour suppressor gene in Wilms’ tumor, a typically pediatric renal tumor (Call et al., 1990). A combination of alternative transcription and translation start sites, splicing, and RNA editing means that WT1 has many isoforms. Human WT1 spans up to 10 exons across multiple isoforms.

All WT1 isoforms contain four zinc finger regions at the C-terminus of the protein which are involved in DNA binding (Haber et al., 1991). The N-terminal region is comprised of proline-glutamine-rich sequences and is involved in RNA and protein interactions. A nine nucleotide (three amino acid – lysine, threonine, serine, or KTS) sequence exists at the 3’ end of exon 9. Alternative splicing leads to certain isoforms retaining or omitting the KTS sequence (Haber et al., 1991). Both +KTS and -KTS isoforms appear to have non-overlapping functions and are expressed in a specific ratio in normal cells (Haber et al., 1991; Hammes et al., 2001). Germline splice-site mutations resulting in reduced +KTS/-KTS ratios are responsible for Frasier syndrome (Barbaux et al., 1997). Alternative splicing of WT1 exon 5 also leads to some isoforms containing a 17 amino acid domain responsible for transcriptional activation through interaction with the prostate apoptosis response factor PAR4 (Richard et al., 2001).

WT1 is involved in cell growth and development. It has roles in, among others, the mesenchymal-to-epithelial transition during kidney and gonad development, the epithelial-to-mesenchymal transition during heart and diaphragm development, sensory neuron differentiation within the central nervous system, and adult tissue homeostasis (reviewed in (Hastie, 2017)). In the developing embryo it is expressed highly in the urogenital system, but in adults it can be found additionally in the central nervous system and in haematopoietic tissues (Menke et al., 1998). In vitro evidence suggests WT1 regulates BCL2 and MYC expression, and interacts with TP53 (Hewitt et al., 1995; Maheswaran et al., 1993).

Other than the tumours for which the gene is named, germline mutations affecting WT1 also variously cause WAGR syndrome (Wilms’ tumour, aniridia, genitourinary anomalies and retardation) (Riccardi et al., 1978), Denys-Drash syndrome (DDS) (Pelletier et al., 1991), the previously mentioned Frasier syndrome, and less clearly Meacham syndrome (Suri et al., 2007).

Role in Cancer

Due to the various and non-overlapping roles of WT1 depending on isoform, expression domain, and stage of development, mutations have diverse effects. WT1 can function as a tumour suppressor (as in Wilms’ Tumour) or as an oncogene (reviewed in (Yang et al., 2007)). Overexpression of WT1 is seen in a number of cancer contexts (Dohi et al., 2009; Hylander et al., 2006; Mikami et al., 2013; Rauscher et al., 2014; Ujj et al., 2016).

Wilms' Tumor

Accounting for 95% of pediatric renal tumors but rare in adults, Wilms’ tumour appears in both sporadic and hereditary forms. The tumor forms from undifferentiated cells and can be caused by multiple developmental errors. Mutations in WT1 were the first to be described (Huff and Saunders, 1993), and occur in ~15% of sporadic Wilms’ tumours (Gessler et al., 1994). In this context WT1 functions as a tumour suppressor. WT1 mutations in Wilms’ tumour are often associated with activating mutations in β-Catenin (CTNNB1) (Breslow et al., 2006; Maiti et al., 2000). WTX (also known as AMER1 or FAM123B) is also frequently mutated in WT1-mutated Wilms’ tumour (Rivera et al., 2007).

Acute Myeloid Leukemia

WT1 mutations occur in approximately 10-20% of adult and paediatric cytogenetically normal acute myeloid leukaemia (CN-AML), and with lower frequency in most other cytogenetic subgroups (Gaidzik et al., 2009; Hollink et al., 2009; Sano et al., 2013; Virappane et al., 2008). Mutations are typically frameshifts in exon 7 which truncate the DNA-binding domain or substitutions within exon 9, although other mutations do occur. Association between WT1 mutations and FLT3-ITD, KIT, and CEBPA biallelic mutations has been observed, but data varies by study (Gaidzik et al., 2009; Hollink et al., 2009; Krauth et al., 2015; Paschka et al., 2008; Sano et al., 2013; Virappane et al., 2008). WT1 mutations appear to be rarer in DNMT3A, ASXL1, TET2, IDH1, or IDH2 mutated AML (Krauth et al., 2015). WT1 and TET2 have been shown to interact, and WT1-mutant AML has aberrant DNA methylation similar to TET2 and IDH1/2 mutants, suggesting overlapping pathways (Rampal et al., 2014).

Complex cytogenetic abnormalities also correlate with reduced WT1 mutation frequency, but there is an increased frequency of WT1 mutations in individuals with t(15;17)/PML-RARA translocations (Krauth et al., 2015). WT1 mutation frequency increases in individuals less than 60 years of age. Overall, WT1 mutation appears to be associated with a poorer prognosis at least in CN-AML (Gaidzik et al., 2009; Hollink et al., 2009; Krauth et al., 2015; Paschka et al., 2008; Sano et al., 2013; Virappane et al., 2008). One report suggests that patients with WT1 and FLT3-ITD mutations may have poorer response to standard induction therapy than patients with FLT3-ITD mutations alone (Summers et al., 2007). WT1 mutations tend to be secondary rather than initiating events in leukemogenesis, and hence may only be present in subclones (Krauth et al., 2015). WT1 vaccination is being investigated as a therapeutic method in haematological malignancies (Brayer et al., 2015; Di Stasi et al., 2015).

Other Cancers

WT1 overexpression enhances ovarian cancer cell proliferation in vitro (Liu et al., 2014). Higher expression of WT1 is associated with higher stage in ovarian cancer and more aggressive clinical features, but evidence for the use of WT1 expression as a prognostic marker for overall survival is mixed (Köbel et al., 2008; Liu et al., 2014; Netinatsunthorn et al., 2006). A meta-analysis of solid cancers including breast cancer, endometrial cancer, colorectal cancer, and glioma among others found that WT1 expression correlated with worse clinical outcomes such as overall and disease-free survival (Qi et al., 2015). WT1-targeting therapies are being explored (Koido et al., 2014; Sawada et al., 2016; Shirakata et al., 2012).

Common Alteration Types

Put your text here and/or fill in the table with an X where applicable

Copy Number Loss	Copy Number Gain	LOH	Loss-of-Function Mutation	Gain-of-Function Mutation	Translocation/Fusion
EXAMPLE: X	EXAMPLE: X	EXAMPLE: X	EXAMPLE: X	EXAMPLE: X	EXAMPLE: X

Internal Pages

Put your text here

EXAMPLE Germline Cancer Predisposition Genes

External Links

Put your text here - Include as applicable links to: 1) Atlas of Genetics and Cytogenetics in Oncology and Haematology, 2) COSMIC, 3) CIViC, 4) St. Jude ProteinPaint, 5) Precision Medicine Knnowledgebase (Weill Cornell), 6) Cancer Index, 7) OncoKB, 8) My Cancer Genome, 9) UniProt, 10) Pfam, 11) GeneCards, 12) GeneReviews, and 13) Any gene-specific databases.

EXAMPLES

TP53 by Atlas of Genetics and Cytogenetics in Oncology and Haematology - detailed gene information

TP53 by COSMIC - sequence information, expression, catalogue of mutations

TP53 by CIViC - general knowledge and evidence-based variant specific information

TP53 by IARC - TP53 database with reference sequences and mutational landscape

TP53 by St. Jude ProteinPaint mutational landscape and matched expression data.

TP53 by Precision Medicine Knowledgebase (Weill Cornell) - manually vetted interpretations of variants and CNVs

TP53 by Cancer Index - gene, pathway, publication information matched to cancer type

TP53 by OncoKB - mutational landscape, mutation effect, variant classification

TP53 by My Cancer Genome - brief gene overview

TP53 by UniProt - protein and molecular structure and function

TP53 by Pfam - gene and protein structure and function information

TP53 by GeneCards - general gene information and summaries

GeneReviews - information on Li Fraumeni Syndrome

References

EXAMPLE Book

1. Arber DA, et al., (2008). Acute myeloid leukaemia with recurrent genetic abnormalities, in World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues, 4th edition. Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, Thiele J, Vardiman JW, Editors. IARC Press: Lyon, France, p117-118.

EXAMPLE Journal Article

1. Li Y, et al., (2001). Fusion of two novel genes, RBM15 and MKL1, in the t(1;22)(p13;q13) of acute megakaryoblastic leukemia. Nat Genet 28:220-221, PMID 11431691.

Notes

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