A Murine Model of K-RAS and β-Catenin Induced Renal Tumors Expresses High Levels of E2F1 and Resembles Human Wilms Tumor

Abstract

Background Wilms tumor (WT) is the most common renal neoplasm of childhood. We previously showed that restricted activation of the WNT/β-catenin pathway in renal epithelium late in kidney development is sufficient to induce small primitive neoplasms with features of epithelial WT. Metastatic disease progression required simultaneous addition of an activating mutation of the oncogene K-RAS. Here, we sought to define the molecular pathways activated in this process and their relationship to human renal malignancies. Methods Affymetrix expression microarray data from murine kidneys with activation of K-ras, Ctnnb1 (β-catenin), or both restricted to renal epithelium were analyzed and compared to publically available expression data from normal and neoplastic human renal tissue. Target genes were verified by immunoblot and immunohistochemistry. Results Mouse kidney tumors with activation of K-ras and Ctnnb1 and human renal malignancies have similar mRNA expression signatures and are associated with activation of networks centered on β-catenin and TP53. Up-regulation of WNT/β-catenin targets (MYC, Survivin, FOXA2, Axin2, Cyclin D1) was confirmed by immunoblotting. K-RAS/β-catenin murine kidney tumors were more similar to human WT than other renal malignancies and demonstrated activation of a TP53 dependent network of genes including the transcription factor E2F1. Up-regulation of E2F1 was confirmed in both murine and human WT samples. Conclusions Simultaneous activation of K-RAS and β-catenin in embryonic renal epithelium leads to neoplasms similar to human WT associated with activation of TP53 and up-regulation of E2F1. Further studies to evaluate the role of TP53 and E2F1 in human WT are warranted.

Functional KRAS mutations and a potential role for PI3K/AKT activation in Wilms tumors

“…We previously reported that coordinate activation of KRAS and b-catenin in murine kidneys causes the formation of primitive renal epithelial neoplasms that are histologically consistent with epithelial predominant WT and that are characterized by excessive ERK and AKT activation (Clark et al, 2011;Yi et al, 2015). To investigate whether KRAS mutations are present in human WT, we profiled 19 human WT specimens using a multiplex PCR, multiplex primer extension, and capillary electrophoresis (SNaPShot method) screen (Dias-Santagata et al, 2010;Lovly et al, 2012;Su et al, 2011).…”

Genetic and chromosomal alterations in Kenyan Wilms Tumor

“…To explore the consistent gain at chromosome 12 observed in this KWT cohort and reported in other WT populations as well, we examined the OncoScan array data for somatic mutations in KRAS, which is the only of 9 genes included on this platform to be located on chromosome 12 and which has been shown in a transgenic WT model to drive disease progression (Clark et al, 2011;Yi et al, 2015). CNG at 12p12.1, the KRAS locus, was observed in 14 of the KWTs (47%), and 6 of these children (43%) are confirmed deceased.…”

Pharmacologic Inhibition of β-Catenin With Pyrvinium Inhibits Murine and Human Models of Wilms Tumor

“…23–25 We have shown that coordinate activation of Ras with β-catenin leads to rapidly progressive, metastatic tumors that demonstrate markedly increased canonical β-catenin pathway activation. 23,24 In large series, similar activation has been demonstrated in the majority of human WT. 26–28 Collectively, this suggests the canonical β-catenin pathway may represent a potential therapeutic target in WT, particularly in those patients with more advanced or high risk disease.…”

“…We have shown that a gene expression signature that distinguishes a mouse model and human WT from normal human kidney or other neoplasms includes marked up-regulation of c-Myc. 24 Mutations in the YEATS domain of the MLLT1 gene have recently also been linked to the development of WT and are characterized by increased MYC expression. 55 Prior work has shown that kidneys of mice harboring activating mutations of K-Ras and β-catenin restricted to the renal epithelium develop metastatic WT and have significantly increased c-Myc and Birc5 ’s protein product, survivin.…”

“…55 Prior work has shown that kidneys of mice harboring activating mutations of K-Ras and β-catenin restricted to the renal epithelium develop metastatic WT and have significantly increased c-Myc and Birc5 ’s protein product, survivin. 24 Survivin is a member of the inhibitor of apoptosis (IAP) family of proteins and, like c-Myc, a downstream target of the canonical Wnt/β-catenin pathway. 53 Through its role in inhibiting cellular apoptosis it has been associated with human malignancy and is being investigated as a potential therapeutic target.…”