Wilms tumors (WTs) are genetically heterogeneous kidney tumors whose cells of origin are unknown. Tumors with WT1 mutations and concomitant loss of the wild-type allele represent a distinct subgroup, frequently associated with mutations in CTNNB1. Here, we describe the establishment and characterization of long-term cell cultures derived from five individual WTs with WT1 mutations. Three of these tumor cell lines also had CTNNB1 mutations and an activated canonical Wnt signaling pathway as measured by β-catenin/T cell-specific transcription factor (TCF) transcriptional activity. Four of the five Wilms cell lines had a stable normal karyotype for at least 25 passages, and four lines showed loss of heterozygosity of chromosome 11p due to mitotic recombination in 11p11. Gene expression profiling revealed that the WT cell lines are highly similar to human mesenchymal stem cells (MSCs) and FACS analysis demonstrated the expression of MSC-specific surface proteins CD105, CD90 and CD73. The stem cell like nature of the WT cells is further supported by their adipogenic, chondrogenic, osteogenic and myogenic differentiation potentials. By generating multipotent mesenchymal precursors from paraxial mesoderm (PAM) in tissue culture using embryonal stem cells, gene expression profiles of PAM and MSCs were described. Using these published gene sets, we found coexpression of a large number of genes in WT cell lines, PAM and MSCs. Lineage plasticity is indicated by the simultaneous expression of genes from the mesendodermal and neuroectodermal lineages. We conclude that WTs with WT1 mutations have specific traits of PAM, which is the source of kidney stromal cells.

Trefoil factor family (TFF) peptides are a group of molecules bearing a characteristic three-loop trefoil domain. They are mainly secreted in mucous epithelia together with mucins but are also synthesized in the nervous system. For many years, TFF peptides were only known for their wound healing and protective function, e.g. in epithelial protection and restitution. However, experimental evidence has emerged supporting a pivotal role of TFF peptides in oncogenic transformation, tumorigenesis and metastasis. Deregulated expression of TFF peptides at the gene and protein level is obviously implicated in numerous cancers, and opposing functions as oncogenes and tumor suppressors have been described. With regard to the regulation of TFF expression, epigenetic mechanisms as well as the involvement of various miRNAs are new, promising aspects in the field of cancer research. This review will summarize current knowledge about the expression and regulation of TFF peptides and the involvement of TFF peptides in tumor biology and cancerogenesis.

Background: Recent studies demonstrated that epigenetic mechanisms are involved in the regulation of trefoil factor family (TFF) peptide expression in cancer. In human tissues with endogenous TFF1, TFF2 or TFF3 gene expression, the corresponding promoter is unmethylated and in organs without TFF expression, the promoter of the three genes is highly methylated. Methods: Retinoblastoma (Rb) cell lines were treated with the DNA methyltransferase inhibitor 5-Aza-2`deoxycytidine (5-Aza-dC), the histone deacetylase inhibitor 4-Phenylbutyric acid (PBA) or both and analyzed for changes (i) in TFF mRNA expression by Real-time PCR and (ii) in the methylation status of the TFF promoters by genomic bisulfite sequencing. Results: The degree of promoter methylation correlates with endogenous TFF expression in the retinoblastoma cell lines analyzed. Nearly all Rb cell lines exhibiting high endogenous TFF1 expression displayed low methylation of the CpGs in the corresponding promoter region. Low expression of TFF3 in Rb cell lines is linked with high density methylation of the TFF3 promoter. 5-Aza-dC treatment induced TFF1 and TFF3 expression in nearly all cell lines investigated and combined treatment with PBA further increased this effect. The number of methylated CpG dinucleotides of the TFF promoter is clearly reduced upon treatment with 5-Aza-dC and combined treatment with PBA further extended the degree of demethylation. Conclusion: Our data clearly show that the expression of TFF3 in retinoblastoma cell lines is epigenetically regulated, whereas the level of TFF1 and TFF2 seems to be regulated by other or additional mechanisms.