Paired box genes, PAX-2 and PAX-8, are not frequently mutated in Wilms tumor

PAX immunoreactivity in poorly differentiated small round cell tumors of childhood

Paired box (PAX) gene antibodies have made it into the mainstream of tumor diagnosis in the recent years. We report the immunoreactivity expression patterns of three PAX genes (PAX2, PAX5 and PAX8) in poorly differentiated small round cell tumors of childhood for possible useful diagnostic applications. We collected and analyzed 123 cases of poorly differentiated small round cell tumors of childhood for their PAX immunoexpression patterns. The results indicated that PAX2 was strongly positive in all alveolar rhabdomyosarcomas and in two-thirds of the kidney clear cell sarcomas, and displayed variable expression in one-half of the embryonal rhabdomyosarcomas. PAX8 immunoexpression was noticed in five and three cases of alveolar rhabdomyosarcomas and embryonal rhabdomyosarcomas, respectively. About one-third of malignant rhabdoid tumors were PAX2-positive and PAX8-positive. All of the Ewing sarcoma and neuroblastoma cases stained negative with all three PAX stains.

PAX immunoreactivity patterns in anaplastic wilms tumors

This immunohistochemistry study explores particular differential immuno expression patterns of PAX genes in unfavorable histology Wilms tumor (UH) and favorable histology Wilms tumor (FH). Some unique features in unfavorable histology Wilms tumor were discovered and they may provide insightful clues of this unique and both clinically and biologically important phenomenon.

WNT5A is regulated by PAX2 and may be involved in blastemal predominant Wilms tumorigenesis

The PAX2 gene encodes a transcription factor expressed during development. In humans, PAX2 mutations cause the renal-coloboma syndrome, whereas homozygous mutations are lethal, causing severe organ malformation, notably in the brain and kidney. Wilms tumor (WT) of the kidney results from a failure in the mesenchymal-epithelial transition, a crucial step partly controlled by PAX2. Downstream target genes regulated by PAX2 are still undefined. We therefore hypothesized that identification and characterization of the genes regulated by PAX2 may improve our understanding of developmentally related malignancies including WT. We used nickel agarose chromatin enrichment, chromatin immunoprecipitation, and the human embryonic kidney-derived cell line HEK293 to identify regulatory elements responding to PAX2. Among others, we identified WNT5A as a gene potentially regulated by PAX2. Here, we demonstrate that WNT5A is a direct target of PAX2 in HEK293 cells, using both transactivation and electrophoretic mobility shift assays. We were unable to find any WNT5A disease-associated mutations after screening a panel of 99 WT samples. However, quantitative reverse transcription-polymerase chain reaction in human favorable-histology WT revealed that approximately 66% of the cases expressed significantly less WNT5A than human fetal kidney. Moreover, the WiT9 WT cell line revealed a weak expression of the WNT5A gene. A correlation of decreased WNT5A expression with predominant blastemal histology tumors suggests a possible inhibitory role in WT pathogenesis. This study underlines the importance of PAX2 in the regulation of WNT5A. Further in vivo study is necessary to determine whether the PAX2 and WNT5A are truly involved in WT pathogenesis.

Identification of a minimal region of loss on the short arm of chromosome 1 in Wilms tumor

We have analyzed the short arm of chromosome 1 using loss of heterozygosity (LOH) analysis in Wilms tumors (WT) to identify a minimal region of loss. 1909 WT, 22 malignant rhabdoid tumors of the kidney and 90 clear cell carcinomas of the kidney (CCSK) were subjected to LOH analysis using five markers flanked by D1S243 and D1S244. 225 WT and 4 CCSK displayed LOH for this region. A group of 16 cases which had lost heterozygosity for at least one locus but also retained heterozygosity for at least one locus within this region were more finely analyzed using a panel of 24 microsatellite markers. A minimum region of loss located between D1S2694 and D1S244 spanning an area of 3.23 Mb was found in 15/16 of these tumors. No evidence for a second locus within this region was identified. This region of loss overlaps that found in neuroblastoma and harbors candidate genes highly expressed in fetal kidney i.e., LZIC, ICAT, and DNB5. Denaturing HPLC and quantitative RT-PCR analysis of these three genes, however, revealed no aberrations in WT samples retaining heterozygosity (8 cases) or displaying LOH 1p (8 cases). Further studies are required to identify the presumed tumor suppressor gene located within this region of 1p.