WILMS’ TUMOR-1 (WT1) PROTEIN EXPRESSION IN GLIOMA CELLS ACTUATES CELLULAR INVASIVENESS- IDENTIFYING ITS TARGET GENES

Previous studies in our laboratory demonstrated the expression of WT1 in a significant number of glioma cells and established its role in promoting tumor cell proliferation. Here, we noted the effect(s) of manipulating WT1 levels on the expression levels of genes that were previously shown to be regulated by WT1. We found no correlation between the expression levels of WT1 and PDGF-A, Snai1 and E-cadherin and a consistent inverse correlation between WT1 and IGF-1R expression in U251-MG cells. To ascertain whether the increased IGF-1R levels resulting from WT1 silencing could account for decreased cellular proliferation, we utilized siRNA mediated knockdown of IGF-1R and found a modest decrease in cellular proliferation. Gene expression profiling in U251-MG cells was then used to identify candidate target genes for WT1. Several genes whose levels directly correlated with WT1 were observed to have putative or established oncogenic role(s) in glioma cells or other malignancies. Among the genes correlated inversely, meanwhile, a tumor-suppressor role was attributed to some. Real time RT-PCR helped to substantiate these microarray findings in U251-MG cells. We also characterized the expression and function of WT1 in U1242-MG and GBM6 cells. Interestingly, in these cells WT1 facilitated cell invasiveness but had no discernible influence on cellular proliferation. The expressions of the candidate WT1 target genes were studied also determined in these 2 cell lines. At least 3 genes were consistently down-regulated with WT1 silencing in the three cell lines- INPP5A, CD97, and TYMS. To determine whether CD97 assisted WT1 in facilitating cellular invasion, we silenced CD97 expression using siRNA and noted a significant decrease in the cells’ ability to invade through Matrigel-coated filters. We propose that WT1 profoundly impacts the glioma cells’ invasive ability, and this function is mediated by CD97 alone or in conjunction with other pro-invasive molecules. Our findings argue for the oncogenic role of WT1 in the specific context of glioma cells. They also point to a novel pro-invasive protein- CD97- in glioma cells. Further studies are necessary to confirm the mechanism by which CD97 promotes invasion as well as to explore its potential as a diagnostic and/or therapeutic target

Novel Report of Expression and Function of CD97 in Malignant Gliomas: Correlation With Wilms Tumor 1 Expression and Glioma Cell Invasiveness Laboratory investigation

Object. The Wilms tumor 1 (WT1) protein—a developmentally regulated transcription factor—is aberrantly expressed in gliomas and promotes their malignant phenotype. However, little is known about the molecular allies that help it mediate its oncogenic functions in glioma cells. Methods. The authors used short interfering RNA (siRNA) to suppress WT1 expression in glioblastoma (GBM) cells and evaluated the effect of this on GBM cell invasiveness. Gene expression analysis was then used to identify the candidate genes that were altered as a result of WT1 silencing. One candidate target, CD97, was then selected for further investigation into its role by suppressing its expression using siRNA silencing, followed by proliferation and invasion assays. Results. WT1 levels were reliably and reproducibly suppressed by siRNA application. This resulted in a significant decrease in cellular invasiveness. Microarray analyses identified the gene products that were consistently downregulated (27) and upregulated (11) with WT1 silencing. Of these, CD97 expression was consistently suppressed across the 3 different GBM cell lines studied and was found on further investigation to significantly impact GBM cell invasiveness. Conclusions. Although CD97 expression in gliomas has not been described previously, we conclude that the possible upregulation of CD97 mediated by WT1 promotes cellular invasiveness—one of the most characteristic and challenging aspects of glial tumor cells. Further studies are needed to clarify the nature of this regulation and its impact, as CD97 could represent a novel target for antiglioma therapies

Novel Report of Expression and Function of CD97 in Malignant Gliomas: Correlation With Wilms Tumor 1 Expression and Glioma Cell Invasiveness Laboratory investigation

Object. The Wilms tumor 1 (WT1) protein—a developmentally regulated transcription factor—is aberrantly expressed in gliomas and promotes their malignant phenotype. However, little is known about the molecular allies that help it mediate its oncogenic functions in glioma cells. Methods. The authors used short interfering RNA (siRNA) to suppress WT1 expression in glioblastoma (GBM) cells and evaluated the effect of this on GBM cell invasiveness. Gene expression analysis was then used to identify the candidate genes that were altered as a result of WT1 silencing. One candidate target, CD97, was then selected for further investigation into its role by suppressing its expression using siRNA silencing, followed by proliferation and invasion assays. Results. WT1 levels were reliably and reproducibly suppressed by siRNA application. This resulted in a significant decrease in cellular invasiveness. Microarray analyses identified the gene products that were consistently downregulated (27) and upregulated (11) with WT1 silencing. Of these, CD97 expression was consistently suppressed across the 3 different GBM cell lines studied and was found on further investigation to significantly impact GBM cell invasiveness. Conclusions. Although CD97 expression in gliomas has not been described previously, we conclude that the possible upregulation of CD97 mediated by WT1 promotes cellular invasiveness—one of the most characteristic and challenging aspects of glial tumor cells. Further studies are needed to clarify the nature of this regulation and its impact, as CD97 could represent a novel target for antiglioma therapies