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All-trans-retinoic acid (RA) has been used to suppress growth of malignant cells and induce epithelial differentiation. We investigated whether RA had a similar effect on Wilms’ tumor, a childhood tumor of the kidney that arises from the undifferentiated metanephric blastema. W13 cells, a cell line derived from a blastemal Wilms’ tumor, were exposed to RA (10−9-10−5 M) and its effects on cell proliferation, gene expression, and differentiation were examined. Treatment of W13 cells with RA resulted in a dose-dependent suppression of growth. Changes in expression of selected genes were determined by Northern analysis. After 24 h, there was a marked dose-dependent down-regulation of N-myc mRNA as well as up-regulation of insulin-like growth factor-II (IGF-II) mRNA. [125I]IGF-II ligand blotting of conditioned medium from RA-treated cultures revealed a dramatic alteration in the pattern of expression of insulin-like growth factor binding proteins (IGFBPs). Examination of RA-treated W13 cultures by light and el...

A blastema-associated antigen (BLA-1) was detected using a monoclonal antibody against malignant blastema from a Wilms' tumor. The localization of BLA-1 was investigated in a series of nine Wilms' cases, five fetal, one childhood, and two adult kidneys. In this series, BLA-1 antibody consistently stained cell surfaces of all Wilms' tumors containing blastemal components. The same staining pattern was maintained in tumors grown as heterotransplants in nude mice. The expression of BLA-1 antigen was examined in normal blastema of fetal kidneys. BLA-1 was immunolocalized to condensed blastemal cells in the nephrogenic zone throughout gestation. In addition, kidney samples from a young child or adults contained no blastemal cells and therefore showed no blastemal cell surface staining. Glomerular mesangial cell staining was demonstrated in kidneys from 12 weeks of gestation through adulthood. This staining in developing and mature glomeruli implies that mesangial cells may be derived from condensed blastemal cells. The finding of a cell surface antigen common to Wilms' blastema, fetal blastema, and mesangial cells has not been previously demonstrated.

The growth rate of primary tumors and derived cell lines is an important identifying trademark to researchers studying the growth and differentiation of pediatric neoplasms. For the in vivo tumor specimen, the mitotic index is utilized to assess growth potential while, in vitro, the determination of the growth curve and doubling time of the cells is employed. Because of the importance of these parameters this laboratory has developed a technique for the simultaneous determination of cell number and mitotic index for adherent cultured cells, as well as solid tumors, using the polycationic dye DAPI (4',6-diamino-2-phenylindole). DAPI, when bound to nuclear DNA, fluoresces, and this property has been utilized to develop an image analysis based technique to determine cell number automatically based on gray scale discrimination. In addition, DAPI staining clearly delineates mitotic figures and this has allowed the simultaneous manual determination of mitotic index for each automatic cell count. This technique was first tested using four different human cell lines and was shown to determine cell growth and mitotic index simultaneously. Lastly, employing an atypical mesoblastic nephroma, it was shown that the mitotic index of the primary tumor could easily be obtained and compared to both the mitotic index of tumor heterotransplant in nude mice and the mitotic index of the tumor-derived cell culture. This technique should be useful in studies assessing the effects of various factors on the growth of adherent cultured cells as well as the accurate determination of the mitotic index in solid tumors.