Biomedical subjects

W M Rideout

Publications and source records attributed to W M Rideout.

21 records · Page 2Linked to original sources

PubMed1990

De novo methylation of the MyoD1 CpG island during the establishment of immortal cell lines.

CpG dinucleotides are unevenly distributed in the vertebrate genome. Bulk DNA is depleted of CpGs and most of the cytosines in the dinucleotide in this fraction are methylated. On the other hand, CpG islands, which are often associated with genes, are unmethylated at testable sites in all normal tissues with the exception of genes on the inactive X chromosome. We used Hpa II/Msp I analysis and ligation-mediated polymerase chain reaction to examine the methylation of the MyoD1 CpG island in adult mouse tissues, early cultures of mouse embryo cells, and immortal fibroblastic cell lines. The island was almost devoid of methylation at CCGG sites in adult mouse tissues and in low-passage mouse embryo fibroblasts. In marked contrast, the island was methylated in 10T 1/2 cells and in six other immortal cell lines showing that methylation of this CpG island had occurred during escape from senescence. The island became even more methylated in chemically transformed derivatives of 10T 1/2 cells. Thus, CpG islands not methylated in normal tissues may become modified to an abnormally high degree during immortalization and transformation.

Animals↗

PubMed1990

Plasminogen activator regulation by transforming growth factor-beta in normal and neoplastic human urothelium.

Plasminogen activators (PA) are thought to participate in the invasive and metastatic processes of malignancies and are known to be modulated by certain growth factors (Danø, K; Andreasen, P.A.; Grondahl-Hansen, J.; Kristensen, P.; Nielsen, L.S.; Skriver, L. Adv. Cancer Res. 44:139-266; 1985 and Laiho, M.; Keski-Oja, J. Cancer Res. 49:2533-2553; 1989). This report describes the effect of TGF-beta on the regulation of secreted PA activity produced by human fetal urothelium and neoplastic urothelial cell lines. Epidermal growth factor was previously shown to induce substantially different effects on PA production by normal versus neoplastic urothelial (Dubeau, L.; Jones, P.A.; Rideout, W.M.; Laug, W.E. Cancer Res. 48:5552-5556; 1988). This report demonstrates that log phase normal urothelium, but not transformed cells, responded to TGF-beta (1-10 ng/mL) by diminishing the total secreted PA activity. Northern and western analyses showed that the reduction in protease activity resulted from an increased level of plasminogen activator inhibitor-1 (PAI-1) mRNA and protein. Additionally, northern analysis of total mRNA levels at varying cell densities demonstrated modulation of tPA, PAI-1, and TGF-beta transcripts in normal urothelial cells as a function of growth in vitro, suggesting the presence of an intact regulatory pathway to control extracellular proteolysis.

Blotting, Western↗

PubMed1988

Differential regulation of plasminogen activators by epidermal growth factor in normal and neoplastic human urothelium.

The regulation of urokinase (u-PA) and tissue plasminogen activator (t-PA) in cultured normal and neoplastic urothelium was examined because plasminogen activators (PAs) are thought to be important in malignancy. Both activators were synthesized by normal urothelial cells grown in vitro under chemically defined conditions. The level of t-PA activity decreased when normal urothelial cells reached saturation density, but was stimulated more than 10-fold by the addition of epidermal growth factor (EGF) to the culture medium. Northern blot analysis showed that the regulation occurred at the transcriptional level. On the other hand u-PA activity was regulated to a lower degree by EGF and was not affected by cell density. Immunohistochemical examination of urothelial cells in histology specimens showed that t-PA was present only in the apical cells facing the lumen, suggesting that the expression of the activity might be a marker for end-stage differentiation in vivo. In contrast to normal cells, tumor cell lines made only u-PA under all conditions tested, and the levels of its expression were either unaffected or slightly decreased by EGF. Tumor cells and normal cells therefore showed substantial differences in protease regulation by EGF.

Cells, Cultured↗