The cell cycle dependence of c-sis gene expression: artifactual conclusions in cells prepared by chemical but not physical techniques.
The c-sis oncogene encoding the B-chain of platelet-derived growth factor (PDGF) may be involved in an autocrine growth stimulation of tumours expressing the PDGF receptor, such as glioblastomas and sarcomas. To investigate whether expression of c-sis RNA is regulated in a cell cycle dependent manner, human A172 glioblastoma cells were synchronized by either centrifugal elutriation or chemical blockage with the DNA synthesis inhibitors hydroxyurea or aphidicolin. In non-perturbed elutriated cells, c-sis RNA levels were lower in the S phase of the cell cycle than in the G1 phase. In contrast, the chemically synchronized cells revealed a transient rise in c-sis RNA shortly after drug release, in early S phase. The RNA changes occurring after release from drug inhibition represent cell recovery from drug induced metabolic disturbances rather than true cell cycle dependent effects.
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Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio 44106.
Jacobberger
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Samols
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Goldthwait
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D016590:Aphidicolin; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics*; D002498:Centrifugation / Q000379:methods; D004273:DNA, Neoplasm / Q000378:metabolism*; D004224:Diterpenes / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000235:genetics; D011519:Proto-Oncogenes / Q000235:genetics*; D012333:RNA, Messenger / Q000302:isolation & purification / Q000378:metabolism*; D012334:RNA, Neoplasm / Q000302:isolation & purification / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000166:cytology / Q000187:drug effects
D004273:DNA, Neoplasm; D004224:Diterpenes; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D012334:RNA, Neoplasm; D016590:Aphidicolin; D006918:Hydroxyurea