The cell cycle dependence of c-sis gene expression : artifactual conclusions in cells prepared by chemical but not physical techniques .

Press RD ; Jacobberger JW ; Samols D ; Goldthwait D

Department of Biochemistry , Case Western Reserve University , Cleveland , Ohio 44106 .

Cell Tissue Kinet 23 : 299-312 ( 1990)

Abstract
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 .