The production of platelet-derived growth factor like (PDGF-like) material by glioblastomas may be involved in the conversion of normal cells to tumor cells. In an investigation of this problem, we have examined some of the properties of the platelet-derived growth factor B-chain mRNA (c-sis mRNA) by a sensitive and quantitative RNA-RNA solution hybridization method. In 5 out of 8 human glioblastoma cell lines, c-sis mRNA was present, and in the line with the highest level, there were approximately 4–10 molecules per cell. The half-lives of the c-sis mRNA in two glioblastoma cell lines were 2.6 and 3.4 h, while in human umbilical vein endothelial (HUVE) and bladder carcinoma (T24) cells they were 1.6 and 2.5 h, respectively. Inhibiting protein synthesis produced no significant alteration of the c-sis mRNA half-lives in the glioblastoma or HUVE cells. The A-U-rich sequence at the 3’ end of the c-sis mRNA therefore does not appear to affect the mRNA stability in the presence of cycloheximide as it does in other transcripts. The similarity of the c-sis mRNA half-lives in normal and tumor cells suggests that regulation of stability of c-sis mRNA is not a major factor in tumorigenesis in the glioblastoma cell lines examined.
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