RETROVIRAL-MEDIATED TRANSDUCTION OF P53 GENE INCREASES TGF-BETA EXPRESSION IN A HUMAN GLIOBLASTOMA CELL-LINE

Transforming growth factor-beta (TGF-beta) has been implicated as a po tent growth regulator; the degree of responses to it, whether positive or negative, generally correlates with the stage of cell differentiat ion in various cell types. We examined the effect of the p53 gene, whi ch participates in the control of cell-cycle progression, on the expre ssion of human TGF-beta. The human glioblastoma cell line SNB-19, whic h expresses the latent form of TGF-beta, was transfected with a retrov iral vector containing wild-type p53 (wt-p53) or p53 with a mutation ( mut-p53) at codon 273. Stable G418-resistant SNB-19 clones were isolat ed. The growth kinetics of wt-p53 transfectants were suppressed compar ed with those of parental cells, vector transfectants, or mut-p53 tran sfectants, as assayed by growth-curve measurements and H-3-thymidine i ncorporation; however, RNA dot blot and Western blot analyses demonstr ated that wt-p53 and mut-p53 transfectants expressed higher amounts of TGF-beta 1 and TGF-beta 2 mRNA and intracellular TGF-beta isoform pro teins, respectively, than parental cells. By means of the biological a ssay for active TGF-beta (Mv1Lu cell-growth-inhibition assay), we obse rved that both transfectants produced active TGF-beta, whereas the par ental cells produced only the latent form. These results suggest that, while only the wt-p53 gene inhibits tumor-cell progression, both wt-p 53 and codon 273-mutated p53 can cause increased TGF-beta expression. (C) 1994 Wiley-Liss, Inc.