Down-regulation of an abundant cellular protein associated with tumor progression.

Abstract

Alteration of gene expression in neoplastic cells can be detected by two-dimensional gel electrophoresis. This study reports the altered synthesis of an abundant cellular protein, p29, accompanying tumorigenic transformation of immortalized fibroblasts induced by transfection with oncogenic DNA. Cell lines derived from morphologically transformed foci synthesized p29 at 60-75% reduced levels compared with untransformed parental cells. Upon inoculation into syngeneic immunocompetent animals, transformed cells gave rise to tumors which were excised and established in culture. The amount of p29 in both focal and tumor-derived lines was inversely correlated with the latent period for tumor formation. In cell lines with a tumor latency of 12-20 days, the level of p29 was decreased by 90-99%. In rapidly tumorigenic cells with a short latency (3-6 days), p29 synthesis was not detectable. These data demonstrate that p29 may be a sensitive and reliable marker for tumor progression of fibroblasts.