Transformation fingerprint: induced STAT3-C, v-Src and Ha-Ras cause small initial changes but similar established profiles in mRNA

Publisher Website
Google Scholar
Abstract
Induced transformation of mouse fibroblasts was carried out by releasing tetracycline-repressed expression of an oncogenic mutant of STAT3, STAT3-C, or of v-Src or Ha-Ras. At 15 days after derepression of each oncogene, DNA microarrays showed elevation (>3-fold) of a similar group of 25 mRNAs compared to untransformed cells. RT–PCR confirmed a number of these mRNA elevations. RNA samples were then analysed at intervals during the first 24 h after doxycycline removal to determine the time of early changes. Extensive changes were not observed by array analysis, except in v-Src-expressing cells where about 10 mRNAs were elevated threefold or more. However, RT–PCR did uncover changes in each derepressed cell type that included some of the changes observed after the 15-day transformation period. In addition, STAT3-C target genes such as BclXI and cyclin D1, which were not observed on array analysis, were elevated by RT–PCR analysis. We conclude, therefore, that early after oncogene induction, transcriptional changes, including those initiated by STAT3-C, may occur only in scarce mRNA and/or to a limited extent. However, with additional time and probably additional cell division, a new epigenetic state is established that is mirrored by a changed transcriptional profile emblematic of transformation by each of three oncogenes.