Global analysis of differential gene expression after transformation with the v-H-ras oncogene in a murine tumor model

Mouse PB-3c mast cells stably transfected with the v-H-ras oncogene induce tumor formation in vivo when implanted into mice. Such tumor cells are char acterized by an autocrine IL-3 loop. DNA microarrays allow simultaneous tra nscript imaging of several thousand genes and the technique was applied in this tumor model to analyse gene expression following malignant transformat ion. Using three independent tumor lines derived from the same precursor th e expression of about 400 out of 11000 genes was modulated in each tumor. A subset of only 75 genes (0.68%) is shared and up- or downregulated in all three lines. A significant portion of this gene pool possesses functions re lated to tumorigenesis such as cell adhesion, signaling or transcriptional regulation. Apart from a number of expressed sequence tags (EST's) we find downregulation of four interferon-inducible genes in the tumor lines. Final ly, when we extrapolate our data to the complete mouse genome, we estimate that about 500 genes are differentially expressed in tumor cells compared t o the precursor cell PB-3c.