Search for oncogenic regulators in an autocrine tumor model using differential display PCR: Identification of novel candidate genes including the calcium channel mtrp6

A hemopoietic multistep tumor model, in which IL-3 dependent PB-3c mast cel ls, following expression of v-H-ras progress in vivo to IL-3 producing auto crine tumors has previously been established. Central for this oncogenic pr ogression is a recessive step, which is reversible by cell fusion and leads to stabilization of IL-3 mRNA with concomitant activation of the autocrine loop. Comparing the IL-3 dependent PB-3c and the IL-3 autocrine V2D1 tumor cells with differential display PCR revealed 12 differentially expressed g enes of which eight were upregulated and four downregulated in the tumor. T hey included four proteases (mouse mast cell protease 2, granzyme B, pepsin ogen F and serine protease 1) and two metabolic enzymes (adenine phosphorib osyltransferase and fructose1,6-bisphosphatase). For validation, expression of the identified genes was tested in independent PB-3c precursor clones a nd their tumor derivatives. Expression of an endogenous retroviral IAP elem ent and three unknown transcripts were consistently upregulated in all tumo r lines. In somatic cell hybrids, two of these unknown cDNAs showed a domin ant and one a recessive expression pattern. One transcript, expressed in th e precursor but downregulated in the tumor cells, was cloned and identified as the murine calcium channel mtrp6.