Abstract 219

BACKGROUND/AIMS: Abnormal expression of a number of kinases in specific cell types, can lead to a transformed phenotype due to unregulated phosphorylation of key proteins. Neoplastic cells display different capabilities for expressing differentiated features, and this is reflected in the variable in vivo biological behaviour and phenotype of tumors with common histogenesis. We have devised strategies to search for serine-threonine kinases which may be relevant for the regulation of Ewing's sarcoma phenotype.

METHODS: By combining PCR with degenerate oligonucleotides for consensus sequences in the 6 and 8 subdomains of the catalytic domain of serine-threonine kinases, and differential hybridization of ordered cDNA libraries, we have isolated different clones, one of which detects a transcript of 3.5 Kb, specifically expressed in melanoma and Ewing's sarcoma. RESULTS: The deduced amino acid sequence reveals a consensus sequence without significant homologies to known genes. Thus, our approach should facilitate the isolation of novel genes differentially expressed in a tissue (or cell type) specific manner.

CONCLUSION: Our study results represent a new contribution to the neuroectodermical origin of Ewing's sarcoma, by the isolation of a clone specifically expressed in two different neoplastic cells of possible neuroectodermical origin. Incorporation of the proto-oncogenes expression to the protocol of Ewing's sarcoma study might help to define additional tumor markers.