A SCREENING METHOD TO IDENTIFY GENES COMMONLY OVEREXPRESSED IN CARCINOMAS AND THE IDENTIFICATION OF A NOVEL COMPLEMENTARY-DNA SEQUENCE

We describe a differential screening method for cDNA libraries which u sed a combination of subtracted and PCR-amplified cDNA probes, and whi ch can be applied to the selection of genes expressed in multiple tiss ues. This technique was used to identify genes commonly overexpressed in breast and basal cell carcinomas. These represent stromally depende nt, invasive tumors with and without metastatic capacity. Thus, this s creening sought to identify genes involved in the early stages of tumo r progression. We identified a total of 16 genes, including c-erbB-2 a nd tissue inhibitor of metalloproteinases 3 whose products have been i mplicated in tumorigenesis or invasion. We also identified a novel seq uence (D52) showing little homology with others described in any speci es, which maps to the human chromosomal band 8q21. In situ RNA hybridi zations of breast carcinoma sections indicated that the D52 gene was e xpressed in cancer cells, whereas other genes identified in the differ ential screening were expressed in fibroblastic or inflammatory cells within the tumor stroma. Thus, the procedure developed in this study s elected genes expressed in a diversity of cell types, indicating its p otential usefulness in other systems.