Identification of differentially expressed genes associated with HER-2/neuoverexpression in human breast cancer cells

Amplification and resulting overexpression of the HER-2/neu proto-oncogene is found in similar to 30% of human breast and 20% of human ovarian cancers . To better understand the molecular events associated with overexpression of this gene in human breast cancer cells, differential hybridization was u sed to identify genes whose expression levels are altered in cells overexpr essing this receptor. Of 16 000 clones screened from an overexpression cell cDNA library, a total of 19 non-redundant clones were isolated including s even whose expression decreases (C clones) and 12 which increase (H clones) in association with HER-2/neu overexpression, Of these, five C clones and 11 H clones have been confirmed to be differentially expressed by northern blot analysis, This group includes nine genes of known function, three prev iously sequenced genes of relatively uncharacterized function and four nove l genes without a match in GenBank. Examination of the previously character ized genes indicates that they represent sequences known to be frequently a ssociated with the malignant phenotype, suggesting that the subtraction clo ning strategy used identified appropriate target genes, In addition, differ ential expression of 12 of 16(75%) cDNAs identified in the breast cancer ce ll lines are also seen in HER-2/neu-overexpressing ovarian cancer cells, in dicating that they represent generic associations with HER-2/neu overexpres sion, Finally, up-regulation of two of the identified cDNAs, one novel and one identified but as yet uncharacterized gene, was confirmed in human brea st cancer specimens in association with HER-2/neu overexpression, Further c haracterization of these genes may yield insight into the fundamental biolo gy and pathogenetic effects of HER-2/neu overexpression in human breast and ovarian cancer cells.