A new cis element is involved in the HER2 gene overexpression in human breast cancer cells.

The HER2 proto-oncogene product is overexpressed in 30% of breast cancers, and this correlates with poor prognosis. Increased levels of HER2 mRNA in breast cancer cell lines result from increased gene transcription. We report the identification of a new 17-bp-long cis sequence located between positions -506 and -489 from the transcription start site.

The 6-kilobase c-erbB2 promoter contains positive and negative regulatory elements functional in human mammary cell lines.

A 6-kilobase fragment extending at the 5'-end of the c-erbB2 protooncogene was isolated from a normal human lymphocyte genomic DNA library. The full-length fragment and five subfragments with identical 3'-ends were obtained by progressive unidirectional deletion from the 5'-end and were cloned in front of the luciferase reporter gene. The hybrid genes were analyzed for transcriptional activity in human mammary cell lines synthesizing low (HBL-100 and T-47D), moderate (MDA-MB-453), or high (BT-474) amounts of the c-erbB2 mRNA and were also analyzed in HeLa cells.

Expression of c-erbB2, TGF-beta 1 and pS2 genes in primary human breast cancers.

The presence of c-erbB2, TGF-beta 1 and pS2 mRNAs was examined in primary breast tumours. The c-erbB2 mRNA was overexpressed in 34% of the tumours. There was a positive, statistically significant correlation between c-erbB2 gene overexpression and nodal status.