A novel transcription factor, OB2-1, is required for overexpression of the proto-oncogene c-erbB-2 in mammary tumour lines.

The c-erbB-2 receptor tyrosine kinase proto-oncogene product is overexpressed in 20-30% of breast carcinomas and this has been shown to correlate with poor prognosis. Previous analysis of tumour-derived lines has demonstrated that although the c-erbB-2 gene is often amplified, overexpression can occur from a single-copy gene. Moreover, whether or not the gene is amplified, overexpressing cells produce 6- to 8-fold more mRNA per gene copy than low-expressing cells. In this paper, we examine the possible mechanisms causing this deregulation of c-erbB-2 mRNA accumulation. Nuclear run-on studies indicated that the extra mRNA accumulation was due to increased transcription of the gene in overexpressing cells. Promoter analyses using c-erbB-2 5' flanking sequences linked to CAT showed that the promoter is more active in overexpressing cells. Coupling promoter deletion functional studies with footprinting experiments, using nuclear extracts derived from both low and overexpressing cells, allowed the identification of a DNA-binding protein, OB2-1, which is considerably more abundant in a range of overexpressing lines. We discuss the possible role of OB2-1 in c-erbB-2 overexpression in breast tumour lines.

Targeting gene transcription: a new strategy to down-regulate c-erbB-2 expression in mammary carcinoma.

Overexpression of the c-erbB-2 proto-oncogene in mammary carcinoma is frequently associated with amplification of the c-erbB-2 gene, but it also occurs from single-copy gene. Studies in mammary-derived cell lines have shown that, whether or not the gene is amplified, there is a 6- to 8-fold increase in the accumulation of c-erbB-2 mRNA per gene copy in overexpressing cells. We have recently shown that this phenomenon is due to increased activity of the c-erbB-2 promoter mediated by the binding of a novel transcription factor, OB2-1, which is present at higher levels in overexpressing cells than in low expressors. OB2-1 activity therefore represents a novel therapeutic target for the down-regulation of c-erbB-2 levels in human cells. As a prototype for this strategy, we show here that the drug sodium aurothiomalate is able to inhibit the DNA-binding activity of OB2-1 in vitro and also to interfere with c-erbB-2 promoter activity in cell-based transfection assays. In addition, endogenous c-erbB-2 immunoreactivity was reduced in cells treated with aurothiomalate as compared with the levels observed in control cells.

Broadcast quality teleconferencing for oncology.

The National Cancer Institute (NCI) in Bethesda, Maryland has developed a broadcast-quality teleconferencing system known as the Telesynergy system to address the need to convey expert information between larger cancer centers and their remote counterparts. This system is available to "Partnerships in Science Program" partners across the U.S. Recently, it has been made available in Ireland under a "Memorandum of Understanding" among the Department of Health and Children of Ireland, the Department of Health and Social Services in Northern Ireland, and the NCI. The Telesynergy system is capable of transmitting not only broadcast-quality teleconferencing among several different sources, but also diagnostic-quality radiology and pathology images. Remote operated microscopes and video cameras allow biopsy specimens to be discussed and manipulated from several different locations. Smear preparations of blood, bone marrow, and other cytological specimens can be examined in detail by a remote operator. The system can also transmit conventional x-ray images and paper documents. The Telesynergy system ensures that each patient, regardless of location, will receive an expert assessment and be given optimal therapy. While the system is currently being developed in Ireland for use in oncology, it is hoped that other specialties can benefit from it in the future.

Expression of the ERBB3 gene product in breast cancer.

Abnormalities of the EGF receptor and/or the related ERBB2 receptor occur in a significant proportion of cases of human breast cancer and are important influences in the behaviour of this tumour type. In this report we demonstrate by nucleic acid analysis and immunohistochemistry that the recently recognised third member of this gene family, ERBB3, shows a wide range of expression in breast cancer, and shows stronger immunoreactivity than that observed in normal tissue in 43 out of 195 cases (22%) of primary breast cancer. Overexpression of ERBB3 appears to result from increased levels of gene transcription since in none of the cell lines or primary cancers analysed did we find evidence of gene amplification. High expression of ERBB3 is positively associated with the presence of lymph node metastases, but there was no demonstrable relationship with patient survival in this series.