Different mechanisms are implicated in ERBB2 gene overexpression in breast and in other cancers

• Published in: British journal of cancer 2003-09, Vol.89 (5), p.899-906
• Main Authors: Vernimmen, D, Gueders, M, Pisvin, S, Delvenne, P, Winkler, R
• Format: Article
• Language: English
• Subjects: AP-2 transcription factor; Biomedical and Life Sciences; Biomedicine; Blotting, Western; Breast Neoplasms - genetics; c-erbB-2 gene; Cancer Research; DNA-Binding Proteins - biosynthesis; Drug Resistance; Epidemiology; ERBB2 promoter; Female; Gene Amplification; Gene Dosage; Gene Expression Regulation, Neoplastic; Genes, erbB-2 - physiology; human; Human health sciences; Humans; immunocytochemistry; Immunohistochemistry; Male; Molecular and Cellular Pathology; Molecular Medicine; Oncologie; Oncology; Ovarian Neoplasms - genetics; Pancreatic Neoplasms - genetics; Prostatic Neoplasms - genetics; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger - analysis; Sciences de la santé humaine; Transcription Factor AP-2; Transcription Factors - biosynthesis; Transcription, Genetic; Transfection; Tumor Cells, Cultured; Up-Regulation
• ISSN: 0007-0920; 1532-1827; 1532-1827
• DOI: 10.1038/sj.bjc.6601200

The ERBB2 gene is overexpressed in 30% of breast cancers and this has been correlated with poor prognosis. ERBB2 is upregulated in other cancers such as prostate, pancreas, colon and ovary. In breast cancer cells, the mechanisms leading to ERBB2 gene overexpression are increased transcription and gene amplification. In these cancers, AP-2 transcription factors are involved in ERBB2 overexpression, and AP-2 levels are correlated with p185 c- erb B-2 levels. In this work, we wanted to know if the same molecular mechanisms are responsible for the ERBB2 upregulation in non-breast cancers. We compared ERBB2 gene copy number, p185 c- erbB -2 and mRNA levels with AP-2 levels in several ovary, prostate, colon and pancreas cancer cells. A moderate expression of erb B-2 mRNA and protein were observed in some cells without gene amplification. In contrast to breast cancer cells, AP-2 factors were absent or low in some non-breast cells which did express ERBB2 . It is thus likely that AP-2 is not a major player in the increased levels of erb B-2 transcripts in non-breast cancer cells. The transcriptional activity of the ERBB2 promoter in colon and ovary cancer cells was estimated using reporter vectors. The results showed that the promoter regions involved in ERBB2 gene overexpression in breast cancer cells are different from those that lead to the gene upregulation in colon and ovary cancers. In conclusion, our results indicate that different transcriptional and post-transcriptional mechanisms are responsible for the increased levels of erb B-2 transcript and protein in breast and non-breast cancer cells.