Ribozyme-mediated down-regulation of ErbB-4 in estrogen receptor-positive breast cancer cells inhibits proliferation both in vitro and in vivo.

Abstract

ErbB-4 is a recently discovered member of the class I receptor tyrosine kinase family (ErbB). Little is known about its expression and its importance in human malignancy. To delineate the biological function of ErbB-4 receptors in breast cancer, we used a hammerhead ribozyme strategy to achieve down-regulation of ErbB-4 receptors in various breast cancer cell lines. We observed that down-regulation of ErbB-4 in estrogen receptor-positive (ER+) human breast cancer cell lines (MCF-7 and T47D), which express relatively high levels of ErbB-4, significantly inhibited colony formation. No effects were observed in estrogen receptor-negative (ER-) MDA-MB-453 cells, which express low levels of endogenous ErbB4 and high levels of ErbB-2 and ErbB-3. This occurred despite the fact that fluorescence-activated cell sorter analysis of these latter cells revealed that the expression of the ErbB-4 receptor was completely abrogated by ribozyme treatment. Furthermore, down-regulation of ErbB-4 in T47D and MCF-7 cells significantly inhibited tumor formation in athymic nude mice (P < 0.03 and P < 0.001, respectively). In addition, NRG-stimulated phosphorylation of ErbB-4- and NRG-induced colony formation was significantly reduced in ribozyme-transfected T47D cells. These data provide the first evidence that elevation of ErbB-4 expression plays a role in the proliferation of some ER+ human breast cancer cell lines (T47D and MCF-7) that express high levels of ErbB-4. We have also investigated the expression of ErbB-4 in human primary breast carcinoma specimens, using immunohistochemical staining with an anti-ErbB-4 monoclonal antibody. ErbB-4 expression was found in 60% of the 50 primary breast tumors examined, and high intense immunoreactivity of ErbB-4 was detected in 18% of these primary breast tumors. ErbB-4 receptor expression appeared to correlate with ER+ primary breast tumors. A similar correlation was also observed in the human breast cancer cell lines. These results provide a better understanding of the biological significance of ErbB-4 receptor in breast cancer. Our data suggest that elevation of the ErbB-4 receptor plays a role in ER+ breast cancer cell proliferation. Moreover, ribozyme technology provides a useful tool to delineate the role of a particular gene product.

• Authors: C K Tang, X Z Concepcion, M Milan, X Gong, E Montgomery, M E Lippman
• Journal: Cancer research (Cancer Res) Vol. 59 Issue 20 Pg. 5315-22 (Oct 15 1999) ISSN: 0008-5472 [Print] United States
• PMID: 10537315 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S., Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Neuregulin-1
• RNA, Catalytic
• Receptors, Estrogen
• ERBB4 protein, human
• ErbB Receptors
• Erbb4 protein, mouse
• Receptor, ErbB-4

Topics

• Animals
• Breast Neoplasms (chemistry, pathology, therapy)
• Cell Division
• Down-Regulation
• ErbB Receptors (analysis, physiology)
• Female
• Humans
• Mammary Neoplasms, Experimental (therapy)
• Mice
• Mice, Nude
• Neuregulin-1 (physiology)
• Phosphorylation
• RNA, Catalytic (physiology)
• Receptor, ErbB-4
• Receptors, Estrogen (analysis)
• Transfection
• Tumor Cells, Cultured