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Neuregulin expression, function, and signaling in human ovarian cancer cells
Lynn M R Gilmour1, Kenneth G Macleod, Alison McCaig
1Cancer Research UK Edinburgh Oncology Unit, Western General Hospital, Edinburgh EH4 2XU, United Kingdom.
Purpose:
To investigate the expression and function of neuregulin (NRG) isoforms in ovarian cancer cell lines and tumor samples.
Experimental Design:
Expression of NRG-1alpha and NRG-1beta proteins were detected by immunohistochemistry and mRNA by RT-PCR. erbB receptor levels and downstream signaling proteins were measured by Western blot analysis.
Results:
Expression of NRG-1alpha and NRG-1beta proteins were detected by immunohistochemistry in 46 of 53 (87%) and 41 of 53 (77%) ovarian carcinomas, respectively. Serous carcinomas express higher levels of NRG-1alpha than endometrioid carcinomas (P = 0.017). NRG mRNA was detected by RT-PCR in 20 of 24 (83%) of ovarian carcinomas and eight of nine (89%) ovarian cancer cell lines. NRG-1alpha stimulated the growth of 5 of 14 cell lines whereas NRG-1beta stimulated 7 of 14 cell lines. The magnitude of NRG growth response was significantly associated with erbB2 expression levels. NRG-1alpha and -1beta (1 nM) growth-stimulated cell lines PE01 and PE06 demonstrated increased tyrosine phosphorylation of erbB2 and elevated tyrosine phosphorylation of ERK1 and ERK2. In contrast, the SKOV-3 cell line, the growth of which was unaffected, did not show these downstream responses. An anti-erbB3 receptor antibody (clone H3.105.5) blocked NRG-1beta growth changes and signaling in these cell lines. Conversely, the anti-erbB4 antibody (clone H4.72.8) enhanced NRG-beta1 growth stimulation. Herceptin also inhibited growth.
Conclusions:
With NRG expression in the majority of ovarian carcinomas and cell lines, there is the potential for autocrine regulation of cell growth. Interfering with ligand-receptor interactions by receptor blocking antibodies suggests erbB3 is primarily involved in NRG-1beta-induced proliferation, with erbB4 having a more complex role.
Insights
Neuregulin (NRG) is expressed in most ovarian cancers, potentially driving cell growth. Blocking NRG-receptor interactions, particularly with erbB3, inhibits cancer cell proliferation, suggesting therapeutic targets.
Area of Science:
- Oncology
- Molecular Biology
- Cell Signaling
Background:
- Neuregulin (NRG) signaling pathways are implicated in various cancers.
- The role of specific NRG isoforms and their receptors in ovarian cancer remains incompletely understood.
Purpose of the Study:
- To investigate the expression and functional significance of neuregulin (NRG) isoforms in ovarian cancer.
- To elucidate the involvement of erbB receptors in NRG-mediated ovarian cancer cell growth.
Main Methods:
- Immunohistochemistry and RT-PCR were used to detect NRG-1alpha and NRG-1beta protein and mRNA expression in ovarian carcinomas and cell lines.
- Western blot analysis assessed erbB receptor levels and downstream signaling proteins (ERK1/2).
- Functional assays evaluated the impact of NRG isoforms on cell proliferation, with specific receptor blocking antibodies (anti-erbB3, anti-erbB4) and Herceptin used to probe signaling pathways.
Main Results:
- NRG-1alpha and NRG-1beta proteins were detected in 87% and 77% of ovarian carcinomas, respectively.
- NRG mRNA was found in 83% of carcinomas and 89% of cell lines, with NRG-1alpha higher in serous carcinomas.
- NRG isoforms stimulated growth in a subset of cell lines, correlating with erbB2 expression. Blocking erbB3 inhibited NRG-1beta-induced growth and signaling, while erbB4 had a complex role; Herceptin also showed inhibitory effects.
Conclusions:
- Neuregulin expression is prevalent in ovarian cancer, suggesting autocrine regulation of cell growth.
- Targeting NRG-receptor interactions, particularly involving erbB3, presents a potential therapeutic strategy for ovarian cancer.
- The complex role of erbB4 in NRG signaling warrants further investigation.