HER2 regulatory control of angiopoietin-2 in breast cancer.
BACKGROUND
HER2 overexpression is a marker of aggressive breast cancer. Tumors that overexpress HER2 induce endothelial cell retraction and endothelial destabilization. Because angiopoietin-2 (Ang-2) also destabilizes microvessels, we postulated that HER2 signaling upregulates Ang-2 as a mechanism of angioinvasion.


METHODS
We tested human breast cancers and breast cancer cell lines for coexpression of HER2 and Ang-2 with Northern blot, reverse transcriptase-polymerase chain reaction, and enzyme-linked immunosorbent assay. Further, we manipulated HER2 signaling with 100 ng/mL MAbHu HER2 (Herceptin; Genentech, San Francisco, Calif) and Heregulin beta1 (100 ng/mL; R&D Systems, Inc, Minneapolis, Minn) to test for HER2 regulation of Ang-2 production.


RESULTS
Three of 4 breast cancer cell lines expressed HER2 protein and Ang-2 mRNA. HER cells, a stably transfected cell line that overexpresses HER2 6-fold, showed a 430% increase in Ang-2 mRNA compared to parental MCF-7 cells. Heregulin beta1 stimulation of HER2 signaling in MCF-7 cells increased Ang-2 by 20% (P <.05). HER2 signaling blockade with 100 ng/mL Herceptin reduced Ang-2 mRNA 90% (P <.001). Five of 11 cancers expressed both HER2 and Ang-2; 2 cancers expressed only Ang-2.


CONCLUSIONS
We conclude that human breast cancers express Ang-2. HER2 signaling appears to regulate Ang-2 expression, although other signaling pathways may also regulate Ang-2. Ang-2 may be a therapeutic target in these cancers and may define which patients would benefit from Herceptin therapy.
Carter
W B
WB
Department of Surgery, Eastern Virginia Medical School, Norfolk, VA, USA.
Ward
M D
MD
D042702:Angiopoietin-2; D001943:Breast Neoplasms / Q000737:chemistry / Q000235:genetics*; D004791:Enzyme Inhibitors; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D018734:Genes, erbB-2; D006801:Humans; D011506:Proteins / Q000032:analysis / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000032:analysis / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured
D042702:Angiopoietin-2; D004791:Enzyme Inhibitors; D011506:Proteins; D012333:RNA, Messenger; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins