Heregulin is sufficient for the promotion of tumorigenicity and metastasis of breast cancer cells in vivo.
Resistance of breast carcinomas to hormonal therapy is a clinical obstacle for the treatment of breast cancer. The molecular mechanisms and the factors involved in the progression of tumors from an estrogen (E2)-dependent to an E2-independent phenotype are not entirely understood. Heregulin (HRG) is a pleiotropic growth factor that binds to the erbB family of receptors, which are correlated with breast cancer progression and an aggressive phenotype in the breast carcinomas overexpressing the receptors. Previous studies in transgenic mice have shown that HRG is sufficient to induce mammary gland transformation and proliferation in the presence of hormonal stimulation. However, these studies did not address the important issue of the E2 independence that is part of the progression of breast cancer. In this study, we investigated the role of HRG in E2 independence. We were able to determine that HRG up-regulation was sufficient for the development of mammary tumors in the absence of E2 stimulation, a situation that mimics the progression of the human disease. We demonstrated that in ovariectomized nude mice, HRG induced E2 independence and antiestrogen resistance and promoted metastasis and preneoplastic transformation of the adjacent mouse mammary tissue. We show that one of the mechanisms by which HRG achieves the aggressive phenotype may be mediated via an increase in activated mitogen-activated protein kinase, an increase in a matrix-degrading enzyme, MMP-9, and the overexpression of vascular endothelial growth factors. The up-regulation of these genes occurred in the absence of any additional stimulation, in an autocrine manner. Our data provide new insights into the mechanisms of breast cancer progression in vivo, and reinforce the important role that HRG plays in this process.
Atlas
Ella
E
Evanston Northwestern Healthcare Research Institute, Northwestern University, Evanston, IL 60201, USA.
Cardillo
Marina
M
Mehmi
Inderjit
I
Zahedkargaran
Hengameh
H
Tang
Careen
C
Lupu
Ruth
R
D000818:Animals; D001365:Axilla; D001943:Breast Neoplasms / Q000503:physiopathology* / Q000556:secondary*; D015197:Carcinogenicity Tests; D002471:Cell Transformation, Neoplastic; D016228:Endothelial Growth Factors / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics; D008207:Lymphatic Metastasis; D008222:Lymphokines / Q000235:genetics; D020935:MAP Kinase Signaling System / Q000502:physiology; D008321:Mammary Glands, Animal / Q000473:pathology; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D008819:Mice, Nude; D020890:Neuregulin-1 / Q000235:genetics* / Q000378:metabolism*; D010052:Ovariectomy; D014407:Tumor Cells, Cultured / Q000201:enzymology / Q000637:transplantation; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D018631:ras Proteins / Q000378:metabolism
D016228:Endothelial Growth Factors; D036341:Intercellular Signaling Peptides and Proteins; D008222:Lymphokines; D020890:Neuregulin-1; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D020780:Matrix Metalloproteinase 9; D018631:ras Proteins