Caveolin-1 gene disruption promotes mammary tumorigenesis and dramatically enhances lung metastasis in vivo. Role of Cav-1 in cell invasiveness and matrix metalloproteinase (MMP-2/9) secretion.
Caveolin-1 (Cav-1) is the principal structural component of caveolae membrane domains in non-muscle cells, including mammary epithelia. There is now clear evidence that caveolin-1 influences the development of human cancers. For example, a dominant-negative mutation (P132L) in the Cav-1 gene has been detected in up to 16% of human breast cancer samples. However, the exact functional role of caveolin-1 remains controversial. Mechanistically, in cultured cell models, Cav-1 is known to function as a negative regulator of the Rasp42/44 MAP kinase cascade and as a transcriptional repressor of cyclin D1 gene expression, possibly explaining its in vitro transformation suppressor activity. Genetic validation of this hypothesis at the in vivo and whole organismal level has been prevented by the lack of a Cav-1 (-/-)-null mouse model. Here, we examined the role of caveolin-1 in mammary tumorigenesis and lung metastasis using a molecular genetic approach. We interbred a well characterized transgenic mouse model of breast cancer, MMTV-PyMT (mouse mammary tumor virus-polyoma middle T antigen), with Cav-1 (-/-)-null mice. Then, we followed the onset and progression of mammary tumors and lung metastases in female mice over a 14-week period. Interestingly, PyMT/Cav-1 (-/-) mice showed an accelerated onset of mammary tumors, with increased multiplicity and tumor burden ( approximately 2-fold). No significant differences were detected between PyMT/Cav-1 (+/+) and PyMT/Cav-1 (+/-) mice, indicating that complete loss of caveolin-1 is required to accelerate both tumorigenesis and metastasis. Molecularly, mammary tumor samples derived from PyMT/Cav-1 (-/-) mice showed ERK-1/2 hyperactivation, cyclin D1 up-regulation, and Rb hyperphosphorylation, consistent with dys-regulated cell proliferation. PyMT/Cav-1 (-/-) mice also developed markedly advanced metastatic lung disease. Conversely, recombinant expression of Cav-1 in a highly metastatic PyMT mammary carcinoma-derived cell line, namely Met-1 cells, suppressed lung metastasis by approximately 4.5-fold. In vitro, these Cav-1-expressing Met-1 cells (Met-1/Cav-1) demonstrated a approximately 4.8-fold reduction in invasion through Matrigel-coated membranes. Interestingly, delivery of a cell permeable peptide encoding the caveolin-1 scaffolding domain (residues 82-101) into Met-1 cells was sufficient to inhibit invasion. Coincident with this decreased invasive index, Met-1/Cav-1 cells exhibited marked reductions in MMP-9 and MMP-2 secretion and associated gelatinolytic activity, as well as diminished ERK-1/2 signaling in response to growth factor stimulation. These results demonstrate, for the first time, that caveolin-1 is a potent suppressor of mammary tumor growth and metastasis using novel in vivo animal model approaches.
Williams
Terence M
TM
Department of Molecular Pharmacology and Medicine, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
Medina
Freddy
F
Badano
Ines
I
Hazan
Rachel B
RB
Hutchinson
John
J
Muller
William J
WJ
Chopra
Neeru G
NG
Scherer
Philipp E
PE
Pestell
Richard G
RG
Lisanti
Michael P
MP
D000818:Animals; D051242:Caveolin 1; D022461:Caveolins / Q000235:genetics*; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D002465:Cell Movement; D002478:Cells, Cultured; D003094:Collagen / Q000494:pharmacology; D019938:Cyclin D1 / Q000096:biosynthesis; D018450:Disease Progression; D004338:Drug Combinations; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D015151:Immunoblotting; D020128:Inhibitory Concentration 50; D007797:Laminin / Q000494:pharmacology; D008175:Lung Neoplasms / Q000556:secondary*; D008297:Male; D015674:Mammary Neoplasms, Animal / Q000235:genetics*; D008324:Mammary Tumor Virus, Mouse / Q000235:genetics; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D019950:Mitogen-Activated Protein Kinase 1 / Q000096:biosynthesis; D048052:Mitogen-Activated Protein Kinase 3 / Q000096:biosynthesis; D009154:Mutation; D009361:Neoplasm Invasiveness; D009362:Neoplasm Metastasis / Q000235:genetics*; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011509:Proteoglycans / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000378:metabolism; D012190:Retroviridae / Q000235:genetics; D013997:Time Factors; D015854:Up-Regulation
C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D004338:Drug Combinations; D007797:Laminin; D010455:Peptides; D011509:Proteoglycans; D011994:Recombinant Proteins; D016160:Retinoblastoma Protein; C059485:matrigel; D019938:Cyclin D1; D003094:Collagen; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020778:Matrix Metalloproteinase 2; D020780:Matrix Metalloproteinase 9