Caveolin-1 Gene Disruption Promotes Mammary Tumorigenesis and Dramatically Enhances Lung Metastasis in Vivo
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Bibliographic record
Abstract
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.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it