Minocycline Inhibits Apoptotic Cell Death in a Murine Model of Partial Flap Loss

For breast reconstruction, the deep inferior epigastric perforator (DIEP) flap has become standard therapy. A feared complication is partial or even total flap loss. In a novel murine model of partial DIEP flap loss, the contribution of apoptotis to flap loss was investigated. The clinically available apoptosis-inhibiting compound minocycline was tested for its ability to reduce cell death. The effect of minocycline on cell proliferation was studied in cell cultures of breast carcinoma. In 12 mice, pedicled DIEP flaps were raised, which were subjected to 15 minutes of ischemia and 4 days of reperfusion. Six mice were treated with minocycline 2 hours before surgery and every 24 hours for 4 days. Apoptosis was revealed by injecting annexin A5 30 minutes before sacrifice. Annexin A5 binds to phosphatidylserines, which are expressed on the cell membrane during apoptotis. Prior to sacrifice, necrosis was measured using planimetry. Minocycline reduced cell death after 4 days from 35.9% (standard deviation - 10.6) to 13.9% (standard deviation - 8.0; p <0.05). Apoptosis, as shown by annexin A5 binding in nontreated animals, was abundant. Minocycline did not influence tumor growth in cell cultures of human breast cancer. Minocycline treatment leads to increased DIEP flap viability in mice. This study widens the perspective in the improvement of free flap survival in patients

Annexin A5 Uptake in Ischemic Myocardium: Demonstration of Reversible Phosphatidylserine Externalization and Feasibility of Radionuclide Imaging

Ischemic insult to the myocardium is associated with cardiomyocyte apoptosis. Because apoptotic cell death is characterized by phosphatidylserine externalization on cell membrane and annexin-A5 (AA5) avidly binds to phosphatidylserine, we hypothesized that radiolabeled AA5 should be able to identify the regions of myocardial ischemia. Methods: Models of brief myocardial ischemia by the occlusion of the coronary artery for 10 min (I-10) and reperfusion for 180 min (R-180) for the detection of phosphatidylserine exteriorization using Tc-99m-labeled AA5 and gamma-imaging were produced in rabbits. Tc-99m-AA5 uptake after brief ischemia was compared with an I-40/R-180 infarct model. Histologic characterization of both myocardial necrosis and apoptosis was performed in ischemia and infarct models. Phosphatidylserine exteriorization was also studied in a mouse model, and the dynamics and kinetics of phosphatidylserine exposure were assessed using unlabeled recombinant AA5 and AA5 labeled with biotin, Oregon Green, or Alexa 568. Appropriate controls were established. Results: Phosphatidylserine exposure after ischemia in the rabbit heart could be detected by radionuclide imaging with Tc-99m-AA5. Pathologic characterization of the explanted rabbit hearts did not show apoptosis or necrosis. Homogenization and ultracentrifugation of the ischemic myocardial tissue from rabbit hearts recovered two thirds of the radiolabeled AA5 from the cytoplasmic compartment. Murine experiments demonstrated that the cardiomyocytes expressed phosphatidylserine on their cell surface after an ischemic insult of 5 min. Phosphatidylserine exposure occurred continuously for at least 6 h after solitary ischemic insult. AA5 targeted the exposed phosphatidylserine on cardiomyocytes; AA5 was internalized into cytoplasmic vesicles within 10-30 min. Twenty-four hours after ischemia, cardiomyocytes with internalized AA5 had restored phosphatidylserine asymmetry of the sarcolemma, and no detectable phosphatidylserine remained on the cell surface. The preadministration of a pan-caspase inhibitor, zVAD-fmk, prevented phosphatidylserine exposure after ischemia. Conclusions: After a single episode of ischemia, cardiomyocytes express phosphatidylserine, which is amenable to targeting by AA5, for at least 6 h. Phosphatidylserine exposure is transient and internalized in cytoplasmic vesicles after AA5 binding, indicating the reversibility of the apoptotic process

GATA3 suppresses metastasis and modulates the tumour microenvironment by regulating microRNA-29b expression

Despite advances in our understanding of breast cancer, patients with metastatic disease have poor prognoses. GATA3 is a transcription factor that specifies and maintains mammary luminal epithelial cell fate, and its expression is lost in breast cancer, correlating with a worse prognosis in human patients. Here, we show that GATA3 promotes differentiation, suppresses metastasis and alters the tumour microenvironment in breast cancer by inducing microRNA-29b (miR-29b) expression. Accordingly, miR-29b is enriched in luminal breast cancers and loss of miR-29b, even in GATA3-expressing cells, increases metastasis and promotes a mesenchymal phenotype. Mechanistically, miR-29b inhibits metastasis by targeting a network of pro-metastatic regulators involved in angiogenesis, collagen remodelling and proteolysis, including VEGFA, ANGPTL4, PDGF, LOX and MMP9, and targeting ITGA6, ITGB1 and TGFB, thereby indirectly affecting differentiation and epithelial plasticity. The discovery that a GATA3-miR-29b axis regulates the tumour microenvironment and inhibits metastasis opens up possibilities for therapeutic intervention in breast cancer