Induction of a hypertrophic growth status of coronary smooth muscle cells is associated with an overexpression of TGF-beta

Rab31-dependent regulation of transforming growth factor ß expression in breast cancer cells

BACKGROUND

The small GTP-binding protein Rab31 plays an important role in the modulation of tumor biological-relevant processes, including cell proliferation, adhesion, and invasion. As an underlying mechanism, Rab31 is presumed to act as a molecular switch between a more proliferative and an invasive phenotype. This prompted us to analyze whether Rab31 overexpression in breast cancer cells affects expression of genes involved in epithelial-to-mesenchymal transition (EMT)-like processes when compared to Rab31 low-expressing cells.

METHODS

Commercially available profiler PCR arrays were applied to search for differentially expressed genes in Rab31 high- and low-expressing CAMA-1 breast cancer cells. Differential expression of selected candidate genes in response to Rab31 overexpression in CAMA-1 cells was validated by independent qPCR and protein assays.

RESULTS

Gene expression profiling of key genes involved in EMT, or its reciprocal process MET, identified 9 genes being significantly up- or down-regulated in Rab31 overexpressing CAMA-1 cells, with the strongest effects seen for TGFB1, encoding TGF-ß1 (> 25-fold down-regulation in Rab31 overexpressing cells). Subsequent validation analyses by qPCR revealed a strong down-regulation of TGFB1 mRNA levels in response to increased Rab31 expression not only in CAMA-1 cells, but also in another breast cancer cell line, MDA-MB-231. Using ELISA and Western blot analysis, a considerable reduction of both intracellular and secreted TGF-ß1 antigen levels was determined in Rab31 overexpressing cells compared to vector control cells. Furthermore, reduced TGF-ß activity was observed upon Rab31 overexpression in CAMA-1 cells using a sensitive TGF-ß bioassay. Finally, the relationship between Rab31 expression and the TGF-ß axis was analyzed by another profiler PCR array focusing on genes involved in TGF-ß signaling. We found 12 out of 84 mRNAs significantly reduced and 7 mRNAs significantly increased upon Rab31 overexpression.

CONCLUSIONS

Our results demonstrate that Rab31 is a potent modulator of the expression of TGF-ß and other components of the TGF-ß signaling pathway in breast cancer cells.

Transforming growth factor-beta is activated by plasmin and inhibits smooth muscle cell death in human saphenous vein

BACKGROUND

The effect of activation of endogenous transforming growth factor-beta (TGF-beta) on smooth muscle cell apoptosis was assessed in human saphenous vein.

METHODS

Segments of human saphenous vein, obtained at the time of bypass graft surgery, were cultured for 14 days. During this time, smooth muscle cells accumulated in the intima as a result of proliferation and migration, partly counterbalanced by apoptotic cell death.

RESULTS

Addition of exogenous TGF-beta(1) had no effect on smooth muscle cell proliferation or apoptosis. However, antibody neutralization of endogenous TGF-beta(1) caused significant increases in smooth muscle cell death in the media and intima without any change in proliferation. A plasmin inhibitor (alpha-N-acetyl-L-lysine methyl ester), a specific urokinase-type plasminogen activator (uPA) inhibitor (amiloride) and an anti-catalytic anti-uPA antibody all caused decreases in the tissue content of active TGF-beta and increases in smooth muscle cell death in the media and intima.

CONCLUSIONS

These data suggest that the amount of TGF-beta in human saphenous vein is sufficient, when in the active form, to protect smooth muscle cells against apoptosis. Adding exogenous TGF-beta(1) has no beneficial effect, but decreasing the amount of active TGF-beta causes smooth muscle cells to undergo apoptosis. Plasmin, generated by uPA, appears to be an important activator of endogenous latent TGF-beta.

Fucoidan Modulates the Effect of Transforming Growth Factor (TGF)-.BETA.1 on Fibroblast Proliferation and Wound Repopulation in in Vitro Models of Dermal Wound Repair

Aberrant wound healing, either causing scarring or chronic wounds, is a significant cause of morbidity. There is therefore, considerable interest in agents which can modulate certain aspects of the wound healing process. Fucoidans, sulphated polyfucose polysaccharides which may be extracted from Fucus spp., have been shown to modulate the effects of a variety of growth factors through mechanisms thought to be similar to the action of heparin. We investigated the interaction between two commercial preparations of fucoidan and transforming growth factor (TGF)-beta(1). These preparations of fucoidan, as well as heparin, inhibited fibroblast proliferation at concentrations from 0.01 to 100 mg/ml. The anti-proliferative effects of 1 ng/ml TGF-beta(1) on dermal fibroblasts were abrogated by fucoidan preparation F7 when used at concentrations over 1 mg/ml. In a three dimensional in vitro model of wound repair, the fibroblast populated collagen lattice or "dermal equivalent", TGF-beta(1) reduced the rate of fibroblast repopulation of a wound defect created by punch biopsy. Addition of fucoidan to the model in the presence of TGF-beta(1) increased the rate of fibroblast repopulation of the wound and at 10 mg/ml of fucoidan the number of cells which had migrated into the wounded defect was similar to that of control cultures. These data suggest that fucoidan has properties which may be beneficial in the treatment of wound healing.

Transforming growth factor beta in cardiovascular development and function

Transforming growth factor betas (TGFbetas) are pleiotropic cytokines involved in many biological processes. Genetic engineering and tissue explanation studies have revealed specific non-overlapping roles for TGFbeta ligands and their signaling molecules in development and in normal function of the cardiovascular system in the adult. In the embryo, TGFbetas appear to be involved in epithelial-mesenchymal transformations (EMT) during endocardial cushion formation, and in epicardial epithelial-mesenchymal transformations essential for coronary vasculature, ventricular myocardial development and compaction. In the adult, TGFbetas are involved in cardiac hypertrophy, vascular remodeling and regulation of the renal renin-angiotensin system. The evidence for TGFbeta activities during cardiovascular development and physiologic function will be given and areas which need further investigation will be discussed.