Biomedical subjects

Edith Aberdam

Publications and source records attributed to Edith Aberdam.

3 recordsLinked to original sources

PubMed2006

SPARC represses E-cadherin and induces mesenchymal transition during melanoma development.

During progression of melanoma, loss of the cell-cell adhesion molecule E-cadherin contributes to uncontrolled growth and invasive behavior of transformed melanocytes. Secreted protein acidic and rich in cysteine (SPARC) is a nonstructural matricellular protein that regulates cell-matrix interactions leading to alterations in cell adhesion and proliferation. Overexpression of SPARC has been associated with progression of various cancers, including melanoma; however, its role in primary tumor development is not well defined. We show that normal human melanocytes overexpressing SPARC adopt a fibroblast-like morphology, concomitant with loss of E-cadherin and P-cadherin expression, and increased expression of mesenchymal markers. Concurrent with these changes, SPARC expression stimulates melanocyte motility and melanoma cell invasion. Expression of SPARC results in transcriptional down-regulation of E-cadherin that correlates with induction of Snail, a repressor of E-cadherin. Conversely, SPARC depletion leads to up-regulation of E-cadherin and reduces Snail levels, and SPARC-null cells exhibit a marked change in their mesenchymal phenotype. Finally, analysis of SPARC, Snail, and E-cadherin levels in melanocytes and malignant melanoma cell lines further supports the functional relationship among these proteins during melanoma progression. Our findings provide evidence for the role of SPARC in early transformation of melanocytes and identify a novel mechanism, whereby tumor-derived SPARC promotes tumorigenesis by mediating Snail induction and E-cadherin suppression.

Cadherins↗

PubMed2005

[Embryonic stem cells and epidermal commitment].

Embryonic stem (ES) cells can be cultured indefinitely, differentiated into many cell types in vitro, thus providing a potentially unlimited supply of cells for cell-based therapy. We recently reported the efficient derivation of ectodermal and epidermal cells from murine ES cells. These differentiated ES cells are able to form, in culture, a multilayered epidermis coupled with an underlying dermal compartment, similar to native skin. This model demons- trates that ES cells have the potential to recapitulate the reciprocal instructive ectodermal-mesodermal commitments, characteristic of embryonic skin formation, clarifies the role of the morphogen BMP-4 in the binary neuroectodermal choice and provides a powerful tool for the study of molecular mechanisms controlling skin development and multipotent epidermal stem cell properties. Its potential for cutaneous cell therapy and dermatocosmetological applications is discussed.

Animals↗

PubMed2002

Glycogen synthase kinase 3beta is activated by cAMP and plays an active role in the regulation of melanogenesis.

In human and mouse, cAMP plays a key role in the control of pigmentation. cAMP, through the activation of protein kinase A, increases the expression of microphthalmia-associated transcription factor (MITF), which in turn stimulates tyrosinase gene expression, to allow melanin synthesis. Beyond this simplified scheme, cAMP inhibits phosphatidylinositol 3-kinase (PI3K), and inhibition of PI3K, by a specific inhibitor, stimulates melanogenesis. However, the link between the PI3K pathway and melanogenesis remained to be elucidated. In this report, we showed that cAMP, through a protein kinase A-independent mechanism, led to inhibition of AKT phosphorylation and activity. Consistent with the role of AKT in the regulation of glycogen synthase kinase 3beta (GSK3beta), cAMP decreased the phosphorylation of GSK3beta and stimulated its activity. Further, experiments were performed to investigate the role of GSK3beta in the regulation of MITF expression and function. We observed that GSK3beta regulated neither MITF promoter activity nor the intrinsic transcriptional activity of MITF but synergized with MITF to activate the tyrosinase promoter. Additionally, lithium, a GSK3beta inhibitor, impaired the response of the tyrosinase promoter to cAMP, and cAMP increased the binding of MITF to the M-box. Taking into account that GSK3beta phosphorylates MITF and increases the ability of MITF to bind its target sequence, our results indicate that activation of GSK3beta by cAMP facilitates MITF binding to the tyrosinase promoter, thereby leading to stimulation of melanogenesis.

Animals↗