Mỹ G. Mahoney

Metastasis-associated protein (MTA)1 enhances migration, invasion, and anchorage-independent survival of immortalized human keratinocytes.

The human metastasis-associated gene (MTA1), a member of the nucleosome remodeling complex with histone deacetylase activity, is frequently overexpressed in biologically aggressive epithelial neoplasms. Here, we extend this observation to squamous carcinoma cells, which express high levels of MTA1 relative to normal or immortalized keratinocytes. To address functional aspects of MTA1 expression, we established variants of human immortalized keratinocytes (HaCaT cells) by expressing MTA1 cDNA in both the sense and antisense orientations. We demonstrate that (1) forced MTA1 expression enhances migration and invasion of immortalized keratinocytes; (2) MTA1 expression is necessary but not sufficient for cell survival in the anchorage independent state; (3) MTA1 contributes to expression of the anti-apoptotic Bcl-2 family member Bcl-xL; (4) MTA1 expression in immortalized keratinocytes depends, in part, on activation of the epidermal growth factor receptor (EGFR). These results establish that, in keratinocytes, MTA1 expression contributes to several aspects of the metastatic phenotype including survival in the anchorage independent state, migration, and invasion.

A role for caveolin-1 in desmoglein binding and desmosome dynamics

Desmoglein-2 (Dsg2) is a desmosomal cadherin that is aberrantly expressed in human skin carcinomas. In addition to its well-known role in mediating intercellular desmosomal adhesion, Dsg2 regulates mitogenic signaling that may promote cancer development and progression. However, the mechanisms by which Dsg2 activates these signaling pathways and the relative contribution of its signaling and adhesion functions in tumor progression are poorly understood. In this study we show that Dsg2 associates with caveolin-1 (Cav-1), the major protein of specialized membrane microdomains called caveolae, which functions in both membrane protein turnover and intracellular signaling. Sequence analysis revealed that Dsg2 contains a putative Cav-1-binding motif. A permeable competing peptide resembling the Cav-1 scaffolding domain bound to Dsg2, disrupted normal Dsg2 staining and interfered with the integrity of epithelial sheets in vitro. Additionally, we observed that Dsg2 is proteolytically processed; resulting in a 95-kDa ectodomain shed product and a 65-kDa membrane-spanning fragment, the latter of which localizes to lipid rafts along with full-length Dsg2. Disruption of lipid rafts shifted Dsg2 to the non-raft fractions, leading to the accumulation of these proteins. Interestingly, Dsg2 proteolytic products are elevated in vivo in skin tumors from transgenic mice overexpressing Dsg2. Collectively, these data are consistent with the possibility that accumulation of truncated Dsg2 protein interferes with desmosome assembly and/or maintenance to disrupt cell–cell adhesion. Furthermore, the association of Dsg2 with Cav-1 may provide a mechanism for regulating mitogenic signaling and modulating the cell-surface presentation of an important adhesion molecule, both of which could contribute to malignant transformation and tumor progression.

Efficacy of mesotherapy in facial rejuvenation: a histological and immunohistochemical evaluation

Background  Mesotherapy, commonly known as “biorejuvenation” or “biorevitalization”, is a technique used to rejuvenate the skin by means of a transdermal injection of a multivitamin solution and natural plant extracts that are thought to improve the signs of skin aging.

Hailey–Hailey disease and tight junctions: Claudins 1 and 4 are regulated by ATP2C1 gene encoding Ca2+/Mn2+ATPase SPCA1 in cultured keratinocytes

Mutations in the ATP2C1 gene encoding Ca2+/Mn2+ ATPase SPCA1 cause Hailey–Hailey disease (HHD, OMIM 16960). HHD is characterized by epidermal acantholysis. We attempted to model HHD using normal keratinocytes, in which the SPCA1 mRNA was down‐regulated with the small inhibitory RNA (siRNA) method. SiRNA inhibition significantly down‐regulated the SPCA1 mRNA, as demonstrated by qPCR, and decreased the SPCA1 protein beyond detectable level, as shown by Western analysis. The expression of selected desmosomal, adherens and tight junction (TJ) proteins was then studied in the SPCA1‐deficient and control keratinocytes cultured in low (0.06 mm) or high (1.2 mm) calcium concentration. The mRNA and protein levels of most TJ components were up‐regulated in non‐treated control keratinocyte cultures upon switch from low to high calcium concentration. In contrast, SPCA1‐deficient keratinocytes displayed high levels of TJ proteins claudins 1 and 4 even in low calcium. ZO‐1 did not, however, follow similar expression patterns. Protein levels of occludin, beta‐catenin, E‐cadherin, desmoplakin, desmogleins 1–3, desmocollin 2/desmocollin 3 and plakoglobin did not show marked changes in SPCA1‐deficient keratinocytes. Indirect immunofluorescence labelling revealed delayed translocation of desmoplakin and desmoglein 3 in desmosomes and increased intracellular pools of TJ and desmosomal components in SPCA1‐inhibited keratinocytes. The results show that SPCA1 regulates the levels of claudins 1 and 4, but does not affect desmosomal protein levels, indicating that TJ proteins are differently regulated. The results also suggest a potential role for claudins in HHD.

Effects of the Nd:YAG 1320-nm laser on skin rejuvenation: Clinical and histological correlations

Abstract The neodymium:yttrium-aluminum-garnet (Nd:YAG) laser is a popular non-ablative treatment used for skin rejuvenation. The purpose of this prospective study was to evaluate the clinical effects, coupled with a quantitative assessment, of the histological changes in response to Nd:YAG 1320-nm laser treatment of periocular wrinkles. Six volunteers with Fitzpatrick skin types III and IV and Glogau class I–II wrinkles were subjected to 3 months of Nd:YAG 1320-nm treatment in the periocular area (six sessions at 2-week intervals). Volunteers were photographed, and skin biopsies were obtained at baseline as well as 3 and 6 months after the start of treatments. Quantitative evaluation of total elastin, newly synthesized tropoelastin, collagen types I, III and VII, and newly synthesized collagen was performed using a computerized morphometric analysis. A noticeable clinical and histological improvement was observed after Nd:YAG 1320-nm treatment. Collagen types I, III and VII, as well as newly synthesized collagen, together with tropoelastin showed a statistically significant increase in response to treatment, while the mean level of total elastin was significantly decreased after treatment. Our data suggest that Nd:YAG 1320 nm is an effective treatment for skin rejuvenation as it stimulates the repair processes, and reverses the clinical, as well as the histopathological, signs of skin aging.

Superficial Dsg2 Expression Limits Epidermal Blister Formation Mediated by Pemphigus Foliaceus Antibodies and Exfoliative Toxins

Cell-cell adhesion mediated by desmosomes is crucial for maintaining proper epidermal structure and function, as evidenced by several severe and potentially fatal skin disorders involving impairment of desmosomal proteins. Pemphigus foliaceus (PF) and staphylococcal scalded skin syndrome (SSSS) are subcorneal blistering diseases resulting from loss of function of the desmosomal cadherin, desmoglein 1 (Dsg1). To further study the pathomechanism of these diseases and to assess the adhesive properties of Dsg2, we employed a recently established transgenic (Tg) mouse model expressing Dsg2 in the superficial epidermis. Neonatal Tg and wild type (WT) mice were injected with purified ETA or PF Ig. We showed that ectopic expression of Dsg2 reduced the extent of blister formation in response to both ETA and PF Ig. In response to PF Ig, we observed either a dramatic loss or a reorganization of Dsg1-α, Dsg1-β, and, to a lesser extent, Dsg1-γ, in WT mice. The Inv-Dsg2 Tg mice showed enhanced retention of Dsg1 at the cell-cell border. Collectively, our data support the role for Dsg2 in cell adhesion and suggest that ectopic superficial expression of Dsg2 can increase membrane preservation of Dsg1 and limit epidermal blister formation mediated by PF antibodies and exfoliative toxins.

Multiple minimally invasive Erbium: Yttrium Aluminum Garnet laser mini‐peels for skin rejuvenation: an objective assessment

Background  As the demand for minimally invasive rejuvenation is increasing, micropeel resurfacing using Erbium:Yttrium Aluminum Garnet (Er:YAG) laser 2940 nm has been reported for the treatment of photoaged skin without ablation of the epidermis. However, little is known about the efficacy and underlying histologic changes associated with this type of treatment.

c-Src/Cav1-dependent activation of the EGFR by Dsg2

The desmosomal cadherin, desmoglein 2 (Dsg2), is deregulated in a variety of human cancers including those of the skin. When ectopically expressed in the epidermis of transgenic mice, Dsg2 activates multiple mitogenic signaling pathways and increases susceptibility to tumorigenesis. However, the molecular mechanism responsible for Dsg2-mediated cellular signaling is poorly understood. Here we show overexpression as well as co-localization of Dsg2 and EGFR in cutaneous SCCs in vivo. Using HaCaT keratinocytes, knockdown of Dsg2 decreases EGFR expression and abrogates the activation of EGFR, c-Src and Stat3, but not Erk1/2 or Akt, in response to EGF ligand stimulation. To determine whether Dsg2 mediates signaling through lipid microdomains, sucrose density fractionation illustrated that Dsg2 is recruited to and displaces Cav1, EGFR and c-Src from light density lipid raft fractions. STED imaging confirmed that the presence of Dsg2 disperses Cav1 from the cell-cell borders. Perturbation of lipid rafts with the cholesterol-chelating agent MβCD also shifts Cav1, c-Src and EGFR out of the rafts and activates signaling pathways. Functionally, overexpression of Dsg2 in human SCC A431 cells enhances EGFR activation and increases cell proliferation and migration through a c-Src and EGFR dependent manner. In summary, our data suggest that Dsg2 stimulates cell growth and migration by positively regulating EGFR level and signaling through a c-Src and Cav1-dependent mechanism using lipid rafts as signal modulatory platforms.

Expression of p53 protein after nonablative rejuvenation: the other side of the coin.

BACKGROUND Disturbance of p53 expression may play an important role in the pathogenesis of ultraviolet (UV) light–induced skin cancer as well as photoaging. OBJECTIVES To objectively evaluate the potential effect of nonablative facial rejuvenation on p53 expression. PARTICIPANTS AND METHODS Thirty patients with Fitzpatrick skin type III to IV were divided into five groups. Each group underwent a different nonablative modality: radiofrequency (RF), intense pulsed light (IPL), electro‐optical synergy (ELOS) (combined RF and IPL), 1,320‐nm neodymium‐doped yttrium aluminum garnet (Nd:YAG) laser, and 2,940‐nm erbium‐doped (Er):YAG laser minipeel. Skin biopsies were obtained before treatment, by the end of treatment, and 3 months after treatment. Biopsies were also taken from 30 controls. Quantitative evaluation of p53 was performed using computer image analysis for immunostained tissues. RESULTS P53 expression was statistically significantly greater at the end of IPL (p = .02) and ELOS (p = .02) treatments than before treatment but was statistically insignificantly lower (p > .05) 3 months after treatment than at the end of treatment. No significant differences (p > .05) were observed in p53 level after RF, 1,320‐nm Nd:YAG, and 2,940‐nm Er:YAG mini‐peel treatments from baseline. CONCLUSIONS The increase in epidermal p53 expression after IPL treatment could increase the risk of skin neoplasia by intense pulsed light‐induced DNA damage which may lead to dysregulation of apoptosis and initiation of skin cancer.

Cell Cycle- and Cancer-Associated Gene Networks Activated by Dsg2: Evidence of Cystatin A Deregulation and a Potential Role in Cell-Cell Adhesion

Cell-cell adhesion is paramount in providing and maintaining multicellular structure and signal transmission between cells. In the skin, disruption to desmosomal regulated intercellular connectivity may lead to disorders of keratinization and hyperproliferative disease including cancer. Recently we showed transgenic mice overexpressing desmoglein 2 (Dsg2) in the epidermis develop hyperplasia. Following microarray and gene network analysis, we demonstrate that Dsg2 caused a profound change in the transcriptome of keratinocytes in vivo and altered a number of genes important in epithelial dysplasia including: calcium-binding proteins (S100A8 and S100A9), members of the cyclin protein family, and the cysteine protease inhibitor cystatin A (CSTA). CSTA is deregulated in several skin cancers, including squamous cell carcinomas (SCC) and loss of function mutations lead to recessive skin fragility disorders. The microarray results were confirmed by qPCR, immunoblotting, and immunohistochemistry. CSTA was detected at high level throughout the newborn mouse epidermis but dramatically decreased with development and was detected predominantly in the differentiated layers. In human keratinocytes, knockdown of Dsg2 by siRNA or shRNA reduced CSTA expression. Furthermore, siRNA knockdown of CSTA resulted in cytoplasmic localization of Dsg2, perturbed cytokeratin 14 staining and reduced levels of desmoplakin in response to mechanical stretching. Both knockdown of either Dsg2 or CSTA induced loss of cell adhesion in a dispase-based assay and the effect was synergistic. Our findings here offer a novel pathway of CSTA regulation involving Dsg2 and a potential crosstalk between Dsg2 and CSTA that modulates cell adhesion. These results further support the recent human genetic findings that loss of function mutations in the CSTA gene result in skin fragility due to impaired cell-cell adhesion: autosomal-recessive exfoliative ichthyosis or acral peeling skin syndrome.