Proliferation, apoptosis, and survivin expression in keratinocytic neoplasms and hyperplasias

Medicinal Plants of the Flora of Kazakhstan Used in the Treatment of Skin Diseases

The skin shows the physiological condition of the body's organs and systems that prevent infections and physical damage. Throughout the ages, in folk medicine, phytotherapy was considered a primary form of treatment in all countries, including Kazakhstan, due to the abundance and availability of plant-based remedies. This paper discusses several medicinal plants that are traditionally used in the treatment of skin diseases in the Republic of Kazakhstan. The chemical composition of these plants was analyzed, with a particular focus on the biologically active basic compounds responsible for their therapeutic efficiency in treating skin ailments.

Mechanisms of the Cytotoxic Effect of Selenium Nanoparticles in Different Human Cancer Cell Lines

In recent decades, studies on the functional features of Se nanoparticles (SeNP) have gained great popularity due to their high biocompatibility, stability, and pronounced selectivity. A large number of works prove the anticarcinogenic effect of SeNP. In this work, the molecular mechanisms regulating the cytotoxic effects of SeNP, obtained by laser ablation, were studied by the example of four human cancer cell lines: A-172 (glioblastoma), Caco-2, (colorectal adenocarcinoma), DU-145 (prostate carcinoma), MCF-7 (breast adenocarcinoma). It was found that SeNP had different concentration-dependent effects on cancer cells of the four studied human lines. SeNP at concentrations of less than 1 μg/mL had no cytotoxic effect on the studied cancer cells, with the exception of the A-172 cell line, for which 0.5 μg/mL SeNP was the minimum concentration affecting its metabolic activity. It was shown that SeNP concentration-dependently caused cancer cell apoptosis, but not necrosis. In addition, it was found that SeNP enhanced the expression of pro-apoptotic genes in almost all cancer cell lines, with the exception of Caco-2 and activated various pathways of adaptive and pro-apoptotic signaling pathways of UPR. Different effects of SeNP on the expression of ER-resident selenoproteins and selenium-containing glutathione peroxidases and thioredoxin reductases, depending on the cell line, were established. In addition, SeNP triggered Ca²⁺ signals in all investigated cancer cell lines. Different sensitivity of cancer cell lines to SeNP can determine the induction of the process of apoptosis in them through regulation of the Ca²⁺ signaling system, mechanisms of ER stress, and activation of various expression patterns of genes encoding pro-apoptotic proteins.

Sortilin regulates keratinocyte proliferation and apoptosis through the PI3K-AKT signaling pathway

Sortilin is found to regulate proliferation and death of different cells, while its role in regulating keratinocyte proliferation and apoptosis is still unknown. In this study, we found that sortilin levels significantly increased in psoriasis patients, and sortilin suppression eliminated the proliferation of HaCaT cells induced by M5 cocktail solution and enhanced the levels of cleaved caspase 3 protein and the Bax/Bcl-2 ratio; however, levels of p-PI3K and p-AKT were decreased. In addition, sortilin silencing remitted the characteristic changes associated with psoriasis-like skin lesions. In summary, suppressed sortilin expression helped inhibit keratinocyte proliferation in HaCaT cells by inactivating PI3K/AKT signaling, which provides a new target for the therapy of psoriasis.

Evaluation and Expression of Survivin in Potentially Malignant Lesions and Squamous Cell Carcinoma: A Comparative Study

Introduction Overexpression of survivin, an anti-apoptotic protein, has been associated with the progression of cancer, resistance to drugs, and a poor prognosis. The expression level of survivin indicates the progression of the disease, early recurrence, and a failure to respond to therapy. Our study was a retrospective analysis performed on archival specimens. Materials and methods The study included a total of 50 histopathologically proven cases of potentially malignant lesions and squamous cell carcinoma. Immunohistochemical staining was carried out using primary rabbit monoclonal antibodies to survivin (PathnSitu, Telangana, India) along with a horseradish peroxidase detection kit (Leica Biosystems, Maharashtra, India). The intensity of staining of survivin in the epithelium was determined, and the data obtained from potentially malignant lesions, oral squamous cell carcinoma, fetal tissue, and normal oral mucosa were compared. Results The expression of survivin was positive in 70% of the samples of oral squamous cell carcinoma followed by 50% from cases of leukoplakia, 20% of oral submucous fibrosis samples, and 10% of lichen planus samples (P < 0.05). Conclusion Malignant transformation of these potentially malignant lesions increases with increased expression of survivin. This expression of the anti-apoptotic protein might be an early phenomenon in the initiation and advancement of oral squamous cell carcinoma. The prognosis of oral squamous cell carcinomas becomes poorer with increased expression of survivin. Therefore, survivin might be helpful as an important therapeutic target because it is expressed more in tumor cells and absent in most adult tissues.

A novel nicastrin mutation in a three-generation Dutch family with hidradenitis suppurativa: a search for functional significance

Background

Mutations in the γ‐secretase enzyme subunits have been described in multiple kindreds with familial hidradenitis suppurativa (HS).

Objective

In this study, we report a novel nicastrin (NCSTN) mutation causing HS in a Dutch family. We sought to explore the immunobiological function of NCSTN mutations using data of the Immunological Genome Project.

Methods

Blood samples of three affected and two unaffected family members were collected. Whole‐genome sequencing was performed using genomic DNA isolated from peripheral blood leucocytes. Sanger sequencing was done to confirm the causative NCSTN variant and the familial segregation. The microarray data set of the Immunological Genome Project was used for thorough dissection of the expression and function of wildtype NCSTN in the immune system.

Results

In a family consisting of 23 members, we found an autosomal dominant inheritance pattern of HS and detected a novel splice site mutation (c.1912_1915delCAGT) in the NCSTN gene resulting in a frameshift and subsequent premature stop. All affected individuals had HS lesions on non‐flexural and atypical locations. Wildtype NCSTN appears to be upregulated in myeloid cells like monocytes and macrophages, and in mesenchymal cells such as fibroblastic reticular cells and fibroblasts. In addition, within the 25 highest co‐expressed genes with NCSTN we identified CAPNS1,ARNT and PPARD.

Conclusion

This study reports the identification a novel NCSTN gene splice site mutation which causes familial HS. The associated immunobiological functions of NCSTN and its co‐expressed genes ARNT and PPARD link genetics to the most common environmental and metabolic HS risk factors which are smoking and obesity.

DUSP1/MKP-1 regulates proliferation and apoptosis in keratinocytes through the ERK/Elk-1/Egr-1 signaling pathway

Psoriasis is an inflammatory skin disease with preference for the skin and joints that occurs due to hyper-proliferation and abnormal apoptosis of keratinocytes. DUSP1 expression in dermal mesenchymal stem cells (MSCs) is obviously lower in psoriasis patients than that in healthy individuals. The present study aimed to explore the roles of DUSP1 in the proliferation and apoptosis of HaCaT cells treated with a cocktail of M5. We showed that DUSP1 was markedly reduced in psoriasis patients and M5-treated HaCaT cells compared with the control subjects. MTT and BrdU assays revealed that overexpression of DUSP1 significantly suppressed the proliferation of HaCaT cells. Furthermore, DUSP1 decreased M5-induced the upregulation of cyclin D1 and Rb. In addition, we demonstrated that forced overexpression of DUSP1 caused an augment of cell apoptosis rate, c-caspase 3 protein level and the Bax/Bcl-2 ratio. Finally, we determined that enhancing DUSP1 expression resulted in the reduction of p-ERK, p-Elk-1 and Egr-1 protein levels using western blot, and the Chromatin immunoprecipitation (ChIP) assay displayed that p-Elk-1 binds to the promoter of Egr-1 in HaCaT cells. The roles of DUSP1 in cell proliferation and apoptosis were abolished by overexpression of Egr-1. In summary, gain function of DUSP1 regulates proliferation and apoptosis of HaCaT cells through the ERK/Elk-1/Egr-1 signaling pathway.

Mitochondrial dysfunction in affected skin and increased mitochondrial DNA in serum from patients with psoriasis

Psoriasis is characterized by keratinocyte proliferation and chronic inflammation, but the pathogenesis is still unclear. Dysregulated mitochondria (mt) could lead to reduced apoptosis and extracellular secretion of mtDNA, acting as "innate pathogen" triggering inflammation. Serum was obtained from healthy volunteers and psoriatic patients. Mitochondrial DNA was extracted from the serum and amplified with quantitative PCR (qPCR). Punch biopsies were obtained from lesional and non-lesional psoriatic skin (10 cm apart) and from healthy volunteers, were placed in RNA later and were stored at -80°C until RNA was extracted and cDNA was synthesized; gene expression of uncoupling protein 2 (UCP2), Dynamin-related protein 1 (Drp1) and calcineurin, involved in the regulation of mitochondria function, was detected with qPCR. Mitochondrial DNA was significantly increased (7s, P = 0.0496 and Cytochrome B, CytB, P = 0.0403) in the serum of psoriatic patients (n = 63) as compared to controls (n = 27). Gene expression was significantly reduced for UCP2 (P = 0.0218), Drp1 (P = 0.0001) and calcineurin (P = 0.0001) in lesional psoriatic skin, as compared to non-lesional or control skin. Increased serum extracellular mtDNA in psoriatic patients and decreased expression of mitochondrial regulatory proteins in psoriatic skin suggest increased inflammation and reduced keratinocyte apoptosis, respectively. Inhibitors of mtDNA secretion and/or UCP2 stimulants may be potential treatment options.

MiR-20a-3p regulates TGF-β1/Survivin pathway to affect keratinocytes proliferation and apoptosis by targeting SFMBT1 in vitro

Psoriasis is a common immune-mediated chronic inflammatory skin disease characterized by abnormal keratinocyte proliferation, differentiation and apoptosis. However, the exact etiology and pathogenesis are still unclear. Evidence is rapidly accumulating for the role of microRNAs in psoriasis. It has been demonstrated that Interleukin-22 (IL-22) plays vital role in T cell-mediated immune response by interacting with keratinocytes in the pathogenesis of psoriasis. The aim of our study was to explore the possible functional role of miR-20a-3p in psoriasis and in IL-22 induced keratinocyte proliferation. Here, we found that miR-20a-3p was down-regulated in psoriatic lesions and in HaCaT cells (human keratinocyte cell line) treated by IL-22 stimulation. Functional experiments showed that overexpression of miR-20a-3p in HaCaT cells suppressed proliferation and induced apoptosis while its knockdown promoted cell proliferation and reduces cell apoptosis. Mechanistically, SFMBT1 was identified as the direct target of miR-20a-3p by dual luciferase reporter assay. SFMBT1 knockdown was demonstrated to inhibit cell growth and induced apoptosis, which was consistent with the function of miR-20a-3p upregulation in HaCaT cells. In addition, results of western blot analysis showed that miR-20a-3p upregulation or SFMBT1 knockdown changed the protein expression levels of TGF-β1 and survivin. Our findings suggest that miR-20a-3p play roles through targeting SFMBT1 and TGF-β1/Survivin pathway in HaCaT cells, and loss of miR-20a-3p in psoriasis may contribute to hyperproliferation and aberrant apoptosis of keratinocytes.

β-Catenin and CD44 Expression in Keratoacanthoma and Squamous Cell Carcinoma of the Skin

CD44 and β-catenin are adhesion molecules expressed on a wide variety of cells. Failure of this expression is believed to lead to disruption of cell-cell adhesion and to neoplasia. The aim of this study was to investigate the staining intensity of CD44 and β-catenin in keratoacanthomas and squamous cell carcinomas of the skin. The proliferation index, PCNA staining, was also evaluated in these cases. The abnormal expression of β-catenin significantly predominated in squamous cell carcinomas (n = 20, 76.9%) compared with keratoacanthomas (P = 0.002, χ2 = 7.8). Most keratoacanthomas (n = 11, 61.1%) more frequently showed strong staining intensity with CD44 compared with squamous cell carcinoma (P = 0.001, χ2 = 13.7). The proliferation index was higher in squamous cell carcinoma (P = 0.000, χ2 = 12.8). These findings suggest that CD44 and β-catenin expression may have an important role in the development of malignancy and in the determination of biological features of keratoacanthoma and squamous cell carcinoma of the skin.

[Expressions of survivin, PI3K and AKT in keratinocytes in skin lesions and their pathogenic role in psoriasis vulgaris]

OBJECTIVE

To explore the role of survivin and PI3K/AKT pathway in the pathogenesis of psoriasis vulgaris (PV).

METHODS

Plaque-like lesions collected from 22 patients with PV in progressive stage and 18 normal control skin specimens were examined using immunohistochemical staining, Western blotting and real-time quantitative PCR for expressions of survivin, PI3K and AKT in the keratinocytes, and their correlation was analyzed. A small interfering RNA (siRNA) was used to knock down AKT in cultured HaCaT cells, and Western blotting was used to detect the changes in the expression of survivin. RESULTS Compared with normal skin, PV lesions showed obviously up-regulated expressions of survivin, PI3K and AKT in the keratinocytes. Survivin expression was positively correlated with PI3K (r=0.4510, P=0.0351) and AKT (r=0.4423, P=0.0393) in the keratinocytes in PV lesions. In cultured HaCaT cells, siRNA-mediated knockdown of AKT caused down-regulation of survivin expression.

CONCLUSION

Survivin and PI3K/AKT signaling pathway may participate in the occurrence and progression of PV.

The HGF/SF Mouse Model of UV-Induced Melanoma as an In Vivo Sensor for Metastasis-Regulating Gene

Cutaneous malignant melanoma is an aggressive and potentially lethal form of skin cancer, particularly in its advanced and therapy-resistant stages, and the need for novel therapeutics and prognostic tools is acute. Incidence of melanoma has steadily increased over the past few decades, with exposure to the genome-damaging effects of ultraviolet radiation (UVR) well-recognized as a primary cause. A number of genetically-engineered mouse models (GEMMs) have been created that exhibit high incidence of spontaneous and induced forms of melanoma, and a select subset recapitulates its progression to aggressive and metastatic forms. These GEMMs hold considerable promise for providing insights into advanced stages of melanoma, such as potential therapeutic targets and prognostic markers, and as in vivo systems for testing of novel therapies. In this review, we summarize how the HGF/SF transgenic mouse has been used to reveal metastasis-regulating activity of four different genes (CDK4^R24C, survivin and NME1/NME2) in the context of UV-induced melanoma. We also discuss how these models can potentially yield new strategies for clinical management of melanoma in its most aggressive forms.

Survivin in autoimmune diseases

Survivin is a protein functionally important for cell division, apoptosis, and possibly, for micro-RNA biogenesis. It is an established marker of malignant cell transformation. In non-malignant conditions, the unique properties of survivin make it indispensable for homeostasis of the immune system. Indeed, it is required for the innate and adaptive immune responses, controlling differentiation and maintenance of CD4⁺ and CD8⁺ memory T-cells, and in B cell maturation. Recently, survivin has emerged as an important player in the pathogenesis of autoimmune diseases. Under the conditions of unreserved inflammation, survivin enhances antigen presentation, maintains persistence of autoreactive cells, and supports production of autoantibodies. In this context, survivin takes its place as a diagnostic and prognostic marker in rheumatoid arthritis, psoriasis, systemic sclerosis and pulmonary arterial hypertension, neuropathology and multiple sclerosis, inflammatory bowel diseases and oral lichen planus. In this review, we summarise the knowledge about non-malignant properties of survivin and focus on its engagement in cellular and molecular pathology of autoimmune diseases. The review highlights utility of survivin measures for clinical applications. It provides rational for the survivin inhibiting strategies and presents results of recent reports on survivin inhibition in modern therapies of cancers and autoimmune diseases.

Survivin, a molecular target for therapeutic interventions in squamous cell carcinoma

Squamous cell carcinoma (SCC) is the most common cancer worldwide. The treatment of locally advanced disease generally requires various combinations of radiotherapy, surgery, and systemic therapy. Despite aggressive multimodal treatment, most of the patients relapse. Identification of molecules that sustain cancer cell growth and survival has made molecular targeting a feasible therapeutic strategy. Survivin is a member of the Inhibitor of Apoptosis Protein (IAP) family, which is overexpressed in most of the malignancies including SCC and totally absent in most of the normal tissues. This feature makes survivin an ideal target for cancer therapy. It orchestrates several important mechanisms to support cancer cell survival including inhibition of apoptosis and regulation of cell division. Overexpression of survivin in tumors is also associated with poor prognosis, aggressive tumor behavior, resistance to therapy, and high tumor recurrence. Various strategies have been developed to target survivin expression in cancer cells, and their effects on apoptosis induction and tumor growth attenuation have been demonstrated. In this review, we discuss recent advances in therapeutic potential of survivin in cancer treatment.

Survivin as a Novel Biomarker in the Pathogenesis of Acne Vulgaris and Its Correlation to Insulin-Like Growth Factor-I

Survivin, a member of the inhibitor of apoptosis protein family, has an important role in cell cycle regulation. Insulin-like growth factor-I (IGF-I) is a polypeptide hormone with wide range of biologic effects including stimulation of lipogenesis in sebaceous glands. Their overexpression in some fibrotic disorders suggests a possible implication of both IGF-I and survivin in the pathogenesis of acne and/or acne scars. The current study aimed to assess and correlate serum levels of IGF-I and survivin in patients with active acne vulgaris and postinflammatory acne scars and to evaluate their lesional expressions in comparison to healthy controls. Serum IGF-I and survivin were estimated using commercially available ELISA kits and their tissues expressions were investigated using Western blotting. Our findings suggest that IGF-I and survivin could play potential roles in the pathogenesis of active acne vulgaris and more importantly in postinflammatory acne scars with significant positive correlation coefficient between serum levels of IGF-I and survivin which support IGF-I-/PI3K-/AKT-mediated downregulation of nuclear expression of FoxO transcription factors resulting in enhanced survivin expression.

Methotrexate treatment provokes apoptosis of proliferating keratinocyte in psoriasis patients

Psoriasis is a chronic inflammatory skin disease characterized by hyper proliferation of keratinocytes. Recent data show that the epidermis thickening in psoriasis may be related to imbalance of homeostasis caused by abnormal apoptotic process. Maintenance of keratinocyte apoptotic process is very important in psoriasis. Methotrexate (MTX) has been used for many years to restore the normal skin in psoriasis condition. However, the exact mechanism of MTX in psoriasis condition is poorly understood. The aim of this study was to examine the role of MTX on keratinocyte apoptosis pathway in psoriasis patients. A total of 58 psoriasis vulgaris patients were recruited for this study. Nonlesional skin biopsies served as control. Skin biopsies of psoriatic patients were collected and analyzed for cytosolic, mitochondria and total cytochrome c by ELISA. Expression of caspase-9, NFκBp65, pAkt1 by western blot, real-time PCR and immunohistochemical analysis of c-FLIP protein was analyzed in nonlesional and lesional skin biopsies before (day 0) and after (at the end of 6 and 12 weeks) MTX treatment. After MTX treatment, a significant increase in cytochrome c was observed when compared with before MTX treatment in psoriasis patients (p < 0.001). Protein and gene expression of cleaved caspase-9 were significantly increased after MTX treatment, whereas the expression of Bcl-xL, c-FLIP, NFκBp65, pAkt1 significantly downregulated after MTX treatment. In conclusion, these results showed that intrinsic apoptotic pathway induced by MTX eventually adds the beneficial therapeutic role of MTX in psoriasis by controlling the acanthosis.

Does Notch play a tumor suppressor role across diverse squamous cell carcinomas?

The role of Notch pathway in tumorigenesis is highly variable. It can be tumor suppressive or pro‐oncogenic, typically depending on the cellular context. Squamous cell carcinoma (SCC) is a cancer of the squamous cell, which can occur in diverse human tissues. SCCs are one of the most frequent human malignancies for which the pathologic mechanisms remain elusive. Recent genomic analysis of diverse SCCs identified marked levels of mutations in NOTCH1, implicating Notch signaling pathways in the pathogenesis of SCCs. In this review, evidences highlighting NOTCH's role in different types of SCCs are summarized. Moreover, based on accumulating structural information of the NOTCH receptor, the functional consequences of NOTCH1 gene mutations identified from diverse SCCs are analyzed, emphasizing loss of function of Notch in these cancers. Finally, we discuss the convergent view on an intriguing possibility that Notch may function as tumor suppressor in SCCs across different tissues. These mechanistic insights into Notch signaling pathways will help to guide the research of SCCs and development of therapeutic strategies for these cancers.

Cytokeratin 17 immunoexpression in actinic keratosis (bowenoid and nonbowenoid) and in Bowen disease

Cytokeratin (CK) 17 immunoexpression has been investigated in nonmelanoma skin cancer as well as in many preinvasive epithelial malignancies. However, there is not any previous study of CK17 immunoexpression in actinic keratosis (AK) or Bowen disease in nonimmunocompromised patients. We evaluated CK17 immunoexpression in 20 cases of AK (10 nonbowenoid and 10 bowenoid) as well as in 10 cases of Bowen disease. We identified expression of CK17 in the superficial layers above the atypical foci. In some cases, there were foci of expression by the full thickness of the epidermis, which was the predominant pattern in very few cases (1 Bowen disease and 1 bowenoid AK). In addition, 1 case of bowenoid AK showed CK17 expression in a "skyline" pattern in the basal layer of the epidermis. Cytokeratin 17 immunostaining did not allow us to distinguish between the 3 entities studied. However, the immunostaining allowed us to distinguish atypical foci in the biopsies, even if atypicality was minimal. In addition, CK17 was useful in identifying surgical borders involved by disease in cases in which the hematoxylin-eosin was difficult to evaluate. Cytokeratin 17 immunoexpression might have a role in evaluating surgical borders in some cases of AK and Bowen disease.

Expression of Bcl-xL and Mcl-1 in the nonmelanoma skin cancers of renal transplant recipients

OBJECTIVES

This study aims to investigate how immunosuppression influences the protein expression of antiapoptotic members of the Bcl-2 family-namely, Bcl-xL and Mcl-1-in nonmelanoma skin cancer (NMSC) and the peritumoral epidermis of renal transplant recipients.

METHODS

NMSC and peritumoral epidermis protein expression of Bcl-xL and Mcl-1 were assessed by immunohistochemistry in renal transplant recipients receiving tacrolimus or sirolimus and the general population not receiving immunosuppression.

RESULTS

NMSC from renal transplant recipients compared with patients not receiving immunosuppressant medications had a reduced Bcl-xL expression intensity (P = .042). Mcl-1 expression intensity in NMSC was decreased in tacrolimus-treated patients compared with sirolimus-treated patients and the nonimmunosuppressed population (P = .024). Bcl-xL expression intensity was increased in peritumoral epidermis compared with NMSC (P = .002).

CONCLUSIONS

It was shown for the first time that Bcl-xL and Mcl-1 expression are widespread in the peritumoral epidermis and NMSC of renal transplant recipients. Importantly in NMSC, Bcl-xL expression was reduced with immunosuppression exposure, and Mcl-1 expression was reduced in tacrolimus-treated compared with sirolimus-treated patients.

Expression of nuclear survivin in normal skin and squamous cell carcinoma: a possible role in tumour invasion

Background:

Survivin is detected in few adult normal cells and it is highly expressed in cancer. Nuclear survivin facilitates cell cycle entry, whereas the mitochondrial pool protects cells from apoptosis. Survivin is overexpressed in keratinocyte stem cells (KSCs) and protects them from apoptosis.

Methods:

As KSCs are at the origin of squamous cell carcinoma (SCC), we evaluated survivin expression in normal and cancerous skin in vivo by immunohistochemistry and western blotting. HaCaT cells overexpressing survivin and wound-healing assay are used. Analysis of variance and Student's T-tests are used for statistical analysis.

Results:

Survivin is localised in both the cytoplasm and nucleus of normal adult and young keratinocytes. Nuclear survivin is detected in one every 10 of 11 basal keratinocytes. When present in suprabasal cells, nuclear survivin is coexpressed with K10 but not with K15 or p75-neurotrophin receptor (p75NTR), a transit amplifying cell marker. Nuclear, but not cytoplasmic, survivin expression markedly increases in actinic keratosis and in SCC in situ, as compared with normal epidermis, and it is highest in poorly differentiated SCC. In SCC tumours, nuclear survivin-positive cells are mainly K10/p75NTR-negative and K15-positive. In poorly differentiated tumours, survivin mostly localises in the deep infiltrating areas. When overexpressed in keratinocytes, survivin increases cell migration.

Conclusion:

High survivin expression and the subcellular localisation of survivin correlate with keratinocyte differentiation and are associated with undifferentiated and more invasive SCC phenotype.

Actinic keratosis: a clinical and epidemiological revision

Actinic keratoses are benign intraepithelial skin neoplasms constituted by atypical proliferation of keratinocytes that may evolve to squamous cell carcinoma. They develop in photoexposed skin areas; they are induced mainly by ultraviolet radiation and are considered cutaneous markers of chronic exposure to sunlight. They develop mainly in adults and older, fair skinned individuals, and are the fourth most common cause of dermatologic consultation in Brazil. Damage to the apoptosis pathway in photoexposed epithelium favors cellular proliferation and the permanence of the lesions. In this revision, the authors assemble the main epidemiological data regarding this disease and suggest that strategies to identify risky phenotypes, early diagnosis, adequate treatment, clinical follow-up, stimulus to skin self examination, photoeducation and photoprotection should be promoted with the aim of avoiding the progression to malignancy and also the prevention and the diagnose of concomitant neoplasms also induced by ultraviolet radiation.

Occurrence of squamous cell carcinoma in an area of lichen simplex chronicus: case report and pathogenetic hypothesis

BACKGROUND

Lichen simplex chronicus is a common skin disorder characterized by circumscribed, lichenified, pruritic plaque secondary to local repetitive trauma, notably rubbing and scratching.

OBJECTIVE

We describe a case of a squamous cell carcinoma arising in a patient with a long-lasting history of lichen simplex chronicus and discuss the potential role of the microenvironment in predisposing the malignant transformation.

CONCLUSION

Here we propose a hypothesis in which rubbing and scratching contribute to an excess of inflammatory mediators, which in turn may lead to alterations in the processes of keratinocyte proliferation and differentiation.

Expression of nuclear factor kappa B and survivin in psoriasis

Background and Objective. Suppression of apoptosis has been proposed as a mechanism responsible for epidermal thickness in psoriasis. Survivin is a member of the inhibitor of apoptosis family. Nuclear factor kappa B (NF-κB) is one of the transcriptional factors that regulate many genes affecting apoptosis. The aim of this study was to determine survivin and NF-κB expressions in psoriasis in comparison with normal epidermis. Patients and Methods. Immunohistochemical expressions of survivin and NF-κB were investigated in 41 psoriatic and 21 normal skin samples. Results. Diffuse nuclear survivin expression in all epidermal layers was seen in all of the psoriatic samples. NF-κB expression in different epidermal locations was seen in all of the psoriatic samples. Nuclear staining was positive in 40 psoriasis samples. Similar survivin and NF-κB expressions were observed in normal skin samples. Conclusion. Since similar expressions are seen in both normal and psoriatic epidermis, no important roles for survivin and NF-κB can be attributed in epidermal proliferation and thickness seen in psoriasis.

Epidermal growth factor receptor expression in mice skin upon ultraviolet B exposure - Seborrheic Keratosis as a coincidental and unique finding

Background:

Ultraviolet B (UVB) is the most damaging component of sunlight. It rapidly activates the epidermal growth factor receptor (EGFR) and generates reactive oxygen species (ROS) in excessive quantities that quickly overwhelm tissue antioxidants.

Setting and Design:

To demonstrate the effects of UVB radiation on EGFR expression in mice skin and to evaluate the role of antioxidants in the exposed group.

Materials and Methods:

After obtaining the approval of the ethical committee, forty mice from BALB/c strain were used in this experiment and were allocated into 3 groups; 10 (control group); 15 (exposure group); and 15 (exposed and treated with antioxidants). Antioxidants were administered through subcutaneous injection. Skin biopsies from all groups were stained with EGFR antibodies. Total antioxidant status (TAS) was evaluated in all groups.

Statistical Analysis:

The data obtained were analyzed using ANOVA, Duncan's test, and Pearson's Correlation.

Results:

The highest EGFR expression in exposure group was of score 3⁺ (53%). The highest EGFR expression in treatment group was score 0 (40%). Apoptotic bodies and dermal mast cells increased in exposure group while decreased in treatment group. The mean values for TAS were measured for each group; control group = 1.2 mmol/l; exposure group = 0.87 mmol/l; treatment group =1.3 mmol/l.

Conclusions:

UVB led to Seborrheic Keratosis (SK) in mice through enhancement of EGFR expression. Antioxidants effectively reduced UVB-induced SK, reduced epidermal changes, apoptotic bodies, and decreased dermal mast cells. TAS measurement declined in exposure group, while it was within normal range in most treated cases.

Expression of apoptosis regulatory markers in the skin of advanced hepatitis-C virus liver patients

BACKGROUND

Hepatitis-C virus (HCV) infection is considered a major worldwide public health problem with a global prevalence. Maintenance of skin homeostasis requires a delicate balance between proliferation, differentiation, and apoptosis. Meanwhile, it is unclear if there is an altered keratinocyte proliferation/apoptosis balance in advanced liver disease with HCV infection.

AIM

This work aimed to evaluate the epidermal thickness and changes in the expression of apoptosis regulatory markers as well as apoptotic index in skin samples of advanced HCV liver patients compared to normal controls.

MATERIALS AND METHODS

Twenty biopsies were taken from apparently normal skin of advanced HCV liver disease patients, as well as five healthy control subjects. These specimens were used for histometric epidermal measurement, immunohistochemical staining of apoptosis regulatory proteins (Bax, Fas, p53, Caspase-3, Bcl-2, Bcl-xL) as well as the TUNEL technique for detection of apoptotic cells.

RESULTS

The mean epidermal thickness was significantly lower than the control group (P=0.000). There were significant overexpression of pro-apoptotic markers (Bax, Fas, P53, and Caspase-3) in patients (P=0.03, 0.03, 0.003, 0.003 respectively), with increased apoptotic index in HCV liver patients (P=0.002) when compared to normal controls. On the other hand, no statistically significant difference were encountered in the expression of antiapoptotic markers (Bcl-2, Bcl-xL) in HCV patients when compared to normal controls (P=0.5, 0.9, respectively).

CONCLUSION

These findings suggest that an alteration in the proliferation/apoptosis balance is present in the skin of HCV liver patients.

Survivin: a dual player in healthy and diseased skin

Survivin belongs to the inhibitor of apoptosis (IAP) protein family, and, in addition to the antiapoptotic functions, it also regulates the cell cycle. The survivin gene generates five major isoforms with diverse and opposite functions. Survivin is highly expressed in cancer and in few normal adult tissues, including skin. It is mostly detected in the nucleus of keratinocyte stem cells (KSCs), but it is also expressed in melanocytes and fibroblasts. Survivin isoforms are differentially detected in subpopulations of human keratinocytes, exerting contrasting activities. Survivin has an important role in the regulation of cell cycle in keratinocytes, and it protects these cells from anoikis and UV-induced apoptosis. In melanoma, survivin is abundantly expressed, and its subcellular localization varies depending upon tumor thickness and invasiveness. Survivin overexpression has been shown in squamous cell carcinoma (SCC), and it is also involved in UVB-induced carcinogenesis. The presence of survivin both in the nucleus and in the cytoplasm throughout the epidermal layers of psoriatic lesions suggests the involvement of this protein in the keratinocyte alterations typical of this disease. Additional studies on the expression of survivin isoforms and their subcellular localization in relation to function will confirm the key role of survivin in the skin and will open the field to new therapeutic strategies for many cutaneous conditions.

The anti-apoptotic protein G1P3 is overexpressed in psoriasis and regulated by the non-coding RNA, PRINS

Psoriasis Susceptibility-Related RNA Gene Induced by Stress (PRINS) is a non-coding RNA overexpressed in lesional and non-lesional psoriatic epidermis and induced by stress. Its function in healthy and psoriatic skin is still not known. Here, we report that PRINS regulates G1P3, a gene with anti-apoptotic effects in keratinocytes. siRNA-mediated inhibition of PRINS gene resulted in altered cell morphology and gene expression alterations, as demonstrated in a microarray experiment. One of the genes regulated by PRINS ncRNA was G1P3, an interferon-inducible gene with anti-apoptotic effects in cancer cells. Interestingly, we found that G1P3 was 400-fold upregulated in hyperproliferative lesional and ninefold upregulated in non-lesional psoriatic epidermis compared to healthy epidermis. In vitro, G1P3 protein levels were highest in proliferating keratinocytes and siRNA-mediated downregulation of G1P3 resulted in increased cell apoptosis. These data indicate that G1P3 inhibits spontaneous keratinocyte apoptosis and hence its high expression in psoriatic skin may contribute to the development of psoriatic lesions. We hypothesize that the deregulation of the PRINS ncRNA may contribute to psoriasis and results in decreased sensitivity to spontaneous keratinocyte apoptosis via the regulation of G1P3.

Survivin expression in canine epidermis and in canine and human cutaneous squamous cell carcinomas

Survivin, a member of the inhibitor of apoptosis protein (IAP) family, is ubiquitously expressed during tissue development, undetectable in most normal tissues, but re-expressed in most cancers, including skin malignancies. Expression of survivin was evaluated retrospectively in 19 canine cutaneous squamous cell carcinomas (SCCs; one in situ; 16 well differentiated; one invasive, one lymph node metastasis) and 19 well differentiated SCCs from human beings. Seven specimens of normal canine skin were included. Immunohistochemical expression of full-length survivin was determined using a commercially available antibody. In addition, apoptotic rate [Terminal deoxynucleotidyl Transferase Biotin-dUTP Nick End Labelling index (TUNEL) index] and mitotic index (MI), counting mitoses in 10 high power fields (HPF), were determined. Scattered survivin positive nuclei were identified in the epidermal basal cell layer of normal canine skin. Nuclear survivin expression was identified in 18 of 19 human and in all canine SCCs, mainly along the base of the tumour cell population. Cytoplasmic survivin expression was rarely observed in human SCCs and in 84.2% of canine SCCs. The TUNEL index ranged from 0.1 to 2.6 in human beings and from 7.5 to 69.4 in dogs, while MIs ranged from 0 to 4 in human beings and dogs. No correlation was found between survivin expression and apoptotic or mitotic rates. Canine and human tumours showed similar nuclear survivin expression, indicating similar functions of the molecule. We demonstrated survivin expression in normal adult canine epidermis. Increased nuclear survivin expression in pre-neoplastic and neoplastic lesions demonstrates a possible association of survivin with development of SCCs in human beings and dogs.

Frequency of apoptotic keratinocytes in the feline epidermis: a retrospective light-microscopic study of skin-biopsy specimens from 327 cats with normal skin or inflammatory dermatoses

A retrospective light-microscopic study was performed on 294 biopsy specimens of haired skin from cats with various feline inflammatory dermatoses and specimens from cats with normal skin. Conditions expected to frequently have apoptotic epidermal keratinocytes (AKs) (including erythema multiforme, systemic lupus erythematosus, thymoma-associated exfoliative dermatitis, solar dermatitis, and viral dermatopathies) were found to have significantly more AKs than other types of inflammatory dermatoses. Nevertheless, we found more than two AKs in many skin-biopsy specimens from inflammatory conditions not expected to have frequent AKs (especially those from ectoparasitic dermatoses). Only a single AK was found in 1/33 cats with normal skin.

Cell death in the skin

The skin is the largest organ of the body and protects the organism against external physical, chemical and biological insults, such as wounding, ultraviolet radiation and micro-organisms. The epidermis is the upper part of the skin that is continuously renewed. The keratinocytes are the major cell type in the epidermis and undergo a specialized form of programmed cell death, called cornification, which is different from classical apoptosis. In keep with this view, several lines of evidence indicate that NF-kB is an important factor providing protection against keratinocyte apoptosis in homeostatic and inflammatory conditions. In contrast, the hair follicle is an epidermal appendage that shows cyclic apoptosis-driven involution, as part of the normal hair cycle. The different cell death programs need to be well orchestrated to maintain skin homeostasis. One of the major environmental insults to the skin is UVB radiation, causing the occurrence of apoptotic sunburn cells. Deregulation of cell death mechanisms in the skin can lead to diseases such as cancer, necrolysis and graft-versus-host disease. Here we review the apoptotic and the anti-apoptotic mechanisms in skin homeostasis and disease.

Endogenous survivin modulates survival and proliferation in UVB-treated human keratinocytes

Survivin is a bi-functional member of inhibitor of apoptosis protein family, as it is able to both inhibit apoptosis and to regulate cell cycle. We investigated the role of survivin in human keratinocytes under normal conditions and during UVB irradiation. Survivin siRNA decreases proliferation and induces apoptosis in human keratinocytes, in a mode consistent with the mitotic catastrophe. Low doses UVB increase survivin expression at earlier times, while high doses down-regulate survivin level. Low doses UVB induce cell cycle arrest in G2/M, while high doses UVB cause apoptosis. Moreover, overexpression of survivin protects keratinocytes from UVB-induced apoptosis, and silencing of survivin renders keratinocytes more susceptible to UVB-induced cell death. Finally, survivin siRNA increases UVB-induced reduction of cell proliferation. Taken together, these results indicate that survivin plays a critical role in epidermal homeostasis in normal conditions and during UVB exposure, with possible implication in skin carcinogenesis.

Evaluation of survivin and NF-kappaB in psoriasis, an immunohistochemical study

BACKGROUND

Suppression of apoptosis is generally one of the accepted pathogenetic mechanisms for psoriasis and any epidermal hyperproliferative states. Survivin is a member of the inhibitor of apoptosis protein family mediating its apoptosis suppressive function by the inhibition of caspase pathway. Nuclear factor kappa B (NF-kappaB) is a transcription factor that regulates hundreds of genes including many critically involved in apoptosis. The aim of this study was to explore the role could be played by survivin and NF-kappaB in psoriasis and the link between them.

METHODS

Thirty cases of lesional psoriasis, 10 perilesional and 10 control specimens from normal skin were studied by immunohistochemical method for expression of survivin and NF-kappaB.

RESULTS

Survivin was detected in 73% of psoriatic lesions distributed either in epidermis, in endothelial cells of proliferating capillaries or in both of them. In non-psoriatic lesions either perilesional or control specimens, survivin was confined to basal layer of epidermis, significantly up regulated in psoriasis in comparison with non-psoriatic lesions (p = 0.0001). Nuclear expression of NF-kappaB was detected in 66% of psoriatic lesions; this active phosphorylated form was significantly over expressed in psoriasis in comparison with normal skin (p = 0.0004). Diffuse nuclear expression of NF-kappaB was significantly associated with up-regulation of survivin in psoriatic plaque (p = 0.03).

CONCLUSIONS

Survivin and NF-kappaB appeared to be important factors in the pathogenesis of psoriasis. Survivin could be the target of NF-kappaB mediating its death signal inhibition pathway in psoriasis.

Expression of apoptosis regulatory proteins p53 and Bcl-2 in skin of patients with chronic renal failure on maintenance haemodialysis

BACKGROUND

Chronic renal failure results in multi-organ system derangement including cardiovascular, gastrointestinal, neurological, endocrinal, blood and dermatological abnormalities. Maintenance of skin homeostasis requires a delicate balance between proliferation, differentiation and apoptosis. p53 and Bcl-2 proteins play a central role in the regulation of apoptosis.

OBJECTIVE

Evaluation of the expression of apoptosis regulatory proteins p53 and Bcl-2 in apparently normal skin of patients, with chronic renal failure on maintenance haemodialysis, with respect to their role in the apoptotic process.

METHODS

Biopsy specimens were obtained from 10 patients with chronic renal failure on maintenance haemodialysis, as well as seven age-matched control subjects. Computer-assisted image analysis was employed to measure epidermal thickness in H&E-stained sections. Immunoperoxidase technique was also used to demonstrate p53 and Bcl-2 proteins and the TUNEL technique for detection of apoptotic cells in these specimens.

RESULTS

The mean epidermal thickness was significantly higher (P < 0.0001) in patients than controls. Meanwhile, no apoptotic cells were detected in the epidermis of patients. On the other hand, a statistically significant difference was observed in both p53 (P = 0.0001) and Bcl-2 expression (P = 0.0003) when comparing patients and controls. Expression of p53 (2.74 +/- 0.84) and Bcl-2 (3.45 +/- 1.35) proteins was higher in skin samples obtained from patients with chronic renal failure and on maintenance haemodialysis than those from control cases (0.5 +/- 0.96 and 0.8 +/- 0.6, respectively). Moreover, Bcl-2 expression in patients was observed in basal as well as squamous cell layers of skin, whereas in control subjects it was confined to the basal cell layer only.

CONCLUSION

These findings suggest that an alteration in the proliferation/apoptosis balance may be present in the skin of such patients.

Melanocyte expression of survivin promotes development and metastasis of UV-induced melanoma in HGF-transgenic mice

We previously found the apoptosis inhibitor Survivin to be expressed in melanocytic nevi and melanoma but not in normal melanocytes. To investigate the role of Survivin in melanoma development and progression, we examined the consequences of forced Survivin expression in melanocytes in vivo. Transgenic (Tg) mouse lines (Dct-Survivin) were generated with melanocyte-specific expression of Survivin, and melanocytes grown from Dct-Survivin mice expressed Survivin. Dct-Survivin melanocytes exhibited decreased susceptibility to UV-induced apoptosis but no difference in proliferative capacity compared with melanocytes derived from non-Tg littermates. Induction of nevi in Dct-Survivin and non-Tg mice by topical application of 7,12-dimethylbenz(a)anthracene did not reveal significant differences in lesion onset (median, 10 weeks) or density (4 lesions per mouse after 15 weeks). Dct-Survivin mice were bred with melanoma-prone MH19/HGF-B6 Tg mice, and all progeny expressing either individual, neither, or both (Survivin/HGF) transgenes were UV-treated as neonates and then monitored for 43 weeks. Melanocytes in neonatal Survivin+/HGF+ mouse skin were less susceptible to UV-induced apoptosis than those from Survivin-/HGF+ mice. Onset of melanocytic tumors was earlier (median, 18 versus 24 weeks; P = 0.01, log-rank test), and overall tumor density was greater (7.7 versus 5.2 tumors per mouse; P = 0.04) in Survivin+/HGF+ compared with Survivin-/HGF+ mice. Strikingly, melanomas arising in Survivin+/HGF+ mice showed a greater tendency for lymph node (35% versus 0%; P = 0.04) and lung (53% versus 22%) metastasis and lower rates of spontaneous apoptosis than those in Survivin-/HGF+ mice. These studies show a role for Survivin in promoting both early and late events of UV-induced melanoma development in vivo.

Metallothionein immunolocalization in actinic skin nonmelanoma carcinomas

Basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are the most frequent skin cancer. Its pathogeny is linked to genotoxic effects of actinic radiation exposure, especially to ultraviolet wavelength. Metallothionein (MT) is a low-molecular weight protein with high affinity for heavy metal. Its intracellular function has been related to heavy metals and free-radical detoxification, although many studies linked MT to protective action against actinic mutagenesis. In other way, overexpression in malignant tumors has been related to worse prognosis. We aimed to evaluate MT immunohistochemical expression in skin cancer associated to actinic radiation. Twenty-six BCC cases, 20 SCC, and 6 normal skin fragments were investigated. Immunohistochemical assay were performed by streptavidin-biotin-peroxidase technique with standard monoclonal antibody (E9). In normal skin, immunostaining was observed in basal layer of the epithelium. In the epithelium adjacent to tumors, suprabasal layer was also intensely labeled. Mean MT immunostaining indices were 18.5+21.2% for BCC and 69.1+14.4% for SCC. This difference was statistically significant. Higher MT expression in SCC as compared with BCC suggests association with tumoral aggressiveness.

Expression of Bcl-2 family proteins in psoriasis

AIM

To elucidate the mechanisms involved in apoptosis of psoriatic keratinocytes by examining the expression of pro-apoptotic (Bak, Bax) and anti-apoptotic (Bcl-2, Bcl-X) Bcl-2 family of proteins, as well as the expression of p53 and Ki-67 proteins in normal skin, and uninvolved and involved psoriatic skin.

METHODS

A total of 90 skin samples (30 cases of involved and uninvolved psoriatic skin and normal skin) were examined immunohistochemically to determine the protein expression of p53, Ki-67, Bcl-2, Bcl-X, Bax, and Bak. The results were quantified and expressed as a percentage of positive keratinocytes.

RESULTS

There was a significant increase in Ki-67 (17.05 vs 3.65; P<0.001), Bcl-X (40.21 vs 13.97; P<0.001), Bak (89.46 vs 73.36; P<0.001), and Bax (50.00 vs 29.25; P<0.001) expression and a decrease in Bcl-2 (3.23 vs 6.25; P=0.008) expression in involved psoriatic skin, as well as an increase in Bcl-X (25.13 vs 13.97; P<0.001) expression in uninvolved psoriatic skin, when compared to normal skin. Samples with higher percentage of Ki-67 positive cells showed a higher percentage of p53 positive cells (correlation coefficient r=0.75 in involved psoriatic samples, P<0.001; r=0.88 in uninvolved psoriatic samples, P<0.001; and r=0.85 in normal skin samples, P<0.001). Samples with higher percentage of p53 positive cells expressed pro-apoptotic Bak and Bax in higher percentage of cells; the correlation coefficients were r=0.74 and r=0.68 in involved psoriatic samples (P<0.001 for both), r=0.75 and r=0.69 in uninvolved psoriatic samples (P<0.001, for both), and r=0.87 and r=0.70 in normal skin samples (P<0.001, for both).

CONCLUSION

Increased expression of Bcl-X protein was associated with psoriatic epidermal hyperplasia. Strong Bax and Bak expression in involved psoriatic skin are probably inhibitory mechanisms counteracting intensive proliferation.

Expression of apoptotic, cell proliferation regulatory, and structural proteins in actinic keratosis and their association with dermal elastosis

BACKGROUND

Actinic keratosis (AK) is a premalignant lesion caused by ultraviolet (UV) radiation and characterized by epithelial and connective tissue alterations. However, little is known about the link between connective and UV-damaged epithelial tissues in AK.

OBJECTIVE AND METHODS

To examine the potential relationship between connective tissue degeneration and molecular alterations in epithelial cells without evident morphologic changes, 30 cases of AK (8, grade I; 10, grade II; 12, grade III), divided into three grades according to the proportion of dermal elastosis (in grade I, up to 30% of collagen degeneration; in grade II, 30-60%; in grade III, more than 60%), were immunohistochemically analyzed for the expression of Ki67, p53, p63, bcl-2, E-cadherin, 34-betaE12, and CD99.

RESULTS

The increase in the solar elastosis grade was associated with an increase in positive cell numbers for all analyzed markers. Basal expression predominated in the lesions with low and moderate levels of connective tissue degeneration, while a basal and suprabasal expression pattern was prevalent in the lesions with high degeneration. In grade I and II lesions, proliferation marker, Ki67, expression was found to be significantly associated with the proapoptotic marker p53, while in grade III lesions, its expression was correlated with the anti-apoptotic marker, bcl-2.

CONCLUSIONS

These results demonstrate that the epithelial expression of apoptotic, cell proliferation, and structural proteins is augmented with the increase of the solar elastosis grade. Thus, the grade of solar elastosis could be a helpful morphologic marker in the assessment of neoplastic changes in sun-damaged skin.

Nature of cell kinetics in psoriatic epidermis

BACKGROUND

Psoriasis vulgaris is a common chronic inflammatory dermatosis. Disorders in keratinocyte proliferation, differentiation, inflammation and immune dysregulation are the major factors implicated in the pathogenesis of psoriasis vulgaris.

METHODS

The study was performed in skin specimens of 25 patients with psoriasis vulgaris and a control group of 10 individuals without a skin disease. Biopsy specimens from lesional and normal skin were analyzed by immunohistochemical method for expressions of Ki-67, Bcl-2, terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling (TUNEL), tumor necrosis factor alpha (TNF-alpha) and nuclear factor kappa B (NF-kappaB). In addition, densities of mast cell infiltration were also investigated.

RESULTS

Ki-67 and TUNEL indexes and TNF-alpha and NF-kappaB expressions were significantly higher in psoriatic epidermis than in normal epidermis (p < 0.05). There was no significant difference at Bcl-2 reactivity between the normal and the psoriatic epidermis (p > 0.05); however, Bcl-2 staining intensity of lymphocytes was higher in psoriatic lesions than in normal dermis (p < 0.05). Additionally, the number of mast cells was significantly higher in psoriatic dermis than in normal skin (p < 0.05).

CONCLUSIONS

There were several complex factors involved in the pathogenesis of psoriasis. We conclude that cellular damage and apoptosis temporarily coincide with epidermal proliferation during the course of psoriatic hyperplasia.

Sodium butyrate induced keratinocyte apoptosis

Apoptosis of keratinocytes is a key mechanism required for epidermal homeostasis and the renewal of damaged cells. Its dysregulation has been implicated in many skin diseases including cancer and hyperproliferative disorders. In the present study, the effect of sodium butyrate, a histone deacetylase inhibitor, on keratinocyte apoptosis was investigated using the HaCaT human keratinocyte cell line. Sodium butyrate induced morphological changes associated with apoptosis and nuclear fragmentation of HaCaTs. Annexin V staining demonstrated that sodium butyrate induced apoptosis in a dose and time-dependent manner with 50% of HaCaTs apoptotic after exposure to 0.8 mg/ml sodium butyrate for 24 h. Apoptosis was associated with upregulation of cell surface expression of the death receptor Fas and activation of the extrinsic caspase pathway, with induction of caspase 8 activity peaking after 8 h. Caspase 3 activity peaked after 24 h and was associated with cleavage of the caspase 3 substrate, poly (ADP-ribose) polymerase (PARP). The intrinsic caspase pathway was not activated as caspase 9 activity was not detected, and there was no change in the expression of terminal differentiation markers keratin 10 and involucrin following sodium butyrate treatment. Together these results indicate that sodium butyrate is a potent inducer of Fas associated apoptosis via caspase activation in HaCaT keratinocytes, an effect that is independent of the induction of terminal differentiation.