Fas ligand is expressed in normal skin and in some cutaneous malignancies

A systematic review of case-control studies of cytokines in blister fluid and skin tissue of patients with Stevens Johnson syndrome and toxic epidermal necrolysis

Stevens Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe cutaneous adverse reactions characterised by keratinocyte apoptosis, necroptosis and epidermal detachment. Several cytokines and cytotoxic proteins have been shown to be elevated in the blood and skin of SJS/TEN sufferers and biologics such as intravenous immune globulin and tumour necrosis factor (TNF)-alpha inhibitors have demonstrated good therapeutic potential. The exact pathogenic model of SJS/TEN however remains elusive. This systematic review aimed to evaluate the case-control studies of cytokines and cytotoxic proteins in the blister fluid and skin of adults with Stevens Johnson syndrome and/or toxic epidermal necrolysis. This review was registered with INPLASY and conducted in accordance with the PRISMA reporting guidelines. Potential bias was assessed using the NIH criteria. Eleven articles describing results from 96 cases and 170 controls were included. Fas, Fas ligand, Interleukin (IL)-8 and B-cell lymphoma (Bcl)-2 were elevated in SJS/TEN blister fluid and skin tissue, compared with healthy controls. IL-2, IL-6, TNF-alpha, tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), interferon-gamma and matrix metalloproteinase-2 were elevated in SJS/TEN blister fluid compared with fluid sampled from lesional controls. Granulysin, IL-33, TGF-beta-1 and IL-13 were elevated in SJS/TEN skin tissue compared with lesional lichen planus tissue, as was IL-13, IFN-gamma, IL-2 and IL-5, when compared with erythema multiforme tissue. A wide array of cytokines and cytotoxic proteins are present at higher concentrations in the blister fluid and skin tissue of SJS/TEN patients compared with healthy and lesional controls. Our findings suggest that these proteins may be pathogenic, as well as possibly markers for diagnosis, disease severity and course. They may also prove to be useful therapeutic targets. More research is needed.

Hinokitiol as a modulator of TLR4 signaling and apoptotic pathways in atopic dermatitis

Atopic dermatitis (AD) poses a significant global health challenge, characterized by dysregulated inflammation and apoptotic processes. This study explores the therapeutic efficacy of hinokitiol, employing a comprehensive in vivo and in vitro approach. Assessment of inflammation-related markers in the animal model included observation of physical appearance, Western blotting, ELISA, and H&E staining. Additionally, the cell culture model enabled the evaluation of apoptosis and ROS levels using MTT assay, crystal violet staining, Western blot, and DCFDA assays. The results revealed hinokitiol's proficiency in ameliorating ear and skin morphology in the DNCB-induced AD model, mediated through the TLR4/MyD88 pathway. Notably, hinokitiol intervention led to a reduction in both M1 and M2 macrophage phenotypes. In vitro investigations demonstrated hinokitiol's ability to enhance cell viability and morphology under TNF-α and IFN-γ induction. Mechanistically, hinokitiol exhibited regulatory effects on apoptosis-related proteins, including Bax, Cytochrome c, Caspase-3, and PARP, thereby averting cellular damage. These findings suggest that hinokitiol is a promising natural compound with significant potential for alleviating inflammation and apoptosis in AD, indicating potential avenues for future therapeutic developments.

Complement Factor D Is a Novel Biomarker and Putative Therapeutic Target in Cutaneous Squamous Cell Carcinoma

Simple Summary

The incidence of the most common metastatic skin malignancy, cutaneous squamous cell carcinoma (cSCC), is growing worldwide, and the prognosis of the metastatic disease is poor. Presently, there are no biomarkers or therapeutic targets for high-risk cSCCs. Recent studies have demonstrated the essential role of autocrine complement synthesis in the progression of cSCC. Here, we have evaluated the role of complement Factor D (FD), the rate-limiting enzyme of the alternative complement pathway, in cSCC development. The results identify FD as a novel biomarker and putative therapeutic target for cSCC and propose the small-molecule FD inhibitor Danicopan as a highly specific drug candidate in the therapy of advanced cSCC. It is expected that the discovery of complement-associated molecular markers for cSCC progression would improve diagnosis, classification, prognostication, and targeted therapy of cSCC and its precursors in the future.

Abstract

Cutaneous squamous cell carcinoma (cSCC) is the most prevalent metastatic skin cancer. Previous studies have demonstrated the autocrine role of complement components in cSCC progression. We have investigated factor D (FD), the key enzyme of the alternative complement pathway, in the development of cSCC. RT-qPCR analysis of cSCC cell lines and normal human epidermal keratinocytes (NHEKs) demonstrated significant up-regulation of FD mRNA in cSCC cells compared to NHEKs. Western blot analysis also showed more abundant FD production by cSCC cell lines. Significantly higher FD mRNA levels were noted in cSCC tumors than in normal skin. Strong tumor cell-associated FD immunolabeling was detected in the invasive margin of human cSCC xenografts. More intense tumor cell-specific immunostaining for FD was seen in the tumor edge in primary and metastatic cSCCs, in metastases, and in recessive dystrophic epidermolysis bullosa-associated cSCCs, compared with cSCC in situ, actinic keratosis and normal skin. FD production by cSCC cells was dependent on p38 mitogen-activated protein kinase activity, and it was induced by interferon-γ and interleukin-1β. Blocking FD activity by Danicopan inhibited activation of extracellular signal-regulated kinase 1/2 and attenuated proliferation of cSCC cells. These results identify FD as a novel putative biomarker and therapeutic target for cSCC progression.

Cytokines and apoptosis in atopic dermatitis

Atopic dermatitis (AD) is the most common chronic inflammatory skin disease. AD affects 10-20% of children worldwide and persists into adulthood in a minority of cases, affecting approximately 2-3% of the adult population, with an increased prevalence over the past decades in developed countries. Atopy is a genetic tendency to overproduce IgE class antibodies in response to common antigens found in the environment. Concurrence of different atopy such as allergic rhinitis or asthma in children with AD is estimated at 80%. AD is characterized by a vicious cycle of an allergic immune response. The emerging picture of the AD is a complex disorder with barrier dysfunction, immunological, genetic and environmental factors all playing key roles. Patients with severe or persistent disease and their families experience significant impairment in their quality of life, and in addition, AD places a heavy economic burden on society as a whole. Pathogenesis, the role of the epidermal barrier, mechanisms of cells apoptosis, the role of T cells and cytokines in AD are discussed in this article.

Fas/FasL pathway and cytokines in keratinocytes in atopic dermatitis - Manipulation by the electromagnetic field

BACKGROUND

Atopic dermatitis (AD) is one of the most frequent skin diseases. Changes of the keratinocytes functionality play a major role in the development of AD. For example, activation of the Fas (CD95)/FasL (CD178) pathway in AD does not lead to extensive apoptosis in skin. Binding of the Fas receptor to its protein ligand-FasL, which are present on the (AD)-modified keratinocytes, should result in the sequential induction of cell death, but there is no evidence of extensive apoptosis of these cells. This suggests that non-apoptotic mechanism of Fas/FasL pathway is commonly encountered, although not examined in the case of AD, phenomenon. An electromagnetic field, which was used to influence cultured cells in this study, can modulate proliferation, apoptosis, differentiation, and metabolism in various cells.

OBJECTIVE

Here, we evaluate the possibility to manipulate the immune activation of AD keratinocytes and their response to the electromagnetic field, which was not tested before.

METHODS

Keratinocytes isolated from the skin of healthy subjects (n = 20) and patients with atopic dermatitis (n = 20) as well as HaCaT and PCS-200-010 cell were exposed to the 900 MHz electromagnetic field for 60 minutes. Cytometric analysis of viability, Fas/FasL, p-ERK, p-p38 and p-JNK expression and Luminex analysis of cytokine concentration were performed in two-time points: 4 and 24 hours after the exposition.

RESULTS

This research has shown upregulated Fas, FasL, p-ERK, p-p38, and p-JNK expression along with increased cytokine secretion (IL-1β, IL-4, IL-8, IL-10, IL-12p70, IL-13, IL-17A, IL-31 and TNFα) by keratinocytes derived from the skin of patients with the AD when compared with healthy control. Exposure of keratinocyte cultures obtained from AD patients to EMF resulted in a decrease of 1β, IL-4, IL-10, IL-12, I L-13, IL-17, IL-31 and TNFα levels. Keratinocytes derived from the skin of AD patients are characterized by elevated Fas and FasL expression when compared to healthy control.

CONCLUSION

Apoptotic and nonapoptotic activation of the Fas/FasL-dependent signaling pathway may play a significant role in the pathogenesis of AD, by adjusting the local cytokine and chemokine environment at the site of inflammation. Moreover, the electromagnetic field exhibits strong immunomodulatory effects on AD-modified keratinocytes.

Involvement of Fas/FasL pathway in the murine model of atopic dermatitis

Objective and design

The aim of this study was to elucidate the role of apoptosis mediated through Fas/FasL pathway using the mouse model of atopic dermatitis (AD).

Materials and treatment

AD was induced by epicutaneous application of ovalbumin (OVA) in wild-type C57BL/6, B6. MRL-Faslpr/J (Fas−) and B6Smn.C3-Faslgld/J (FasL−) mouse strains.

Methods

Skin samples were subjected to staining for Fas/FasL expression, M30 epitope and assessment of inflammatory response via immunohistochemical staining. Cytokine and chemokine production was assessed by real-time PCR.

Results

In comparison to wild-type mice, OVA sensitization of Fas- and FasL-deficient mice led to increased epidermal and dermal thickness, collagen deposition and local inflammation consisting of macrophages, neutrophils and CD4+ T cells. Fas- and FasL-deficient mice showed increased total counts of regulatory T cells (Tregs) and IgE levels in blood as well as increased expression of IL-1β, IL-4, IL-5, IL-13 and TGF-1β mRNA in comparison to wild-type mice. On the other hand, expression of CXCL9 and CXCL10, IL-17 mRNAs in the skin samples in Fas- and FasL-deficient mice was decreased.

Conclusions

Our results show that lack of the Fas-induced apoptosis leads to exacerbation of AD characteristics such as Th2 inflammation and dermal thickening. Therefore, Fas receptor can play an important role in AD pathogenesis by controlling development of the local inflammation.

The expression of selected proapoptotic molecules in dermatitis herpetiformis

The role of the process of apoptosis is investigated in the pathogenesis of many autoimmune diseases; however at present, there is not much information about its role in dermatitis herpetiformis. Skin biopsies were taken from 18 DH patients and from 10 healthy subjects. The localization and expression of Bax, Fas, FasL, TRAIL, TRAIL-R in skin lesions, and perilesional skin were studied by immunohistochemistry. Expression of Bax, Fas, and Fas ligand was detected in the keratinocytes in skin biopsies from DH patients. Expression of TRAIL and TRAIL receptor was confirmed in epidermis, infiltration cells, and some fibroblasts. The expression of examined molecules in biopsies from healthy people was observed only in single cells. There were statistically significant differences between lesional, perilesional, and healthy skin of control group in Bax expression analysis and between lesional skin and control group in Fas, FasL, and TRAIL expression. There were statistically significant differences between control group and perilesional skin in Bax and FasL expression. Our results show that selected proapoptotic molecules may take part in pathogenesis of dermatitis herpetiformis, but the role of apoptosis in this process is not clear.

FasL and TRAIL signaling in the skin during cutaneous leishmaniasis - implications for tissue immunopathology and infectious control

Cutaneous leishmaniasis (CL) is associated with chronic inflammation and ulceration of the skin. Tissue macrophages serve as host cells and immune activation is necessary for parasite clearance. The balance between immune-mediated tissue destruction and successful clearance of infection is delicate and ulceration has been proposed to be a result of infiltration of activated immune cells into the skin. FasL and TRAIL play a dual role in skin homeostasis through induction of apoptosis as well as proinflammatory signaling. During leishmaniasis, dysregulation of both FasL and TRAIL has been described by us and others but the resulting pathogenic effects in the skin during human leishmaniasis are not fully elucidated. Targeting disease specific immune deviations has proven to be a promising new approach for the therapy of autoimmune diseases. Potentially, targeting FasL or TRAIL in combination with microcidals could offer a future treatment strategy to reduce the disfiguring immunopathology associated with CL. In this mini review we will discuss how FasL and TRAIL-induced signaling may influence on the extent of tissue inflammation and the efficacy of parasite clearance in leishmaniasis.

Serpin peptidase inhibitor clade A member 1 (SerpinA1) is a novel biomarker for progression of cutaneous squamous cell carcinoma

The incidence of keratinocyte-derived nonmelanoma skin cancers is increasing worldwide because of cumulative recreational exposure to sunlight. At present, no specific molecular markers are available for assessing the progression of premalignant actinic keratoses to invasive cutaneous squamous cell carcinoma (SCC). We examined the role of the Serpin family in skin SCCs. Expression profiling of cutaneous SCC cell lines (n = 8) revealed up-regulation of SerpinA1 compared with normal epidermal keratinocytes (n = 5). Analysis with quantitative RT-PCR showed that the mean level of SerpinA1 mRNA was markedly up-regulated in cutaneous SCC cell lines (n = 8) compared with in normal keratinocytes. SerpinA1 production by SCC cells was dependent on p38 mitogen-activated protein kinase activity and was up-regulated by epidermal growth factor, tumor necrosis factor-α, interferon-γ, and IL-1β. Immunostaining of tissue arrays with 148 human tissue samples revealed tumor cell-associated expression of SerpinA1 in 19 of 36 actinic keratoses, 22 of 29 Bowen's disease samples, 67 of 71 sporadic SCCs, and all 12 recessive dystrophic epidermolysis bullosa-associated SCCs examined. Moreover, tumor cell-associated SerpinA1 staining was detected in all chemically induced mouse skin SCCs studied (n = 17). Overexpression of SerpinA1 mRNA was also detected by quantitative RT-PCR in chemically induced mouse skin SCCs (n = 14) compared with control tissues (n = 14). These data identify SerpinA1 as a novel tumor cell-associated biomarker for progression of cutaneous SCCs.

Aberrant expression of Fas and FasL pro-apoptotic proteins in basal cell and squamous cell carcinomas

BACKGROUND

Fas and FasL are cell-surface receptors involved in apoptosis. Aim.  To investigate Fas and FasL expression levels in basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) to gain an insight into the mechanisms of Fas/FasL apoptosis and immune evasion in epidermal tumours.

METHODS

Real-time PCR and streptavidin-biotin immunohistochemistry techniques were used to detect Fas and FasL expression in BCC, SCC and normal skin specimens.

RESULTS

Fas and FasL mRNA expression and immunostaining levels were lower in the 21 BCC specimens than in normal skin, whereas they were higher in the 15 SCC specimens than in normal skin.

CONCLUSION

FasL immunostaining correlated with the capability of the tumour to invade and metastasize; the absent or weak immunostaining in the BCC specimens correlated with low capability, and the strong staining in the SCC specimens correlated with high capability.

Expression of FasL in squamous cell carcinomas of the cervix and cervical intraepithelial neoplasia and its role in tumor escape mechanism

BACKGROUND

To date, several mechanisms have been described by which malignant cells escape from the immune system. One of these is through the expression of FasL. The authors hypothesized that the Fas/FasL interaction enables cervical carcinoma cells to induce apoptosis of the cells of the immune system and thereby escape from them.

METHODS

The authors tested the expression of FASL on the surface of cervical carcinoma tissues. Next, they stained the same cervical tissues with anti-human leukocyte common antigen and TUNEL to identify apoptotic cells. An in vitro functional assay was then done to test if the FASL expressed on the surface of cervical carcinoma cell lines was or was not responsible for inducing apoptosis in T-cells. Finally, they compared the expression of FASL on normal and dysplastic cervical tissues.

RESULTS

Ninety-four percent of the cervical carcinoma tissues the authors tested expressed FasL and the majority of the apoptotic cells in the specimens were leukocytes with very few tumor cells. In the in vitro functional assay, only the Fasl expressing cell line and not the Fasl negative cell line was able to induce apoptosis of the Fas-expressing Jurkat cells. On examining the normal cervical tissues, the authors found that the expression of Fasl was confined to the basal cell layer with loss of expression observed in the suprabasal layers, which made it an immune privileged site. Conversely, there was persistent expression of FasL in the dysplastic layers in cervical dysplasia and squamous cell carcinoma specimens.

CONCLUSIONS

The findings of the current study support the authors' hypothesis that persistent expression of FasL plays a role in the ability of cervical carcinoma cells to escape from the immune system.

Fas-ligand gene silencing in basal cell carcinoma tissue with small interfering RNA

Basal cell carcinoma (BCC) is the most frequent cancer in the Caucasian population. Cells of BCC strongly express Fas-ligand (FasL), a member of the tumor necrosis family, which induces apoptosis in Fas receptor-expressing cells. It has been suggested that by expression of FasL, BCC cells may evade the attack of Fas-positive immune effector cells allowing the tumor to expand. Thus, downregulation of FasL should prime BCC to the assault of immune effector cells. Recently, it has been shown that RNA interference is a highly successful approach to specifically silence a gene of interest in single cells and some animal models. However, RNAi in human tissues has not been shown so far. Here, we provide evidence that small interfering RNAs (siRNAs) efficiently transfect tumor tissue ex vivo and silence the gene of interest. We demonstrate that a specific siRNA efficiently downregulates FasL not only in FasL-positive indicator cells but also in surgically excised BCC tissue at both the protein and the mRNA level. The successful transfection of tumor tissues with siRNAs now allows to test the function of the molecule under study and opens up the investigation of other target genes in the tumor.

Inhibition of smoothened signaling prevents ultraviolet B-induced basal cell carcinomas through regulation of Fas expression and apoptosis

Abnormal activation of the hedgehog-signaling pathway is the pivotal abnormality driving the growth of basal cell carcinomas (BCCs), the most common type of human cancer. Antagonists of this pathway such as cyclopamine may therefore be useful for treatment of basal cell carcinomas and other hedgehog-driven tumors. We report here that chronic oral administration of cyclopamine dramatically reduces ( approximately 66%) UVB induced basal cell carcinoma formation in Ptch1(+/-) mice. Fas expression is low in human and murine basal cell carcinomas but is up-regulated in the presence of the smoothened (SMO) antagonist, cyclopamine, both in vitro in the mouse basal cell carcinoma cell line ASZ001 and in vivo after acute treatment of mice with basal cell carcinomas. This parallels an elevated rate of apoptosis. Conversely, expression of activated SMO in C3H10T1/2 cells inhibits Fas expression. Fas/Fas ligand interactions are necessary for cyclopamine-mediated apoptosis in these cells, a process involving caspase-8 activation. Our data provide strong evidence that cyclopamine and perhaps other SMO antagonists are potent in vivo inhibitors of UVB-induced basal cell carcinomas in Ptch1(+/-) mice and likely in humans because the majority of human basal cell carcinomas manifest mutations in PTCH1 and that a major mechanism of their inhibitory effect is through up-regulation of Fas, which augments apoptosis.

Intravenous immunoglobulin does not improve outcome in toxic epidermal necrolysis

Intravenous Immunoglobulin (IVIG) has been proposed as a beneficial therapy for toxic epidermal necrolysis (TEN). However, this has been based on a limited amount of Class 5 evidence. To compare outcomes in TEN patients treated in our burn unit since 1999, when we began to use IVIG (IG group), with TEN patients treated between 1995 and 1999 who did not receive IVIG (control group). Retrospective cohort review of the records of all TEN patients admitted between April 5, 1995 and December 4, 2002. There were 16 patients in the IG group (age 53 +/- 21 years, with initial rash involving 65 +/- 29% TBSA) and 16 patients in the control group (age 52 +/- 20 years, with initial rash involving 65 +/- 27% TBSA). The IG group received 0.7 +/- 0.2 g/kg/day of IVIG for 4 +/- 1 days. There were no significant differences between the groups with respect to the length of stay, duration of mechanical ventilation, severity of systemic inflammatory response syndrome and multiple organ dysfunction syndrome, or the incidence of sepsis. Significant progression of the wound occurred in 13% of the IG patients and in 27% of control patients, whereas no wound progression was observed in 47% of the IG patients and in 18% of the control patients (P =.299). The time to healing did not differ between IG and control groups (11.2 +/- 3.6 vs 11.4 +/- 2.6 days, respectively). There was no significant difference in the mortality rate between the IG group (25%) and the control group (38%). There were no complications from IVIG aside from one case of hyponatremia from the hypotonic IVIG solution. Although there may have been a trend towards less severe wound progression in patients who received IVIG, this was not associated with any substantial improvement in outcome in our TEN patients. A prospective randomized study with a larger sample size is needed to confirm our findings.

Increased Fas ligand expression by T cells and tumour cells in the progression of actinic keratosis to squamous cell carcinoma

BACKGROUND

In the counterattack model of tumorigenesis, it has been proposed that tumours develop resistance to attack from Fas ligand (FasL)-expressing cytotoxic T cells by downregulating Fas (immune escape), while at the same time upregulating FasL expression to induce apoptosis in Fas-expressing T cells (counterattack).

OBJECTIVES

The aim of this study was to examine Fas and FasL expression on tumour cells and infiltrating T cells during the progression of actinic keratoses (AK), the benign precursor lesion, to squamous cell carcinoma (SCC).

PATIENTS AND METHODS

Samples of AK (n = 20) and SCC (n = 20) were collected from immunocompetent patients attending dermatology clinics. Double-label immunohistochemistry was performed on frozen sections using mouse monoclonal antibodies to Fas or FasL, simultaneously with a rabbit polyclonal antibody to either CD3 or cytokeratin, markers of T cells and keratinocytes, respectively. Cell densities and the optical density of tumour Fas expression were measured using image analysis.

RESULTS

FasL-expressing T cells were observed in nine of 19 SCCs, compared with three of 20 AKs (P < 0.05). FasL-expressing tumour cells were found in nine of 18 SCCs, compared with only one of 20 AK specimens (P < 0.005). There was no difference in the number of Fas-expressing T cells infiltrating AK and SCC. Fas expression by keratinocytes, measured by optical density, was lower in SCC (range 0.1-40, median 17) compared with AK (range 4-62, median 25) (P < 0.05).

CONCLUSIONS

These results suggest that the greater numbers of FasL-expressing T cells infiltrating into SCC compared with AK are targeting Fas-expressing tumour cells. As AK cells progress to SCC, they subvert this T-cell-mediated killing of tumour cells by downregulating their Fas expression (immune escape). Furthermore, tumour cells upregulate their expression of FasL, possibly as a counterattack measure to induce apoptosis in the increased number of tumour-infiltrating T cells. Thus changes in Fas/FasL-mediated interactions between T cells and tumour cells occur during the progression of AK into SCC.

Ageing of human epidermis: the role of apoptosis, Fas and telomerase

BACKGROUND

Aged human epidermis is characterized by morphological changes including flattening of the dermal-epidermal junction and a decrease in thickness.

OBJECTIVES

To determine the roles of proliferation, apoptosis, Fas (CD95), Fas ligand (FasL) and telomerase in changes of human epidermis during ageing.

METHODS

Human epidermis from aged subjects (n = 14; mean age 70.7 years) and young subjects (n = 14; mean age 23.4 years) was studied by histology, immunohistochemistry, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling assay for apoptotic cells and reverse transcription-polymerase chain reaction to determine epidermal thickness, proliferation (Ki-67), apoptosis, expression of Fas and FasL, and telomerase activity.

RESULTS

Aged skin was associated with thinning of the epidermis, decreased proliferation, and increased apoptosis below the granular layer. This was associated with increased epidermal expression of Fas and FasL. Telomerase activity was similar in aged and young epidermis.

CONCLUSIONS

Fas/FasL-mediated apoptosis, along with decreased proliferation, may have a role in changes of human epidermis during ageing. Telomerase activity did not appear to be limiting in young vs. old human epidermis.

Intravenous immunoglobulin prophylaxis for recurrent Stevens-Johnson syndrome

Human intravenous immunoglobulin has been described as a treatment for patients with Stevens-Johnson syndrome and toxic epidermal necrolysis. We describe the prophylactic use of intravenous immunoglobulin to prevent Stevens-Johnson syndrome in a woman undergoing cardiac catheterization with a previous history of four episodes of Stevens-Johnson after receiving intravenous contrast dye.

IFNα induces Fas expression and apoptosis in hedgehog pathway activated BCC cells through inhibiting Ras-Erk signaling

Basal cell carcinoma (BCC), the most common form of human cancer, is understood to be associated with activation of the sonic hedgehog pathway, through loss-of-function mutations of tumor suppressor PTCH1 or gain-of-function mutations of smoothened. Interferon (IFN)-based therapy is quite effective in BCC treatment, but the molecular basis is not well understood. Here we report a novel mechanism by which IFNalpha mediates apoptosis in BCCs. In the presence of IFNalpha, we observed increased apoptosis in a BCC cell line ASZ001, in which PTC is null, and therefore with constitutive activation of the sonic hedgehog pathway. We demonstrate that SMO agonist Ag-1.4 mediates activation of extracellular signal-regulated kinase (Erk) phosphorylation, which is abrogated by IFNalpha in sonic hedgehog responsive C3H10T1/2 cells. In transient transfection experiments, we demonstrate that IFNalpha inhibits Erk phosphorylation and serum response element activation induced by expression of SMO, Gli1, PDGFRalpha and activated Raf, but not activated mitogen-activated Erk-regulating kinase (Mek), suggesting that IFNalpha targets mainly on Mek function. We further show that IFNalpha induces expression of Fas in BCC cells through interfering with Mek function. The role of the Fas-L/Fas signaling axis in IFNalpha-mediated apoptosis is demonstrated by the fact that addition of Fas-L neutralizing antibodies, just as caspase-8 inhibitor Z-IETD-FMK, effectively prevents IFNalpha-mediated apoptosis. Thus, our data indicate that IFNalpha-based BCC therapy induces Fas expression and apoptosis through interfering with Mek function.

Intralesional interferon in basal cell carcinoma: how does it work?

Basal cell carcinoma (BCC) is the most common skin cancer among Caucasians, and its incidence is increasing. Intralesional injection of interferon alpha (IFN alpha) has been shown to provide a safe and effective treatment for BCCs. The predominant mechanism for the effect of IFN alpha on BCC has been partially identified. We have shown that in untreated patients, BCC cells constitutively express CD95 ligand (CD95L), but not the receptor. BCC cells make use of the CD95 ligand to escape from a local immune response by averting the attack from activated CD95 receptor-positive CD4+ T cells. The CD95L of BCC cells is functional as CD95+ target cells incubated on BCC cryosections become apoptotic and are lysed. In IFN alpha-treated patients BCC cells express not only CD95L but also CD95 receptor, and regress by committing suicide or fratricide through apoptosis induction via CD95 receptor-CD95L interaction. Peritumoral infiltrating cells, predominantly CD4+ T cells, may support regression of BCC by the secretion of cytokines such as IFN gamma or interleukin-2 which may also be responsible for the up-regulation of CD95 on BCC cells.

Increased expression of Fas on human epidermal cells after in vivo exposure to single-dose ultraviolet (UV) B or long-wave UVA radiation

BACKGROUND

Apoptosis has been proposed to act as an important mechanism for eliminating keratinocytes that have been irreversibly damaged by ultraviolet (UV) irradiation. One way to induce apoptosis in keratinocytes is through activation of the cell surface receptor Fas (CD95), either with the ligand (FasL) or directly with UV radiation.

OBJECTIVES

To investigate the regulation of Fas and FasL expression in human skin and the formation of apoptotic cells after in vivo exposure to UVB or long-wave UVA radiation.

METHODS

Volunteers were irradiated with either 3 minimal erythema doses (MED) of UVB (n = 6) or 3 MED of long-wave UVA (n = 6) on buttock skin 12, 24 and 72 h before skin punch biopsies were taken. Expression of Fas and FasL was demonstrated by immunohistochemistry on cryostat sections. Apoptosis was assessed by the terminal deoxynucleotidyl transferase-mediated fluorescein-deoxyuridine triphosphate nick-end labelling reaction.

RESULTS

In five of six subjects, exposure to UVB radiation resulted in increased homogeneous expression of Fas on epidermal cells, with greatest expression at 24 and 72 h after irradiation. In all subjects, exposure to long-wave UVA resulted in increased homogeneous expression of Fas on epidermal cells, with greatest expression at 12 h after irradiation. In five of six subjects, exposure to UVB radiation resulted in temporarily decreased expression of FasL, but after 72 h the expression of FasL had returned to the preirradiation level. The expression of FasL on epidermal cells after exposure to long-wave UVA showed considerable variation. UVB irradiation was a stronger inducer of epidermal apoptosis than was UVA irradiation. The number of apoptotic epidermal cells did not correlate with expression of Fas or FasL.

CONCLUSIONS

In human skin the expression of Fas on epidermal cells increases after in vivo exposure to UVB or long-wave UVA. Exposure to UVB causes a temporary decrease in the expression of FasL on epidermal cells.

Molecular and cellular biology of basal cell carcinoma

The finding of mutations in the PTCH gene in both Gorlin's syndrome and sporadic basal cell carcinomas has significantly advanced our understanding of the molecular defects that lead to the formation of these tumours. Knowledge of the specific molecular and functional changes that have taken place in these tumours will help us devise more defined therapies, as well as give us a better understanding of normal molecular pathways involved in skin development and function. The following is a summary of our current understanding of the molecular and cellular biology of basal cell carcinoma.

Fas and Fas ligand: expression and soluble circulating levels in cutaneous malignant melanoma

BACKGROUND

The Fas/Fas ligand (FasL) system plays a key part in maintaining tissue homeostasis via the induction of apoptosis. Functional impairment of the Fas/FasL system is associated with the development and progression of malignancies. Malignant melanoma cells and tissues have been shown to express Fas and FasL to variable extents.

OBJECTIVES

To demonstrate the expression and the presence of soluble circulating levels of Fas and FasL in cutaneous malignant melanoma.

METHODS

Biopsy specimens of 42 patients with primary melanoma and nine patients with cutaneous metastatic melanoma were obtained for immunohistochemistry studies. All patients were followed for at least 5 years. In another 46 patients with melanoma (15 stage I and II; 11 stage III; and 20 stage IV) and in 10 healthy volunteer control subjects circulating levels of Fas and FasL were analysed with commercial ELISA tests.

RESULTS

FasL was strongly positive in 38 (90%) of 42 primary melanomas; two of nine metastases did not express FasL. In the primary melanomas Fas was strongly or intensely positive in 17 (40%), moderately or weakly positive in 10 (24%) and negative in 15 (36%) of 42 melanomas. Soluble Fas plasma levels in patients with metastatic malignant melanoma were significantly elevated over those in the control group (P = 0.01).

CONCLUSIONS

The absence of Fas in most of the thick melanomas that did not metastasize, and in insitu melanomas, might be taken as a theoretical factor for a good prognosis. Soluble Fas is increased in patients with metastatic melanoma and might be associated with poor prognosis.

Keratinocytes constitutively express the CD95 ligand molecule on the plasma membrane: an in situ immunoelectron microscopy study on ultracryosections of normal human skin

BACKGROUND

Tissue homeostasis is mainly preserved by cytolytic functions. Cytolytic cells, when expressing the CD95 ligand (Fas-L) molecule on the cell membrane, are able to kill CD95 (Fas)-expressing target cells. Although cultured epidermal keratinocytes (KC) have been shown to express Fas-L, and normal skin has been shown to bear Fas-L mRNA, efforts so far to find possible constitutive Fas-L expression on the cell membrane by resting KC in normal human epidermis (i.e. in a functionally active location) have been inconclusive.

OBJECTIVES

The aim of the present study was therefore to show the constitutive expression of Fas-L on the plasma membrane of KC.

METHODS

Gold immunoelectronmicroscopy, a highly specific and sensitive immunodetection system, was performed in situ on skin sections obtained by ultracryomicrotomy, without previous embedding (i.e. in conditions strictly similar to the in vivo situation).

RESULTS

Relatively few (51.55 +/- 28.61), 10-nm colloidal gold particles were observed at the cell surface of KC in the basal layer of the epidermis and an even smaller (P < 0.005) number of gold granules was detected in the KC of the spinous layer.

CONCLUSIONS

Although scanty, the constitutive Fas-L expressed on the surface of KC can bind Fas expressed by possible occasional inflammatory cells entering the epidermis, and kill them, so preventing inflammation. Fas-L-expressing KC could moreover induce apoptosis of epidermal cells bearing viral or neoplastic antigens. Thus, the expression of Fas-L by KC may contribute to the preservation of epidermal homeostasis in vivo.

Aberrant expression of apoptosis-related molecules in psoriatic epidermis

Apoptosis is a physiological form of cell death that is responsible for the deletion of cells. Epidermal keratinocytes are supposed to be regulated by cell proliferation and cell death leading to structural homeostasis. Psoriatic skin shows marked thickening of the epidermis, suggesting the imbalance of the homeostasis, which might be related to abnormal apoptotic process. We investigated the expression of various apoptosis-related molecules in the psoriatic hyperproliferative epidermis. Real time quantitative RT-PCR analyses revealed that mRNAs of Fas, Bcl-xL, Bax and ICAD (inhibitor of caspase 3-related DNase) of the psoriatic involved epidermis were increased by 4.2-, 2.8-, 2.6- and 5.6-fold, respectively, compared with the uninvolved epidermis. In contrast, Bcl-2 expression in the involved epidermis was one-third suppressed compared with the uninvolved epidermis. No significant difference in the expression of mRNAs of Fas ligand or CAD (caspase 3-related DNase) was detected between the involved and uninvolved epidermis. Western blot analysis and immunohistochemical studies showed compatible results obtained by RT-PCR analyses. Although active caspase 3 was slightly increased in the involved epidermis, apoptotic cells were marginally detected. These results indicate that psoriatic epidermis shows aberrant expression of apoptosis-related molecules representing suppressed apoptotic process, which might be related to characteristic histopathology.

Ultraviolet B irradiation induces apoptosis of keratinocytes by direct activation of Fas antigen

Ultraviolet B (UVB) irradiation induces apoptosis of keratinocytes, where p53 has been suggested to play an important role. Recently we have shown that UVB irradiation induces apoptosis of SV40-transformed human keratinocytes (SVHK cells). Because p53 function is impaired in SVHK cells by large T antigen, a UVB-induced p53-independent apoptotic pathway was suggested. We investigated the UVB-induced apoptotic pathway using various keratinocytes. Cultured mouse keratinocytes of homozygous p53 deficient mice (p53(-/-)) were markedly resistant to UVB-induced apoptosis compared with keratinocytes from wild or heterozygous p53 deficient mice (p53(-/+)). Twenty per cent of keratinocytes derived from p53 (-/-) mice, however, induced apoptosis following UVB irradiation. Analysis using caspase inhibitors disclosed activation of caspase 8 and 3 in UVB-irradiated SVHK cells. Keratinocytes derived from MRL/lpr mice, which have mutated Fas antigen, showed diminished UVB-induced apoptosis suggesting that Fas antigen is significantly involved in UVB-induced apoptosis. Immunohistochemical analysis revealed that UVB irradiation induces aggregation of Fas antigen showing a dense dot-like staining, which was also observed in SVHK cells treated with agonistic anti-Fas antibody, CH11. Pretreatment of antagonistic anti-Fas antibody, ZB4, inhibited CH11-induced but not UVB-induced multimerization of Fas antigen. Furthemore, UVB irradiation did not affect the basal expression of Fas ligand mRNA, protein and soluble Fas ligand. These results indicate that UVB irradiation induces multimerization of Fas antigen that results in apoptosis without the Fas ligand.

Treatment of drug-induced toxic epidermal necrolysis (Lyell's syndrome) with intravenous human immunoglobulins

Toxic epidermal necrolysis (TEN) is a rare drug-induced life-threatening disease. Currently, the disease is only treated by supportive and antiseptic measures. Quite recently intravenous immunoglobulins (IG) were shown to be a promising TEN treatment. The rationale for their use is based on the fact that keratinocyte apoptosis in TEN involves the CD95 (APO-1/Fas) cell surface receptor-ligand system. We successfully treated a TEN patient with high dose of intravenous IG. The clinical recovery appeared exceptionally rapid. Immunohistochemistry showed that the IG action probably developed on the CD95 receptor-ligand system at the keratinocytes surface.

Ultraviolet light downregulates CD95 ligand and TRAIL receptor expression facilitating actinic keratosis and squamous cell carcinoma formation

Long-term ultraviolet light exposure of human skin epidermis in Caucasians is associated with an increased risk for the development of melanoma and nonmelanoma skin cancers. Ultraviolet radiation not only induces DNA damage in epidermal cells, it also interferes with skin homeostasis, which is maintained by a unique distribution pattern of apoptosis-inducing and apoptosis-preventing molecules. We demonstrate that, beside CD95 ligand, TRAIL and TRAIL receptors also function as important sensors in the human epidermis preserving skin integrity and preventing cell transformation. Ultraviolet irradiation extensively changes the expression pattern of some of these molecules, diminishing their sensor function. In particular, CD95 ligand and to a somewhat lesser extent TRAIL receptors are downregulated upon ultraviolet light exposure. CD95 ligand downregulation is not due to protein degradation as in situ hybridization experiments strongly support a transcriptional regulation. The downregulation of these molecules with sensor function increases the risk that aberrant cells are less efficiently eliminated. This concept is supported by the fact that the expression of these molecules is also low or absent in actinic keratosis, a precancerous state that has developed as the consequence of long-term ultraviolet exposure. Progression to invasive neoplasms is then accompanied by an upregulation of CD95 ligand and a downregulation of CD95 and of the TRAIL receptors. The high expression of CD95 ligand, TRAIL, and FLIP in squamous cell carcinoma may then contribute to the immune escape of the tumor, whereas the lack of expression of CD95 and TRAIL receptors prevents autolysis of the tumor.

UVA and UVB wavebands modulate expression of fasL in mouse skin epidermis

In our previous report, we observed different cytokine modulation in mouse epidermis by the UVA and UVB wavebands. In the present investigations, the effects of irradiation with UVA and UVB on the Fas(CD95)/FasL system have been studied because apoptosis mediated by the interaction between Fas and FasL has been suggested recently to be associated with UVB-induced immunosuppression in mouse skin. Our results show that UVA irradiation following UVB irradiation has the ability to reduce the up-regulation of FasL expression in mouse skin resulting from the UVB irradiation.

A comparative study of Fas and Fas-ligand expression during melanoma progression

BACKGROUND

Impaired regulation of apoptosis is known to be associated with the development of various cancers. Fas receptor (APO-1/CD95) binding to its ligand, Fas-ligand (Fas-L), has been shown to trigger apoptosis in various cell types.

OBJECTIVES

In this study, we examined CD95 and Fas-L expression on primary and metastatic melanoma cells from patients to investigate a potential correlation between these measures of apoptosis and different disease stages.

PATIENTS AND METHODS

Primary melanoma cells were obtained after surgical resection from 19 patients and metastatic cells from fine-needle aspiration of lymph nodes or palpable subcutaneous lesions in 25 patients. Normal skin cells were obtained at skin biopsy of 10 healthy donors.

RESULTS

Flow cytometric analysis revealed that CD95 and Fas-L expression was detected in all the kinds of cell studied. In whole cell suspensions, CD95 expression was significantly higher (P < 0.0001) in normal skin cells than in melanoma cells, whatever the stage studied. By contrast, we observed an increase in Fas-L expression in melanoma cells compared with normal ones. Subsequently, using a double staining method, we studied these measures on HMB45+ cells, a specific marker for melanoma cells, and found that CD95 expression was significantly higher (P = 0.0005) in primary than in metastatic cells while Fas-L expression was significantly increased (P = 0. 0004) in metastatic compared with primary cells. Furthermore, a relationship was found between CD95 or Fas-L expression and Breslow thickness; as primary melanoma thickness progressively increased, the percentage of HMB45+ CD95+ cells decreased while that of HMB45+ Fas-L+ cells concurrently increased.

CONCLUSIONS

These results suggest that downregulation of CD95 and upregulation of Fas-L in melanoma might be considered as concomitant with disease progression.

Murine xenogeneic immune responses to the human testis: a presumed immune-privileged tissue

INTRODUCTION

Immune privilege provides a natural paradigm for potentially down-regulating allogeneic and xenogeneic inflammatory immune responses. Fas ligand has been suggested as a general underlying mechanism of immune privilege; the human Fas ligand has been shown to ligate murine Fas in vitro.

METHODS

In this study, we examined whether the human testicular xenograft, a presumed immune-privileged tissue would have prolonged survival in mice. In addition, in vitro and in vivo murine xenogeneic immune responses to the human testicular xenografts were characterized using MHC class I, MHC class II, CD4, CD8, CD4/8 knockout mice.

RESULTS

Unlike in rodent testis, Fas ligand mRNA is not expressed and Fas is highly expressed in human testis. Human testicular xenografts are immunogenic, and do not induce any preferential pattern of recipient systemic Th1 or Th2 cytokine bias. Interestingly, an indefinite survival of the human testicular xenografts is observed in murine MHC class II knockout mice, whereas the human skin xenografts were rejected without a delay. In vivo murine immune responses to human testicular xenografts require a recipient MHC class II-dependent CD4 T cell-mediated process that appears to depend on B7-1/B7-2 costimulatory signals.

CONCLUSIONS

Our results demonstrate that the concept of immune privilege, as defined by the expression of Fas ligand and prolonged survival after transplantation, cannot be extended to human testis. The stringent restriction of murine xenogeneic immune responses to discordant human testicular xenografts to the indirect MHC class II-dependent CD4 T cell-mediated pathway suggests a potential venue for immune modulation to induce tolerance across a discordant species barrier.

Inhibition of collagenase-3 (MMP-13) expression in transformed human keratinocytes by interferon-gamma is associated with activation of extracellular signal-regulated kinase-1,2 and STAT1

Collagenase-3 (MMP-13) is characterized by an exceptionally wide substrate specificity and restricted expression. MMP-13 is specifically expressed by transformed human keratinocytes in squamous cell carcinomas in vivo and its expression correlates with their invasion capacity. Here, we show, that interferon-gamma (IFN-gamma) markedly inhibits expression of MMP-13 by human cutaneous SCC cells (UT-SCC-7) and by ras-transformed human epidermal keratinocytes (A-5 cells) at the transcriptional level. In addition, IFN-gamma inhibits collagenase-1 (MMP-1) expression in these cells. IFN-gamma abolished the enhancement of MMP-13 and MMP-1 expression by transforming growth factor-beta (TGF-beta) and tumor necrosis factor-alpha (TNF-alpha), and inhibited invasion of A-5 cells through type I collagen. IFN-gamma also rapidly and transiently activates extracellular signal-regulated kinase 1,2 (ERK1,2) and blocking ERK1,2 pathway (Raf/MEK1,2/ERK1,2) by specific MEK1,2 inhibitor PD98059 partially (by 50%) prevents Ser-727 phosphorylation of STAT1 and suppression of MMP-13 expression by IFN-gamma. Furthermore, Ser-727 phosphorylation of STAT1 by ERK1,2, or independently of ERK1,2 activation is associated with marked reduction in MMP-13 expression. These observations identify a novel role for IFN-gamma as a potent inhibitor of collagenolytic activity and invasion of transformed squamous epithelial cells, and show that inhibition of MMP-13 expression by IFN-gamma involves activation of ERK1,2 and STAT1.

Immunohistochemical localization of FAP-1, an inhibitor of Fas-mediated apoptosis, in normal and neoplastic human tissues

Fas, a death receptor, is widely expressed in human tissue, but its expression, although a prerequisite for the induction of apoptosis, does not predict its biological function. To understand the mechanisms of Fas resistance in human tissues in vivo, we performed immunohistochemistry using an antibody against Fas-associated phosphatase-1 (FAP-1), which interacts with the cytosolic domain of Fas and inhibits Fas-mediated apoptosis. In normal human tissues, FAP-1 immunostaining was easily detected, for example, in renal tubules, skeletal muscle, myocardiocytes, pituitary gland, parathyroid gland, pancreatic islets, hepatocytes, testicular germ cells, prostatic glands, neurons, epithelium of fallopian tube, endometrial glands, trophoblasts, bronchial epithelial cells, and some types of gastrointestinal epithelial cells. In 123 (78%) of 158 cancers of various origins, including breast carcinomas, stomach carcinomas, colon carcinomas, lung carcinomas and several types of sarcomas, variable intensities of FAP-1 expression were evident. Taken together, these findings demonstrated that FAP-1 is widely expressed in normal human tissues and partly overlapped with Fas expression described in earlier reports, suggesting that FAP-1 may have an important role in the regulation of apoptosis in vivo. In addition, FAP-1 expression in cancers suggests that many cancers may be resistant to Fas-mediated apoptosis through the action of FAP-1 in vivo.

Immunohistochemical analysis of Fas ligand expression in normal human tissues

Cross-linking of Fas and Fas ligand (FasL) induces apoptosis in Fas-bearing cells and regulates apoptosis. Fas is widely expressed in normal human tissues, but FasL expression has been considered to be restricted to lymphoid tissues. Recent studies have demonstrated that FasL is also expressed in some nonlymphoid tissues. To screen the in situ expression of FasL in normal human tissues, immunohistochemistry was performed using paraffin-embedded human tissues. FasL immunostaining was easily detected in testis, neurons, trophoblasts, tonsil, lymph node, Paneth cells, hepatocytes, renal tubular epithelium and bronchial epithelium, consistent with previous reports. Surprisingly, FasL was also expressed in many other cell types, including thymic medulla, skeletal muscle, cardiac muscle, pituitary gland, parathyroid gland, prostate glands, oocytes, epithelium of fallopian tube, endometrial glands, and gastric parietal cells. These findings demonstrate that FasL is widely expressed in human tissues and suggest that wide but cell-type specific expression of FasL may not only be implicated in the regulation of immune homeostasis but also in the regulation of cell death and life in many cell types in vivo.

Transitional cell carcinoma expresses high levels of Fas ligand in vivo

OBJECTIVE

To characterize the Fas-Fas ligand system, a main apoptotic pathway, in transitional cell carcinoma (TCC) of the urinary bladder, by analysing the expression of Fas and Fas ligand (FasL) in TCC samples.

MATERIALS AND METHODS

Archival paraffin-embedded tissues from 37 patients with TCC were analysed by immunohistochemistry to determine Fas and FasL expression.

RESULTS

Fas and FasL were detected on the cell surface and cytoplasm of respectively 34 (92%) and all cases analysed. The expression of Fas and FasL did not differ with the cytological grade of TCC.

CONCLUSION

The high expression of FasL in TCC, reported for the first time in the present study, suggests that FasL may contribute to the immune escape of TCC through killing Fas-bearing lymphocytes. Co-expression of Fas with FasL also suggests that TCC may have pathways resistant to Fas-mediated autocrine cell suicide.