Expression of c-kit ligand in human keratinocytes

A Clinical and Biochemical Evaluation of a Temperature-Controlled Continuous Non-Invasive Radiofrequency Device for the Treatment of Melasma

Background

Melasma shows characteristic histological features of photoaged skin.

Objective

We evaluated the effect of dermal rejuvenation using a temperature-controlled continuous non-invasive radiofrequency (RF) device on melasma.

Methods

Continuous skin heating at the temperature of 43°C for 20 minutes was performed in ten subjects with melasma who underwent 3 tri-weekly RF sessions. Pigmentation was evaluated with Mexameter® and investigator’s global assessment (IGA). Immunohistochemical staining and image analysis was performed to evaluate biopsies from melasma skin before and after the treatment.

Results

The lesional melanin index was decreased by 13.7% at week 9. IGA score was improved from 3.50 at baseline to 2.95 at week 9. No significant adverse event was reported. Histologic analysis revealed reduced melanin and increased collagen density and thickness. The expression of procollagen-1 and type IV collagen was increased after the treatment. The number of p16^INK4A-positive senescent fibroblasts was reduced after the treatment, while the expression of heat shock protein 70 and 90 was increased. Stromal derived factor-1, a senescence-associated anti-melanogenic factor secreted from the fibroblasts, was up-regulated after the treatment, while the level of c-kit was not changed.

Conclusion

Thermal skin stimulation by the temperature-controlled continuous RF device improved melasma through dermal rejuvenation.

An update on Vitiligo pathogenesis

Vitiligo, the most common depigmenting disorder of the skin, is undergoing a period of intense advances in both disease understanding and therapeutic possibilities leading the way to the beginning of a new era for the disorder. Its pathophysiology has gathered the attention of researchers for years, and many advances have been made in the clarification of the interaction between different factors that result in depigmented macule formation. The complex interplay between non-immunological and immunological factors in vitiligo is key for the development of the disease, and the participation of cells other than melanocytes, such as keratinocytes, fibroblasts, natural killer cells, and innate lymphoid cells, has been shown. Recent advances have also brought to the understanding of the complex part played by a specific subtype of T cells: T-resident memory cells. This review analyzes some of the most recent insights in vitiligo pathogenesis underlining the interactions between different cell types, which are the basis for the therapeutic approaches under development.

Sorafenib-associated hand-foot skin reaction: practical advice on diagnosis, mechanism, prevention, and management

Introduction: Sorafenib is a multitargeted tyrosine kinase inhibitor, which has been mainly used in the treatment of advanced hepatocellular carcinoma and renal cancer. However, hand-foot skin reaction (HFSR), as one of the most common adverse reactions, have hindered its long-term clinical application. At present, the mechanism of its occurrence has not been clearly studied and it leads to the lack of effective means of intervention. This article reviews known mechanism and management methods of HFSR caused by sorafenib.Areas covered: The author reviews HFSR caused by the treatment of sorafenib including the mechanism and management. English language reports located through PubMed are reviewed.Expert opinion: There are some conjectures about the mechanism of HFSR. However, the mechanism of HFSR induced by sorafenib is still unclear at present. In the absence of understanding the mechanism of HFSR, the most common method for clinical treatment of sorafenib-induced HFSR is dose down-regulation or discontinuation of treatment, which affects efficacy and even survival. Future research should focus on the mechanism of HFSR to find out new ways for prevention. Precautionary measures before the occurrence of HFSR can also be studied in the future.

Risk of hand-foot skin reaction associated with vascular endothelial growth factor-tyrosine kinase inhibitors: A meta-analysis of 57 randomized controlled trials involving 24,956 patients

BACKGROUND

Multiple randomized controlled trials have assessed hand-foot skin reaction (HFSR) caused by vascular endothelial growth factor receptor-tyrosine kinase inhibitors (VEGFR-TKIs).

OBJECTIVE

We performed a meta-analysis to determine the incidence and the relative risk (RR) of HFSR associated with these agents.

METHODS

Databases were searched for relevant studies. Statistical analyses were conducted to calculate the summary incidences, RR, and 95% confidence intervals (CIs) by using random-effects or fixed-effects models according to the heterogeneity of the included studies.

RESULTS

A total of 24,956 patients from 57 studies were included. The overall incidence of all-grade and high-grade HFSR associated with VEGFR-TKIs was 35.0% (95% CI, 28.6%-41.6%) and 9.7% (95% CI, 7.3%-12.3%), respectively. The use of VEGFR-TKIs significantly increased the risk of developing all-grade (RR, 5.09; 95% CI, 3.52-7.35; P < .001) and high-grade (RR, 9.42; 95% CI, 5.59-15.90; P < .001) HFSR. Subgroup analyses revealed that the risk of HFSR was significantly increased according to tumor type, VEGFR-TKI, trial phase, treatment regimen, and control therapy. No evidence of publication bias was observed.

LIMITATION

High heterogeneity in most studies.

CONCLUSION

High risk of HFSR is prone to develop in cancer patients receiving VEGFR-TKIs.

Familial progressive hyper- and hypopigmentation: a report on a Chinese family and evidence for genetic heterogeneity

BACKGROUND

Familial progressive hyper- and hypopigmentation (FPHH) is a rare genodermatosis that is characterized by diffuse hyper- and hypopigmented spots on the skin and mucous membranes. It is caused by a pathogenic mutation of the KITLG gene.

OBJECTIVES

To investigate the clinical features and mutation of the KITLG gene in a Chinese family with FPHH.

METHODS

Histopathological and immunohistochemical analysis of lesions from the proband was performed. The KITLG gene was screened for the presence of mutations.

RESULTS

A Chinese family containing 14 individuals with FPHH was described, and the proband was a 5-year-old girl showing diffuse hyper- and hypopigmented lesions on her extremities and trunk. Histopathological and immunohistochemical staining for S100 and HMB45 of skin biopsy specimens from the hyperpigmented areas showed a striking increase in melanin throughout the epidermis, especially in the basal cell layer, and staining of hypopigmented area specimens displayed lower levels of melanin in the epidermis. Mutation analysis of the KITLG gene was performed, but no mutation was found.

STUDY LIMITATIONS

The new pathogenic gene was not found.

CONCLUSION

A family with FPHH was described. Analysis revealed that its members did not have any mutations of the KITLG gene, which provided evidence for genetic heterogeneity of this genodermatosis.

Concurrent hand-foot skin reaction and hair depigmentation with sunitinib: report of a case and literature review of kinase inhibitors and blocking antibodies

Kinase inhibitors have revolutionized cancer therapy by becoming the first-line agents for advanced solid malignancies replacing the traditional chemotherapeutic agents. Cutaneous side-effects with these drugs are common, but owing to their infrequent use in Indian patients, our current knowledge of toxicity is scanty and primarily based on the western literature. Cutaneous reactions can adversely affect patients' quality of life (QoL) and can lead to dose modifications and treatment interruptions. The report discusses concurrent hand-foot skin reaction (HFSR) and hair depigmentation in an Indian patient being treated with sunitinib for advanced renal cell carcinoma. The pathogenesis and treatment strategies for this characteristic phenomenon and other cutaneous toxicities of kinase inhibitors have also been reviewed.

Sorafenib and sunitinib: A dermatologist's perspective

Sorafenib and sunitinib are inhibitors of tumor angiogenesis have recently generated curiosity regarding its role in cutaneous toxicities, which has severely affected the daily activities resulting in interruption or dose modification of therapy in renal cell carcinoma and hepatocellular carcinomas. We discuss the pathophysiology, adverse cutaneous effects and their grading, potential high risk factors, role of gene polymorphism, critical period of hand-foot skin reaction development and their management.

A randomized multicenter phase II trial on the efficacy of a hydrocolloid dressing containing ceramide with a low-friction external surface for hand-foot skin reaction caused by sorafenib in patients with renal cell carcinoma

BACKGROUND

The purpose of this study was to investigate the usefulness of a hydrocolloid dressing containing ceramide for hand-foot skin reaction (HFSR) on the soles of the feet in metastatic renal cell carcinoma (RCC) patients treated with sorafenib.

PATIENTS AND METHODS

Patients with grade 1 HFSR on the soles of the feet were randomly assigned in to two groups. One group received a hydrocolloid dressing containing ceramide (arm A) and the other received 10% urea cream (arm B). Patients in both groups applied treatment to the affected sites on the soles of the feet, but not to the hands. The primary end point was the incidence of grade 2 or 3 HFSR on the soles of the feet in the first 4 weeks.

RESULTS

Thirty-three patients were assessed (17 in arm A and 16 in arm B), and there were no significant differences in baseline characteristics between the two groups. During the observation period of this study, grade 2 or 3 HFSR on the soles of the feet was found in 29% of patients in arm A and was significantly less than the 69% in arm B (P=0.03). The incidence of HFSR on the hands, however, was similar in both arms. The median time to grade 2 or 3 HFSR on the soles of the feet was also significantly longer in arm A than in arm B (P=0.03).

CONCLUSIONS

These results indicate that a hydrocolloid dressing containing ceramide prevented the worsening of HFSR caused by sorafenib in metastatic RCC patients.

CLINICAL TRIAL REGISTRATION NUMBER

UMIN000002016.

Role of keratinocytes in the development of vitiligo

Vitiligo is an acquired depigmentary disorder of the skin that results from the loss of functioning epidermal melanocytes. Most studies on vitiligo have concentrated on the abnormality of melanocytes rather than the abnormality of keratinocytes; however, epidermal melanocytes form a functional and structural unit with neighboring keratinocytes. In fact, direct cell-to cell contact stimulates in vitro proliferation of melanocytes, and growth factors produced by adjacent keratinocytes regulate the proliferation and differentiation of melanocytes. The potential role of keratinocyte-derived cytokines has also been presented. We focused on the structural changes in vitiliginous keratinocytes, which may result in loss of melanocytes, to examine the pathomechanism of vitiligo. The results of a comparison between depigmented and normally pigmented epidermis in patients with vitiligo showed that the keratinocytes in the depigmented epidermis were more vulnerable to apoptosis. Impaired Phosphatidylinositol 3-kinase (PI3K)/serine/threonine protein kinase (Akt) activation followed by reduced nuclear factor-κB activation under increased tumor necrosis factor-α levels was demonstrated as a mechanism for keratinocyte apoptosis. The role of aquaporin 3 in keratinocyte apoptosis was addressed based on the relationship between the PI3K/AKT pathway and the E-cadherin-catenin complex. Apoptotic keratinocytes induced a lower expression of keratinocyte-derived factors, including stem cell factor, in depigmented epidermis, resulting in passive melanocyte death.

Meta-analysis of dermatological toxicities associated with sorafenib

A meta-analysis was performed to determine the type, incidence and risks of dermatological toxicities associated with the multikinase inhibitor sorafenib. A literature search was performed using the electronic databases PubMed and EMBASE, and conference abstracts published by the American Society of Clinical Oncology. Eligible studies included prospective phase II or III clinical trials, and expanded-access programmes (i.e. outside a clinical trial) of patients with solid tumours assigned sorafenib at a starting dose of 400 mg twice daily. The overall incidences and risk ratios of dermatological toxicities associated with sorafenib were analysed. For patients assigned sorafenib, the overall incidence of all-grade rash/desquamation was 35.4% (95% CI 0.29-0.43), hand-foot skin reaction (HFSR) 39.0% (95% CI 0.32-0.47), alopecia 25.5% (95% CI 0.18-0.35), pruritus 14.0% (95% CI 0.10-0.20) and dry skin 14.1% (95% CI 0.10-0.20). High-grade rash/desquamation events occurred in 5.0% (95% CI 0.04-0.07), HFSR in 9.0% (95% CI 0.082-0.098), alopecia in 4/1793, pruritus in 2/1265 and dry skin in 0/1689 of patients assigned sorafenib. Meta-analysis of risk ratio showed that sorafenib was associated with a significantly increased risk of rash/desquamation [risk ratio (RR) 2.73; 95% CI 1.66-4.49)], HFSR (RR 7.50; 95% CI 3.90-14.40) and alopecia (RR 7.55; 95% CI 5.26-10.84) in patients with solid tumours, but risk of pruritus (RR 1.80; 95% CI 0.77-4.22) or dry skin (RR 2.18; 95% CI 0.88-5.40) was not increased. In conclusion, the most frequent dermatological toxicities associated with sorafenib were HFSR, rash/desquamation, alopecia, pruritus and dry skin. There was a significantly increased risk of HFSR, rash/desquamation and alopecia with sorafenib compared with placebo. Skin toxicities were mainly mild or moderate in severity. Appropriate prevention and management are recommended.

TAK1 regulates SCF expression to modulate PKBα activity that protects keratinocytes from ROS-induced apoptosis

Dysregulated reactive oxygen species (ROS) generation contributes to many human pathologies, including cancer and diabetes. During normal wound repair, inflammation-induced ROS production must be tightly controlled, but the mechanisms reining their generation remain unclear. Herein, we show that transforming growth factor β-activated kinase 1 (TAK1) directly regulates stem cell factor (SCF) expression, which activates the protein kinase B (PKB)α pro-survival pathway in a cell-autonomous manner to protect keratinocytes from ROS-mediated cell death. TAK1 is a pivotal inflammatory mediator whose expression was transiently elevated during wound healing, paralleling the ROS production profile. TAK1 deficiency in keratinocytes led to increased apoptosis in response to anoikis and TNF-α treatment and was associated with elevated ROS level as analyzed by FACS. Using organotypic skin co-culture and comparative growth factor array analysis, we revealed a cell-autonomous mechanism that involved the SCF/c-Kit/PKBα signaling cascade. Ectopic expression of TAK1 or treatment with exogenous recombinant SCF restored the increased ROS production and apoptotic cell death in TAK1-deficient keratinocytes. Conversely, normal keratinocytes treated with various inhibitors targeting the SCF/c-Kit/PKBα pathway exhibited increased ROS production and TNF-α- or anoikis-induced apoptosis. Our study reveals a novel anti-apoptotic role for SCF in keratinocytes and identifies TAK1 as a novel player uniting inflammation and ROS regulation in skin redox biology.

Sorafenib-associated hand-foot syndrome in Japanese patients

Sorafenib (Nexavar) is an oral multi-kinase inhibitor that targets tumor growth and angiogenesis, having encouraging efficacy and tolerability in patients with metastatic renal cell carcinoma (RCC) and other tumors. However, hand-foot syndrome (HFS), a frequently reported adverse event under sorafenib treatment, sometimes causes interruption of the treatment or dose reduction. This study was conducted to review sorafenib-associated HSF in Japanese patients, to facilitate improvement of the management of HFS in clinical practice. We reviewed the combined results on HFS in three sorafenib studies in Japanese patients: (A) a phase II study of metastatic renal cell carcinoma; (B) a phase I study of solid tumor; and (C), phase I study of hepatocellular carcinoma. Severity of HFS was graded as 1-3 based on the modified grading scale of National Cancer Institute - Common Toxicity Criteria version 2.0 and Common Terminology Criteria for Adverse Events version 3.0. A total of 189 patients were included for analyses. The incidence of all-grade HFS was 51% (55% in A, 39% in B and 44% in C), and the incidence of grade 3 HFS was 7% (9% in A, 0% in B and 7% in C). Incidence of HFS seemed dose-dependent. These events were observed within 3-9 weeks after initiation of sorafenib treatment. The majority of HFS was manageable with symptomatic treatment and HFS caused permanent discontinuation of sorafenib in only one patient (in study A). The incidence of sorafenib-associated HFS is high compared to other adverse events. However, the present analyses showed that HFS under sorafenib treatment is well manageable in Japanese patients.

Cutaneous adverse effects in patients treated with the multitargeted kinase inhibitors sorafenib and sunitinib

BACKGROUND

The multitargeted kinase inhibitors sorafenib and sunitinib have improved treatment of solid tumours including renal cell carcinoma and hepatocellular carcinoma by offering better clinical responses. However, sorafenib and sunitinib are commonly associated with cutaneous toxicity.

OBJECTIVES

We conducted this study to make a clinical assessment of the cutaneous toxicities induced by the oral multitargeted kinase inhibitors sorafenib and sunitinib.

METHODS

Retrospectively, we reviewed medical records of patients receiving multitargeted kinase inhibitors, including 109 patients on sorafenib for the treatment of renal cell carcinoma or hepatocellular carcinoma and 119 patients receiving sunitinib for treatment of renal cell carcinoma or a gastrointestinal stromal tumour. Clinical data on cutaneous toxicities were collated. We describe the incidences and intensities of toxicities, and analyse the data statistically.

RESULTS

The most common cutaneous toxicity was hand-and-foot skin reaction (HFSR). Other cutaneous toxicities included alopecia, stomatitis, skin discoloration (hair or face), subungual splinter haemorrhage, facial swelling, facial erythema and xerosis. HFSR and severe stomatitis required therapy modifications to relieve symptoms, but other cutaneous toxicities did not affect treatment course. HFSR was observed in 48% of patients treated with sorafenib and 36% of those treated with sunitinib. Median time to onset was 18.4 days in patients receiving sorafenib and 32.4 days in those receiving sunitinib. HFSR and stomatitis were early symptoms compared with other cutaneous toxicities. Patients with severe HFSR were likely to develop the symptoms at early phases of therapy. A significant correlation between the severity of HFSR and development of alopecia and stomatitis was found.

CONCLUSIONS

Multitargeted kinase inhibitors are associated with a significant risk of various cutaneous adverse events. HFSR is the commonest and most serious cutaneous toxicity in patients treated with these drugs.

Gain-of-function mutation of KIT ligand on melanin synthesis causes familial progressive hyperpigmentation

Familial progressive hyperpigmentation (FPH) is an autosomal-dominantly inherited disorder characterized by hyperpigmented patches in the skin, present in early infancy and increasing in size and number with age. The genetic basis for FPH remains unknown. In this study, a six-generation Chinese family with FPH was subjected to a genome-wide scan for linkage analysis. Two-point linkage analysis mapped the locus for FPH at chromosome 12q21.31-q23.1, with a maximum two-point LOD score of 4.35 (Ø = 0.00) at D12S81. Haplotype analysis confined the locus within an interval of 9.09 cM, flanked by the markers D12S1667 and D12S2081. Mutation profiling of positional candidate genes detected a heterozygous transversion (c. 107A-->G) in exon 2 of the KIT ligand (KITLG) gene, predicted to result in the substitution of a serine residue for an asparagine residue at codon 36 (p.N-->S). This mutant "G" allele cosegregated perfectly with affected, but not with unaffected, members of the FPH family. Function analysis of the soluble form of sKITLG revealed that mutant sKITLGN36S increased the content of the melanin by 109% compared with the wild-type sKITLG in human A375 melanoma cells. Consistent with this result, the tyrosinase activity was significantly increased by mutant sKITLGN36S compared to wild-type control. To our knowledge, these data provided the first genetic evidence that the FPH disease is caused by the KITLGN36S mutation, which has a gain-of-function effect on the melanin synthesis and opens a new avenue for exploration of the genetic mechanism of FPH.

Risk of hand-foot skin reaction with the multitargeted kinase inhibitor sunitinib in patients with renal cell and non-renal cell carcinoma: a meta-analysis

Hand-foot skin reaction (HFSR) is an emerging issue in cancer treatment with multitargeted tyrosine kinase inhibitors (TKIs), leading to morbidity, suboptimal dosing, and poor compliance. The overall risk of HFSR is not clear for sunitinib, a TKI effective for metastatic renal cell carcinoma (RCC) and gastrointestinal stromal tumor. We therefore conducted a systematic review and a meta-analysis to determine the risk of developing HFSR with sunitinib. Databases from PubMed and Web of Science for articles from July 1966 until July 2007 and abstracts presented at the American Society of Clinical Oncology conferences were searched to identify relevant studies. Eligible studies were prospective clinical trials that had described events of HFSR for patients who received singleagent sunitinib. Incidence and relative risk (RR) were calculated using a random-effects or fixed-effects model. A total of 5005 patients with RCC and other cancers from 10 clinical trials were included for analysis. Among patients receiving sunitinib, the summary incidences of all-grade and high-grade HFSR were 18.9% (95% CI, 14.1%-24.8%) and 5.5% (95% CI, 3.9%-7.9%), respectively. Interestingly, patients with RCC have significantly decreased risk of HFSR compared with patients with non-RCC malignancy (RR, 0.56; 95% CI, 0.50-0.64; P < .001). In addition, sunitinib was associated with a significantly increased risk of all-grade HFSR (RR, 9.86; 95% CI, 3.1-31.31; P < .001) in comparison with controls. There is a significant risk of developing HFSR in patients with cancer receiving sunitinib. Adequate monitoring and intervention are recommended for reducing the toxicity.

Hand-foot skin reaction increases with cumulative sorafenib dose and with combination anti-vascular endothelial growth factor therapy

PURPOSE

Sorafenib, a vascular endothelial growth factor (VEGF) receptor-2 and RAF kinase inhibitor, commonly causes skin toxicity. We retrospectively analyzed dermatologic toxicity in patients receiving combined antiangiogenic therapy involving sorafenib and bevacizumab.

EXPERIMENTAL DESIGN

Castration-resistant prostate cancer and metastatic non-small cell lung cancer patients were accrued to phase II studies, receiving sorafenib 400 mg twice daily. A phase I study explored sorafenib 200 to 400 mg twice daily with bevacizumab 5 to 10 mg/kg every 2 weeks in patients with advanced solid tumors. The probability of development of maximum grade of dermatologic toxicity as a function of the cumulative dose of sorafenib was determined. Additional analyses compared extent of toxicity, pharmacokinetics, and patient risk factors.

RESULTS

Ninety-six patients were enrolled: 54 received sorafenib and 42 received bevacizumab/sorafenib. Hand-foot skin reaction (HFSR) was observed in 50 of 96 (52%) patients. Grade 2 to 3 HFSR developed in 16 of 54 (30%) sorafenib patients and 24 of 42 (57%) bevacizumab/sorafenib patients (P=0.012) and was associated with cumulative sorafenib exposure (P=0.0008). Twenty-four of 42 phase I patients randomized to start with bevacizumab had increased risk of grade 2 to 3 HFSR than those starting with sorafenib (P=0.013) after adjusting for association between HFSR risk and hypertension (P=0.01), which was the only toxicity associated with HFSR. There was no association between HFSR and baseline history of neuropathy, prior taxane/platinum treatment, or systemic sorafenib levels.

CONCLUSIONS

Sorafenib-related HFSR is associated with increasing cumulative sorafenib dose. HFSR is increased in patients treated with bevacizumab/sorafenib combination anti-VEGF therapy, and this finding is not explained by pharmacokinetic interaction between the two agents. Our results suggest that the pathophysiology of HFSR may be related to VEGF inhibition.

Risk of hand-foot skin reaction with sorafenib: a systematic review and meta-analysis

BACKGROUND

Hand-foot skin reaction (HFSR) is a dose-limiting toxicity associated with sorafenib, an oral multi-kinase inhibitor with clinical activity against solid tumors. This study was conducted to determine the risk of developing HFSR among patients receiving sorafenib.

PATIENTS AND METHODS

Databases from Pubmed, Web of Science, and abstracts presented at the American Society of Clinical Oncology annual meetings from 2004 through July, 2007 were searched to identify relevant studies. Eligible studies were prospective clinical trials using single agent sorafenib. The summary incidence rate and the relative risk (RR) were calculated using random-effects model.

RESULTS

A total of 4 883 patients in 11 trials with metastatic tumors were included for analysis. Among patients receiving sorafenib, the summary incidence of all-grade HFSR was 33.8% (95% CI: 24.5-44.7%) with significant difference between patients with RCC and non-RCC malignancy (RR 1.52, 95% CI: 1.32-1.75%, p<0.001). The incidence of high-grade HFSR was 8.9% (95% CI: 7.3-10.7%). In addition, sorafenib was associated with a significant increased risk of HFSR with RR of 6.6 (95% CI: 3.7 to 11.7, p<0.001) in comparison with controls.

CONCLUSION

There is a significant risk of HFSR associated with sorafenib. Proper management and further study are recommended to reduce the risk.

The dermal stem cell factor and c-kit are overexpressed in melasma

BACKGROUND

The pathogenesis of melasma has not yet been clearly demonstrated. We tried to determine whether the stem cell factor (SCF) and its receptor c-kit are involved in the mechanism of hyperpigmentation of melasma because this factor is highly implicated in the stimulation of melanocyte function in vitro and in vivo.

OBJECTIVES

The present study was conducted to investigate the expression of SCF and c-kit on the lesions of melasma compared with nonlesional skin.

PATIENTS/METHODS

Skin samples were obtained from lesional and nonlesional facial skin of 60 Korean women with melasma. Immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed to determine the expression of SCF and c-kit in melasma.

RESULTS

The expression of SCF was significantly increased at the lesional dermis compared with nonlesional dermis. However, there was no significant difference in the expression of SCF in lesional and nonlesional epidermis. The expression of c-kit was significantly increased at lesional epidermis compared with nonlesional skin. RT-PCR of SCF and c-kit mRNAs demonstrated increased expression of both types of transcripts in the lesional skin compared with nonlesional skin.

CONCLUSIONS

These results suggest that the increased expression of SCF in the dermis and of c-kit in the epidermis play an important role in the mechanism of hyperpigmentation in melasma.

Less keratinocyte-derived factors related to more keratinocyte apoptosis in depigmented than normally pigmented suction-blistered epidermis may cause passive melanocyte death in vitiligo

Stem cell factor (SCF) of keratinocyte origin regulates melanocyte growth and survival. Deprivation of survival factors causes the apoptosis of melanocytes. Vitiligo often develops following physical trauma, even if this is minor. The exact mechanism of the Koebner phenomenon in vitiligo is unclear. Apoptosis of keratinocytes, which occurs more in depigmented suction-blistered epidermis than in the normally pigmented counterpart, could reduce levels of keratinocyte-derived factors such as SCF and basic fibroblast growth factor (bFGF). Levels of SCF expression were examined in the depigmented and normally pigmented paired epidermis of 19 patients with vitiligo, and bFGF expression in six patients. The expression of SCF (p<0.001) and bFGF was usually reduced in the depigmented compared with the normally pigmented epidermis. Apoptosis of cultured normal human keratinocytes, which was induced by staurosporine, resulted in a concentration-dependent decrease in levels of SCF mRNA and protein. Normal human melanocytes proliferated more in medium containing SCF or keratinocyte (XB-2) feeder than in medium with neither. Deprivation of SCF or keratinocyte feeder in the culture medium induced a marked decrease in melanocytes as a result of apoptosis. Therefore, lower expression of keratinocyte-derived factors, including SCF, in vitiliginous keratinocytes, which could result from keratinocyte apoptosis, might be responsible for passive melanocyte death and may explain the Koebner phenomenon.

Scarring alopecia associated with mastocytosis

BACKGROUND

Mastocytosis is comprised of a group of heterogeneous diseases involving various organs. Urticaria pigmentosa is the most common manifestation of cutaneous mastocytosis; others include mastocytoma, diffuse mastocytosis, and telangiectasia macularis eruptiva perstans.

METHODS

We describe a case of indolent mastocytosis presenting as scarring alopecia. The scalp biopsy revealed a perifollicular and dermal inflammatory infiltrate composed predominantly of mast cells, which was confirmed by tryptase and Giemsa stains.

RESULTS

The preponderance of mast cells in the biopsy prompted testing for urine N-methylhistamine levels, which were elevated and confirmed the diagnosis of mastocytosis. This is the first report of mastocytosis presenting as scarring alopecia.

CONCLUSIONS

This case suggests that the diagnosis of mastocytosis should be entertained in patients presenting with scarring alopecia accompanied by an intense mast cell infiltrate on scalp biopsy and also supports the notion that mast cells may be involved in the pathogenesis of alopecia.

Dry environment increases mast cell number and histamine content in dermis in hairless mice

BACKGROUND

A variety of skin diseases, such as atopic dermatitis, senile xerosis or psoriasis tends to worsen during the dry winter season. These skin diseases are also characterized by itch sensation.

OBJECTIVES

To evaluate the generation of histamine in the dermis of hairless mice kept under various conditions of environmental humidity.

MATERIALS AND METHODS

We carried out the quantification of mast cell population and evaluated the histamine content in the epidermis, dermis and serum of the mice kept under various conditions of environmental humidity.

RESULTS

Histamine content in the dermis of the mice kept in a low environmental humidity (relative humidity < 10%) for 3 and 5 days was significantly higher than that of the mice kept in a high environmental humidity (relative humidity > 80%) for the same period of time. No significant difference was observed on the histamine content in the epidermis between the two humidity groups. The number of mast cells in the dermis of the mice kept in the low environmental humidity was significantly higher than that of the mice kept in the high environmental humidity. Topical application of petrolatum reduced the level of histamine in the dermis of the mice under the low environmental humidity.

CONCLUSIONS

These results suggest that a low environmental humidity increases mast cell number and dermal histamine content.

Vasoactive intestinal peptide and cytokines enhance stem cell factor production from epidermal keratinocytes DJM-1

Stem cell factor can induce mast cell proliferation and melanocyte activation. Vasoactive intestinal peptide has been suggested to play a part in inflammatory dermatoses, such as atopic dermatitis. The aim of this study was to investigate the possible role of stem cell factor in atopic dermatitis by analyzing epidermal stem cell factor production induced by vasoactive intestinal peptide and cytokines. Full-length type stem cell factor transcript was detected in normal human epidermal keratinocytes, and a human epidermal keratinocyte cell line DJM-1, as well as normal human dermal fibroblasts, using reverse transcription-polymerase chain reaction. Spliced-type stem cell factor transcript was detected in both DJM-1 cells and normal human epidermal keratinocytes. Western blot analysis with stem cell factor antibody revealed a protein of the known molecular size of membrane-bound stem cell factor in the lysates of all three cell types. Stem cell factor immunoreactivity was found in the cytoplasm and the membrane of both DJM-1 cells and normal human epidermal keratinocytes using confocal laser scanning microscope. We examined the effects of vasoactive intestinal peptide and cytokines on stem cell factor production of DJM-1 cells using enzyme-linked immunosorbent assays. Stem cell factor contents significantly increased in culture supernatants of DJM-1 cells treated with 1000 nm vasoactive intestinal peptide and/or cytokines, including interleukins 4 and 13, tumor necrosis factor-alpha, and interferon-gamma. Overall, these results suggest that several inflammatory cytokines (T helper 1 and 2) and vasoactive intestinal peptide from mast cells and nerve endings are capable of inducing stem cell factor production from epidermal keratinocytes in atopic dermatitis.

Control of the differentiation state and function of human epidermal Langerhans cells by cytokines in vitro

Langerhans cells can originate in vitro from immature precursors stimulated with granulocyte macrophage-colony-stimulating factor (GM-CSF), tumour necrosis factor (TNF)-alpha and stem cell factor (SCF). We asked whether these cytokines also control the differentiation state of Langerhans cells within the epidermis and upon leaving this tissue. We harvested sheets of human epidermis by controlled dispase hydrolysis of keratomes, cultured them in RPMI and 10% fetal calf serum for 48 h and analysed the sheets and the cells migrated spontaneously into the medium, most of which were Langerhans cells containing Birbeck granules. By flow cytometry, the intensity of CD1a expression was reduced quite evenly among Langerhans cells migrated from sheets within 48 h. The cells in the sheets underwent loss of dendrites, with a significant reduction in the cell perimeter that was prevented by GM-CSF and TNF-alpha together. Either of these cytokines induced expression of CD18 by cells in the sheets and those in the medium. Moreover, TNF-alpha induced expression of CD54 by cells in the medium, but not by those retained in the sheets, whereas human SCF induced, dose dependently, expression of CD54 by cells in the sheets, but not from those in the medium. The proliferation of allogeneic lymphocytes was much higher when stimulating Langerhans cells were harvested from cultures with any cytokine, rather than from cultures without cytokines. We conclude the following: (i) GM-CSF and TNF-alpha help to maintain full differentiation of Langerhans cells within the epidermis; (ii) cytokine influence on Langerhans cells adhesiveness is in part context dependent; and (iii) pretreatment with cytokines influences positively the number or accessory activity of Langerhans cells on lymphocytes during subsequent mixed leucocyte reaction.

Possible contribution of stem cell factor in psoriasis vulgaris

It is suggested that mast cell is implicated to play a role in the pathogenesis of psoriasis. In this study, to determine the role of stem cell factor (SCF), which is a growth factor of mast cells, we have examined the immunohistochemical localization and serum level of SCF in patients with psoriasis vulgaris. Immunohistochemical analysis revealed diffuse staining for SCF on keratinocytes in acanthotic epidermis in psoriasis, along with endothelial cells and fibroblasts. Serum SCF level, which was measured by enzyme-linked immunosorbent assay (ELISA), was significantly increased in patients with psoriasis vulgaris (1033+/-334 pg/ml) (n=24) than that of normal subjects (666+/-196 pg/ml) (n=15) (P<0.05). However, serum SCF did not show a correlation with the disease severity assessed by psoriasis activity and severity index (PASI) score. As patients with psoriasis vulgaris occasionally complain itching, next we divided 20 patients into two groups, those with itching (Group I) (n=8) and those without (Group II) (n=12), and compared the mast cell number located in the papillary dermis between thickened psoriatic epidermis, serum SCF and plasma histamine levels. Results showed that mast cell numbers (56.3+/-22.3/mm(2) in Group I vs 31.5+/-10. 3/mm(2) in Group II, P<0.05) and plasma histamine level (1.5+/-0.59 ng/ml vs 0.39+/-0.15 ng/ml, P<0.01) were significantly higher in patients of Group I than those of patients of Group II, however, the difference of serum SCF level (1132+/-368 pg/ml vs 890+/-373 pg/ml) did not reach a statistical significance. Finally, in a separate experiment, we examined whether exogenous SCF is capable of inducing psoriatic architecture on the transplanted uninvolved psoriatic skin onto severe combined immunodeficient (SCID) mice. SCF injection for 2 weeks could not induce a psoriasiform architecture such as acanthosis on the transplanted uninvolved psoriatic skin, although mast cells were increased in number. These results raised a possibility that keratinocyte-derived SCF plays a role, in part, in the increased number of mast cells in the papillary dermis of psoriasis, which may lead pruritus associated with psoriasis. Elevated serum SCF level may also be responsible for increment of mast cells in psoriasis vulgaris. Mast cell-derived factor stimulated by exogenous SCF could not induce psoriatic epidermis, suggesting that other factors such as activated lymphocytes or macrophages are further required for the development of psoriatic lesions.

Horizontal and vertical pigment spread into surrounding piebald epidermis and hair follicles after suction blister epidermal grafting

Following the earlier description of Carnot and Deflandre in 1896, pigment spread phenomenon in mammals was investigated using immunogenetically marked melanocytes (Billingham and Silver, Quart. Rev. Biol. 1960 35: 1-40; Billingham and Silver, Ann. N.Y. Acad. Sci. 1963 100: 348-363). In spite of a number of similar studies on vitiligo lesions, detailed evaluation of pigment spread in piebald lesions has not been reported. To gain further insight into the pigment spread phenomenon in human skin, five piebald patients were studied, on whom suction blister epidermal grafting therapy onto piebald patches was performed. In the present study, pigmentation of all epidermal grafts from normally pigmented areas spread horizontally. It was also found that pre-existing white hairs in recipient sites became pigmented within 1 year after epidermal grafting. Immunofluorescence studies using melanocyte-specific antibody NKI/beteb revealed the newly induced presence of melanocytes in the newly pigmented hair follicles. Further, to study the possible mechanisms inhibiting melanocyte migration from normal skin into piebald lesions, epidermis was grafted from border zones (containing both normal and piebald skin) into the center of hypopigmented lesions. Melanocytes clearly migrated through the border zone of grafted epidermis into surrounding recipient hypopigmented sites.

A fibrogenic cytokine, platelet-derived growth factor (PDGF), enhances mast cell growth indirectly via a SCF- and fibroblast-dependent pathway

Mast cell hyperplasia is often observed in dermatoses characterized by fibrosis. Evidence has accumulated showing that a potent fibrogenic cytokine, platelet-derived growth factor (PDGF), plays a pathogenic role in dermal fibrosis. To clarify the mechanism of mast cell hyperplasia associated with fibrosis, we investigated the effect of PDGF on mast cell proliferation and the expression of stem cell factor (SCF), a potent growth factor for mast cells, in fibroblasts. When mouse bone marrow-derived mast cells (BMMC) were cultured on a NIH/3T3 fibroblast monolayer, mast cell proliferation was stimulated in both cell number and total histamine content by all isoforms of PDGF (-AA, -AB, and -BB); however, none of the isoforms had any effect on [3H] thymidine incorporation in BMMC in the absence of fibroblasts. The effect of PDGF-AB and -BB were abrogated either by the addition of anti-PDGF-AB antibody or by the separation of mast cells and fibroblasts by a permeable membrane filter with a pore size of 0.2 microm. Immunoblotting of the NIH/3T3 fibroblasts treated with PDGF revealed an enhanced expression of SCF in the membrane fraction and the effect of PDGF was neutralized by the addition of antibody against SCF. Moreover, no effect of PDGF was observed when BMMC were prepared from W/W(v) mice that lack functional c-kit as the SCF receptor or when 3T3 fibroblasts were prepared from Sl/Sl(d) mice that lack membrane-bound SCF. These results suggest that the fibrogenic cytokine PDGF stimulates mast cell hyperplasia via the expression of membrane-bound SCF by fibroblasts in association with fibrosis of the skin.

Biological characterization of human fibroblast-derived mitogenic factors for human melanocytes

To clarify the paracrine linkage between human fibroblasts and melanocytes in cutaneous pigmentation, we studied the effects of human fibroblast-derived factors on the proliferation of human melanocytes. In medium conditioned for 4 days with human fibroblast culture, factors were produced that markedly stimulated DNA synthesis of human melanocytes. The stimulatory effect was higher in medium conditioned with fibroblasts from aged skin than in medium conditioned with fibroblasts from young skin, and was interrupted by inhibitors of tyrosine kinase, such as tyrphostin, genistein and herbimycin, but not by inhibitors of protein kinases C and A, such as H-7 and phloretin. The conditioned medium was also capable of activating mitogen-activated protein kinase of human melanocytes, with old fibroblasts being more effective than young ones. Analysis of factors released into the conditioned medium revealed that levels of hepatocyte growth factor (HGF) and stem cell factor (SCF) were increased in old-fibroblast-conditioned medium compared with young-fibroblast-conditioned medium. In contrast, levels of basic fibroblast growth factor (bFGF) were similar in both media. When the conditioned medium was treated with HGF antibody with or without SCF antibody, the increase in DNA synthesis by human melanocytes was decreased to 20% of the elevated level, whereas antibodies to bFGF had no effect. Analysis of the medium conditioned for 4 days after cytokine application demonstrated that, of the cytokines tested, interleukin 1alpha and tumour necrosis factor alpha are highly effective in stimulating HGF secretion by old fibroblasts. HGF and SCF, but not bFGF, were markedly increased in culture medium in the presence of IL-1alpha, and this stimulatory effect was confined to young human fibroblasts. These findings suggest that SCF and HGF derived from human fibroblasts may play a part in regulating cutaneous pigmentation during inflammation and aging.

Release of stem cell factor from a human keratinocyte line, HaCaT, is increased in differentiating versus proliferating cells

Stem cell factor, a recently discovered growth factor for hematopoietic stem cells, mast cells, and melanocytes, was initially reported to be produced by fibroblasts. In this study, we investigated the secretion of this factor from human HaCaT cells during in vitro culture and compared it to synthesis by cells in the skin. Release of stem cell factor from freshly cultured keratinocytes was comparable to that of HaCaT cells and was nearly half that produced by fibroblasts and umbilical vein endothelial cells. No stem cell factor was detectable in culture supernatants of melanocytes. HaCaT cells underwent spontaneous differentiation after a period of proliferation until confluency. Depending on duration of culture, they released increasing amounts of stem cell factor (approximately 150 pg/10(6) cells on day 3 (proliferating cells) vs approximately 450 pg/10(6) cells on day 14 (differentiating cells) measured by enzyme-linked immunosorbent assay. Stimulation for 24 h with the calcium ionophore A 23187 (10(-6) to 10(-8) M) further enhanced release. Western blot analysis of HaCaT cell lysates with a stem cell factor antibody revealed two proteins with the known molecular weights of membrane-bound and soluble stem cell factor. By semiquantitative reverse transcriptase polymerase chain reaction, full-length as well as spliced type stem cell factor mRNA was found to be increased in differentiating versus proliferating HaCaT cells. Keratinocytes are thus potentially important sources of stem cell factor in human skin, and HaCaT cells provide a useful model for further studies of stem cell factor from keratinocytes.

Immunity at the surface: homeostatic mechanisms of the skin immune system

The coordinated function of multiple epidermal and dermal cell populations allows the skin immune system to respond rapidly and effectively to a wide variety of insults occurring at the interface of the organism and its environment. Keratinocytes are the first line of defense in the skin immune system, and keratinocyte-derived cytokines are pivotal in mobilizing leukocytes from blood and signaling other cutaneous cells. Cytokine-mediated cellular communication also enables dermal fibroblasts and endothelial cells lining the cutaneous vasculature to participate in immune and inflammatory responses. Skin is an important site for antigen presentation, and both epidermal Langerhans cells and dermal dendritic cells play pivotal roles in T cell-mediated immune responses to antigens encountered in skin. Proinflammatory signaling pathways are necessarily balanced by a variety of regulatory pathways that help maintain the homeostatic functioning of the skin immune system.

Expression of stem cell factor in cutaneous mastocytosis

Stem cell factor has recently been identified as a potent growth factor for bone marrow stem cells, melanocytes and mast cells. In order to evaluate its possible role in human mastocytosis, skin lesions from 13 patients with urticaria pigmentosa and five patients with mastocytomas, and normal skin specimens from five healthy donors were studied by immunohistochemistry, using polyclonal and monoclonal (hkl-12) antibodies against stem cell factor, and a monoclonal antibody (YB5.B8) against its receptor, the c-kit proto-oncogene product. Stem cell factor expression was noted in all sections studied, with an equal distribution pattern for both antibodies, but a weaker intensity with the hkl-12 reagent. Cytoplasmic staining was noted in keratinocytes, Langerhans cells, sweat gland ductal lining cells, mast cells, endothelial cells and spindle-shaped dermal stromal cells. An intense, diffusely granular reaction pattern was noted in all cells, except for a sparse, coarsely granular pattern in mast cells and stromal cells. In urticaria pigmentosa, staining was weaker in keratinocytes, but more prominent in Langerhans cells. In all sections, toluidine blue-positive mast cells and TA 99-positive basal epidermal melanocytes were the only cells to react with the c-kit antibody. Mastocytomas and urticaria pigmentosa lesions thus exhibit different patterns of stem cell factor expression. However, a possible pathogenetic role of this factor in mastocytosis remains to be determined.