Cylindroma as Tumor of Hair Follicle Origin

S, Balakrishnan S. Solitary Dermal Cylindroma in an Uncommon Site: A Rare Case Report

Cylindroma, a benign skin appendage tumor, mostly occurs in the head and neck region. They present as pink to purple, smooth-surfaced, solitary or multiple nodular lesions, mostly affecting middle-aged and elderly women. A clinical diagnosis of cylindroma is unusual but must be considered clinically. We report an unusual case of solitary benign dermal cylindroma that occurred in an uncommon site in a 54-year-old female. She came with complaints of painful swelling on the left side of her chest wall for six months. Histopathological examination of the mass revealed a well-defined tumor composed of nests and islands of a dual population of tumor cells surrounded by pink basement membrane-like material. These nests of cells are arranged in a "jigsaw" puzzle fashion, which is typical of cutaneous cylindroma. The thick pink material surrounding the epithelial cell islands is periodic acid Schiff stain (PAS) positive.

Recurrent Cylindroma of the Scalp: A Cytomorphological Evaluation at Fine Needle Aspiration Cytology

Specific diagnosis of adnexal tumours at fine needle aspiration cytology (FNAC) is challenging. In a recurrent scalp tumour, a startling array of lesions ranging from benign to malignant tumours fall into differential diagnosis. Accurate preoperative diagnosis is essential for planning management and to improve clinical outcome. Herein, we report a rare case of recurrent cylindroma of the scalp in a 62-year-old male patient. Cytology smears showed tight clusters of round to oval basaloid cells, few clusters with peripheral palisading. Basement membrane material was seen surrounding the cell clusters. FNAC diagnosis of a benign adnexal tumour, possibly cylindroma, was made. The diagnosis was confirmed at histopathology. We emphasize the decisive role of FNAC in arriving at an accurate diagnosis of a recurrent scalp tumour.

Genetic Testing in CYLD Cutaneous Syndrome: An Update

CYLD cutaneous syndrome (CCS) is an inclusive label for the inherited skin adnexal tumour syndromes Brooke–Spiegler Syndrome (BSS-OMIM 605041), familial cylindromatosis (FC – OMIM 132700) and multiple familial trichoepitheliomas (MFT-OMIM 601606). All three syndromes arise due to germline pathogenic variants in CYLD, a tumour suppressor gene (OMIM 605018). CCS is transmitted in an autosomal dominant pattern, and has variable expressivity, both of the three syndromic phenotypes, and of the severity of tumour burden. Age-related penetrance figures are not precisely reported. The first tumours typically appear during puberty and progressively accumulate through adulthood. Penetrance is typically high, with equal numbers of males and females affected. Genetic testing is important for confirmation of the clinical diagnosis, genetic counselling and family planning, including preimplantation diagnosis. Additionally, identified CCS patients may be eligible for future clinical trials of non-surgical pre-emptive interventions that aim to prevent tumour growth. In this update, we review the clinical presentations of germline and mosaic CCS. An overview of the germline pathogenic variant spectrum of patients with CCS reveals more than 100 single nucleotide variants and small insertions and deletions in coding exons, most frequently resulting in predicted truncation. In addition, a minority of patients have large deletions involving the CYLD gene, intronic pathogenic variants that affect splicing, or inversions. We discuss germline and somatic testing approaches. Somatic testing of tumour tissue, relevant in mosaic CCS, can reveal recurrently detected pathogenic variants when two or more tumours are tested. This can influence genetic testing of children, who may inherit this as a germline variant, and inform genetic counselling and prenatal diagnosis. Finally, we discuss testing technologies that are currently used, their benefits and limitations, and future directions for genetic testing in CCS.

An Update on the Role of Ubiquitination in Melanoma Development and Therapies

The ubiquitination system plays a critical role in regulation of large array of biological processes and its alteration has been involved in the pathogenesis of cancers, among them cutaneous melanoma, which is responsible for the most deaths from skin cancers. Over the last decades, targeted therapies and immunotherapies became the standard therapeutic strategies for advanced melanomas. However, despite these breakthroughs, the prognosis of metastatic melanoma patients remains unoptimistic, mainly due to intrinsic or acquired resistances. Many avenues of research have been investigated to find new therapeutic targets for improving patient outcomes. Because of the pleiotropic functions of ubiquitination, and because each step of ubiquitination is amenable to pharmacological targeting, much attention has been paid to the role of this process in melanoma development and resistance to therapies. In this review, we summarize the latest data on ubiquitination and discuss the possible impacts on melanoma treatments.

On-site cytological diagnosis of cylindroma: A case report

A 70-year-old female presented with a swelling in the right auricle for 6 months. Rapid onsite stain and routine cytology revealed clusters of small, round to oval cells with hyperchromatic nuclei, inconspicuous nucleoli, and scant cytoplasm. The background had basement membrane type material and appeared dark magenta colored pinkish globular material. Hence a cytological diagnosis of skin adnexal tumor possibly cylindroma was made. The excision of the lesion also showed features of cylindroma. Rapid onsite staining and cytology of subcutaneous location of the tumor in the absence of primary salivary gland tumors may help to diagnose such rare cases.

Inherited pulmonary cylindromas: extending the phenotype of CYLD mutation carriers

Background

Germline mutations in the tumour suppressor gene CYLD are recognized to be associated with the development of multiple cutaneous cylindromas. We encountered such a patient who presented with breathlessness because of multiple pulmonary cylindromas.

Objectives

To search for clinical and radiological features of multiple pulmonary cylindromas in a cohort of 16 patients with CYLD mutations.

Methods

A retrospective case‐note review was carried out in a tertiary dermatogenetics clinic where CYLD mutation carriers are reviewed on an annual basis. In‐depth investigation was carried out for patients with pulmonary tumours.

Results

Four patients had radiological imaging of their lungs, of which two had multiple pulmonary cylindromas that were confirmed histologically. Serial computed tomography monitoring allowed for pre‐emptive endobronchial laser ablation, preventing major airway obstruction and pulmonary collapse.

Conclusions

Pulmonary cylindromas are an unrecognized, but infrequently symptomatic, aspect of the phenotype in these patients that can have implications for patient care. They should be considered in patients with a high tumour burden that present with respiratory symptoms, and where appropriate, monitored with serial imaging.

What's already known about this topic?

Germline mutations in the tumour suppressor gene CYLD are recognized to be associated with the development of multiple cutaneous cylindromas, spiradenomas and trichoepitheliomas.

Beyond the skin, salivary gland tumours are seen in less than approximately 5% of patients, but otherwise the tropism of this disease is recognized as exclusively cutaneous.

What does this study add?

We report multiple pulmonary cylindromas in two patients out of a series of 16 patients, a previously unreported aspect of this genetic disease.

Deep phenotyping with radiological, histological and genetic approaches provides evidence that supports that these tumours are similar to cutaneous cylindromas and share a cytokeratin signature seen in cutaneous cylindroma.

What is the translational message?

Patients with this rare disease should be investigated if they present with new symptoms of respiratory disease.

These data inform the clinical surveillance and management of patients with this rare condition and also inform the longstanding debate on benign metastases.

https://doi.org/10.1111/bjd.17046 available online

https://goo.gl/Uqv3dl

The cylindromatosis (CYLD) gene and head and neck tumorigenesis

Germline CYLD mutation is associated with the development of a rare inheritable syndrome, called the CYLD cutaneous syndrome. Patients with this syndrome are distinctly presented with multiple tumors in the head and neck region, which can grow in size and number over time. Some of these benign head and neck tumors can turn into malignancies in some individuals. CYLD has been identified to be the only tumor suppressor gene reported to be associated with this syndrome thus far. Here, we summarize all reported CYLD germline mutations associated with this syndrome, as well as the reported paired somatic CYLD mutations of the developed tumors. Interestingly, whole-exome sequencing (WES) studies of multiple cancer types also revealed CYLD mutations in many human malignancies, including head and neck cancers and several epithelial cancers. Currently, the role of CYLD mutations in head and neck carcinogenesis and other cancers is poorly defined. We hope that this timely review of recent findings on CYLD genetics and animal models for oncogenesis can provide important insights into the mechanism of head and neck tumorigenesis.

Eccrine cylindroma of the face and scalp

Cylindroma is a benign skin adnexal tumor of eccrine differentiation. Clinically, they are disfiguring lesions that can mimic a malignancy. Cylindromas can be single or multiple and commonly involve the scalp (turban tumor) and face. Multiple cylindromas can have a syndromic association as seen in Brooke–Spiegler syndrome and familial cylindromatosis. We present a case of non familial cylindroma of the face that clinically mimicked a basal cell carcinoma. The histopathology was confirmatory. Herein we also highlight the utility of a simple and inexpensive histochemical stain Periodic Acid Schiff in supporting the diagnosis.

DUBs, the regulation of cell identity and disease

The post-translational modification of proteins with ubiquitin represents a complex signalling system that co-ordinates essential cellular functions, including proteolysis, DNA repair, receptor signalling and cell communication. DUBs (deubiquitinases), the enzymes that disassemble ubiquitin chains and remove ubiquitin from proteins, are central to this system. Reflecting the complexity and versatility of ubiquitin signalling, DUB activity is controlled in multiple ways. Although several lines of evidence indicate that aberrant DUB function may promote human disease, the underlying molecular mechanisms are often unclear. Notwithstanding, considerable interest in DUBs as potential drug targets has emerged over the past years. The future success of DUB-based therapy development will require connecting the basic science of DUB function and enzymology with drug discovery. In the present review, we discuss new insights into DUB activity regulation and their links to disease, focusing on the role of DUBs as regulators of cell identity and differentiation, and discuss their potential as emerging drug targets.

Cylindroma: an update

This paper reviews the recent literature on cylindroma, a rare tumor originating from the cutaneous adnexal structures of the scalp and face. Benign cylindroma is more frequent in women, and there are solitary and multiple forms, which are autosomal. Malignant cylindroma can occur in the Brooke-Spiegler syndrome, and malignant transformation is more frequent in multiple variants than in solitary tumors. Its histopathological basis is controversial, and its origin is unknown, although it is known that there is a genetic basis for onset of these tumors in Brooke-Spiegler syndrome.

[Tumors of the scalp: special aspects of selected examples]

BACKGROUND

Tumors of the scalp display some clinical, histological and prognostic characteristics. Early recognition of tumors is hampered by dense hair growth which can result in delayed diagnosis.

MATERIAL AND METHODS

Taking current literature into consideration atypical fibroxanthoma, cutaneous angiosarcoma, melanoma of the scalp, some adnexal tumors including the proliferating trichilemmal tumor as well as cutaneous metastases from visceral malignancies will be discussed.

RESULTS

Based on the fact that early scalp tumors are clinically difficult to recognize, they are often diagnosed at a late stage. Angiosarcomas belong to the most aggressive skin tumors and show a rapid growth with unfavorable prognosis. Malignant melanoma on the head has a more serious prognosis in comparison to other locations of the body. Cutaneous metastases are mostly a sign of an advanced tumor stage with a fatal prognosis. The various types of adnexal tumors are mostly benign. In exceptional cases rapid growth and ulceration may be an indicator for the development of an adnexal carcinoma. On the scalp tumors with sweat gland differentiation are more frequent than tumors with follicular differentiation. This shows that the general view that adnexal tumors develop from local adnexal structures is wrong.

CONCLUSION

Scalp lesions in which the diagnosis is unclear should be biopsied or excised early. Based on the result of the histological examination further therapy can be determined.

Nuclear expression of the deubiquitinase CYLD is associated with improved survival in human hepatocellular carcinoma

Background & Aims

The deubiquitinase CYLD removes (K-63)-linked polyubiquitin chains from proteins involved in NF-κB, Wnt/ß-catenin and Bcl-3 signaling. Reduced CYLD expression has been reported in different tumor entities, including hepatocellular carcinoma (HCC). Furthermore, loss of CYLD has been shown to contribute to HCC development in knockout animal models. This study aimed to assess subcellular CYLD expression in tumor tissues and its prognostic significance in HCC patients undergoing liver resection or liver transplantation.

Methods

Subcellular localization of CYLD was assessed by immunohistochemistry in tumor tissues of 95 HCC patients undergoing liver resection or transplantation. Positive nuclear CYLD staining was defined as an immunhistochemical (IHC) score ≥3. Positive cytoplasmic CYLD staining was defined as an IHC score ≥6. The relationship with clinicopathological parameters was investigated. Cell culture experiments were performed to analyze subcellular CYLD expression in vitro.

Results

Cytoplasmic CYLD expression was observed in 57 out of 95 (60%) HCC specimens (^cyt°CYLD⁺). Nuclear CYLD staining was positive in 52 out of 95 specimens (55%, ^nucCYLD⁺). 13 out of 52 ^nucCYLD⁺ patients (25%) showed a lack of cytoplasmic CYLD expression. ^nucCYLD⁺ was associated with prolonged overall survival in patients after resection or liver transplantation (P = 0.007). 5-year overall survival rates were 63% in ^nucCYLD⁺vs. 26% in ^nucCYLD^- patients. Nuclear CYLD staining strongly correlated with tumor grading (P<0.001) and Ki67 positivity (P = 0.005). ^nucCYLD⁺ did not prove to be an independent prognostic parameter. In vitro, Huh7, Hep3B and HepG2 showed reduced CYLD levels compared to the non-malignant liver cell line THLE-2. Induction of CYLD expression by doxorubicin treatment led to increased cytoplasmic and nuclear expression of CYLD.

Conclusions

Expression of nuclear CYLD is a novel prognostic factor for improved survival in patients with HCC undergoing liver resection or transplantation.

Cylindroma with Stromal Adipose Tissue Metaplasia versus Arising in a Background of Nevus Lipomatosus

Nevus lipomatosus superficialis is a rare type of connective tissue nevus. Cylindroma is a benign skin appendage tumor with a predilection for the scalp of older females. We describe the case of a 56-year-old woman with a scalp lesion demonstrating histopathologic features consistent with benign cylindroma arising within a nevus lipomatosus superficialis. To our knowledge, this lesion has not been raised in the literature in the differential for cylindroma with what is presumed to be stromal adipose metaplasia.

Cylindroma of the breast: a rare case report

Cylindroma is a benign adnexal tumor, which occurs as solitary dermal nodules on the scalp and forehead. Cylindroma of the breast is a rare lesion. Fine-needle aspiration is often the first line of investigation. In this communication, we illustrate the cytomorphological feature of cylindroma in a 61-year-old female patient who presented with a breast lump. Fine-needle aspiration cytology in this case reveals the islands of tumor cells formed a “jig-saw” pattern, along with the bland, basaloid cells associated with globular, extracellular material. These features are typical of cylindroma, but differential diagnosis of adenoidcystic carcinoma should always be kept in mind as the management of both tumors are different.

Familial dermal eccrine cylindromatosis with emphasis on histology and genetic mapping

Familial cylindromatosis (FC) is an autosomal dominant disorder with apparently complete penetrance, but variable expression. There is an increasing evidence that FC is clinically, genetically, and histologically heterogeneous disorder as the simultaneous occurrence of cylindromas and other tumors of skin appendages within the affected individuals and families. The presence of multiple scalp cylindromas is often associated with autosomal dominant Brooke-Spielger syndrome, a condition in which there are co-existent facial trichoepitheliomas and spiradenomas. We present here a case of multiple cylindromatosis in a family affecting many members successively.

Cylindroma transforming into basal cell carcinoma in a patient with Brooke-Spiegler syndrome

BACKGROUND

Brooke-Spiegler syndrome is a rare condition with a predisposition to develop cutaneous adnexal neoplasms, especially cylindromas, trichoepitheliomas and spiradenomas. Malignant transformation of cylindromas is rare. In such cases usually cylindrocarcinomas develop within these lesions. We present an unusual case of basal cell carcinoma developing within a preexisting cylindroma.

MAIN OBSERVATIONS

58-year-old woman with a 30-year history of multiple dermal cylindromas extensively involving her scalp was referred for dermatological treatment. The patient reported that one of the long-lasting lesions, 5.5 cm in size, ulcerated within the foregoing few weeks. Histopathology confirmed cylindromas and basal cell carcinoma within the ulcerating tumor. Surgical excision of largest cylindroma tumors led to cosmetic and functional improvement. Magnetic resonance and computed tomography showed tumor infiltration into the skull lamina externa. Metastases were excluded by chest radiography and abdominal ultrasound examination.

CONCLUSION

Patients with Brooke-Spiegler syndrome should be followed-up for malignant transformation of skin tumors to prevent deep penetration and possible metastases.

CYLD: a deubiquitination enzyme with multiple roles in cancer

The post-translational modification of different proteins via direct ubiquitin attachment is important for various cellular processes. Dysregulation of components of the ubiqutin system have been linked to many diseases including cancer. CYLD is a deubiquitination enzyme that can cleave the lysine 63-linked polyubiquitin chains from target proteins and regulate cell survival or cell proliferation. Since loss of CYLD expression can be observed in different types of human cancer, it is now well established that CYLD acts as a tumor suppressor gene. Besides its loss of function in human tumors by gene deletion or mutation, CYLD expression can be downregulated at the RNA level if necessary through transcriptional regulation or at the protein level through post-translational modifications. This article summarizes recent advances that link CYLD to different types of human cancer. Identification of CYLD-mediated signaling pathways during the progression of cancer will provide a solid foundation for diagnosis and lead to the development of novel tools for cancer therapy.

GLI1-dependent transcriptional repression of CYLD in basal cell carcinoma

CYLD is a deubiquitination enzyme that regulates different cellular processes, such as cell proliferation and cell survival. Mutation and loss of heterozygosity of the CYLD gene causes development of cylindromatosis, a benign tumour originating from the skin. Our study shows that CYLD expression is dramatically downregulated in basal cell carcinoma (BCC), the most common cancer in humans. Reduced CYLD expression in basal cell carcinoma was mediated by GLI1-dependent activation of the transcriptional repressor Snail. Inhibition of GLI1 restored the CYLD expression-mediated Snail signaling pathway, and caused a significant delay in the G1 to S phase transition, as well as proliferation. Our data suggest that GLI1-mediated suppression of CYLD has a significant role in basal cell carcinoma progression.

Runx1 directly promotes proliferation of hair follicle stem cells and epithelial tumor formation in mouse skin

Runx1/AML1 is a transcription factor implicated in tissue stem cell regulation and belongs to the small Runx family of cancer genes. In the hair follicle (HF), Runx1 epithelial deletion in morphogenesis impairs normal adult hair homeostasis (cycle) and blocks adult hair follicle stem cells (HFSCs) in quiescence. Here, we show that these effects are overcome later in adulthood. By deleting Runx1 after the end of morphogenesis, we demonstrate its direct role in promoting anagen onset and HFSC proliferation. Runx1 deletion resulted in cyclin-dependent kinase inhibitor Cdkn1a (p21) upregulation. Interfering with Runx1 function in cultured HFSCs impaired their proliferation and normal G(0)/G1 and G(1)/S cell cycle progression. The proliferation defect could be rescued by Runx1 readdition or by p21 deletion. Chemically induced skin tumorigenesis in mice turned on broad Runx1 expression in regions of the skin epithelium, papillomas, and squamous cell carcinomas. In addition, it revealed reduced rates of tumor formation in the absence of Runx1 that were accompanied by decreased epithelial levels of phospho-Stat3. Runx1 protein expression was similar in normal human and mouse hair cycles. We propose that Runx1 may act as a skin oncogene by directly promoting proliferation of the epithelial cells.

Tumor mapping in 2 large multigenerational families with CYLD mutations: implications for disease management and tumor induction

OBJECTIVES

To comprehensively ascertain the extent and severity of clinical features in affected individuals from 2 large families with proven heterozygous mutations in the CYLD locus and to correlate these findings with the 3 appendageal tumor predisposition syndromes (familial cylindromatosis, Brooke-Spiegler syndrome, and multiple familial trichoepitheliomas) known to be associated with such germline mutations.

DESIGN

Interfamilial and intrafamilial observational study.

SETTING

Tertiary genetic and dermatology referral center.

PARTICIPANTS

Thirty-four individuals recruited from 2 large multigenerational families with CYLD mutations. Clinical details, history, and tumor maps were obtained from all participants; in 18, the information was corroborated by detailed clinical examination.

MAIN OUTCOME MEASURES

Tumor density, distribution and histologic findings, associated medical conditions, patient symptoms, and impact of disease on quality of life.

RESULTS

The severity of penetrance and phenotype varied within families. Although an approximately equal female to male predisposition was noted, 5 women and 1 man (of 26 patients surveyed [23%]) had undergone total scalp removal. The average age at onset was 16 years (range, 8-30 years). Symptoms reported by affected patients included painful tumors (in 12 of 23 patients [52%] who answered the question), conductive deafness, and sexual dysfunction. Of the 26 surveyed patients, tumors were noted on the scalp in 21 (81%), on the trunk in 18 (69%), and in the pubic area in 11 (42%). Tumor mapping provided clinical evidence that correlated with hormonally stimulated hair follicles being particularly vulnerable to loss of heterozygosity and tumor induction.

CONCLUSIONS

The burden of disease at sites other than the head and neck appears to be underreported in the literature and greatly affects quality of life. Differentiation between the clinical diagnoses has little prognostic or clinical utility in genetic counseling, even within individuals from the same family. Thus, we suggest an encompassing diagnosis of "CYLD cutaneous syndrome." Finally, the clinical distribution of tumors suggests that hormonal factors may play an important role in tumor induction in these patients.

Update of cylindromatosis gene (CYLD) mutations in Brooke-Spiegler syndrome: novel insights into the role of deubiquitination in cell signaling

Germline mutations in the cylindromatosis (CYLD) gene have been described in families with cylindromas, trichoepitheliomas, and/or spiradenomas. Brooke-Spiegler syndrome (BSS) is the autosomal dominant predisposition to skin appendageal neoplasms including cylindromas, trichoepitheliomas, and/or spiradenomas. We review the clinical features, molecular genetics, and the animal models of BSS. To date, a total of 51 germline CYLD mutations have been reported, occurring in exons 9-20, in 73 families with diverse ethnic and racial backgrounds. Of 51 mutations, 86% are expected to lead to truncated proteins. The seven missense mutations reported to date occur only within the ubiquitin (Ub)-specific protease (USP) domain of the CYLD protein and most are associated exclusively with multiple familial trichoepithelioma (MFT). CYLD functions as a tumor suppressor gene. CYLD encodes a deubiquitinating (DUB) enzyme that negatively regulates the nuclear factor (NF)-kappaB and c-Jun N-terminal kinase (JNK) pathways. CYLD DUB activity is highly specific for lysine 63 (K63)-linked Ub chains but has been shown to act on K48-linked Ub chains as well. In 2008, the CYLD USP domain was crystallized, revealing that the truncated Fingers subdomain confers CYLD's unique specificity for K63-linked Ub chains. Recent work using animal models revealed new roles for CYLD in immunity, lipid metabolism, spermatogenesis, osteoclastogenesis, antimicrobial defense, and inflammation.

Malignant cylindroma of the scalp arising in a setting of multiple cylindromatosis: a case report

An unusual case of malignant cylindroma of the scalp arising in a 79-year-old white female with multiple cylindromatosis is presented. The tumor apparently arose from a cylindroma and had features of spiradenoma. Multiple cylindromatosis is an uncommon hereditary autosomal dominant disease, which is characterized by multiple skin adnexal tumors like cylindromas and trichoepitheliomas and occasional spiradenomas. Cylindroma is an uncommon benign tumor, which originates from skin appendages and is most commonly found on the scalp and face with a strong predilection for middle-aged and elderly females. Although cylindromas are usually benign neoplasms, carcinoma arising in such neoplasms is rare with only sporadic reports in literature. Her family history was negative for a similar disease. The patient's main concern was painful lesions over her right ear that interfered with wearing of her glasses. The clinical, histological immunohistochemical features, and treatment are presented along with a review of the literature.

Truncation of the catalytic domain of the cylindromatosis tumor suppressor impairs lung maturation

Cyld encodes a 956-amino acid deubiquitinating enzyme (CYLD), which is a negative regulator of nuclear factor kappaB and mitogen-activated protein kinase pathways. Mutations that truncate and inactivate the carboxyl-terminal deubiquitinating domain of CYLD underlie the development of skin appendage tumors in humans, whereas down-regulation of Cyld expression has been associated with the development of various types of human malignancies including lung cancer. To establish an animal model of human CYLD inactivation and characterize the biological role of CYLD in vivo, we generated mice carrying a homozygous deletion of Cyld exon 9 (Cyld(Delta 9/Delta 9) mice) using a conditional approach. Deletion of exon 9 would cause a carboxyl-terminal truncation of CYLD and inactivation of its deubiquitinating activity. In accordance with previous studies, fibroblasts from Cyld(Delta 9/Delta 9) embryos had hyperactive nuclear factor kappaB and c-Jun kinase pathways compared with control fibroblasts. Cyld(Delta 9/Delta 9) newborn mice were smaller than wild-type littermates with a short and kinky tail and no major developmental defects. However, Cyld(Delta 9/Delta 9) mice died shortly after birth from apparent respiratory dysfunction. Histological examination of E18.5 Cyld(Delta 9/Delta 9) lungs demonstrated an immature phenotype characterized by hyperplasic mesenchyme but apparently normal epithelial, smooth muscle. and endothelial structures. Our study identifies an important role of CYLD in lung maturation, which may underlie the development of many cases of lung cancer.

Cell death in the skin

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

Down-regulation of CYLD expression by Snail promotes tumor progression in malignant melanoma

High malignancy and early metastasis are hallmarks of melanoma. Here, we report that the transcription factor Snail1 inhibits expression of the tumor suppressor CYLD in melanoma. As a direct consequence of CYLD repression, the protooncogene BCL-3 translocates into the nucleus and activates Cyclin D1 and N-cadherin promoters, resulting in proliferation and invasion of melanoma cells. Rescue of CYLD expression in melanoma cells reduced proliferation and invasion in vitro and tumor growth and metastasis in vivo. Analysis of a tissue microarray with primary melanomas from patients revealed an inverse correlation of Snail1 induction and loss of CYLD expression. Importantly, tumor thickness and progression-free and overall survival inversely correlated with CYLD expression. Our data suggest that Snail1-mediated suppression of CYLD plays a key role in melanoma malignancy.

Five new CYLD mutations in skin appendage tumors and evidence that aspartic acid 681 in CYLD is essential for deubiquitinase activity

Brooke-Spiegler syndrome, familial cylindromatosis, and familial trichoepithelioma are autosomal-dominant genetic predispositions for benign tumors of skin appendages caused by mutations in the CYLD gene localized on chromosome 16q12-q13. The encoded protein functions as ubiquitin-specific protease (UBP), which negatively regulates NF-kappaB and c-Jun N-terminal kinase (JNK) signaling. We investigated five families affected with these skin neoplasms and identified four premature stop codons and the novel missense mutation D681G in a family in which 11 of 12 investigated tumors were trichoepitheliomas. CYLD protein harboring this missense mutation had a significant reduced ability to inhibit TNF receptor-associated factor (TRAF)2- and TRAF6-mediated NF-kappaB activation, tumor necrosis factor-alpha (TNFalpha)-induced JNK signaling, and to deubiquitinate TRAF2. CYLD-D681G was coimmunoprecipitated by TRAF2, but was unable to cleave K63-linked polyubiquitin chains. Aspartic acid 681 is highly conserved in CYLD homologues and other members of the UBP family, but does not belong to the Cys and His boxes providing the CYLD catalytic triad (Cys601, His871, and Asp889). As reported previously, the homologous residue D295 of HAUSP/USP-7 forms a hydrogen bond with the C-terminal end of ubiquitin and is important for the enzymatic activity. These results underline that D681 in CYLD is required for cleavage of K63-linked polyubiquitin chains.

Hair follicle stem cells: walking the maze

The discovery of epithelial stem cells (eSCs) in the bulge region of the outer root sheath of hair follicles in mice and man has encouraged research into utilizing the hair follicle as a therapeutic source of stem cells (SCs) for regenerative medicine, and has called attention to the hair follicle as a highly instructive model system for SC biology. Under physiological circumstances, bulge eSCs serve as cell pool for the cyclic regeneration of the anagen hair bulb, while they can also regenerate the sebaceous gland and the epidermis after injury. More recently, melanocyte SCs, nestin+, mesenchymal and additional, as yet ill-defined "stem cell" populations, have also been identified in or immediately adjacent to the hair follicle epithelium, including in the specialized hair follicle mesenchyme (connective tissue sheath), which is crucial to wound healing. Thus the hair follicle and its adjacent tissue environment contain unipotent, multipotent, and possibly even pluripotent SC populations of different developmental origin. It provides an ideal model system for the study of central issues in SC biology such as plasticity and SC niches, and for the identification of reliable, specific SC markers, which distinguish them from their immediate progeny (e.g. transient amplifying cells). The current review attempts to provide some guidance in this growing maze of hair follicle-associated SCs and their progeny, critically reviews potential or claimed hair follicle SC markers, highlights related differences between murine and human hair follicles, and defines major unanswered questions in this rapidly advancing field.

Lhx2--decisive role in epithelial stem cell maintenance, or just the "tip of the iceberg"?

Stem cell self renewal, maintenance and differentiation are influenced by the convergence of intrinsic cellular signals and extrinsic microenvironmental cues from the surrounding stem cell niche. However, the specific signals involved are often still poorly understood. This is also true for skin epithelial stem cells. Recently, by transcriptionally profiling of embryonic hair progenitors in mice, Rhee et al. have managed to define how murine hair follicle epithelial stem cells are specified and maintained in an undifferentiated state. These authors have identified Lhx2 as a transcription factor functionally positioned downstream of signals necessary to specify hair follicle stem cells such as p63 or NFkappaB, but upstream of signals like Wnt/beta-catenin, Bmp or Shh that are required to drive activated stem cells via the production of transient amplifying cells into terminal differentiation.

Current insights into the regulation of programmed cell death by NF-kappaB

The nuclear factor-kappaB (NF-kappaB) transcription factors have emerged as major regulators of programmed cell death (PCD) whether via apoptosis or necrosis. In this context, NF-kappaB's activity has important ramifications for normal tissue development, homoeostasis and the physiological functions of various cell systems including the immune, hepatic, epidermal and nervous systems. However, improper regulation of PCD by NF-kappaB can have severe pathologic consequences, ranging from neurodegeneration to cancer, where its activity often precludes effective therapy. Although NF-kappaB generally protects cells by inducing the expression genes encoding antiapoptotic and antioxidizing proteins, its role in apoptosis and necrosis can vary markedly in different cell contexts, and NF-kappaB can sensitize cells to death-inducing stimuli in some instances. This article describes our current knowledge of the role of NF-kappaB in apoptosis and necrosis, and focuses on the many advances since we last reviewed this rapidly evolving topic in Oncogene 3 years ago. There has been substantial progress in understanding NF-kappaB's mode of action in apoptosis and necrosis and the mechanisms that regulate its anti- vs proapoptotic activities. These recent developments shed new light on the role of NF-kappaB in many disease conditions including tumor development, tumor progression and anticancer treatment.