Spiradenocylindroma of the kidney: clinical and genetic findings suggesting a role of somatic mutation of the CYLD1 gene in the oncogenesis of an unusual renal neoplasm

Mechanisms orchestrating the enzymatic activity and cellular functions of deubiquitinases

Deubiquitinases (DUBs) are required for the reverse reaction of ubiquitination and act as major regulators of ubiquitin signaling processes. Emerging evidence suggests that these enzymes are regulated at multiple levels in order to ensure proper and timely substrate targeting and to prevent the adverse consequences of promiscuous deubiquitination. The importance of DUB regulation is highlighted by disease-associated mutations that inhibit or activate DUBs, deregulating their ability to coordinate cellular processes. Here, we describe the diverse mechanisms governing protein stability, enzymatic activity, and function of DUBs. In particular, we outline how DUBs are regulated by their protein domains and interacting partners. Intramolecular interactions can promote protein stability of DUBs, influence their subcellular localization, and/or modulate their enzymatic activity. Remarkably, these intramolecular interactions can induce self-deubiquitination to counteract DUB ubiquitination by cognate E3 ubiquitin ligases. In addition to intramolecular interactions, DUBs can also oligomerize and interact with a wide variety of cellular proteins, thereby forming obligate or facultative complexes that regulate their enzymatic activity and function. The importance of signaling and post-translational modifications in the integrated control of DUB function will also be discussed. While several DUBs are described with respect to the multiple layers of their regulation, the tumor suppressor BAP1 will be outlined as a model enzyme whose localization, stability, enzymatic activity, and substrate recognition are highly orchestrated by interacting partners and post-translational modifications.

Copy number variation of ubiquitin- specific proteases genes in blood leukocytes and colorectal cancer

Ubiquitin-specific proteases (USPs) play important roles in the regulation of many cancer-related biological processes. USPs copy number variation (CNVs) may affect the risk and prognosis of colorectal cancer (CRC). We detected CNVs of USPs genes in 468 matched CRC patients and controls, estimated the associations between the USPs genes CNVs and CRC risk and prognosis and their interactions with environmental factors on CRC risk. Finally, we generated five CRC risk predictive models with different CNVs patterns combining with environmental factors (EF). We identified significant association between CYLD deletion and CRC risk (ORadj = 4.18, 95% CI: 2.03-8.62), significant association between USP9X amplification and CRC risk (ORadj = 2.30, 95% CI: 1.48-3.57), and significant association between USP11 deletion and CRC risk (ORadj = 3.49, 95% CI: 1.49-8.64). There were significant gene-environment and gene-gene interactions on CRC risk. The area under the receiver operating characteristic curve (AUC) of EF + SIG (deletion of CYLD and USP11, amplification of USP9X) model was significantly larger than any other models (AUC = 0.75, 95% CI: 0.74-0.77). We did not identify significant associations between CNVs of the three genes and CRC prognosis. CNVs of CYLD, USP9X, and USP11 are significantly associated with the risk of CRC. Gene-gene and gene-environment interactions might also play an important role in the development of CRC.

Role of Deubiquitinases in Human Cancers: Potential Targeted Therapy

Deubiquitinases (DUBs) are involved in various cellular functions. They deconjugate ubiquitin (UBQ) from ubiquitylated substrates to regulate their activity and stability. Studies on the roles of deubiquitylation have been conducted in various cancers to identify the carcinogenic roles of DUBs. In this review, we evaluate the biological roles of DUBs in cancer, including proliferation, cell cycle control, apoptosis, the DNA damage response, tumor suppression, oncogenesis, and metastasis. This review mainly focuses on the regulation of different downstream effectors and pathways via biochemical regulation and posttranslational modifications. We summarize the relationship between DUBs and human cancers and discuss the potential of DUBs as therapeutic targets for cancer treatment. This review also provides basic knowledge of DUBs in the development of cancers and highlights the importance of DUBs in cancer biology.

miR-181d regulates human dendritic cell maturation through NF-κB pathway

OBJECTIVES

MicroRNAs (miRNAs) are considered as the cellular regulators which post-transcriptionally modulate gene expression in diverse biological processes including cell development and immunity. In this study, we investigated functions of miR-181d in dendritic cells (DCs) maturation, and the underlying mechanisms were also explored.

MATERIALS AND METHODS

Here we did the miRNA screening in human DCs in response to lipopolysaccharides (LPS) by quantitative real-time PCR (qRT-PCR). The expressions of DCs maturation markers were measured after miRNA mimics transfections. The pharmacological inhibitors of signalling pathways were applied to examine miR-181d effect on DCs maturation by Western blot. Luciferase assay and mixed lymphocyte reaction (MLR) were also performed to reveal the target gene of miR-181d and test the viability of T cells treated with miR-181d transfected DCs.

RESULTS

Overexpression of miR-181d per se is sufficient to promote DCs maturation, and up-regulate CD80 and CD83 expressions without LPS. Besides, we showed that miR-181d activated NF-κB pathway and also promoted the expression of pro-inflammatory cytokine IL12 and TNF-α. Inhibition of NF-κB pathway suppressed DCs maturation. Luciferase reporter assay and target gene knockdown assay indicated that miR-181d targets regulator cylindromatosis (CYLD), a primary negative regulator of NF-κB pathway. MLR assay showed that miR-181d-transfected DCs could promote T-cell proliferation than iDCs in vitro.

CONCLUSION

Our study demonstrates that miR-181d is required for DCs maturation through the activation of NF-κB pathway by targeting CYLD.

Action of YM155 on clear cell renal cell carcinoma does not depend on survivin expression levels

The dioxonapthoimidazolium YM155 is a survivin suppressant which has been investigated as an anticancer agent in clinical trials. Here, we investigated its growth inhibitory properties on a panel of immortalized and patient derived renal cell carcinoma (RCC) cell lines which were either deficient in the tumour suppressor von Hippel-Lindau (VHL) protein or possessed a functional copy. Neither the VHL status nor the survivin expression levels of these cell lines influenced their susceptibility to growth inhibition by YM155. Of the various RCC lines, the papillary subtype was more resistant to YM155, suggesting that the therapeutic efficacy of YM155 may be restricted to clear cell subtypes. YM155 was equally potent in cells (RCC786.0) in which survivin expression had been stably silenced or overexpressed, implicating a limited reliance on survivin in the mode of action of YM155. A follow-up in-vitro high throughput RNA microarray identified possible targets of YM155 apart from survivin. Selected genes (ID1, FOXO1, CYLD) that were differentially expressed in YM155-sensitive RCC cells and relevant to RCC pathology were validated with real-time PCR and western immunoblotting analyses. Thus, there is corroboratory evidence that the growth inhibitory activity of YM155 in RCC cell lines is not exclusively mediated by its suppression of survivin. In view of the growing importance of combination therapy in oncology, we showed that a combination of YM155 and sorafenib at ½ x IC50 concentrations was synergistic on RCC786.0 cells. However, when tested intraperitoneally on a murine xenograft model derived from a nephrectomised patient with clear cell RCC, a combination of suboptimal doses of both drugs failed to arrest tumour progression. The absence of synergy in vivo highlighted the need to further optimize the dosing schedules of YM155 and sorafenib, as well as their routes of administration. It also implied that the expression of other oncogenic proteins which YM155 may target is either low or absent in this clear cell RCC.

Epidermal CYLD inactivation sensitizes mice to the development of sebaceous and basaloid skin tumors

The deubiquitinase-encoding gene Cyld displays a dominant genetic linkage to a wide spectrum of skin-appendage tumors, which could be collectively designated as CYLD mutant-syndrome (CYLD^m-syndrome). Despite recent advances, little is understood about the molecular mechanisms responsible for this painful and difficult-to-treat skin disease. Here, we generated a conditional mouse model with epidermis-targeted expression of a catalytically deficient CYLD^m through K14-Cre-mediated deletion of exon 9 (hereafter refer to Cyld^EΔ9/Δ9 ). Cyld^EΔ9/Δ9 mice were born alive but developed hair and sebaceous gland abnormalities and dental defects at 100% and 60% penetrance, respectively. Upon topical challenge with DMBA/TPA, these animals primarily developed sebaceous and basaloid tumors resembling human CYLD^m-syndrome as opposed to papilloma, which is most commonly induced in WT mice by this treatment. Molecular analysis revealed that TRAF6-K63-Ubiquitination (K63-Ub), c-Myc-K63-Ub, and phospho-c-Myc (S62) were markedly elevated in Cyld^EΔ9/Δ9 skin. Topical treatment with a pharmacological c-Myc inhibitor induced sebaceous and basal cell apoptosis in Cyld^EΔ9/Δ9 skin. Consistently, c-Myc activation was readily detected in human cylindroma and sebaceous adenoma. Taken together, our findings demonstrate that Cyld^EΔ9/Δ9 mice represent a disease-relevant animal model and identify TRAF6 and c-Myc as potential therapeutic targets for CYLD^m-syndrome.

Ibrutinib downregulates a subset of miRNA leading to upregulation of tumor suppressors and inhibition of cell proliferation in chronic lymphocytic leukemia

The lymph node (LN) is the site of chronic lymphocytic leukemia (CLL) cell activation and proliferation. Aberrant microRNA (miRNA) expression has been shown to have a role in CLL pathogenesis; however, a comparison of miRNA expression between CLL cells in the LN and the peripheral blood (PB) has previously not been reported. On the basis of the analysis of 17 paired LN and PB samples from CLL patients, we identify a panel of miRNAs that are increased in LN CLL cells correlating with an activation phenotype. When evaluated in CLL cells from 38 patients pre and post treatment with ibrutinib, a subset of these miRNAs (miR-22, miR-34a, miR-146b and miR-181b) was significantly decreased in response to ibrutinib. A concomitant increase in putative miRNA target transcripts (ARID1B, ARID2, ATM, CYLD, FOXP1, HDAC1, IBTK, PTEN and SMAD4) was also observed. Functional studies confirmed targets of ibrutinib-responsive miRNAs to include messenger RNA transcripts of multiple tumor suppressors. Knockdown of endogenous miR-34a and miR146b resulted in increased transcription of tumor suppressors and inhibition of cell proliferation. These findings demonstrate that ibrutinib downregulates the expression of a subset of miRNAs related to B-cell activation leading to increased expression of miRNA targets including tumor suppressors and a reduction in cell proliferation.

UV Irradiation Triggers Cylindromatosis Translocation, Modification, and Degradation in a Proteasome-Independent Manner

The tumor suppressor, cylindromatosis (CYLD), is a negative regulator of NF-κB signaling by removing lysine 63-linked ubiquitin chains from multiple NF-κB signaling components, including TRAF2, TRAF6, and NEMO. How CYLD itself is regulated, however, remains yet to be characterized. In this study, we present the first evidence that UV irradiation is able to induce CYLD translocation from the cytoplasm to microtubules and that the cytoskeleton-associated CYLD is subject to posttranslational modification and degradation in a proteasome-independent manner. By immunostaining, we found that CYLD displayed microtubule-like filament localization under ultraviolet (UV) irradiation. Further studies revealed that the cytoskeleton-associated CYLD underwent posttranslational modification, which in turn contributed to CYLD degradation in an unknown manner, distinct from proteasome-mediated degradation under normal conditions. Collectively, our data suggest that UV-induced CYLD degradation might serve as an underlying mechanism for UV-induced NF-κB pathway activation.

A case of Brooke-Spiegler syndrome with a novel mutation in the CYLD gene in a patient with aggressive non-Hodgkin's lymphoma

PURPOSE

Brooke-Spiegler syndrome (BSS, familial cylindromatosis) is a rare hereditary disease characterized by multiple tumors of the skin appendages predominantly located in the head and neck region, such as cylindromas, trichoepitheliomas, or spiradenomas. It is caused by an autosomal dominant mutation in the CYLD gene, mapped on chromosome 16q12-13. Association with secondary malignant neoplasms has been reported. Until now 51 different mutations in 73 families have been reported; 41 % of them constitute frameshift mutations, resulting in an interruption of the expression of the gene product CYLD. CYLD is a deubiquitinating enzyme and plays an important role in (NF)-κB pathway signaling, a central pathway for apoptosis regulation. Mutation-induced loss of function leads to constitutive activation of NF-κB.

METHODS

Here, we report the case of a 48-year-old female patient diagnosed with an abdominal aggressive non-Hodgkin's lymphoma. The patient presented with multiple cylindromas of the capillitium. The patient's mother also has a mild form of late-onset cylindromas. Due to the typical clinical features indicating BSS, genotyping from peripheral blood was performed. A c.2465insAACA mutation in exon 17 of the CYLD gene, leading to a frameshift, was detected in the patient and in the patient's mother.

RESULTS/CONCLUSIONS

This is the first description of this hereditary mutation in exon 17 of the CYLD gene. There have been several reports on patients with CYLD mutations and different types of malignancies. However, a coincidence with aggressive non-Hodgkin's lymphoma has not been reported yet.

Breast Neoplasms with Dermal Analogue Differentiation (Mammary Cylindroma): Report of 3 Cases and a Proposal for a New Terminology

Salivary gland-like and dermal analogue tumours of the breast are rare lesions that can be diagnostically challenging for pathologists. Data on the clinical behaviour and molecular characterisation of these mammary tumours are limited and their designation is mainly based on similar salivary gland or skin lesions. In this study, we present three cylindromatous breast tumours. These lesions were located within the breast, had ill-defined margins and were composed of nests containing a dual population of cytologically bland cells, surrounded at least partially by basement membrane-like material. The lack of cytological atypia and absence of mitoses led to the diagnosis of benign mammary cylindroma in 1 case. The expression of oestrogen receptor, focal absence of basement membrane material and the focal infiltrative nature together with patchy absence of peripheral basement membrane supported the diagnosis of malignancy in the other 2 cases. We discuss the morphological criteria, immunohistochemical profile and diagnostic pitfalls of these tumours. We also review the literature including previously reported cases of mammary cylindroma and differential diagnoses to be considered before making a diagnosis. We propose the term 'mammary tumours with cylindromatous differentiation', implying their uncertain malignant nature, and propose management strategies.

Functional nature of a novel mutant CYLD observed in pediatric lymphoblastic B-cell leukemia

The Deubiquitinating enzyme, Cylindromatosis (CYLD), has been established as a crucial regulator of B-cells. The present study was addressed to identify the nature of CYLD-dependent RNomics in patients of pediatric age group with B-ALL. The study revealed the presence of a novel mutant CYLD of 55 kDa in these patients. The mutant CYLD displayed its ability to restrict the cells in G2 phase of cell cycle, down-regulate PLK-1 and block the nuclear translocation of BCL3. Based upon these results, we propose that this mutant CYLD has the capacity to act as a differential marker characteristic of B-cell lymphoblastic leukemia. Pediatr Blood Cancer 2015;62:1066-1069. © 2015 Wiley Periodicals, Inc.

A novel CYLD germline mutation in Brooke-Spiegler syndrome

BACKGROUND

Brooke-Spiegler syndrome (BSS) is a rare, inherited, autosomal dominant disorder characterized by the development of multiple adnexal neoplasms including spiradenomas, cylindromas, trichoepitheliomas and major and minor salivary glands neoplasms. This syndrome encompasses a wide variability of clinical phenotypes depending on the variable number of tumours present in the given patient.

OBJECTIVE

Somatic mutations in adjunct to CYLD germline mutations may play a central role in the development of the tumour phenotype and in the genotype-phenotype correlations.

METHODS

Blood sample and paraffin embedded tissue biopsied from three cylindromas, one trichoepithelioma and one spiradenomas were collected after obtaining informed consent from our patient and genomic DNA was isolated.

RESULTS

We found out a novel germline mutation in the CYLD gene in exon 15 that resulted in the deletion of one nucleotide. This gives rise to a premature translational termination codon at amino acid position 693 prior to four Cys-X-X-Cys pairs and one of the two catalytic domains of ubiquitin carboxy-terminal hydrolases. In only one cylindroma we detected the same germline mutation (c.2070delT/p.F690FfsX3) in addition to two somatic events (I645V and R936X). The presence of this unique mutation could be linked to the peculiar phenotype of our patient who presented an attenuated form of BSS, an autosomal dominant inheritance with low penetrance and no additional visceral tumours.

CONCLUSIONS

The overall phenotype of our patient may support the hypothesis that somatic mutations in adjunct to CYLD germline mutations may play a central role in the development of the tumour phenotype and in the genotype-phenotype correlations.

Brooke–Spiegler syndrome tumor spectrum beyond the skin: a patient carrying germline R936X CYLD mutation and a somatic CYLD mutation in Brenner tumor

ABSTRACT: 

Brooke–Spiegler syndrome is a hereditary disorder characterized by a predisposition to the development of skin appendage neoplasms and the major and minor salivary glands neoplasms. The role of the CYLD mutation in visceral neoplasms is still unclear, except for the parathyroid tumor. We report the case of a 46-year-old patient with multiple cylindromas and trichoepitheliomas, a Brenner tumor of the ovary and a negative family history for Brooke–Spiegler phenotype. Genetic analysis revealed R936X germline mutation in the proband, but not in the patient’s relatives. The same somatic mutation was found in the Brenner tumor, together with a novel missense CYLD mutation (D889N), which has never been reported in the literature. A founder effect for R936X has been hypothesized due to its high prevalence; surprisingly, in our case, this mutation seems to be recognized as a de novo mutation. Future studies involving a greater number of cases, through the clinical analysis of the familial tumor spectrum and the associated molecular pathways, are necessary to understand possible genotype/phenotype correlations and the underlying molecular mechanisms.

Clinical significance of down-regulated cylindromatosis gene in chronic lymphocytic leukemia

Loss of cylindromatosis gene (CYLD) expression has been observed in various cancers, including chronic lymphocytic leukemia (CLL). As a deubiquitination enzyme, CYLD regulates the proliferation, development and activation of lymphoid cells. Here we determined the CYLD mRNA expression by quantitative polymerase chain reaction (PCR) in 125 patients with CLL. CYLD was considerably down-regulated in CLL cells compared to normal B cells. Low CYLD expression was associated with unmutated status of the immunoglobulin heavy-chain variable-region (IGHV) gene (p = 0.0018) and CD38 positivity (p = 0.0499). Patients with high CYLD expression showed a trend toward improved overall survival (OS) (10-year OS: CYLD high: 94.74%, CYLD low: 52.71%; p = 0.0534). For patients with mutated IGHV gene, high CYLD was also associated with better OS (10-year OS: CYLD high: 100%, CYLD low: 66.67%; p = 0.0547). In conclusion, low CYLD expression identifies a subgroup of patients with CLL with inferior outcome, indicating the role of CYLD as a tumor suppressor in the pathogenesis of CLL.

Involvement of microRNA-181b in the gemcitabine resistance of pancreatic cancer cells

BACKGROUND/OBJECTIVES

MicroRNAs (miRs) have been shown to regulate the sensitivity to several chemotherapeutic agents in various types of cancers. MiR-181b is one of such regulators, yet its importance in pancreatic cancer is not determined so far. The aim of this study was to investigate the relationship between microRNA (miR)-181b expression and gemcitabine resistance in pancreatic cancer cells.

METHODS

The effects of overexpression or knockdown of miR-181b on four pancreatic cancer cell lines exposed to gemcitabine were examined. The induction of apoptosis and the changes of the cylindromatosis (CYLD) protein were examined. Furthermore, the effect of small interference RNA for CYLD (siCYLD) on cell viability and the relationship between CYLD and nuclear factor kappa B (NF-κB) were investigated.

RESULTS

The expression of miR-181b was higher in BxPC3, Panc1 and PSN1 cells compared with MiaPaCa2 cells. Pre-miR-181b transfection into MiaPaCa2 cells increased their gemcitabine resistance, whereas anti-miR-181b transfection into the other pancreatic cancer cell lines reduced their resistance to gemcitabine and led to the induction of apoptosis. The protein levels of CYLD were increased by anti-miR-181b in Panc1 and PSN1 cells. Inhibition of CYLD increased the NF-κB activity and gemcitabine resistance in Panc1 and PSN1 cells.

CONCLUSIONS

The present study demonstrated that miR-181b was associated with the resistance of pancreatic cancer cells to gemcitabine, and verified that miR-181b enhances the activity of NF-κB by inhibiting CYLD, leading to the resistance to gemcitabine. Our results suggest that miR-181b is a potential target for decreasing gemcitabine resistance.

CYLD downregulation is correlated with tumor development in patients with hepatocellular carcinoma

The cylindromatosis (CYLD) gene is involved in tumor progression by acting as a negative regulator of nuclear factor-κB (NF-κB). However, the clinical significance of CYLD in patients with hepatocellular carcinoma (HCC) remains unclear. To demonstrate the clinical significance of CYLD expression, we analyzed CYLD gene expression in 124 paired HCC and non-tumor tissues using quantitative reverse transcription-polymerase chain reaction (qRT-PCR). CYLD gene expression was detected in the patients and the cut-off value was determined by the median value of tumor-to-non-tumor (T/N) ratio. qRT-PCR analysis showed that a low CYLD expression was associated with a high serum α-fetoprotein (AFP) value. Patients in the low CYLD expression group exhibited poorer overall survival compared to those in the high expression group (P=0.0406). Protein expression of CYLD was also investigated in 70 patients with HCC using immunohistochemistry. The findings showed that CYLD protein expression in tumor tissue was associated with CYLD gene expression (P=0.031). The findings of the present study suggest that CYLD is clinically associated with tumor development in HCC patients.

CYLD inhibits melanoma growth and progression through suppression of the JNK/AP-1 and β1-integrin signaling pathways

The molecular mechanisms mediating CYLD tumor suppressor function appear to be manifold. Here, we demonstrated that, in contrast to the increased levels of pJNK, CYLD was decreased in a majority of melanoma cell lines and tissues examined. Exogenous expression of CYLD but not its catalytically deficient mutant markedly inhibited melanoma cell proliferation and migration in vitro and subcutaneous tumor growth in vivo. In addition, the melanoma cells expressing exogenous CYLD were unable to form pulmonary tumor nodules following tail-vein injection. At the molecular level, CYLD decreased β1-integrin and inhibited pJNK induction by TNFα or cell-attachment to collagen IV. Moreover, CYLD induced an array of other molecular changes associated with modulation of the ‘malignant’ phenotype, including a decreased expression of cyclin D1, N-cadherin and nuclear Bcl3, and an increased expression of p53 and E-cadherin. Most interestingly, co-expression of the constitutively active MKK7 or c-Jun mutants with CYLD prevented the above molecular changes, and fully restored melanoma growth and metastatic potential in vivo. Our findings demonstrate that JNK/AP-1 signaling pathway underlies the melanoma growth and metastasis that is associated with CYLD loss-of-function. Thus, restoration of CYLD and inhibition of JNK and β1-integrin function represent potential therapeutic strategies for treatment of malignant melanoma.

Ubiquitylation in immune disorders and cancer: from molecular mechanisms to therapeutic implications

Conjugation of ubiquitin to proteins (ubiquitylation) has emerged to be one of the most crucial post-translational modifications controlling virtually all cellular processes. What was once regarded as a mere signal for protein degradation has turned out to be a major regulator of molecular signalling networks. Deregulation of ubiquitin signalling is closely associated with various human pathologies. Here, we summarize the current knowledge of ubiquitin signalling in immune deficiencies and cancer as well as the available therapeutic strategies targeting the ubiquitin system in combating these pathogenic conditions.

A clinicopathologic and molecular biologic study of patients presenting with few adnexal tumors (two to four) from the morphological spectrum of Brooke-Spiegler syndrome

We report 11 individuals, each presenting with few (2-4) adnexal neoplasms histologically confirmed as belonging to the spectrum of lesions typical for Brooke-Spiegler syndrome (BSS) and/or multiple familial trichoepitheliomas. These include spiradenoma, cylindroma, spiradenocylindroma, and trichoblastoma variants. Our objective was to clarify whether this is merely a sporadic, albeit unusual, occurrence of multiple neoplasms in these patients or whether they are related to BSS and its phenotypic variant, multiple familial trichoepithelioma. Six patients presented with 2 neoplasms, 4 had 3 lesions and the last had 4 lesions. In none was there any family history of similar lesions. The 28 neoplasms consisted of 7 spiradenomas, 6 cylindromas, 5 spiradenocylindromas, and 11 trichoblastomas (6 trichoepitheliomas and 5 with mixed patterns). In 1 patient only with 2 spiradenomas, both tumors harbored identical CYLD sequence alterations (c.1112C>A/S371X) in the CYLD gene and both showed loss of heterozygosity on chromosome 16q. The remaining cases yielded neither germ line nor somatic alterations in CYLD. It is concluded that the presentation with few (2-4) cylindromas, spiradenomas, spiradenocylindromas, and trichoepitheliomas is a sporadic occurrence, and that these patients do not have any relationship to BSS.

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.

CYLD inhibits tumorigenesis and metastasis by blocking JNK/AP1 signaling at multiple levels

CYLD has been recognized as a tumor suppressor due to its dominant genetic linkage to multiple types of epidermal tumors and a range of other cancers. The molecular mechanisms governing CYLD control of skin cancer are still unclear. Here, we showed that K14-driven epidermal expression of a patient-relevant and catalytically deficient CYLD truncated mutant (CYLD(m)) sensitized mice to skin tumor development in response to 7,12-dimethylbenz[α]anthracene (DMBA)/(12-O-tetradecanoylphorbol-13-acetate) TPA challenge. Tumors developed on transgenic mice were prone to malignant progression and lymph node metastasis and displayed increased activation of c-Jun-NH2-kinase (JNK) and the downstream c-Jun and c-Fos proteins. Most importantly, topical application of a pharmacologic JNK inhibitor significantly reduced tumor development and abolished metastasis in the transgenic mice. Further in line with these animal data, exogenous expression of CYLD(m) in A431, a human squamous cell carcinoma (SCC) cell line, markedly enhanced cell growth, migration, and subcutaneous tumor growth in an AP1-depdendent manner. In contrast, expression of the wild-type CYLD inhibited SCC tumorigenesis and AP1 function. Most importantly, CYLD(m) not only increased JNK activation but also induced an upregulation of K63 ubiquitination on both c-Jun and c-Fos, leading to sustained AP1 activation. Our findings uncovered c-Jun and c-Fos as novel CYLD targets and underscore that CYLD controls epidermal tumorigenesis through blocking the JNK/AP1 signaling pathway at multiple levels.

An inactivating CYLD mutation promotes skin tumor progression by conferring enhanced proliferative, survival and angiogenic properties to epidermal cancer cells

In this study, we demonstrate that the expression in tumorigenic epidermal cells of a catalytically inactive form of CYLD (CYLD(C/S)) that mimics the identified mutations of cyld in human tumors and competes with the endogenous CYLD results in enhanced cell proliferation and inhibition of apoptosis; it also stimulates cell migration and induces the expression of angiogenic factors, including vascular endothelial growth factor-A. Altogether, these characteristics indicate an increased oncogenicity of the tumorigenic epidermal CYLD(C/S) mutant cells in vitro. Moreover, we show the increase in malignancy of epidermal squamous cell carcinomas that express the CYLD(C/S) transgene in an in vivo xenograft model. Tumors carrying the mutated CYLD(C/S) exhibit a fast growth, are poorly differentiated and present a robust angiogenesis. CYLD(C/S) tumors are also characterized by their elevated proliferation rate and decreased apoptosis. In contrast with previous studies showing the development of benign tumors by mutations in the CYLD gene, here we provide evidence that the occurrence of mutations in the CYLD gene in tumorigenic epidermal cells (carrying previous mutations) increases the aggressiveness of carcinomas, mainly through enhancement of the expression of angiogenic factors, having therefore a key role in epidermal cancer malignancy.

CYLD: a tumor suppressor deubiquitinase regulating NF-kappaB activation and diverse biological processes

Protein ubiquitination is a reversible reaction, in which the ubiquitin chains are deconjugated by a family of deubiquitinases (DUBs). The presence of a large number of DUBs suggests that they likely possess certain levels of substrate selectivity and functional specificity. Indeed, recent studies show that a tumor suppressor DUB, cylindromatosis (CYLD), has a predominant role in the regulation of NF-kappaB, a transcription factor that promotes cell survival and oncogenesis. NF-kappaB activation involves attachment of K63-linked ubiquitin chains to its upstream signaling factors, which is thought to facilitate protein-protein interactions in the assembly of signaling complexes. By deconjugating these K63-linked ubiquitin chains, CYLD negatively regulates NF-kappaB activation, which may contribute to its tumor suppressor function. CYLD also regulates diverse physiological processes, ranging from immune response and inflammation to cell cycle progression, spermatogenesis, and osteoclastogenesis. Interestingly, CYLD itself is subject to different mechanisms of regulation.

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.

Deubiquitinating enzymes as novel anticancer targets

Tagging proteins with mono- or poly-ubiquitin is now recognized as a multifaceted and universal means of regulating cell growth and physiology. It does so by controlling the cellular lifetime of nearly all eukaryotic proteins and the cellular localization of many critical proteins. Enzymes of the ubiquitin pathway add (ligases) or remove (deubiquitinases [DUBs]) ubiquitin tags to or from their target proteins in a selective fashion. Similarly to the kinases and their corresponding phosphatases, ubiquitin ligases and DUBs have become actively studied molecular oncology targets for drug discovery. Approximately 79 functional DUBs exist in the human proteome, suggesting that selective intervention is a reasonable therapeutic objective, with the goal of downregulating or ablating oncogene products or, alternatively, upregulating or sparing tumor suppressors. In the following review, this fascinating class of regulatory enzymes will be described, and specific examples of DUBs that are viable targets for anticancer therapy will be considered.

Ubiquitin and ubiquitin-like proteins in cancer pathogenesis

Ubiquitin and ubiquitin-like proteins (Ubls) are signalling messengers that control many cellular functions, such as cell proliferation, apoptosis, the cell cycle and DNA repair. It is becoming apparent that the deregulation of ubiquitin pathways results in the development of human diseases, including many types of tumours. Here we summarize the common principles and specific features of ubiquitin and Ubls in the regulation of cancer-relevant pathways, and discuss new strategies to target ubiquitin signalling in drug discovery.

Low-grade Adnexal Carcinoma of the Skin With Multidirectional (Glandular, Trichoblastomatous, Spiradenocylindromatous) Differentiation

The conjoint occurrence of follicular, sebaceous, or apocrine differentiations in a cutaneous adnexal neoplasm is a known event, more often encountered in benign neoplasms, whereas reports of cutaneous malignant adnexal tumors with bilineage or trilineage differentiation are few. A new case of a cutaneous malignant adnexal neoplasm with multidirectional differentiation is reported here. A 57-year-old woman presented with a long-standing, slowly growing, asymptomatic solitary tumor the size of a large nut in the coccygeal area, which was surgically excised. Ten years after the surgery, there was no evidence of recurrence or metastasis. Microscopically, the neoplasm was located in the dermis with focal extension into the subcutis. It was asymmetric, horizontally oriented, and mostly composed of small nodules that varied in shape from round and oval aggregations to elongated strands and irregular islands; the nodules were either clustered, formed a jigsaw puzzle-like pattern or were dispersed. The nodules were composed of small basaloid cells sometimes intermixed with larger cells with ample cytoplasm forming glandular structures. Rare nodules resembled elements seen in a spiradenoma by containing scattered lymphocytes and globules of hyalinized eosinophilic basal membrane material. The stroma was paucicellular, but focally it resembled that seen in perifollicular mesenchyme. Mitotic figures, including abnormal ones, were infrequent, but mild nuclear pleomorphism, nuclear crowding, and individual cell necrosis were easily appreciable in both small basaloid cells and cells with clear cytoplasm. Perineural invasion was apparent. We classified this tumor as a well-differentiated adnexal carcinoma demonstrating combined follicular and apocrine differentiation. It differs from previously published cases of malignant adnexal tumors with multidirectional differentiation and further exemplifies the spectrum of diversity encountered in malignant proliferations with differentiation toward the folliculosebaceous-apocrine unit.

Cyld inhibits tumor cell proliferation by blocking Bcl-3-dependent NF-kappaB signaling

Mutations in the CYLD gene cause tumors of hair-follicle keratinocytes. The CYLD gene encodes a deubiquitinase that removes lysine 63-linked ubiquitin chains from TRAF2 and inhibits p65/p50 NF-kappaB activation. Here we show that mice lacking Cyld are highly susceptible to chemically induced skin tumors. Cyld-/- tumors and keratinocytes treated with 12-O-tetradecanoylphorbol-13 acetate (TPA) or UV light are hyperproliferative and have elevated cyclin D1 levels. The cyclin D1 elevation is caused not by increased p65/p50 action but rather by increased nuclear activity of Bcl-3-associated NF-kappaB p50 and p52. In Cyld+/+ keratinocytes, TPA or UV light triggers the translocation of Cyld from the cytoplasm to the perinuclear region, where Cyld binds and deubiquitinates Bcl-3, thereby preventing nuclear accumulation of Bcl-3 and p50/Bcl-3- or p52/Bcl-3-dependent proliferation. These data indicate that, depending on the external signals, Cyld can negatively regulate different NF-kappaB pathways; inactivation of TRAF2 controls survival and inflammation, while inhibition of Bcl-3 controls proliferation and tumor growth.

Case of the Brooke-Spiegler syndrome

A 36-year-old woman presented with lesions on her scalp, face and trunk. Histopathological examination of these lesions demonstrated facial trichoepithelioma, and scalp cylindroma. A solitary nodule on the trunk had features of cylindroma, spiradenoma and trichoepithelioma, a previously unreported occurrence. Based on the clinical picture, the diagnosis of Brooke-Spiegler syndrome was established. Genetic studies confirmed the diagnosis, demonstrating a splice site mutation, designated 1518+2T>C, on the CYLD1 gene of chromosome 16q12-q13.

Cylindroma of the Breast of Skin Adnexal Type

Four cases of solitary cylindroma of the breast of skin adnexal type are described. The tumors were morphologically and immunophenotypically identical to their dermal counterparts. They arose in close proximity to the nipple, such as the retroareolar area of the breast and in intimate association with the lactiferous ducts, suggesting an origin from the latter structures. One case occurred in a woman with hereditary multiple cylindromatosis (Brooke-Spiegler syndrome). This is the second reported case of this hereditary syndrome with extracutaneous manifestations and the first case in which the breast is involved.