Mutations in the mevalonate pathway genes in Chinese patients with porokeratosis.

BACKGROUND: Porokeratosis (PK, MIM 175800) is a chronic autosomal dominant cutaneous keratinization disorder, which has a wide variety of clinical manifestations. OBJECTIVES: We analysed the molecular basis of 10 families and 12 sporadic cases with different subtypes of porokeratosis in the Chinese population. METHODS: Genomic DNA was extracted from peripheral blood samples. Mutation screening was performed by direct sequencing of exons and flanking intron-exon boundaries for the entire coding region of four mevalonate pathway genes and SLC17A9 gene. RESULTS: We detected three novel mutations and seven previously described mutations by direct sequence analysis of the PCR products. Mutations p.Phe249Ser and p.Asn292Ser in mevalonate decarboxylase (MVD) were the most common mutations in this PK cohort; their presence was 27.3% and 13.6% respectively. CONCLUSIONS: This study extended the mutation spectrum of PK in the Chinese Han population and provided further evidence for the genetic basis of PK. We first identified MVD simultaneously responsible for porokeratosis palmaris et plantaris disseminate development and confirmed the genotype-phenotype correlations.

Cornoid lamellation revisited: apropos of porokeratosis with emphasis on unusual clinicopathological variants.

Porokeratosis is a family of several disorders characterized histologically by the presence of cornoid lamellae. The presence of cornoid lamellae represents an abnormal form of keratinization, which unifies all types of porokeratosis. A significant variation in lesional morphology can result from peculiarities involving the cornoid lamellae and changes related to epidermal hyperplasia and dermal inflammation. This diversity has led to the recognition of several unusual clinicopathological variants of porokeratosis in recent years. Cornoid lamellation, however, is not pathognomonic of porokeratosis and can be seen in some inflammatory and inherited cutaneous disorders and also as an incidental finding. Some of these conditions can be confused with an atypical presentation of porokeratosis and vice versa. An awareness of the broad morphological spectrum of porokeratosis is crucial to avoid missing the diagnosis when appearances are far from typical. This issue is critical in patient management given the potential premalignant nature of porokeratosis.

Haploinsufficiency for AAGAB causes clinically heterogeneous forms of punctate palmoplantar keratoderma.

Palmoplantar keratodermas (PPKs) are a group of disorders that are diagnostically and therapeutically problematic in dermatogenetics. Punctate PPKs are characterized by circumscribed hyperkeratotic lesions on the palms and soles with considerable heterogeneity. In 18 families with autosomal dominant punctate PPK, we report heterozygous loss-of-function mutations in AAGAB, encoding α- and γ-adaptin-binding protein p34, located at a previously linked locus at 15q22. α- and γ-adaptin-binding protein p34, a cytosolic protein with a Rab-like GTPase domain, was shown to bind both clathrin adaptor protein complexes, indicating a role in membrane trafficking. Ultrastructurally, lesional epidermis showed abnormalities in intracellular vesicle biology. Immunohistochemistry showed hyperproliferation within the punctate lesions. Knockdown of AAGAB in keratinocytes led to increased cell division, which was linked to greatly elevated epidermal growth factor receptor (EGFR) protein expression and tyrosine phosphorylation. We hypothesize that p34 deficiency may impair endocytic recycling of growth factor receptors such as EGFR, leading to increased signaling and cellular proliferation.

Altered gene expression in squamous cell carcinoma arising from congenital unilateral linear porokeratosis.

Congenital unilateral linear porokeratosis (CULP) is a rare disorder of keratinization that shares clinical and molecular similarities with psoriasis. It also has an increased risk for malignant transformation to cutaneous squamous cell carcinoma (SCC). We investigated the expression of psoriasin, human beta-defensin-2, cathelicidin antimicrobial peptide/LL-37, e-cadherin, involucrin, p16(INK4a) , p53, cyclin D1 and microchromosome maintenance protein 7 in healthy skin and in lesions of psoriasis, CULP and SCC from the same patient. p16(INK4a) was overexpressed in CULP but not in the subsequent SCC. Psoriasin was overexpressed in psoriasis, CULP and SCC compared with healthy skin. Speculatively, p16(INK4a) and psoriasin could be involved in the pathogenesis of CULP. Moreover, psoriasin may play a role in the malignant transformation of CULP to SCC.

Reassessment of microarray expression data of porokeratosis by quantitative real-time polymerase chain reaction.

BACKGROUND: Porokeratosis (PK) is a heterogeneous group of keratinization disorders that exhibit similarities with psoriasis at both the clinical and molecular levels. METHODS: The transcript levels of keratin (KRT) 6A, 16, 17, S100A7, A8, A9, p53 and three candidate genes (i.e. SART3, SSH1 and ARPC3) were reassessed in pairwise lesional and uninvolved skin from nine patients with PK by real-time quantitative polymerase chain reaction (RTQ-PCR). RESULTS: The results of RTQ-PCR confirmed that KRT6A, 16, S100A7, A8 and A9 (p = 0.008) were mostly up-regulated in the lesional skin when compared with uninvolved skin. Different from the microarray data, there was no significant difference observed in KRT17 expression patterns between lesional and normal-appearing skin (p = 0.066). No statistical difference was observed in p53 and three candidate genes' expression patterns between lesional and uninvolved skin. CONCLUSIONS: In the present study, 9 of the 10 gene expression measured by RTQ-PCR in PK were statistically comparable to microarray data. KRT6A was identified as specific biomarker for porokeratotic keratinocytes, as it was the most significantly up-regulated gene in the nine patient samples.

Gene expression profiling of porokeratosis.

BACKGROUND: Porokeratosis (PK) represents a heterogeneous group of disorders of keratinization and has a wide variety of clinical manifestations. PK may exhibit similarities with psoriasis at both clinical and molecular levels. The genetic basis and pathogenesis for PK remain elusive. METHODS: We studied the transcriptional profiles of three pairwise lesional and uninvolved skin biopsies from patients with different subtypes of PK using the Illumina BeadArray platform. RESULTS: A total of 37 upregulated genes were identified in our study, including wound-induced keratins, S100 calcium-binding protein genes involved in epidermal differentiation, as well as genes involved in mediating intercellular communication and the immune response. To our knowledge, this is the first study that characterizes the immune profile of PK lesions. CONCLUSIONS: Here, we report that keratinocytes (KCs)-harboring lesions have activated and overexpressed wound-induced keratin genes, which appear to be coregulated with other genes involved in mediating epidermal differentiation, intercellular communication and immunity. This study, from the perspective of gene profiling, supports that gene misregulation in PK mimics that of psoriasis. Our data indicate that the genes implicated in the T-cell-mediated immune response pathway and activation of KCs play a key role in the pathogenesis of PK.

Immunohistochemical study of cyclooxygenase-2 and p53 expression in skin tumors.

Overexpression of cyclooxygenase-2 (COX-2) has been demonstrated in various cancers, including experimentally promoted tumors, gastrointestinal cancers, breast tumors and skin tumors. The mechanism that controls COX-2 expression is not yet clear. Currently, it is reported that COX-2 expression is frequently associated with mutated p53 genes. The goal of this study was to evaluate the expression patterns of COX-2 and p53 in several skin tumors and their correlation. An immunohistochemical method was used to investigate the expression of COX-2 and p53 proteins on formalin-fixed, paraffin-embedded tissue specimens of squamous cell carcinomas (SCC), basal cell carcinomas (BCC), Bowen's disease (BD), actinic keratosis (AK) and porokeratosis. The expression of COX-2 increased in 50% (5/10) of SCC, 80% (8/10) of BCC, 40% (4/10) of BD, 50% (5/10) of AK, and 20% (2/10) of porokeratosis cases. The expression of p53 increased in 90% (9/10) of SCC, 70% (7/10) of BCC, 70% (7/10) of BD, 50% (5/10) of AK, and 40% (4/10) of porokeratosis cases. COX-2 positivity rates of the p53-positive skin tumors were 56%, 100%, 57%, 80% and 25% in SCC, BCC, BD, AK and porokeratosis, respectively. However, the correlation between p53 and COX-2 expression in skin tumors was not statistically significant (P > 0.05). Our results indicate that skin COX-2 and p53 may play roles in skin tumors, but that there is no apparent correlation between the two markers.

Gene expression profiling of porokeratosis demonstrates similarities with psoriasis.

BACKGROUND: Porokeratosis (PK) is a clinically heterogeneous entity associated with sharply demarcated, annular, or serpiginous lesions with a hyperkeratotic ridge. This disorder is associated with aberrant keratinocyte differentiation that histologically manifests as a stack of parakeratin termed the cornoid lamella; this structure represents the peripheral hyperkeratotic ridge of clinical lesions. Histologically, the keratinocytes forming the cornoid lamella demonstrate an altered differentiation program. However, the molecular basis of PK remains incompletely understood. METHODS: As a first step in characterizing PK at the molecular level, gene expression profiling was performed on a cornoid lamella isolated from a large, Mibelli-type porokeratotic lesion. As a control, gene expression profiling of peripheral uninvolved epidermis was also performed. The gene expression profile of cornoid lamellar keratinocytes was compared with similar profiles obtained from a psoriatic plaque and cutaneous squamous cell carcinoma. RESULTS: Our study demonstrates a striking similarity between the gene expression profiles of PK and psoriasis. In addition, novel markers of the porokeratotic keratinocytes were identified, including keratin 16, S-100 A8 and A9, and connexin 26. CONCLUSIONS: This study supports the hypothesis that PK is a disorder of hyperproliferative keratinocytes exhibiting similarity at the molecular level to psoriasis. Consequently, some therapeutic modalities efficacious for psoriasis may be of benefit in PK.

p53 alterations in porokeratosis.

BACKGROUND: Porokeratosis (PK) is a group of cutaneous entities characterized by disordered epidermal keratinization and by a predisposition to develop malignant transformation. The molecular mechanism of this carcinogenesis remains unclear, but p53 has been proposed as a mediator of this process. p53 overexpression, detected by immunohistochemistry, has frequently been reported in PK, and p53 mutations are direct results of ultraviolet (UV) skin exposure and are directly involved in most common skin cancers. METHODS: Eleven cases of Mibelli-type PK, one of them associated with a squamous cell carcinoma, were reviewed. Formalin-fixed, paraffin-embedded archival tissue from these cases was immunostained for p53 and used for DNA extraction for the analysis of p53 mutations by polymerase chain reaction and single-strand conformation polymorphism. RESULTS: Increased p53 expression was confirmed in all cases. Most of them showed a discontinuous labeling, often stronger at the base of the cornoid lamella. No relation with sun exposure was observed. Finally, no p53 mutations were found at the gene levels more frequently damaged in human cancers called "hot spots". CONCLUSIONS: p53 alterations can be involved in the pathogenesis of the PK and the carcinogenesis arising in some of the lesions. Since p53 gene inactivation in human cancer is related to mutation and/or loss, the absence of genetic damage could indicate that p53 alterations are only at the protein level, leading to an abnormal cell-cycle control. UV exposure does not seem to play a main role in the process.

Premature apoptosis of keratinocytes and the dysregulation of keratinization in porokeratosis.

BACKGROUND: Porokeratosis is a dyskeratotic disorder of the skin characterized by cornoid lamella with parakeratosis, hyperkeratosis and loss of granular layers. The pathogenesis of porokeratosis and the mechanism(s) of its abnormal keratinization are still unknown. OBJECTIVE: To elucidate the mechanism(s) of abnormal keratinization that leads to the formation of cornoid lamellae in porokeratosis. METHODS: Apoptosis of keratinocytes was assessed in the skin of seven patients by an in situ apoptosis assay based on the terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labelling (TUNEL) reaction. Patterns of loricrin and involucrin expression were examined by immunohistochemistry. RESULTS: TUNEL-positive keratinocytes were observed in the epidermis underlying the cornoid lamella in all cases examined. Furthermore, loricrin expression was interrupted there, in contrast to involucrin, which was expressed diffusely in the lesional epidermis. CONCLUSIONS: These results suggest that an abnormal early keratinocyte apoptosis accompanied by dysregulation of terminal differentiation of those cells may be involved in the pathogenesis of porokeratosis.

Disseminated porokeratosis with fatal metastatic squamous cell carcinoma: an additional case of "malignant disseminated porokeratosis".

We report on a patient with a disseminated form of porokeratosis in whom bowenoid lesions and squamous cell carcinoma developed in an apparent sequential progression. Local and disseminated metastases ensued, resulting in the death of the patient. Furthermore, we found an overexpression of the p53 protein in the keratinocytes beneath and adjacent to the cornoid lamella in the porokeratotic lesion and throughout the epidermis in a bowenoid lesion. Although malignancy has been reported previously in various types of porokeratosis, the development of fatal metastatic squamous cell carcinoma in the setting of this disease is a rare event. The histopathologic findings of this case document the association of porokeratotic lesions with bowenoid dysplasia and aggressive squamous cell carcinoma and confirm that a p53 functional aberration can be important in a malignant outcome such as this.

Nitric oxide and endothelin-1,2 in actinic keratosis and basal cell carcinoma: changes in nitric oxide/endothelin ratio.

BACKGROUND: Nitric oxide (NO) is an inorganic free radical gas which has cytostatic/cytotoxic actions in tumoral tissues, including gynecologic, breast, and colon cancer. Nitric oxide is also a multifunctional signaling molecule active in many cells of the body, including endothelial cells, macrophages, monocytes, hepatocytes, mast cells, osteoblasts, and astrocytes. Endothelin-1 (ET-1) is a 21-amino acid peptide that stimulates the proliferation of vascular smooth muscle cells, fibroblasts, and keratinocytes, and plays a role in the expression of proto-oncogenes (c-myc, c-fos), which precedes cell proliferation. Similar to NO, ET is secreted by different cell types, including macrophages, monocytes, hepatocytes, endothelial cells, vascular smooth muscle cells, and various tumor cells. Elevated ET-1 levels are observed in pulmonary, hepatocellular, and prostate cancers. Actinic keratosis (AK) and basal cell carcinoma (BCC) are common skin tumors with accentuated hyperkeratinization, hyperpigmentation, and keratinocyte proliferation. AIM: To investigate plasma NOx (nitrite/nitrate -- the end products of NO metabolism), ET, and the NOx/ET ratio in patients with AK and BCC in comparison with healthy controls. METHODS: NOx, ET, and the NOx/ET ratio were measured in 13 patients with AK, 12 patients with BCC, and in 16 healthy controls. RESULTS: Data analysis indicated a significant increase in plasma NOx, ET, and NOx/ET values in BCC patients in comparison with controls (P < 0.001, P < 0.05 and P < 0.001, respectively). Plasma ET levels in AK were also increased in comparison with controls (P < 0.001). When the two study groups (AK and BCC) were compared, a significant increase (P < 0.001) in the NOx/ET ratio in BCC was found. CONCLUSIONS: The increased plasma ET and NOx levels in AK and, especially, BCC are probably the result of and/or reason for the accentuated hyperkeratinization, hyperpigmentation, and keratinocyte proliferation. The increased production of ET and NO by keratinocytes may function as growth and cytotoxic factors and potential mitogens, and may accelerate further proliferation of these skin tumors. In addition, the increased NOx/ET ratio probably reflects a disturbed equilibrium between these two substances, leading to cell damage and tumor promotion and proliferation.

Guess what! Porokeratosis of Mibelli.

A 72-year-old man had noticed, in his early forties, the appearance of well-defined papulous hyperkeratotic lesions, with increasing growth, located on both sides of his feet. After twenty-five years he consulted a dermatologist for the first time. Physical examination showed annular papules and rose-coloured plaques with atrophic centres, some of them hypopigmented, with higher and irregular borders, separated from the surrounding skin by longitudinal and well-defined furrows. The lesions presented variable sizes and shapes, some of them punctate, involving exclusively and in a bilateral form, both sides, back and sole of the feet (Figs. 1 and 2). The patient did not report any subjective symptoms. He was immunocompetent and did not remember that any relative had the same disease, nor had he been subjected to radiation treatment.