GAB2 induces tumor angiogenesis in NRAS-driven melanoma.

GAB2 is a scaffold protein with diverse upstream and downstream effectors. MAPK and PI3K signaling pathways are known effectors of GAB2. It is amplified and overexpressed in a variety of human tumors including melanoma. Here we show a previously undescribed role for GAB2 in NRAS-driven melanoma. Specifically, we found that GAB2 is co-expressed with mutant NRAS in melanoma cell lines and tumor samples and its expression correlated with metastatic potential. Co-expression of GAB2(WT) and NRAS(G12D) in melanocytes and in melanoma cells increased anchorage-independent growth by providing GAB2-expressing cells a survival advantage through upregulation of BCL-2 family of anti-apoptotic factors. Of note, collaboration of GAB2 with mutant NRAS enhanced tumorigenesis in vivo and led to an increased vessel density with strong CD34 and VEGFR2 activity. We found that GAB2 facilitiated an angiogenic switch by upregulating HIF-1α and VEGF levels. This angiogenic response was significantly suppressed with the MEK inhibitor PD325901. These data suggest that GAB2-mediated signaling cascades collaborate with NRAS-driven downstream activation for conferring an aggressive phenotype in melanoma. Second, we show that GAB2/NRAS signaling axis is non-linear and non-redundant in melanocytes and melanoma, and thus are acting independent of each other. Finally, we establish a link between GAB2 and angiogenesis in melanoma for the first time. In conclusion, our findings provide evidence that GAB2 is a novel regulator of tumor angiogenesis in NRAS-driven melanoma through regulation of HIF-1α and VEGF expressions mediated by RAS-RAF-MEK-ERK signaling.

Are dark-skinned people really protected from ultraviolet radiation?

BACKGROUND: Premature ageing of the skin (photoageing) results from the action of ultraviolet radiation (UVR) on skin. One of the histopathological findings of photoageing is the presence of solar elastosis in the dermis. Skin pigmentation is protective against UVR. AIM: To evaluate the presence of solar elastosis in dark-skinned people. METHODS: Normal facial skin biopsies of 147 dark-skinned and 140 light-skinned people were examined histopathologically for solar elastosis. The degree of solar elastosis was graded on a five-point scale by a panel of dermatopathologists blinded to patient demographics. RESULTS: There were 112 of 140 (80%) light-skinned and 50 of 147 (34%) dark-skinned patients with high-grade solar elastosis. In the dark-skinned patient group, high-grade solar elastosis was seen in 29 of 61 (47.5%) Hispanic and 5 of 49 (10.2%) African American subjects. CONCLUSIONS: Dark-skinned people are not completely protected from the effects of UVR.

CYLD mutations in familial skin appendage tumours.

BACKGROUND: Germ-line mutations in CYLD are found in patients with familial skin appendage tumours. The protein product functions as a deubiquitinase enzyme, which negatively regulates NF-kappaB and c-Jun N-terminal kinase signalling. Brooke-Spiegler syndrome (BSS) is characterised by cylindromas, trichoepitheliomas and spiradenomas, whereas in familial cylindromatosis (FC) patients present with cylindromas and in multiple familial trichoepitheliomas (MFT) with trichoepitheliomas as the only skin tumour type. Although described as distinct entities, recent studies suggest that they are within the spectrum of a single entity. OBJECTIVE: To investigate the mutation spectrum of CYLD and possible genotype-phenotype correlations. METHODS: 25 families including 13 BSS, 3 FC, and 9 MFT families were examined and evaluated for mutations in the CYLD gene. RESULTS: In total, 18 mutations in CYLD, including 6 novel mutations, were identified in 25 probands (72%). The mutation frequencies among distinct phenotypes were 85% for BSS, 100% for FC, and 44% for MFT. The majority of the mutations were insertions, deletions or nonsense mutations leading to formation of truncated proteins. All mutations were located between exons 9 to 20, encoding the NEMO binding site and the catalytic domain. Genotype-phenotype analysis failed to reveal a correlation between the types of mutations and their location within the gene and the patients' phenotypes and disease severity. CONCLUSIONS: This study provides further evidence on the role of CYLD in the pathogenesis of skin appendage tumours characterised by cylindromas, trichoepitheliomas and/or spiradenomas, but the molecular mechanisms of CYLD in skin tumorigenesis and the reasons for phenotypic variability remain to be explored.

CYLD mutations underlie Brooke-Spiegler, familial cylindromatosis, and multiple familial trichoepithelioma syndromes.

Brooke-Spiegler syndrome (BSS), familial cylindromatosis (FC), and multiple familial trichoepithelioma (MFT), originally described as distinct inherited disorders, are characterized by a variety of skin appendage neoplasms. Mutations in the CYLD gene are found in individuals with these syndromes. We describe a single family with affected members exhibiting either the FC or the MFT phenotypes associated with a mutation in the CYLD gene. These findings support the notion that BSS, FC, and MFT represent phenotypic variation of a single defect. Of interest, one of the affected individuals described in this report exhibits a severe phenotype illustrating the morbidity of the disorder.

Genetics of skin appendage neoplasms and related syndromes.

In the past decade the molecular basis of many inherited syndromes has been unravelled. This article reviews the clinical and genetic aspects of inherited syndromes that are characterised by skin appendage neoplasms, including Cowden syndrome, Birt-Hogg-Dube syndrome, naevoid basal cell carcinoma syndrome, generalised basaloid follicular hamartoma syndrome, Bazex syndrome, Brooke-Spiegler syndrome, familial cylindromatosis, multiple familial trichoepitheliomas, and Muir-Torre syndrome.

Identification of novel type VII collagen gene mutations resulting in severe recessive dystrophic epidermolysis bullosa.

In this work, we studied the proband in a small nuclear family of Chinese and Dutch/German descent and identified two novel mutations in the type VII collagen gene leading to recessive dystrophic epidermolysis bullosa, Hallopeau-Siemens variant (HS-RDEB). The maternal mutation is a single base pair deletion of a cytosine nucleotide in exon 26, designated 3472delC, resulting in a frameshift and a premature termination codon (PTC) within the same exon, 7 bp downstream of the site of the mutation. The paternal mutation is a G-->A transition located at the 5' donor splice site within intron 51, designated IVS51 + 1G-->A. This mutation leads to the activation of a cryptic splice site, 32 bp downstream of the mutation site and to subsequent aberrant out-of-frame splicing, resulting in two alternative mRNA transcripts and a downstream PTC. To our knowledge, these two mutations have not been previously reported. These findings extend the body of evidence for compound heterozygous mutations leading to HS-RDEB and provide the basis for prenatal diagnosis in this family.

Evaluation of germline CDKN2A, ARF, CDK4, PTEN, and BRAF alterations in atypical mole syndrome.

Atypical mole syndrome is a sporadic or an inherited condition with an increased risk of melanoma. Germline mutations in the CDKN2A, ARF, CDK4 and somatic mutations in the PTEN and BRAF genes have been associated with melanoma. In this study, we evaluated genes associated with familial and sporadic melanoma for mutations in 28 probands with the atypical mole syndrome. No sequence alterations in the coding regions or in the splice junctions of CDKN2A, ARF, CDK4, PTEN or BRAF were identified. These data suggest that genes evaluated in this study are unlikely to be candidate genes for atypical mole syndrome and support the notion that unknown susceptibility gene/s for this disease exist.

Identification of a recurrent mutation in the CYLD gene in Brooke-Spiegler syndrome.

Brooke-Spiegler syndrome is an autosomal dominantly inherited disease with predisposition to neoplasms of the skin appendages. The disease has been mapped to 16q, and mutations in the CYLD gene have been identified in families with this disorder. We describe an individual with BSS exhibiting clinical heterogeneity in which a heterozygous frameshift mutation in CYLD, 2172delA, has been identified. These findings extend the body of evidence that mutations in CYLD are involved in Brooke-Spiegler syndrome and provide additional information for phenotype-genotype correlation.

A novel mutation in the ARS (component B) gene encoding SLURP-1 in a family with Mal de Meleda.

Mal de Meleda is a rare, autosomal recessive form of palmoplantar keratoderma. The disease has been mapped to chromosome 8 qter, and recently mutations in the ARS (component B) gene have been identified in families with this disorder. We describe a small family of Turkish origin with Mal de Meleda and identified a novel homozygous mutation, L98P, in ARS (component B). These findings extend the body of evidence implicating mutations in the ARS (component B) gene in Mal de Meleda.

Identification of a recurrent mutation in keratin 6a in a patient with overlapping clinical features of pachyonychia congenita types 1 and 2.

Pachyonychia congenita is characterized by hypertrophic nail dystrophy and associated ectodermal features. PC-1 subtype is associated with mutations in keratins 6a or 16, whereas PC-2 subtype is linked to mutations in keratins 6b or 17. The correlation between the mutated gene and the type of PC has generally been consistent. In this report, we describe a case with overlapping clinical features of PC-1 and PC-2 in which a mutation in K6a was identified.

Identification of a PTEN mutation in a family with Cowden syndrome and Bannayan-Zonana syndrome.

Cowden syndrome (CS) and Bannayan-Zonana syndrome (BZS) are two inherited hamartoma syndromes characterized by distinct phenotypic features. Mutations in the PTEN gene have been identified in patients with CS and BZS, suggesting the presence of a common genetic basis. We describe a single kindred with individuals manifesting both CS and BZS phenotypes (CS/BZS overlap family) in which we have identified a novel mutation in PTEN by DNA sequencing. We have confirmed these results by means of restriction enzyme analysis. The presence of individuals with CS and BZS within the same family, and moreover the identification of identical PTEN gene mutations in these individuals, suggest that these two syndromes represent different phenotypic expressions of one disease. Furthermore, these findings imply that, like patients with CS, individuals with BZS should be monitored for the onset of malignancy.

Association of splicing defects in PTEN leading to exon skipping or partial intron retention in Cowden syndrome.

Cowden syndrome (CS) and Bannayan Zonana syndrome (BZS) are two autosomal dominantly inherited conditions characterized by hamartomas. Mutations in PTEN, a tumor suppressor gene located on chromosome 10q23, have been identified in patients with phenotypic findings of both CS and BZS. These mutations are found throughout the entire gene, with exon 5 being the most common site, and include point mutations, insertions and deletions. To date, 11 point mutations at the splice junctions of the PTEN gene have been reported, however, data on the alterations in the transcripts have been lacking. In this study, we have identified three novel splice site mutations in PTEN, in two families with CS and in one individual with BZS. One mutation affected the splice-acceptor site, which resulted in out-of-frame skipping of an entire exon. By contrast, the other two mutations affected the splice-donor sites, and both showed inclusion of partial intronic sequences in the transcript due to activation of cryptic splice sites. These data demonstrate mRNA alterations as a consequence of splice site mutations in the PTEN gene.

Identification of PTEN mutations in metastatic melanoma specimens.

CONTEXT: PTEN, a tumour suppressor gene located on chromosome 10q23, develops somatic mutations in various tumours and tumour cell lines including brain, endometrium, prostate, breast, kidney, thyroid, liver, and melanoma. OBJECTIVES: To investigate the mutational profile of this gene further, as well as its role in tumour progression in melanoma. DESIGN, SETTINGS: We examined 21 metastatic melanoma samples for 10q23 allelic losses and PTEN sequence alterations. Additionally, we screened these samples for mutations in CDKN2A, a gene in which alterations are well documented in primary melanoma as well as in the germline of familial melanoma. RESULTS: Loss of heterozygosity (LOH) at 10q23 was observed in 33% (7/21) of the samples tested. We identified four sequence alterations in PTEN (19%) and two in CDKN2A (9.5%). Of interest, only one case showed mutations in both genes. CONCLUSIONS: These data support the notion that PTEN alterations occur in some metastatic melanomas, and that mutation of this gene plays a role in the progression of some forms of melanoma.

Germline PTEN mutations in three families with Cowden syndrome.

Cowden syndrome (CS) is an autosomal dominant inherited disorder characterized by hamartomas in a variety of tissues including the skin, thyroid, breast, endometrium, and the brain. Individuals with CS are predisposed to development of malignancy in these organs, especially the breast and the thyroid. We describe 3 unrelated individuals with CS associated with germline PTEN mutations. While the frameshift (375insTTTA) and the missense (Gly69Arg) mutations reported herein are novel in CS, the nonsense (Arg130stop) mutation has been described in 2 families with CS and in a single family exhibiting both CS and Bannayan Zonana phenotype.

Mutation report: identification of a germline mutation in keratin 17 in a family with pachyonychia congenita type 2.

Pachyonychia congenita type 2 (PC-2), also known as Jackson-Lawler type PC, is an autosomal dominant disorder characterized by hypertrophic nail dystrophy associated with focal keratoderma and multiple pilosebaceous cysts. It has been demonstrated that PC-2 is associated with germline mutations in the keratin 17 (K17) gene and in its expression partner keratin 6b. In this report, we describe a novel germline mutation in K17, M88T, in a family with PC-2.

Phenotypic findings of Cowden syndrome and Bannayan-Zonana syndrome in a family associated with a single germline mutation in PTEN.

Cowden syndrome (CS) and Bannayan-Zonana syndrome (BZS) are two hamartoma syndromes with distinct phenotypic features. Although partial clinical overlap exists between CS and BZS, they are considered to be separate entities. PTEN has been identified as the susceptibility gene for both disorders, suggesting allelism. We have identified a germline mutation, R335X, in PTEN in a family consisting of two female members with the phenotypic findings of CS and two male members with the phenotypic findings of BZS. To our knowledge, this is the first report that shows the presence of separate subjects with CS and with BZS in a single family associated with a single germline PTEN mutation.