Leopold Groesser

Postzygotic HRAS and KRAS mutations cause nevus sebaceous and Schimmelpenning syndrome

Nevus sebaceous is a common congenital cutaneous malformation. Affected individuals may develop benign and malignant secondary tumors in the nevi during life. Schimmelpenning syndrome is characterized by the association of nevus sebaceous with extracutaneous abnormalities. We report that of 65 sebaceous nevi studied, 62 (95%) had mutations in the HRAS gene and 3 (5%) had mutations in the KRAS gene. The HRAS c.37G>C mutation, which results in a p.Gly13Arg substitution, was present in 91% of lesions. Nonlesional tissues from 18 individuals had a wild-type sequence, confirming genetic mosaicism. The HRAS c.37G>C mutation was also found in 8 of 8 associated secondary tumors. Mosaicism for HRAS c.37G>C and KRAS c.35G>A mutations was found in two individuals with Schimmelpenning syndrome. Functional analysis of HRAS c.37G>C mutant cells showed constitutive activation of the MAPK and PI3K-Akt signaling pathways. Our results indicate that nevus sebaceous and Schimmelpenning syndrome are caused by postzygotic HRAS and KRAS mutations. These mutations may predispose individuals to the development of secondary tumors in nevus sebaceous.

Phacomatosis Pigmentokeratotica Is Caused by a Postzygotic HRAS Mutation in a Multipotent Progenitor Cell

Phacomatosis pigmentokeratotica (PPK) is a rare epidermal nevus syndrome characterized by the co-occurrence of a sebaceous nevus and a speckled lentiginous nevus. The coexistence of an epidermal and a melanocytic nevus has been explained by two homozygous recessive mutations, according to the twin spot hypothesis, of which PPK has become a putative paradigm in humans. However, the underlying gene mutations remained unknown. Multiple tissues of six patients with PPK were analyzed for the presence of RAS, FGFR3, PIK3CA, and BRAF mutations using SNaPshot assays and Sanger sequencing. We identified a heterozygous HRAS c.37G>C (p.Gly13Arg) mutation in four patients and a heterozygous HRAS c.182A>G (p.Gln61Arg) mutation in two patients. In each case, the mutations were present in both the sebaceous and the melanocytic nevus. In the latter lesion, melanocytes were identified to carry the HRAS mutation. Analysis of various nonlesional tissues showed a wild-type sequence of HRAS, consistent with mosaicism. Our data provide no genetic evidence for the previously proposed twin spot hypothesis. In contrast, PPK is best explained by a postzygotic-activating HRAS mutation in a multipotent progenitor cell that gives rise to both a sebaceous and a melanocytic nevus. Therefore, PPK is a mosaic RASopathy.

Mosaic Activating Mutations in GNA11 and GNAQ Are Associated with Phakomatosis Pigmentovascularis and Extensive Dermal Melanocytosis

Common birthmarks can be an indicator of underlying genetic disease but are often overlooked. Mongolian blue spots (dermal melanocytosis) are usually localized and transient, but they can be extensive, permanent, and associated with extracutaneous abnormalities. Co-occurrence with vascular birthmarks defines a subtype of phakomatosis pigmentovascularis, a group of syndromes associated with neurovascular, ophthalmological, overgrowth, and malignant complications. Here, we discover that extensive dermal melanocytosis and phakomatosis pigmentovascularis are associated with activating mutations in GNA11 and GNAQ, genes that encode Gα subunits of heterotrimeric G proteins. The mutations were detected at very low levels in affected tissues but were undetectable in the blood, indicating that these conditions are postzygotic mosaic disorders. In vitro expression of mutant GNA11R183C and GNA11Q209L in human cell lines demonstrated activation of the downstream p38 MAPK signaling pathway and the p38, JNK, and ERK pathways, respectively. Transgenic mosaic zebrafish models expressing mutant GNA11R183C under promoter mitfa developed extensive dermal melanocytosis recapitulating the human phenotype. Phakomatosis pigmentovascularis and extensive dermal melanocytosis are therefore diagnoses in the group of mosaic heterotrimeric G-protein disorders, joining McCune-Albright and Sturge-Weber syndromes. These findings will allow accurate clinical and molecular diagnosis of this subset of common birthmarks, thereby identifying infants at risk for serious complications, and provide novel therapeutic opportunities.

Presence of Human Polyomavirus 6 in Mutation-Specific BRAF Inhibitor-Induced Epithelial Proliferations

IMPORTANCE A frequent adverse effect of mutation-specific BRAF inhibitor therapy is the induction of epithelial proliferations including cutaneous squamous cell carcinomas. To date, the only factor identified contributing to their development is the activation of the mitogen-activated signal transduction cascade by mutations in the RAS genes. However, these mutations explain only 60% of the tumors; hence, it is important to identify what is causing the remaining tumors. OBJECTIVE To test for the presence of human papillomaviruses (HPVs) and the recently identified human polyomaviruses (HPyVs), Merkel cell polyomavirus (MCPyV), and trichodysplasia spinulosa-associated polyomavirus (TSPyV), as well as HPyV-6, HPyV-7, HPyV-9, and HPyV-10, in epithelial proliferations occurring after BRAF inhibitor therapy to determine whether these oncogenic viruses may contribute to BRAF inhibitor-induced skin tumors. DESIGN, SETTING, AND PARTICIPANTS Retrospective study at a university hospital in Austria of epithelial proliferations that developed in patients with melanoma after initiation of treatment with the BRAF inhibitor vemurafenib. Samples were analyzed for (1) presence of the most frequently observed RAS mutations by SNaPshot technology, (2) detection of the viruses by real-time polymerase chain reaction, and (3) presence of capsid proteins of the most abundantly detected virus by immunohistochemical analysis. MAIN OUTCOMES AND MEASURES RAS mutational status, as well as HPV and HPyV presence, in BRAF inhibitor-induced epithelial proliferations. RESULTS Eighteen biopsy samples from 6 patients were retrieved from our hospitals archive. We identified RAS mutations in 10 (62%) of the 16 samples with clear results. DNA of HPyV-9, HPyV-10, and TSPyV were virtually absent in the samples. MCPyV DNA was present in 13 of 18 samples, and HPV, HPyV-6, and HPyV-7 DNA were present in all samples. In general, the amount of DNA encoding the latter viruses was rather low, with the exception of HPyV-6 in several samples of 1 individual patient. Notably, the relevance of the presence of HPyV-6 in the epithelial proliferation was underlined by immunohistochemical detection of the core protein VP1 of HPyV-6. CONCLUSIONS AND RELEVANCE The presence of both high HPyV-6 DNA load and VP1 protein suggests that polyomaviruses may contribute to the epithelial proliferations observed in patients receiving BRAF inhibitor therapy, albeit the relative impact as compared with that of RAS mutations appears circumstantial.

BRAF and RAS Mutations in Sporadic and Secondary Pyogenic Granuloma

Pyogenic granuloma (PG) is a common benign vascular skin lesion presenting as a rapidly growing angiomatous papule. The pathogenesis of most sporadic PGs and PGs associated with port wine stains (PWSs) remains elusive. We report that of 10 PGs secondarily arisen on a PWS, 8 showed a BRAF c.1799T>A (p.(Val600Glu)) and 1 a NRAS c.182A>G (p.(Gln61Arg)) mutation. The GNAQ c.548G>A mutation was identified in the PG and in the respective underlying PWS, indicating that PGs originate from cells of the PWS. In contrast to PG, 12 papulonodular lesions, which had developed in the PWSs of seven patients, showed a RAS and BRAF wild-type status. In sporadic PG we identified the BRAF c.1799T>A mutation in 3 of 25, a BRAF c.1391G>A mutation in 1 of 25, and a KRAS c.37G>C mutation in 1 of 25. Mutation-specific immunohistochemical detection of BRAF p.(Val600Glu) confirmed endothelial cells as carriers of the mutation in secondary and sporadic PG. Our study identifies the BRAF c.1799T>A mutation as a major driver mutation in the pathogenesis of, particularly, secondary PG. These data shed light on the hitherto undetermined genetic basis of PG and classify PG as a benign neoplasm.

FGFR3, PIK3CA and RAS mutations in benign lichenoid keratosis

Background  Benign lichenoid keratoses (BLKs) are solitary skin lesions which have been proposed to represent a regressive form of pre‐existent epidermal tumours such as solar lentigo or seborrhoeic keratosis. However, the genetic basis of BLK is unknown.

Activating mutations in the RAS/mitogen-activated protein kinase signaling pathway in sporadic trichoblastoma and syringocystadenoma papilliferum.

Trichoblastoma (TB) and syringocystadenoma papilliferum (SCAP) are both rare adnexal skin lesions occurring either sporadically or as secondary neoplasms in sebaceous nevi. TB and SCAP associated with sebaceous nevi have been shown to carry the same HRAS mutation as the underlying nevus. However, the genetic background of sporadic TB and SCAP has remained unknown. Therefore, we screened 18 sporadic TBs and 23 sporadic syringocystadenoma papillifera from 41 patients for the presence of activating mutations in RAS genes and other oncogenes. Using a RAS SNaPshot assay, HRAS mutations were detected in 2 (11%) of 18 sporadic TB and 6 (26%) of 23 sporadic syringocystadenoma papillifera. A KRAS mutation was identified in 1 sporadic SCAP. High-throughput oncogene mutation profiling furthermore identified BRAF V600E mutations in sporadic syringocystadenoma papillifera, which could be validated in 12 (52%) of 23 lesions using a BRAF SNaPshot assay. BRAF and RAS mutations were mutually exclusive in sporadic syringocystadenoma papillifera. No BRAF mutation could be detected in 3 syringocystadenoma papillifera secondarily arisen from a sebaceous nevus as well as in sporadic TB. In 14 lesions carrying an oncogenic mutation, nonlesional control tissue from the epidermal margin revealed a wild-type sequence, thus proving the somatic character of the mutation. Our results indicate that activation of the RAS-mitogen-activated protein kinase pathway by BRAF and RAS mutations contributes significantly to the tumorigenesis of sporadic SCAP and, less frequently, of sporadic TB.

Naevus marginatus revisited: a combined organoid and nonorganoid epidermal naevus caused by HRAS mutation.

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Fractional Carbon Dioxide Laser Resurfacing of Rhytides and Photoaged Skin - A Prospective Clinical Study on Patient Expectation and Satisfaction

Fractional CO2‐laser resurfacing is increasingly used for treating rhytides and photoaged skin because of its favorable benefit‐risk ratio. A key outcome measure and treatment goal in aesthetic laser therapy is patient satisfaction. However, few data are available on patient‐reported outcomes after fractional ablative skin‐resurfacing.

Low incidence of oncogenic EGFR, HRAS, and KRAS mutations in seborrheic keratosis.

Abstract:Seborrheic keratosis (SK) represents a frequent epidermal skin tumor. Although lacking a malignant potential, these tumors reveal multiple oncogenic mutations. A previous study identified activating mutations in 89% of SK, particularly in FGFR3 and PIK3CA genes. The aim of this study was to identify further oncogenic mutations in human SK. Therefore, we screened for mutations in EGFR, FGFR2, PIK3R1, HRAS, KRAS, and NRAS genes using both Sanger sequencing of selected exons and a multiplex SNaPshot assay in 58 SK of 14 patients. We identified a somatic EGFR p.L858R mutation in 1 SK. Furthermore, the HRAS mutations p.G13R (2/58 SK) and p.Q61L (2/58 SK) were found. These mutations have not been described in human SK yet. In addition, 1 SK revealed the KRAS p.G12V mutation, which has already been reported in SK. No mutations were detected in FGFR2, PIK3R1, and NRAS genes. The results of this study suggest that activating mutations of EGFR, HRAS, and KRAS contribute to the pathogenesis of human SK, although at a lower frequency than FGFR3 and PIK3CA mutations. FGFR2, PIK3R1, and NRAS mutations obviously do not have a significant role in the development of SK.