N-RAS mutation at codon 12, 13 or 61 is associated with transformation; yet, in melanoma, such alterations are nearly exclusive to codon 61. Here, we compared the melanoma susceptibility of an N-RasQ61R knock-in allele to similarly designed K-RasG12D and N-RasG12D alleles. With concomitant p16INK4a inactivation, K-RasG12D or N-RasQ61R expression efficiently promoted melanoma in vivo, whereas N-RasG12D did not. Additionally, N-RasQ61R mutation potently cooperated with Lkb1/Stk11 loss to induce highly metastatic disease. Functional comparisons of N-RasQ61R and N-RasG12D revealed little difference in the ability of these proteins to engage PI3K or RAF. Instead, N-RasQ61R showed enhanced nucleotide binding, decreased intrinsic GTPase activity and increased stability when compared to N-RasG12D. This work identifies a faithful model of human N-RAS mutant melanoma, and suggests that the increased melanomagenecity of N-RasQ61R over N-RasG12D is due to heightened abundance of the active, GTP-bound form rather than differences in the engagement of downstream effector pathways.

Immune-mediated antitumor responses occur in patients with metastatic melanoma (MM), and therapies designed to augment such responses are clinically beneficial. Despite the immunogenicity of melanoma, immunomodulatory therapies fail in the majority of patients with MM. An inability of DCs to sufficiently activate effector cells may, in part, underlie this failure of the antitumor response seen in most patients. In this work, we show that mutation of N-RAS or B-RAF, signature genetic lesions present in most MMs, potently induced the expression of cell-surface CD200, a repressor of DC function. Employing 2 independent, genomewide microarray analyses, we identified CD200 as a highly dynamic, downstream target of RAS/RAF/MEK/ ERK activation in melanoma. CD200 protein was similarly overexpressed in human melanoma cell lines and primary tumors. CD200 mRNA expression correlated with progression and was higher in melanoma than in other solid tumors or acute leukemia. Melanoma cell lines expressing endogenous CD200 repressed primary T cell activation by DCs, while knockdown of CD200 by shRNA abrogated this immunosuppressive effect. These data indicate that in addition to its effects on growth, survival, and motility, ERK activation in MM attenuates a host antitumor immune response, implicating CD200 and its interaction with the CD200 receptor as a potential therapeutic target for MM. IntroductionMelanoma, the most lethal form of skin cancer, has increased in incidence and mortality over the last 3 decades. Metastatic disease that is not amenable to surgery is generally refractory to therapy and, therefore, ultimately lethal. Standard chemotherapy typically produces response rates on the order of 10%, and radiotherapy plays only a limited role in disease palliation. Despite these sobering facts, some optimism has been engendered by recent advances in our molecular understanding of the disease, particularly the finding that approximately 80% of metastatic melanomas (MMs) harbor mutually exclusive activating mutations of either N-RAS or B-RAF (reviewed in ref. 1). These lesions lead to activation of the RAF/MEK/ERK/MAPK pathway, which in turn controls the transcription of hundreds if not thousands of genes related to cellular proliferation, survival, and motility (2). Although work in murine models and pharmacological approaches have suggested that RAS-RAF activation is required not only for tumor formation, but also for tumor maintenance (3, 4), the cell-biological effects of ERK activation that are most relevant for tumor formation and progression have not been fully established.Arguably, the evidence for a clinically valuable anticancer immune response is stronger in MM than any other human malignancy (reviewed in refs. 5-8). Functional T cells restricted to melanoma antigens can be readily recovered from patients with MM, establishing the tumor's immunogenicity in humans (5-7, 9).

Background: Traction alopecia is hair loss due to prolonged or repetitive tension on the hair. Diagnostic challenges may be encountered if the clinical suspicion for traction is not high, or if the history of traction is remote or not obtained. Since pathologic features can vary dramatically with the stage of the disorder clinico-pathologic correlation is essential. We have made the observation that the presence of retained hairs along the frontal and/or temporal rim, which we termed the "fringe sign", is a finding that can be see in both early and late traction alopecia, and thus may be a useful clinical marker of the condition. Objective: To determine the frequency of the fringe sign in a series of patients with a diagnosis of traction alopecia. Methods: This was a retrospective single-center review. Results: Over a 3.5 year period the diagnosis of traction alopecia was made in 41women. Twelve of the 41 patients were Hispanic (29%). The average age of our cohort was 34. Thirty-five (85%) of all women and 100% of women who had traction involving the marginal hair line had the fringe sign. The majority of African American women (54%) compared to 17% of the Hispanic women had some clinical sign of scalp inflammation(most frequently scalp scaling). Fourteen biopsies(58%) were available for review. Histopathologic findings included retained sebaceous glands (100%) and an increase in vellus-sized hairs (50%), a decrease in terminal hairs (100%), fibrotic fibrous tracts (100%), and sparse lyphocytic inflammation (57%). Trichomalacia was only noted in only one of the biopsies. Limitations: Retrospective analysis, uncontrolled study. Conclusions: Hispanic women as well as African American women are at high risk for traction alopecia. The fringe sign was a sensitive and specific clinical feature of traction alopecia when it involved the marginal hair line. Retained sebaceous glands, decreased terminal hairs, and fibrotic fibrous tracts were noted in all histopathologic specimens.

Cutaneous meningioma is a rare tumor that most commonly occurs on the scalp and occurs in both congenital and acquired forms. It invokes a wide clinical differential diagnosis, but diagnosis is based on characteristic histologic and cytologic findings. Congenital lesions can often present years after birth and even in adult patients. Acquired lesions occur in adulthood. We review histologic, cytologic, and electron microscopic findings and explore how these are used to separate this entity from other entities in the differential diagnosis. While ultrastructural and cytologic findings are similar to those of more common intracranial meningiomas, these tumors exhibit a range of histologic differences. A lack of awareness of this entity precludes correct diagnosis.

BACKGROUND BRAF mutation status, and therefore eligibility for BRAF inhibitors, is currently determined by sequencing methods. We assessed the validity of VE1, a monoclonal antibody against the BRAF V600E mutant protein, in the detection of mutant BRAF V600E melanomas as classified by DNA pyrosequencing. METHODS The cases were 76 metastatic melanoma patients with only one known primary melanoma who had had BRAF codon 600 pyrosequencing of either their primary (n=19), metastatic (n=57) melanoma, or both (n=17). All melanomas (n=93) were immunostained with the BRAF VE1 antibody using a red detection system. The staining intensity of these specimens was scored from 0 – 3+ by a dermatopathologist. Scores of 0 and 1+ were considered as negative staining while scores of 2+ and 3+ were considered positive. RESULTS The VE1 antibody demonstrated a sensitivity of 85% and a specificity of 100% as compared to DNA pyrosequencing results. There was 100% concordance between VE1 immunostaining of primary and metastatic melanomas from the same patient. V600K, V600Q, and V600R BRAF melanomas did not positively stain with VE1. CONCLUSIONS This hospital-based study finds high sensitivity and specificity for the BRAF VE1 immunostain in comparison to pyrosequencing in detection of BRAF V600E in melanomas.