Expression of an oncogene in a primary cell can, paradoxically, block proliferation by inducing senescence or apoptosis through pathways that remain to be elucidated. Here we perform genome-wide RNA-interference screening to identify 17 genes required for an activated BRAF oncogene (BRAFV600E) to block proliferation of human primary fibroblasts and melanocytes. Surprisingly, we find a secreted protein, IGFBP7, has a central role in BRAFV600E-mediated senescence and apoptosis. Expression of BRAFV600E in primary cells leads to synthesis and secretion of IGFBP7, which acts through autocrine/paracrine pathways to inhibit BRAF-MEK-ERK signaling and induce senescence and apoptosis. Apoptosis results from IGFBP7-mediated upregulation of BNIP3L, a proapoptotic BCL2 family protein. Recombinant IGFBP7 (rIGFBP7) induces apoptosis in BRAFV600E-positive human melanoma cell lines, and systemically administered rIGFBP7 markedly suppresses growth of BRAFV600E-positive tumors in xenografted mice. Immunohistochemical analysis of human skin, nevi, and melanoma samples implicates loss of IGFBP7 expression as a critical step in melanoma genesis.

Perspectives in DermatopathologyCutaneous sebaceous neoplasms as markers of Muir-Torre syndrome: a diagnostic algorithmSebaceous gland neoplasms such as adenoma, epithelioma, and carcinoma are uncommon cutaneous tumors. Although sporadic, their occurrence is clinically significant because of their association with Muir-Torre syndrome (MTS). MTS is a rare autosomal dominant genodermatosis characterized by the occurrence of sebaceous gland neoplasms and/or keratoacanthomas associated with visceral malignancies that include gastrointestinal and genitourinary cancers. MTS is usually the result of germline mutation in one or more of the DNA mismatch repair (MMR) genes. MMR genes commonly implicated include MSH-2 and MLH-1 and, more recently, MSH-6. Recent evidence suggests that immunohistochemistry is very sensitive and effective in detecting these defects in cutaneous tumors in MTS. In addition, the genetic instability of cutaneous and visceral tumors in MTS caused by the defects in MMR genes can also be detected, using polymerase chain reaction (PCR)-based techniques, for microsatellite instability (MSI). Given that some sebaceous neoplasms represent cutaneous markers of MTS, what should we as dermatopathologists be advocating? Should we be looking for absence/loss of MMRs in all sebaceous neoplasms? When should we recommend assaying for MSI? This review attempts to address all of these issues with a view to streamlining the work-up of a patient presenting for the first time with a sebaceous neoplasm and no prior personal or family history of internal malignancies.Abbas O, Mahalingam M. Cutaneous sebaceous neoplasms as markers of Muir-Torre syndrome: a diagnostic algorithm.

Our recent experience indicates that the desmoplastic variant of tumor of the follicular infundibulum (TFI) is not, as previously believed, entirely uncommon. To clarify the defining clinical and microscopic features of TFI with special relevance to the histologic variants, we retrospectively reviewed cases with a histologic diagnosis of TFI between 1999 and 2008. Of the 74 cases retrieved, 53 TFI cases in 50 patients were identified with an incidence approximating 17 per 100,000. Clinically, TFI seems to be slightly more common in men (52% vs. 48%) and more common on the head and neck (around 77%) and presents as plaques (approximately 47%) and as multiple lesions (6%). Histologically, the majority showed classic features of a horizontal plate-like proliferation of large, bland-appearing, pale epithelial cells. Other features included an eosinophilic cuticle (70%), ductal differentiation (45%), cornoid lamellae (17%), and desmoplasia (11%). Of interest, approximately one fourth (25%) were associated with other cutaneous lesions, which included basal cell carcinoma, actinic keratosis, desmoplastic malignant melanoma, junctional melanocytic nevus, tricholemmoma, and epidermal inclusion cyst. In addition to expanding the constellation of the clinical and histopathologic findings, the increased association with other cutaneous lesions in the current study suggests that TFI may represent an epidermal reaction pattern.

Oncogenic mutations in BRAF and NRAS occur in 70% of melanomas. In this study, we identify a microRNA, miR-146a, that is highly upregulated by oncogenic BRAF and NRAS. Expression of miR-146a increases the ability of human melanoma cells to proliferate in culture and form tumors in mice, whereas knockdown of miR-146a has the opposite effects. We show these oncogenic activities are due to miR-146a targeting the NUMB mRNA, a repressor of Notch signaling. Previous studies have shown that pre-miR-146a contains a single nucleotide polymorphism (C>G rs2910164). We find that the ability of pre-miR-146a/G to activate Notch signaling and promote oncogenesis is substantially higher than that of pre-miR-146a/C. Analysis of melanoma cell lines and matched patient samples indicates that during melanoma progression pre-miR-146a/G is enriched relative to pre-miR-146a/C, resulting from a C-to-G somatic mutation in pre-miR-146a/C. Collectively, our results reveal a central role for miR-146a in the initiation and progression of melanoma.DOI: http://dx.doi.org/10.7554/eLife.01460.001

Even though immunohistochemical comparisons of microcystic adnexal carcinoma vs infiltrative basal cell carcinoma and desmoplastic trichoepithelioma exist, they are mostly restricted to the use of a single stain. In addition, a comparison with squamous cell carcinoma has not been reported previously. In this study, we compare the expression of cytokeratin (CK) 15, CK7, CK20, CK903, carcinoembryonic antigen (CEA), CD10, CD15 and BerEP4 in 13 microcystic adnexal carcinoma, eight desmoplastic trichoepithelioma, 10 infiltrative basal cell carcinoma, and eight squamous cell carcinoma of which five exhibited ductal differentiation. We found that the majority of microcystic adnexal carcinoma (92%) and desmoplastic trichoepithelioma (100%) cases expressed CK15 while the infiltrative basal cell carcinoma and squamous cell carcinoma cases were all negative. Forty percent of infiltrative basal cell carcinoma expressed CK7; while only two microcystic adnexal carcinoma cases (15%) and one squamous cell carcinoma with ductal differentiation (12%) expressed CK7 in the remaining three tumor categories. None of the desmoplastic trichoepithelioma expressed CK7. All tumors were strongly positive for CK903. While the neoplastic cells were negative, luminal staining of ductal structures was noted for CK7, CD15 and CEA in some of the microcystic adnexal carcinoma, desmoplastic trichoepithelioma and squamous cell carcinoma with ductal differentiation cases. Sixty percent of infiltrative basal cell carcinoma, 31% of microcystic adnexal carcinoma, and 25% of squamous cell carcinoma express CD10. BerEP4 expression was noted in 38% of microcystic adnexal carcinoma, 57% of desmoplastic trichoepithelioma, 100% of infiltrative basal cell carcinoma, and 38% of squamous cell carcinoma. In conclusion, we found CK15 to be a useful marker in distinguishing microcystic adnexal carcinoma from infiltrative basal cell carcinoma and squamous cell carcinoma with ductal differentiation. Our experience indicates that microcystic adnexal carcinoma and desmoplastic trichoepithelioma have a similar immunohistochemical profile that is, CK15 þ and BerEP4 þ /À; thus, additional studies are needed to separate these two entities.

Our findings of differential follicular localization of stem cells underscore follicular progenitor cell heterogeneity and suggest the target in scarring alopecia is not merely follicular bulge stem cells but involves stem cells in the inner and outer aspect of the ORS. Enhanced expression of nestin in the infundibular region in scarring alopecia indicates availability of an accessible, in vivo niche of potential utility as an autologous source of stem cells for therapeutic application.

Throughout adult life, the epidermis and the hair follicle undergo a perpetual cycle of growth, regression and rest. Stem cells in the epidermis not only ensure the maintenance of epidermal homeostasis and hair regeneration, but also contribute to repair of the epidermis after injury. These stem cells lie within specific niches in the hair follicle and the epidermis. The availability of monoclonal antibodies that can be used on formalin-fixed paraffin-embedded tissue has greatly facilitated the use of this methodology as an adjunct to uncovering stem cell niches. In this review, we attempt to provide an overview of the potential markers available to identify and study stem cells in an effort to providing a better understanding of the pathogenesis of skin diseases including disorders of hair loss and malignancies. The potential uses of these markers in prognosis and in expanding the therapeutic options in several disorders will also be addressed.

Cancer cells acquire several traits that allow for their survival and progression, including the ability to evade the host immune response. However, the mechanisms by which cancer cells evade host immune responses remain largely elusive. Here we study the phenomena of immune evasion in malignant melanoma cells. We find that the tumor suppressor phosphatase and tensin homolog (PTEN) is an important regulator of the host immune response against melanoma cells. Mechanistically, PTEN represses the expression of immunosuppressive cytokines by blocking the phosphatidylinositide 3-kinase (PI3K) pathway. In melanoma cells lacking PTEN, signal transducer and activator of transcription 3 activates the transcription of immunosuppressive cytokines in a PI3K-dependent manner. Furthermore, conditioned media from PTEN-deficient, patient-derived short-term melanoma cultures and established melanoma cell lines blocked the production of the interleukin-12 (IL-12) in human monocyte-derived dendritic cells. Inhibition of IL-12 production was rescued by restoring PTEN or using neutralizing antibodies against the immunosuppressive cytokines. Furthermore, we report that PTEN, as an alternative mechanism to promote the host immune response against cancer cells, represses the expression of programmed cell death 1 ligand, a known repressor of the host immune response. Finally, to establish the clinical significance of our results, we analyzed malignant melanoma patient samples with or without brisk host responses. These analyses confirmed that PTEN loss is associated with a higher percentage of malignant melanoma samples with non-brisk host responses compared with samples with brisk host responses. Collectively, these results establish that PTEN functions as a melanoma tumor suppressor in part by regulating the host immune response against melanoma cells and highlight the importance of assessing PTEN status before recruiting melanoma patients for immunotherapies.