William Damsky

BrafV600E cooperates with Pten loss to induce metastatic melanoma

Mutational activation of BRAF is the earliest and most common genetic alteration in human melanoma. To build a model of human melanoma, we generated mice with conditional melanocyte-specific expression of BRafV600E. Upon induction of BRafV600E expression, mice developed benign melanocytic hyperplasias that failed to progress to melanoma over 15–20 months. By contrast, expression of BRafV600E combined with Pten tumor suppressor gene silencing elicited development of melanoma with 100% penetrance, short latency and with metastases observed in lymph nodes and lungs. Melanoma was prevented by inhibitors of mTorc1 (rapamycin) or MEK1/2 (PD325901) but, upon cessation of drug administration, mice developed melanoma, indicating the presence of long-lived melanoma-initiating cells in this system. Notably, combined treatment with rapamycin and PD325901 led to shrinkage of established melanomas. These mice, engineered with a common genetic profile to human melanoma, provide a system to study melanomas cardinal feature of metastasis and for preclinical evaluation of agents designed to prevent or treat metastatic disease.

Infection of New- and Old-World Aedes albopictus (Diptera: Culicidae) by the Intracellular Parasite Wolbachia: Implications for Host Mitochondrial DNA Evolution

Abstract Wolbachia are cytoplasmically inherited, endosymbiotic bacteria known to infect a wide variety of arthropods. Polymerase chain reaction (PCR) amplification of the Wolbachia surface protein (wsp) gene was used to assay the infection of geographically disparate populations of Aedes albopictus (Skuse) by Wolbachia. Nine North American, four South American, one Hawaiian, and four Old World populations of A. albopictus were all doubly infected with both the wAlbA and wAlbB strains of Wolbachia. A 365-bp region of the wAlbA wsp gene was sequenced from seven geographically disparate host populations, and all sequences were identical. Similarly, a 474-bp region of the wAlbB wsp gene was sequenced from the same populations, and all sequences were identical. These results suggest a role for Wolbachia infection in causing the previously established pattern of low mitochondrial DNA variability, but average nuclear gene diversity, within and among populations of A. albopictus.

Melanoma metastasis: new concepts and evolving paradigms.

Melanoma progression is typically depicted as a linear and stepwise process in which metastasis occurs relatively late in disease progression. Significant evidence suggests that in a subset of melanomas, progression is much more complex and less linear in nature. Epidemiologic and experimental observations in melanoma metastasis are reviewed here and are incorporated into a comprehensive model for melanoma metastasis, which takes into account the varied natural history of melanoma formation and progression.

JAK inhibitors in dermatology: The promise of a new drug class

&NA; New molecularly targeted therapeutics are changing dermatologic therapy. Janus kinase–signal transducer and activator of transcription (JAK‐STAT) is an intracellular signaling pathway upon which many different proinflammatory signaling pathways converge. Numerous inflammatory dermatoses are driven by soluble inflammatory mediators, which rely on JAK‐STAT signaling, and inhibition of this pathway using JAK inhibitors might be a useful therapeutic strategy for these diseases. Growing evidence suggests that JAK inhibitors are efficacious in atopic dermatitis, alopecia areata, psoriasis, and vitiligo. Additional evidence suggests that JAK inhibition might be broadly useful in dermatology, with early reports of efficacy in several other conditions. JAK inhibitors can be administered orally or used topically and represent a promising new class of medications. The use of JAK inhibitors in dermatology is reviewed here.

mTORC1 Activation Blocks BrafV600E-Induced Growth Arrest but Is Insufficient for Melanoma Formation

Braf(V600E) induces benign, growth-arrested melanocytic nevus development, but also drives melanoma formation. Cdkn2a loss in Braf(V600E) melanocytes in mice results in rare progression to melanoma, but only after stable growth arrest as nevi. Immediate progression to melanoma is prevented by upregulation of miR-99/100, which downregulates mTOR and IGF1R signaling. mTORC1 activation through Stk11 (Lkb1) loss abrogates growth arrest of Braf(V600E) melanocytic nevi, but is insufficient for complete progression to melanoma. Cdkn2a loss is associated with mTORC2 and Akt activation in human and murine melanocytic neoplasms. Simultaneous Cdkn2a and Lkb1 inactivation in Braf(V600E) melanocytes results in activation of both mTORC1 and mTORC2/Akt, inducing rapid melanoma formation in mice. In this model, activation of both mTORC1/2 is required for Braf-induced melanomagenesis.

Decoding melanoma metastasis.

Metastasis accounts for the vast majority of morbidity and mortality associated with melanoma. Evidence suggests melanoma has a predilection for metastasis to particular organs. Experimental analyses have begun to shed light on the mechanisms regulating melanoma metastasis and organ specificity, but these analyses are complicated by observations of metastatic dormancy and dissemination of melanocytes that are not yet fully malignant. Additionally, tumor extrinsic factors in the microenvironment, both at the site of the primary tumor and the site of metastasis, play important roles in mediating the metastatic process. As metastasis research moves forward, paradigms explaining melanoma metastasis as a step-wise process must also reflect the temporal complexity and heterogeneity in progression of this disease. Genetic drivers of melanoma as well as extrinsic regulators of disease spread, particularly those that mediate metastasis to specific organs, must also be incorporated into newer models of melanoma metastasis.

Mouse melanoma models and cell lines

Mouse models of melanoma have roots in the early 1900¢s when melanocytic tumors arose spontaneously in inbred mouse strains (Cloudman, 1941; Green, 1962; Harding and Passey, 1930). These spontaneous melanomas (probably the most well known of which is B16) were transplantable to congenic mice and could also be cultured, studied, and manipulated in vitro. Due to the utility of these models, they have been a central means by which to address basic questions in melanoma biology. In the latter part of the 20th century, researchers began to employ mutagens like UV irradiation and 7,12Dimethylbenz(a)anthracene (DMBA), as well as tumor promoting agents such as croton oil ⁄ 12-O-tetradecanoylphorbol-13-acetate (TPA) in order to generate melanomas in mice. These pioneering studies (summarized in Table 1), gave rise to melanomas and cutaneous neoplasms. After the advent of transgenic mouse technology, two early approaches were successful in producing melanocytic neoplasms in mice (Iwamoto et al., 1991; Klein-Szanto et al., 1991). One used the methallothionein promoter to drive Ret expression, while the latter used the tyrosinase promoter to drive SV40 T cell antigen expression. In addition to generalized melanosis, these transgenic mice developed ocular melanocytic neoplasms that often precluded development of cutaneous melanomas. Through the 1990s and early 2000s, several more transgenic models were developed (summarized in Table 1), which mostly employed melanocyte-specific expression of mutated Ras or activation of the c-Met-HGF ⁄ SF signaling axis. Changes to cell-cycle control elements also aided this effort by using either melanocyte-specific activation of Cdk4 and ⁄ or Cdkn2a-deficient backgrounds (p16 and ⁄ or p19). Although these models were important in confirming the tumor initiating role of these genetic changes, they often had long latencies and were incompletely penetrant. More recently, an increased understanding of the genetic changes that occur in human melanoma coupled with technical advances in mouse modeling have led to the development of novel and particularly useful models. Braf activating mutations have been described to occur in 50% of melanomas (Davies et al., 2002). Additionally, near universal activation of the PI3K ⁄ Akt ⁄ mTOR signaling pathway (often through inactivation of Pten) has

Development of bullous pemphigoid during nivolumab therapy

Bregs: B regulatory cells BP: bullous pemphigoid CTLA-4: cytotoxic T-lymphocyteeassociated protein 4 IRAE: immune-related adverse events PD-1: programmed cell death protein 1 PD-L1: programmed death ligand

Genetics of Cutaneous T Cell Lymphoma: From Bench to Bedside

Opinion statementCutaneous T cell lymphomas (CTCLs) are non-Hodgkin lymphomas of skin homing T cells. Although early-stage disease may be limited to the skin, tumor cells in later stage disease can populate the blood, the lymph nodes, and the visceral organs. Unfortunately, there are few molecular biomarkers to guide diagnosis, staging, or treatment of CTCL. Diagnosis of CTCL can be challenging and requires the synthesis of clinical findings, histopathology, and T cell clonality studies; however, none of these tests are entirely sensitive or specific for CTCL. Treatment of CTCL is often empiric and is not typically based on specific molecular alterations, as is common in other cancers. In part, limitations in diagnosis and treatment selection reflect the limited insight into the genetic basis of CTCL. Recent next-generation sequencing has revolutionized our understanding of the mutational landscape in this disease. These analyses have uncovered ultraviolet radiation and recombination activating gene (RAG) endonucleases as important mutagens. Furthermore, these studies have revealed potentially targetable oncogenic mutations in the T cell receptor complex, NF-κB, and JAK-STAT signaling pathways. Collectively, these somatic mutations drive lymphomagenesis via cancer-promoting changes in proliferation, apoptosis, and T cell effector function. We expect that these genetic findings will launch a new era of precision medicine in CTCL.

The YUMM lines: a series of congenic mouse melanoma cell lines with defined genetic alterations

The remarkable success of immune therapies emphasizes the need for immune‐competent cancer models. Elegant genetically engineered mouse models of a variety of cancers have been established, but their effective use is limited by cost and difficulties in rapidly generating experimental data. Some mouse cancer cell lines are transplantable to immunocompetent host mice and have been utilized extensively to study cancer immunology. Here, we describe the Yale University Mouse Melanoma (YUMM) lines, a comprehensive system of mouse melanoma cell lines that are syngeneic to C57BL/6, have well‐defined human‐relevant driver mutations, and are genomically stable. This will be a useful tool for the study of tumor immunology and genotype‐specific cancer biology.