John T Seykora

University of Pennsylvania, Filadelfia, Pennsylvania, United States

Are you John T Seykora?

Claim your profile

Publications (77)397.18 Total impact

  • Cancer Research 08/2015; 75(15 Supplement):806-806. DOI:10.1158/1538-7445.AM2015-806 · 9.28 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Deletion of the entire CDKN2B-CDKN2A gene cluster is among the most common genetic events in cancer. The tumor-promoting effects are generally attributed to loss of CDKN2A-encoded p16 and p14ARF tumor suppressors. The degree to which the associated CDKN2B-encoded p15 loss contributes to human tumorigenesis is unclear. Here we show that CDKN2B is highly upregulated in benign melanocytic nevi, contributes to maintaining nevus melanocytes in a growth-arrested premalignant state, and is commonly lost in melanoma. Using primary melanocytes isolated directly from freshly excised human nevi naturally expressing the common BRAF(V600E) activating mutation, nevi progressing to melanoma, and normal melanocytes engineered to inducibly express BRAF(V600E), we show that BRAF activation results in reversible, TGFβ-dependent, p15 induction that halts proliferation. Further, we engineer human skin grafts containing nevus-derived melanocytes to establish a new, architecturally faithful, in vivo melanoma model, and demonstrate that p15 loss promotes the transition from benign nevus to melanoma. Copyright © 2015, American Association for Cancer Research.
    Cancer Discovery 07/2015; 75(15 Supplement). DOI:10.1158/2159-8290.CD-15-0196 · 19.45 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The space environment exposes astronauts to risks of acute and chronic exposure to ionizing radiation. Of particular concern is possible exposure to ionizing radiation from a solar particle event (SPE). During an SPE, magnetic disturbances in specific regions of the Sun result in the release of intense bursts of ionizing radiation, primarily consisting of protons that have a highly variable energy spectrum. Thus, SPE events can lead to significant total body radiation exposures to astronauts in space vehicles and especially while performing extravehicular activities. Simulated energy profiles suggest that SPE radiation exposures are likely to be highest in the skin. In the current report, we have used our established miniature pig model system to evaluate the skin toxicity of simulated SPE radiation exposures that closely resemble the energy and fluence profile of the September, 1989 SPE using either conventional radiation (electrons) or proton simulated SPE radiation. Exposure of animals to electron or proton radiation led to dose-dependent increases in epidermal pigmentation, the presence of necrotic keratinocytes at the dermal-epidermal boundary and pigment incontinence, manifested by the presence of melanophages in the derm is upon histological examination. We also observed epidermal hyperplasia and a reduction in vascular density at 30 days following exposure to electron or proton simulated SPE radiation. These results suggest that the doses of electron or proton simulated SPE radiation results in significant skin toxicity that is quantitatively and qualitatively similar. Radiation-induced skin damage is often one of the first clinical signs of both acute and non-acute radiation injury where infection may occur, if not treated. In this report, histopathology analyses of acute radiation-induced skin injury are discussed. Copyright © 2015 The Committee on Space Research (COSPAR). Published by Elsevier Ltd. All rights reserved.
    Life sciences and space research 06/2015; 6. DOI:10.1016/j.lssr.2015.06.003
  • John Seykora · Tzvete Dentchev · David J Margolis
    [Show abstract] [Hide abstract]
    ABSTRACT: Atopic dermatitis (AD) is a common chronic, episodic inflammatory ailment(1) . Recent studies have shown that AD is a life-long disease that often begins in early childhood and that persists into adulthood. AD is at least in part associated with a dysfunctional skin barrier often due to loss of function (LOF) mutations of filaggrin (FLG).(2) Although the impact of FLG LOF on skin barrier function is less certain.(3) While mutations of FLG are relatively common in Asian and European children with AD they were very infrequently found in those of African ancestry.(2;4) This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.
    Experimental Dermatology 05/2015; DOI:10.1111/exd.12749 · 4.12 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Chimeric antigen receptors (CARs) are synthetic molecules designed to redirect T cells to specific antigens. CAR-modified T cells can mediate long-term durable remissions in B cell malignancies, but expanding this platform to solid tumors requires the discovery of surface targets with limited expression in normal tissues. The variant III mutation of the epidermal growth factor receptor (EGFRvIII) results from an in-frame deletion of a portion of the extracellular domain, creating a neoepitope. We chose a vector backbone encoding a second-generation CAR based on efficacy of a murine scFv-based CAR in a xenograft model of glioblastoma. Next, we generated a panel of humanized scFvs and tested their specificity and function as soluble proteins and in the form of CAR-transduced T cells; a low-affinity scFv was selected on the basis of its specificity for EGFRvIII over wild-type EGFR. The lead candidate scFv was tested in vitro for its ability to direct CAR-transduced T cells to specifically lyse, proliferate, and secrete cytokines in response to antigen-bearing targets. We further evaluated the specificity of the lead CAR candidate in vitro against EGFR-expressing keratinocytes and in vivo in a model of mice grafted with normal human skin. EGFRvIII-directed CAR T cells were also able to control tumor growth in xenogeneic subcutaneous and orthotopic models of human EGFRvIII(+) glioblastoma. On the basis of these results, we have designed a phase 1 clinical study of CAR T cells transduced with humanized scFv directed to EGFRvIII in patients with either residual or recurrent glioblastoma (NCT02209376). Copyright © 2015, American Association for the Advancement of Science.
    Science translational medicine 02/2015; 7(275):275ra22. DOI:10.1126/scitranslmed.aaa4963 · 14.41 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Inflammation develops in response to foreign agents or injuries and is crucial to the healing process. However, persistent unresolved inflam­ mation can contribute to the development of can­ cer (Coussens et al., 2013). Despite the wealth of information implicating inflammation in tumor development, the specific role of different cells, especially myeloid cells, in this process remains largely unclear. Myeloid cells are an important component of inflammation. There is now ample evidence of abnormalities in the myeloid com­ partment in cancer, which manifests in inhi­ bition of differentiation of DCs, polarization of macrophages (Ms) toward M2 functional state, and dramatic expansion of myeloid­derived suppressor cells (MDSCs; Gabrilovich et al., 2012). MDSCs represent a heterogeneous population of pathologically activated myeloid cells that includes precursors of neutrophils (polymorpho­ nuclear neutrophils [PMNs]), Ms, DCs, and cells at earlier stages of myeloid cell differentia­ tion (Gabrilovich and Nagaraj, 2009; Peranzoni et al., 2010; Youn et al., 2012). In mice, these cells are defined as Gr­1 + CD11b + cells with the CORRESPONDENCE Dmitry Gabrilovich: dgabrilovich@wistar.org
    Journal of Experimental Medicine 02/2015; 212(3). DOI:10.1084/jem.20140835 · 13.91 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Colorimetric staining techniques such as immunohistochemistry (IHC), immunofluorescence (IF) and histochemistry (HC) provide useful information regarding the localization and relative amount of a molecule/substance in skin. We have developed a novel, straightforward method to assess colorimetric staining by combining features from two open-source software programs. As a proof of principle, we demonstrate the utility of this approach by analyzing changes in skin melanin deposition during the radiation-induced tanning response of Yucatan mini-pigs. This method includes a visualization step to validate the accuracy of color selection before quantitation to ensure accuracy. The data show that this method is robust and will provide a means to obtain accurate comparative analyses of staining in IHC/IF/HC samples. This article is protected by copyright. All rights reserved.
    Experimental Dermatology 11/2014; 24(2). DOI:10.1111/exd.12594 · 4.12 Impact Factor
  • Journal for Immunotherapy of Cancer; 11/2014
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A functional epidermal skin barrier requires the formation of a cornified envelope from terminally differentiating keratinocytes. During this process, multiple genetic and environmental signals coordinately regulate protein expression and tissue differentiation. Here we describe a critical role for hypoxia-inducible factors (HIFs) in the regulation of filaggrin expression and skin barrier formation. Similar to other mammalian tissues, fetal epidermis in mice is normally O2-deprived. Simultaneous deletion of Hif1a and Hif2a in murine epidermis revealed defects in keratinocyte terminal differentiation and epidermal barrier formation. Mice lacking Hif1a and Hif2a in the epidermis exhibited dry flaky skin, impaired permeability barrier, and enhanced sensitivity to cutaneous allergens. These defects were correlated with stratum granulosum attenuation and reduced filaggrin expression. Hypoxic treatment of primary keratinocytes induced filaggrin (Flg) gene expression in a HIF1α- and HIF2α-dependent manner, suggesting that one mechanism by which Hif1a and Hif2a loss causes epidermal barrier defects in mice lies in Flg dysregulation. Therefore, low O2 tension is an essential component of the epidermal environment that contributes to skin development and function.Journal of Investigative Dermatology accepted article preview online, 07 July 2014; doi:10.1038/jid.2014.283.
    Journal of Investigative Dermatology 07/2014; 135(2). DOI:10.1038/jid.2014.283 · 6.37 Impact Factor
  • Source
    Adam I Rubin · John T Seykora
    Journal of Cutaneous Pathology 10/2013; DOI:10.1111/cup.12228 · 1.56 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: : Microcystic adnexal carcinoma (MAC) is an uncommon, locally aggressive, malignant cutaneous tumor with pilar and eccrine differentiation. Mohs micrographic surgery is the treatment of choice for this condition, but specific histological findings can complicate MAC removal and leave doubt as to whether the tumor has been completely removed. Here we describe the clinical and pathological characteristics of a case in which a patient with an MAC underwent multiple reexcisions because of the presence of benign subclinical syringomatous proliferations adjacent to the primary lesion. Our case raises awareness of syringomatous proliferation, a benign process histologically similar but behaviorally distinct from a primary MAC. This experience highlights the importance of continued communication between dermatopathologists and dermatologic surgeons in providing quality patient care.
    The American Journal of dermatopathology 09/2013; 36(2). DOI:10.1097/DAD.0b013e3182a041a6 · 1.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The skin is colonized by a plethora of microbes that include commensals and potential pathogens, but it is currently unknown how cutaneous host immune mechanisms influence the composition, diversity, and quantity of the skin microbiota. Here we reveal an interactive role for complement in cutaneous host-microbiome interactions. Inhibiting signaling of the complement component C5a receptor (C5aR) altered the composition and diversity of the skin microbiota as revealed by deep sequencing of the bacterial 16S rRNA gene. In parallel, we demonstrate that C5aR inhibition results in down-regulation of genes encoding cutaneous antimicrobial peptides, pattern recognition receptors, and proinflammatory mediators. Immunohistochemistry of inflammatory cell infiltrates in the skin showed reduced numbers of macrophages and lymphocytes with C5aR inhibition. Further, comparing cutaneous gene expression in germ-free mice vs. conventionally raised mice suggests that the commensal microbiota regulates expression of complement genes in the skin. These findings demonstrate a component of host immunity that impacts colonization of the skin by the commensal microbiota and vice versa, a critical step toward understanding host-microbe immune mutualism of the skin and its implications for health and disease. Additionally, we reveal a role for complement in homeostatic host-microbiome interactions of the skin.
    Proceedings of the National Academy of Sciences 08/2013; 110. DOI:10.1073/pnas.1307855110 · 9.81 Impact Factor
  • 05/2013; 149(5):637-9. DOI:10.1001/jamadermatol.2013.75
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We determined the feasibility of using an anti-desmoglein (Dsg) monoclonal antibody, Px44, to deliver a biologically active protein to keratinocytes. Recombinantly produced Px44-green fluorescent protein (GFP) injected into mice and skin organ culture delivered GFP to the cell surface of keratinocytes. We replaced GFP with tumor necrosis factor -related apoptosis-inducing ligand (TRAIL) to produce Px44TRAIL. We chose TRAIL as a biologic model because it inhibits activated lymphocytes and causes apoptosis of hyperproliferative keratinocytes, features of various skin diseases. Px44TRAIL formed a trimer, the biologically active form of TRAIL. Standard assays of TRAIL activity showed that Px44TRAIL caused apoptosis of Jurkat cells and inhibited interferon-γ production by activated CD4+ T cells. Enzyme-linked immunoassay with Px44TRAIL showed delivery of TRAIL to Dsg. Immunofluorescence with Px44TRAIL incubated on skin sections and cultured keratinocytes or injected into mouse skin, human organ culture or human xenografts detected TRAIL on keratinocytes. Px44TRAIL caused apoptosis of hyperproliferative, but not differentiating, cultured keratinocytes through binding to Dsg3. Foldon, a small trimerization domain, cloned into Px44TRAIL maintained its stability and biological activity at 37(o) for at least 48 hr. These data suggest that such targeted therapy is feasible and may be useful for hyperproliferative and inflamed skin diseases.Journal of Investigative Dermatology accepted article preview online, 25 February 2013; doi:10.1038/jid.2013.85.
    Journal of Investigative Dermatology 02/2013; 133(9). DOI:10.1038/jid.2013.85 · 6.37 Impact Factor
  • Michael D Gober · Hasan M Bashir · John T Seykora
    [Show abstract] [Hide abstract]
    ABSTRACT: The American Cancer Society estimates that skin cancer is the most prevalent of all cancers with over 2 million cases of nonmelanoma skin cancer each year and 75,000 melanoma cases in 2012. Representative animal cancer models are important for understanding the underlying molecular pathogenesis of these cancers and the development of novel targeted anticancer therapeutics. In this review, we will discuss some of the important animal models that have been useful to identify important pathways involved in basal cell carcinoma, squamous cell carcinoma, and melanoma.
    CANCER AND METASTASIS REVIEW 11/2012; 32(1-2). DOI:10.1007/s10555-012-9410-8 · 7.23 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: Vemurafenib, a novel selective small molecule inhibitor of BRAF, has recently been shown to be effective in the treatment of melanomas harboring the BRAF V600E mutation. Similar to the broad-spectrum RAF inhibitor sorafenib, vemurafenib induces development of squamous cell carcinomas and keratoacanthomas as a side effect of therapy. OBJECTIVE: We sought to detail additional cutaneous adverse effects of vemurafenib and a similar BRAF inhibitor, dabrafenib. METHODS: We evaluated the clinical and histologic feature of skin side effects developing on vemurafenib or dabrafenib therapy in 14 patients. RESULTS: Eight patients developed one or more squamous cell carcinomas, and 11 patients formed benign verrucous keratoses. Eight patients developed single lesions and/or widespread eruptions with histopathologic findings of acantholytic dyskeratosis, consistent with warty dyskeratomas and Darier- or Grover-like rashes, respectively. One patient developed palmoplantar hyperkeratosis, and darkening of existing nevi and new nevi within 2 months of starting vemurafenib. Side effects presented as early as 1 week after beginning therapy, with a mean time of onset of 12.6 weeks in our cohort. LIMITATIONS: This study was limited by the small number of cases, all from a single institution. CONCLUSION: Selective BRAF inhibitor therapy is associated with the development of malignant and benign growths, including keratoacanthoma-like squamous cell carcinomas, warty dyskeratomas, and verrucous keratoses, along with widespread eruptions with histologic features of acantholytic dyskeratosis. Given the potential for malignant lesions to develop on treatment, awareness of potential adverse effects of these agents is necessary, and a low threshold for biopsy of new growths is recommended.
    Journal of the American Academy of Dermatology 05/2012; 67(6). DOI:10.1016/j.jaad.2012.04.008 · 5.00 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Equestrian perniosis (EP) is a rare condition in which patients develop tender burning nodular plaques on their bilateral thighs after riding in the cold. These lesions tend to resolve rapidly with minimal exposure to cold, and wearing loose, layered warm clothing. Unlike acral perniosis, EP has no known systemic disease associations, although 2 reported cases did have elevated cold agglutinins. The histology of this disease is similar to perniosis; however, EP is distinct in that the perivascular lymphocytic infiltrate prominently involves the fat. In this case report, we discuss the clinical and histological findings in 2 cases of EP, including the first documented in a man.
    The American Journal of dermatopathology 04/2012; 35(2). DOI:10.1097/DAD.0b013e31824c221f · 1.43 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: MicroRNAs (miRNAs) regulate the expression of many mammalian genes and play key roles in embryonic hair follicle development; however, little is known of their functions in postnatal hair growth. We compared the effects of deleting the essential miRNA biogenesis enzymes Drosha and Dicer in mouse skin epithelial cells at successive postnatal time points. Deletion of either Drosha or Dicer during an established growth phase (anagen) caused failure of hair follicles to enter a normal catagen regression phase, eventual follicular degradation and stem cell loss. Deletion of Drosha or Dicer in resting phase follicles did not affect follicular structure or epithelial stem cell maintenance, and stimulation of anagen by hair plucking caused follicular proliferation and formation of a primitive transient amplifying matrix population. However, mutant matrix cells exhibited apoptosis and DNA damage and hair follicles rapidly degraded. Hair follicle defects at early time points post-deletion occurred in the absence of inflammation, but a dermal inflammatory response and hyperproliferation of interfollicular epidermis accompanied subsequent hair follicle degradation. These data reveal multiple functions for Drosha and Dicer in suppressing DNA damage in rapidly proliferating follicular matrix cells, facilitating catagen and maintaining follicular structures and their associated stem cells. Although Drosha and Dicer each possess independent non-miRNA-related functions, the similarity in phenotypes of the inducible epidermal Drosha and Dicer mutants indicates that these defects result primarily from failure of miRNA processing. Consistent with this, Dicer deletion resulted in the upregulation of multiple direct targets of the highly expressed epithelial miRNA miR-205.
    Development 04/2012; 139(8):1405-16. DOI:10.1242/dev.070920 · 6.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Cutaneous squamous cell carcinoma (cSCC) is the second most common human cancer with over 250,000 new cases annually in the US and is second in incidence only to basal cell carcinoma. cSCC typically manifests as a spectrum of progressively advanced malignancies, ranging from a precursor actinic keratosis (AK) to squamous cell carcinoma (SCC) in situ (SCCIS), invasive cSCC, and finally metastatic SCC. In this Review we discuss clinical and molecular parameters used to define this range of cutaneous neoplasia and integrate these with the multiple experimental approaches used to study this disease. Insights gained from modeling cSCCs have suggested innovative therapeutic targets for treating these lesions.
    The Journal of clinical investigation 02/2012; 122(2):464-72. DOI:10.1172/JCI57415 · 13.77 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Viral-associated trichodysplasia of immunosuppression is a rare cutaneous eruption that is characterized by follicularly based shiny papules and alopecia with characteristic histopathologic findings of abnormally anagen follicules with excessive inner root sheath differentiation. Prior reports have described the histopathologic characteristics on vertical sections; however, to our knowledge, immunohistochemical analysis of polyomavirus proteins has not been previously performed. We discuss the thorough diagnostic evaluation and therapy of an unusual case of viral-associated trichodysplasia due to a newly described human polyomavirus that occurred in a patient with posttreatment chronic lymphocytic leukemia and an abnormal white blood cell count. Unique to our study is the immunohistochemical staining for the polyomavirus middle T antigen, which demonstrated positive staining of cellular inclusions within keratinocytes that compose the inner root sheath. Further evaluation with scanning electron microscopy and polymerase chain reaction analysis of viral DNA confirmed the presence of the virus. Treatment with topical cidofovir resulted in dramatic clinical improvement and hair regrowth. Several tools, including immunohistochemical staining for the polyomavirus middle T antigen, can be used to identify the pathogenic virus associated with viral-associated trichodysplasia. This case highlights the utility of multiple diagnostic modalities and a robust response to a topical therapeutic agent, cidofovir.
    Archives of dermatology 02/2012; 148(2):219-23. DOI:10.1001/archdermatol.2011.1413 · 4.31 Impact Factor

Publication Stats

2k Citations
397.18 Total Impact Points

Institutions

  • 2000–2015
    • University of Pennsylvania
      • • Department of Pathology and Laboratory Medicine
      • • Department of Dermatology
      • • Perelman School of Medicine
      Filadelfia, Pennsylvania, United States
  • 2007–2013
    • William Penn University
      Filadelfia, Pennsylvania, United States
  • 2002–2012
    • Hospital of the University of Pennsylvania
      • Department of Dermatology
      Philadelphia, Pennsylvania, United States
  • 2004
    • The Children's Hospital of Philadelphia
      Filadelfia, Pennsylvania, United States