@phdthesis{AlcantarinoMenescal2012,
  author    = {Alcantarino Menescal, Luciana},
  title     = {In vivo characterization of genetic factors involved in Xmrk driven melanoma formation in Medaka (Oryzias latipes): a closer look at braf, Stat5 and c-myc},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-70762},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Melanoma arises from the malignant transformation of melanocytes and is one of the most aggressive forms of human cancer. In fish of the genus Xiphophorus, melanoma development, although very rarely, happens spontaneously in nature and can be induced by interspecific crossing. The oncogenic receptor tyrosine kinase, Xmrk, is responsible for melanoma formation in these fishes. Since Xiphophorus are live-bearing fishes and therefore not compatible with embryonic manipulation and transgenesis, the Xmrk melanoma model was brought to the medaka (Oryzias latipes) system. Xmrk expression under the control of the pigment cell specific mitf promoter leads to melanoma formation with 100\% penetrance in medaka. Xmrk is an orthologue of the human epidermal growth factor receptor (EGFR) and activates several downstream signaling pathways. Examples of these pathways are the direct phosphorylation of BRAF and Stat5, as well as the enhanced transcription of C-myc. BRAF is a serine-threonine kinase which is found mutated at high frequencies in malignant melanomas. Stat5 is a transcription factor known to be constitutively activated in fish melanoma. C-myc is a transcription factor that is thought to regulate the expression of approximately 15\% of all human genes and is involved in cancer progression of a large number of different tumors. To gain new in vivo information on candidate factors known to be involved in melanoma progression, I identified and analysed BRAF, Stat5 and C-myc in the laboratory fish model system medaka. BRAF protein motifs are highly conserved among vertebrates and the results of this work indicate that its function in the MAPK signaling is maintained in medaka. Transgenic medaka lines carrying a constitutive active version of BRAF (V614E) showed more pigmented skin when compared to wild type. Also, some transiently expressing BRAF V614E fishes showed a disrupted eye phenotype. In addition, I was able to identify two Stat5 copies in medaka, named Stat5ab/a and Stat5ab/b. Sequence analysis revealed a higher similarity between both Stat5 sequences when compared to either human Stat5a or Stat5b. This suggests that the two Stat5 copies in medaka arose by an independent duplication processes. I cloned these two Stat5 present in medaka, produced constitutive active and dominant negative gene versions and successfully established transgenic lines carrying each version under the control of the MITF promoter. These lines will help to elucidate questions that are still remaining in Stat5 biology and its function in melanoma progression, like the role of Stat5 phosphorylation on tumor invasiveness. In a third project during my PhD work, I analysed medaka C-myc function and indentified two copies of this gene in medaka, named c-myc17 and c-myc20, according to the chromosome where they are located. I produced conditional transgenic medaka lines carrying the c-myc17 gene coupled to the hormone binding domain of the estrogen receptor to enable specific transgene activation at a given time point. Comparable to human C-myc, medaka C-myc17 is able to induce proliferation and apoptosis in vivo after induction. Besides that, C-myc17 long-term activation led to liver hyperplasia. In summary, the medaka models generated in this work will be important to bring new in vivo information on genes involved in cancer development. Also, the generated transgenic lines can be easily crossed to the melanoma developing Xmrk medaka lines, thereby opening up the possibility to investigate their function in melanoma progression. Besides that, the generated medaka fishes make it possible to follow the whole development of melanocytes, since the embryos are transparent and can be used for high throughput chemical screens.},
  subject      = {Japank{\"a}rpfling},
  language  = {en}
}
@phdthesis{Haydn2012,
  author    = {Haydn, Johannes},
  title     = {Regulation of ERK1/2 signaling in melanoma},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-85727},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Die Mechanismen in einer Zelle, die die Genexpression und somit den Stoffwechsel, das Wachstum und das gesamte Zellverhalten steuern, sind ebenso bedeutsam f{\"u}r das Verst{\"a}ndnis der grundlegenden Biologie einer lebenden Zelle wie f{\"u}r die Vorg{\"a}nge der Krebsentstehung. Dabei bilden hochvernetzte, und strikt regulierte Signaltransduktionswege die Basis f{\"u}r ein belastbares und zugleich hochflexibles regulatorisches Netzwerk. Die St{\"o}rung solcher Signalkaskaden kann zum einen urs{\"a}chlich aber auch modifizierend auf die Bildung von Tumoren wirken. Die von Rezeptortyrosinkinasen (RTK) und RAS abh{\"a}ngigen Signalwege, die zur Aktivierung von AKT und ERK1/2 f{\"u}hren, sind hierbei von besonderem Interesse f{\"u}r die Entstehung des malignen Melanoms. Mutationen in Komponenten dieser Wege (z.B. NRAS, BRAF oder PTEN), die die Signalst{\"a}rke erh{\"o}hen kommen in Melanomen sehr h{\"a}ufig vor. Im ersten Teil dieser Arbeit wurden die unterschiedlichen und vielf{\"a}ltigen Funktionen von MKP2, einem Feedbackregulator des ERK1/2-Weges, unter verschiedenen zellul{\"a}ren Rahmenbedingungen, untersucht. Des Weiteren wird eine Funktion des zum AP1-Komplex geh{\"o}renden FOSL1, einem unter transkriptioneller Kontrolle des ERK1/2-Weges stehendem Transkriptionsfaktors, hinsichtlich der Steuerung der Zell-Proliferation gezeigt. Weiterhin habe ich Aspekte der direkten pharmakologischen Inhibition des ERK1/2-Weges hinsichtlich ihres Effekts auf die Ausl{\"o}sung von Apoptose untersucht. Aufgrund der H{\"a}ufigkeit von Mutationen in Genen, die f{\"u}r Proteine des ERK1/2-Weges kodieren (z.B. NRASQ61K, BRAFV600E), gilt die Inhibition dieses Signalwegs als vielversprechende Strategie zur Behandlung des Melanoms. Auch wenn klinische Studien, die Inhibitoren f{\"u}r MEK oder RAF als Einzelmedikamente verwenden, bei mehrmonatiger Behandlung sehr erfolgreich sind, konnten so keine langfristigen Erfolge erzielt werden. Aus diesem Grund werden nun Kombinationstherapien, die einen Inhibitor des ERK1/2-Weges und eine weitere Form der Therapie kombinieren, untersucht. Der zweite Teil dieser Arbeit beschreibt, dass der spezifische MEK Inhibitor PD184352 Melanomzellen vor der Apoptosewirkung von Cisplatin sch{\"u}tzen kann. Einzelbehandlung mit Cisplatin f{\"u}hrt hierbei zur Akkumulation von DNA Sch{\"a}den, die wiederum Caspase-abh{\"a}ngig Apoptose induzieren. Zus{\"a}tzliche Anwendung des MEK Inhibitors verringerte jedoch in einigen Zelllinien das Potential von Cisplatin, Apoptose auszul{\"o}sen. Diese Zellen zeigten eine verst{\"a}rkte Aktivierung der Serin/Threonin-KInase AKT nach MEK Inhibition. Diese AKT Aktivierung f{\"u}hrte zur Inaktivierung der FOXO Transkriptionsfaktoren, was wiederum die Expression des pro-apoptotischen BH3-only Proteins PUMA verringerte. PUMA selbst ist ein wichtiger Bestandteil der Apoptose Maschinerie, die durch Cisplatin aktiviert wird. Die im Rahmen dieser Arbeit erhaltenen Befunde deuten darauf hin, dass RTKs, im besonderen EGFR, bei diesem Crosstalk eine Rolle spielen. Diese Ergebnisse zeigen, dass die Inhibition des RAS/RAF/MEK/ERK Signalweges im Melanom nicht zwangsl{\"a}ufig von Vorteil sein muss, falls die Zellen gleichzeitig mit einem genotoxischen Medikament behandelt werden. Hier kann sie sogar die {\"U}berlebensf{\"a}higkeit von Melanomzellen unter Apoptose induzierenden Bedingungen verbessern.},
  subject      = {Melanom},
  language  = {en}
}
@article{TomeiAdamsUccellinietal.2012,
  author    = {Tomei, Sara and Adams, Sharon and Uccellini, Lorenzo and Bedognetti, Davide and De Giorgi, Valeria and Erdenebileg, Narnygerel and Libera Ascierto, Maria and Reinboth, Jennifer and Liu, Qiuzhen and Bevilacqua, Generoso and Wang, Ena and Mazzanti, Chiara and Marincola, Francesco M.},
  title     = {Association between HRAS rs12628 and rs112587690 polymorphisms with the risk of melanoma in the North American population},
  series = {Medical Oncology},
  volume    = {29},
  journal   = {Medical Oncology},
  number    = {5},
  doi       = {dx.doi.org/10.1007/s12032-012-0255-3},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-126834},
  pages     = {3456-3461},
  year      = {2012},
  abstract  = {HRAS belongs to the RAS genes superfamily. RAS genes are important players in several human tumors and the single-nucleotide polymorphism rs12628 has been shown to contribute to the risk of bladder, colon, gastrointestinal, oral, and thyroid carcinoma. We hypothesized that this SNP may affect the risk of cutaneous melanoma as well. HRAS gene contains a polymorphic region (rs112587690), a repeated hexanucleotide -GGGCCT- located in intron 1. Three alleles of this region, P1, P2, and P3, have been identified that contain two, three, and four repeats of the hexanucleotide, respectively. We investigated the clinical impact of these polymorphisms in a case-control study. A total of 141 melanoma patients and 118 healthy donors from the North America Caucasian population were screened for rs12628 and rs112587690 polymorphisms. Genotypes were assessed by capillary sequencing or fragment analysis, respectively, and rs12628 CC and rs112587690 P1P1 genotypes significantly associated with increased melanoma risk (OR = 3.83, p = 0.003; OR = 11.3, p = 0.033, respectively), while rs112587690 P1P3 frequency resulted significantly higher in the control group (OR = 0.5, p = 0.017). These results suggest that rs12628 C homozygosis may be considered a potential risk factor for melanoma development in the North American population possibly through the linkage to rs112587690.},
  language  = {en}
}