Východiská: Malígny melanóm je jedným z najagresívnejších druhov rakoviny. Melanóm primárne vzniká z pigment produkujúcich buniek melanocytov, ktoré sa vyznačujú špecifickými mechanizmami prežívania. Kľúčové postavenie v metabolizme melanómu má transkripčný faktor asociovaný s mikroftalmiou (microphthalmia-associated transcription factor – MITF-M). MITF-M sa zapája do regulácie expresie veľkého počtu génov riadiacich procesy melanogenézy, proliferácie, diferenciácie a prežitia melanocytov. Expresia tohto transkripčného faktora v melanocytoch je aktivovaná niekoľkými signálnymi cestami, pričom blokovanie jeho expresie, alebo funkcie môže znamenať poruchu v regulácii antiapoptotických mechanizmov. MITF-M taktiež ovplyvňuje aktivitu matrixovej metaloproteinázy 14 (matrix metalloproteinase – MMP14), ktorá je zodpovedná za zmenu tvaru melanocytov a za zvýšenie ich pohyblivosti a invazivity. V ľudských melanocytoch s invazívnym fenotypom bola zistená veľmi nízka hladina expresie MITF-M, čo naznačuje že tento transkripčný faktor pôsobí ako supresor metastatického procesu. V rakovinových bunkách s nízkou hladinou expresie cytozolového/nukleárneho β-katenínu, vzniká malé množstvo proteínu MITF-M, ktorý nedokáže inhibovať transkripciu MMP 14. Tento enzým katalyzuje degradáciu laminínu a fibronektínu, čím dochádza k zmene tvaru melanocytov, k zvýšemiu ich pohyblivosti a invazivity. Ciele: Táto prehľadová práca popisuje regulačnú dráhu aktivácie MITF-M, jeho zapojenie do proliferácie transformovaných melanocytov ako aj jeho úlohu pri zvyšovaní invazivity malígneho melanómu. Detailné pochopenie mechanizmov fungovania signálnej dráhy MITF-M je vysoko aktuálnou témou a môže pomôcť pri vývoji nových tak diagnostických, ako aj terapeutických aplikácií pri liečbe pacientov s malígnym melanómom.

Background: Malignant melanoma is one of the most aggressive types of cancers. Melanoma is derived from pigment-producing cells, melanocytes, which are characterized by a specific survival mechanism. Microphthalmia-associated transcription factor (MITF-M) plays a role in the metabolism of melanoma and is involved in the regulation of the expression of multiple genes mediating processes such as melanogenesis, proliferation, differentiation, and melanocyte survival. The expression of this transcription factor in melanocytes is activated by several signaling pathways, and reduced expression or function of MITF-M can cause the dysregulation of anti-apoptotic mechanisms. MITF-M is also involved in matrix metalloproteinase 14 (MMP14) activity, which is responsible for shape changes in melanocytes and increases in their motility and invasiveness. Very low levels of expression of MITF-M are found in human melanocytes with an invasive phenotype, indicating that this transcription factor acts as a suppressor of the metastatic process. Cancer cells with low expression of cytosolic/nuclear β-catenin have a small amount of MITF-M 14 that is insufficient to inhibit MMP transcription. The enzyme catalyzes the degradation of laminin and fibronectin, thereby changing the shape of melanocytes, which leads to their increased mobility and invasiveness. Aims: This review describes the regulatory pathway of MITF-M activation, its involvement in the proliferation of transformed melanocytes, and its role in increasing the invasiveness of malignant melanoma. A detailed understanding of the MITF-M signaling pathway is highly topical and could help to develop new diagnostic and therapeutic applications for patients with malignant melanoma.

• MeSH
• invazivní růst nádoru MeSH
• lidé MeSH
• melanocyty metabolismus   MeSH
• melanom * genetika   metabolismus   MeSH
• nádorová transformace buněk * metabolismus   MeSH
• nádory kůže genetika   metabolismus   MeSH
• proliferace buněk MeSH
• transkripční faktor spojený s mikroftalmií * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• práce podpořená grantem MeSH
• přehledy MeSH

The tissue-specific control of gene activation in melanocytes is directed by the microphthalmia-associated transcription factor (MITF), a master regulator of melanocyte development and differentiation. Tyrosinase is a rate-limiting enzyme in melanin biosynthesis and a prototypic MITF target. While the expression of tyrosinase is restricted to pigmented cells, the transfected tyrosinase promoter is active in a broad range of cell types if ectopic MITF is co-expressed. Here we used the E1A oncoprotein and its mutants as repressors of both the transiently transfected and endogenous tyrosinase promoter. We report that the requirement of the E1A N-terminus for repression of the MITF-activated tyrosinase promoter and the sensitivity to derepression by the histone deacetylase inhibitor trichostatin Aare distinct when the activity of the transiently transfected or the endogenous promoter is analysed in U2-OS cells. Thus, for transiently transfected versus chromatin-embedded promoter, the activity of obligatory MITF seems to be executed through different mechanisms of transcriptional coactivation.

• MeSH
• adenovirové proteiny E1A genetika   MeSH
• financování vládou MeSH
• lidé MeSH
• melanom experimentální genetika   MeSH
• polymerázová řetězová reakce s reverzní transkripcí metody   využití   MeSH
• transkripční faktor spojený s mikroftalmií genetika   MeSH
• tyrosinasa genetika   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• srovnávací studie MeSH

Melanin production is the primary mechanism protecting human skin against the UV light-induced damage. The polymeric compound melanin is synthesized within melanocytes in the specialized subcellular organelles, termed melanosomes, which are then transferred to surrounding keratinocytes. The genes for melanin synthesis and deposition are coordinately expressed in melanocytes. The transcription factor MITF, which has been reported to activate more than 25 genes in pigment cells, has emerged as an essential regulator not only for melanocyte development, proliferation and survival, but also for the expression of enzymes and structural proteins ensuring the production of melanin. MITF is a transcriptional activator of several genes which encode melanosome-localized proteins involved both in melanin synthesis and in melanosome biogenesis and transport, including genes whose mutations are associated with human oculocutaneous and ocular forms of albinism. Here, we outline the mechanisms of transcriptional regulation of genes associated with the biosynthesis of melanin in melanocytes and melanoma cells. MITF is crucial in this process, while several other factors seem to have only an auxiliary role to play under specific circumstances.

• MeSH
• biologické modely MeSH
• fyziologický stres MeSH
• lidé MeSH
• melaniny biosyntéza   MeSH
• melanocyty cytologie   fyziologie   MeSH
• melanom genetika   patofyziologie   MeSH
• melanozomy fyziologie   MeSH
• pigmentace kůže genetika   fyziologie   MeSH
• promotorové oblasti (genetika) MeSH
• sekvence nukleotidů MeSH
• trans-aktivátory genetika   fyziologie   MeSH
• transkripční faktor spojený s mikroftalmií genetika   fyziologie   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH

Microphthalmia-associated transcription factor (MITF) activates the expression of melanocyte-specific markers and promotes the survival of embryonic, adult and malignant melanocytes. Although numerous MITF-dependent downstream genes have been identified, the mechanisms by which the MITF activity is coregulated remain elusive. Here we used a non-melanocytic cell line U2-OS as a model in which MITF evokes transcription of a paradigmatic MITF target tyrosinase and show that the adenoviral E1A protein represses the MITF-driven transcription in these cells. The E1A CR1 domain (which alone is insufficient to bind p300) was sufficient for repression, while the N-terminus, through which E1A binds the p300/CBP proteins and other coactivators, was unable to repress. Correspondingly, CR1 inhibited colony formation of MITF-positive, but not MITF-negative, melanoma cells. The repression by CR1 was largely independent of the PCAF-binding motif, previously recognized to be necessary for suppression of muscle-specific enhancer. Interestingly, CR1 conferred transcriptional competence to the MITF-CR1 chimera in which the MITF portion was rendered transcription-deficient. Moreover, MITF mutants defective in binding to p300/CBP in vivo still activated transcription, further supporting a p300/CBP-independent coactivation of MITF targets. MITF is amplified in a subset of melanomas and is thought to be required for sustained proliferation of malignant melanocytes. Our results suggest that understanding how CR1 represses Mitf activity may reveal a route to melanoma therapy.

• MeSH
• adenovirové proteiny E1A chemie   MeSH
• aktivace enzymů MeSH
• aktivace transkripce MeSH
• down regulace MeSH
• financování organizované MeSH
• histonacetyltransferasy metabolismus   MeSH
• lidé MeSH
• melanom enzymologie   genetika   patologie   MeSH
• molekulární sekvence - údaje MeSH
• mutantní proteiny chemie   MeSH
• nádorové buněčné linie MeSH
• regulace genové exprese enzymů MeSH
• regulace genové exprese u nádorů MeSH
• represorové proteiny metabolismus   MeSH
• sekvence aminokyselin MeSH
• terciární struktura proteinů MeSH
• testy nádorových kmenových buněk MeSH
• transkripční faktor spojený s mikroftalmií genetika   MeSH
• transkripční faktory p300-CBP metabolismus   MeSH
• tyrosinasa genetika   metabolismus   MeSH
• vazba proteinů MeSH
• Check Tag
• lidé MeSH

Cutaneous tumors with melanocytic differentiation represent a broad group of neoplasms of both melanocytic and non-melanocytic origin. Besides traditional members such as clear-cell sarcoma (CCS) and PEComa, the latter group has recently expanded to also include MITF::CREM fusion-associated tumors, but the available data are limited. Herein, we present a third case of this rare neoplasm which occurred in the temporal region in a 1-year-old girl. It was an infiltratively growing polypoid dermal-based lesion lacking an intraepidermal component. It consisted of cellular solid sheets or small nests of epithelioid to spindled cells with a predominantly eosinophilic and much less commonly clear cytoplasm. The nuclei had round to ovoid shape and exhibited moderate to high-grade atypia and prominent nucleoli. The mitotic activity was 11 mitoses per 10 high-power fields, and atypical mitotic figures were present. Immunohistochemically, the tumor was strongly positive with S100 protein, SOX10, and MITF, while HMB45, tyrosinase, and Melan A were negative. Extensive molecular analysis revealed only MITF::CREM gene fusion. There had no evidence of disease 9 months after the diagnosis. These tumors need to be distinguished from malignant tumors with melanocytic differentiation, primarily from melanoma. However, additional cases still need to be studied to precisely define their biological potential and establish their nosologic status.

• MeSH
• buněčná diferenciace MeSH
• kojenec MeSH
• lidé MeSH
• melanocyty patologie   MeSH
• melanom * diagnóza   MeSH
• modulátor elementu responzivního pro cyklický AMP metabolismus   MeSH
• nádorové biomarkery analýza   MeSH
• nádory kůže * patologie   MeSH
• sarkom z jasných buněk * genetika   MeSH
• transkripční faktor spojený s mikroftalmií genetika   metabolismus   MeSH
• Check Tag
• kojenec MeSH
• lidé MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• kazuistiky MeSH

p21/ WAF1/ Cip1 (p21), a cyclin-dependent kinase inhibitor, may act as an antioncogene, but may also behave as a tumor promoting factor by inhibiting apoptosis. p21 is also a transcriptional regulator, exerting this activity independently of cyclin-dependent kinases. Increased p21 protein levels were found in a subset of melanomas. However, the mechanism(s) contributing to the tolerance of high p21 levels in melanoma cells remains unexplained. Here, we show that the p21 protein positively regulates the promoter of microphthalmia-associated transcription factor (MITF), a transcription factor which plays a central role in the expression of melanocyte-specific genes, lineage determination, and survival of melanoma cells. p21 activated the MITF promoter-reporter, occupied the promoter in vivo and cooperated with cAMP response element binding protein (CREB) in promoter activation. In addition, p21 knockdown by shRNA resulted in a decrease of MITF protein and promoter activity, and p21 protein levels correlated with MITF mRNA in most cell lines tested. As the p21 gene is a known transcriptional target of MITF, the reciprocal stimulation of transcription may constitute a positive-feedback loop reinforcing MITF expression in melanoma cells. Our results might help explain the tolerance of increased p21 levels found in some melanomas.

• MeSH
• inhibitor p21 cyklin-dependentní kinasy metabolismus   MeSH
• lidé MeSH
• melanom genetika   metabolismus   MeSH
• messenger RNA genetika   metabolismus   MeSH
• nádorové buněčné linie MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• promotorové oblasti (genetika) MeSH
• regulace genové exprese u nádorů MeSH
• transkripční faktor spojený s mikroftalmií genetika   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The dysregulation of gene expression is an enabling hallmark of cancer. Computational analysis of transcriptomics data from human cancer specimens, complemented with exhaustive clinical annotation, provides an opportunity to identify core regulators of the tumorigenic process. Here we exploit well-annotated clinical datasets of prostate cancer for the discovery of transcriptional regulators relevant to prostate cancer. Following this rationale, we identify Microphthalmia-associated transcription factor (MITF) as a prostate tumor suppressor among a subset of transcription factors. Importantly, we further interrogate transcriptomics and clinical data to refine MITF perturbation-based empirical assays and unveil Crystallin Alpha B (CRYAB) as an unprecedented direct target of the transcription factor that is, at least in part, responsible for its tumor-suppressive activity in prostate cancer. This evidence was supported by the enhanced prognostic potential of a signature based on the concomitant alteration of MITF and CRYAB in prostate cancer patients. In sum, our study provides proof-of-concept evidence of the potential of the bioinformatics screen of publicly available cancer patient databases as discovery platforms, and demonstrates that the MITF-CRYAB axis controls prostate cancer biology.

• MeSH
• alfa-krystaliny - řetězec B genetika   MeSH
• buňky PC-3 MeSH
• lidé MeSH
• myši nahé MeSH
• myši MeSH
• nádorové buněčné linie MeSH
• nádorové supresorové proteiny genetika   MeSH
• nádory prostaty genetika   patologie   MeSH
• prognóza MeSH
• regulace genové exprese u nádorů genetika   MeSH
• transkripční faktor spojený s mikroftalmií genetika   MeSH
• transkripční faktory genetika   MeSH
• transkriptom genetika   MeSH
• výpočetní biologie metody   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Transkripční faktor MITF (microphthalmia-associated transcription factor) je klíčovým regulátorem embryonálního vývoje melanocytové linie a aktivuje transkripci asi 30 genů mezi kterými jsou geny specifické pro diferenciaci melanocytů, jejich proliferacia viabilitu. MITF je nutný i pro přežívání melanomových buněk. Lokální remodelace chromatinu specifickými komplexy je nutná pro expresi MITF i některých jeho cílových genů. Zablokováním transkripční aktivity faktoru MITF je možné docílit ztrátu proliferace a přežívání melanomových buněk v kultuře. Cílem projektu tedy bude identifikovat nejvhodnější molekulární postup úplné inhibice aktivity a/nebo exprese MITF a pomocí metody microarrays detekovat další cílové geny transkripčně závislé na MITF nutné kproliferaci a k blokování apoptozy u melanomových buněk. Výsledky ukáží na faktory účastnící se progrese melanomu a na mechanismus jejich exprese, a mohou být podkladem pro cílenou genovou terapii nádoru, jenž je rezistentní chemo- i radio-terapii.; Transcription factor MITF (microphthalmia-associated transcription factor) is a key regulator of the development of embryonic melanocytes and activates about 30 genes among which are differentiation markers and genes maintaining the viability of melanocytes. Moreover, MITF is also required for the viability melanoma cells. Local chromatin remodeling at promoters is required for the expression of MITF and some of its targets. Blocking of the MITF expression could be therefore used to inhibit the viability and proliferation of melanoma cells. The aim of this project is to identify a suitable molecular approach to fully inhibit expression and/or activity of MITF and to detect additional MITF targets which are crucial for proliferation and maintenance of antiapoptotic signals in melanoma cells. The results will improve our understanding of the role of MITF in melanoma progression and may be a route to targeted gene therapy of this chemo- and radio-therapy resistant tumor.

• MeSH
• cílená molekulární terapie MeSH
• genetická terapie MeSH
• individualizovaná medicína MeSH
• malá interferující RNA MeSH
• melanom terapie   MeSH
• molekulární patologie MeSH
• restrukturace chromatinu MeSH
• sekvenční analýza RNA MeSH
• transkripční faktor spojený s mikroftalmií antagonisté a inhibitory   genetika   MeSH

• Konspekt
• Patologie. Klinická medicína
• NLK Obory
• dermatovenerologie
• onkologie
• biologie
• NLK Publikační typ
• závěrečné zprávy o řešení grantu IGA MZ ČR

Melanoma arises from neural crest-derived melanocytes which reside mostly in the skin in an adult organism. Epithelial-mesenchymal transition (EMT) is a tumorigenic programme through which cells acquire mesenchymal, more pro-oncogenic phenotype. The reversible phenotype switching is an event still not completely understood in melanoma. The EMT features and increased invasiveness are associated with lower levels of the pivotal lineage identity maintaining and melanoma-specific transcription factor MITF (microphthalmia-associated transcription factor), whereas increased proliferation is linked to higher MITF levels. However, the precise role of MITF in phenotype switching is still loosely characterized. To exclude the changes occurring upstream of MITF during MITF regulation in vivo, we employed a model whereby MITF expression was inducibly regulated by shRNA in melanoma cell lines. We found that the decrease in MITF caused only moderate attenuation of proliferation of the whole cell line population. Proliferation was decreased in five of 15 isolated clones, in three of them profoundly. Reduction in MITF levels alone did not generally produce EMT-like characteristics. The stem cell marker levels also did not change appreciably, only a sharp increase in SOX2 accompanied MITF down-regulation. Oppositely, the downstream differentiation markers and the MITF transcriptional targets melastatin and tyrosinase were profoundly decreased, as well as the downstream target livin. Surprisingly, after the MITF decline, invasiveness was not appreciably affected, independently of proliferation. The results suggest that low levels of MITF may still maintain relatively high proliferation and might reflect, rather than cause, the EMT-like changes occurring in melanoma.

• MeSH
• buněčná diferenciace * účinky léků   MeSH
• doxorubicin farmakologie   MeSH
• epitelo-mezenchymální tranzice účinky léků   genetika   MeSH
• fenotyp MeSH
• invazivní růst nádoru MeSH
• kontrolní body buněčného cyklu účinky léků   genetika   MeSH
• lidé MeSH
• melanom genetika   patologie   MeSH
• messenger RNA genetika   metabolismus   MeSH
• nádorové biomarkery metabolismus   MeSH
• nádorové buněčné linie MeSH
• nádorové kmenové buňky účinky léků   metabolismus   MeSH
• pohyb buněk účinky léků   genetika   MeSH
• proliferace buněk účinky léků   MeSH
• regulace genové exprese u nádorů účinky léků   MeSH
• transkripční faktor spojený s mikroftalmií genetika   metabolismus   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Metastasized malignant melanoma has a poor prognosis because of its intrinsic resistance to chemotherapy and radiotherapy. The central role in the melanoma transcriptional network has the transcription factor MITF (microphthalmia-associated transcription factor). It has been shown recently that the expression of MITF and some of its target genes require the SWI/SNF chromatin remodeling complex. Here we demonstrate that survival of melanoma cells requires functional SWI/SNF complex not only by supporting expression of MITF and its targets and but also by activating expression of prosurvival proteins not directly regulated by MITF. Microarray analysis revealed that besides the MITF-driven genes, expression of proteins like osteopontin, IGF1, TGFß2 and survivin, the factors known to be generally associated with progression of tumors and the antiapoptotic properties, were reduced in acute BRG1-depleted 501mel cells. Western blots and RT-PCR confirmed the microarray findings. These proteins have been verified to be expressed independently of MITF, because MITF depletion did not impair their expression. Because these genes are not regulated by MITF, the data suggests that loss of BRG1-based SWI/SNF complexes negatively affects survival pathways beyond the MITF cascade. Immunohistochemistry showed high expression of both BRM and BRG1 in primary melanomas. Exogenous CDK2, osteopontin, or IGF1 each alone partly relieved the block of proliferation imposed by BRG1 depletion, implicating that more factors, besides the MITF target genes, are involved in melanoma cell survival. Together these results demonstrate an essential role of SWI/SNF for the expression of MITF-dependent and MITF-independent prosurvival factors in melanoma cells and suggest that SWI/SNF may be a potential and effective target in melanoma therapy.

• MeSH
• apoptóza genetika   MeSH
• chromozomální proteiny, nehistonové genetika   metabolismus   MeSH
• cyklin-dependentní kinasa 2 genetika   metabolismus   MeSH
• DNA-helikasy genetika   metabolismus   MeSH
• imunohistochemie MeSH
• inhibitory apoptózy genetika   metabolismus   MeSH
• insulinu podobný růstový faktor I genetika   metabolismus   MeSH
• jaderné proteiny genetika   metabolismus   MeSH
• lidé MeSH
• melanom genetika   metabolismus   patologie   MeSH
• nádorové buněčné linie MeSH
• névus genetika   metabolismus   patologie   MeSH
• osteopontin genetika   metabolismus   MeSH
• polymerázová řetězová reakce s reverzní transkripcí MeSH
• proliferace buněk MeSH
• RNA interference MeSH
• sekvenční analýza hybridizací s uspořádaným souborem oligonukleotidů MeSH
• stanovení celkové genové exprese MeSH
• transformující růstový faktor beta2 genetika   metabolismus   MeSH
• transkripční faktor spojený s mikroftalmií genetika   metabolismus   MeSH
• transkripční faktory genetika   metabolismus   MeSH
• viabilita buněk genetika   MeSH
• western blotting MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH