scholarly journals The cytosolic role of EZH2-IMPDH2 complex in melanoma progression and metastasis via GTP regulation

2021 ◽  
Author(s):  
Gamze Kuser Abali ◽  
Fumihito Noguchi ◽  
Pacman Szeto ◽  
Youfang Zhang ◽  
Cheng Huang ◽  
...  
Keyword(s):  
Melanoma Cell ◽  
Ribosome Biogenesis ◽  
Inosine Monophosphate Dehydrogenase ◽  
Independent Manner ◽  
Human Patient ◽  
Polycomb Repressive Complex 2 ◽  
Cbs Domain ◽  
Human Melanocytes ◽  
Normal Human ◽  
Clonogenic Cell

Abstract The enhancer of zeste homolog 2 (EZH2) oncogene is a histone methyltransferase that functions canonically as a catalytic subunit of the polycomb repressive complex 2 (PRC2) to tri-methylate histone H3 at Lys 27 (H3K27me3). Although targeting of EZH2 methyltransferase is a promising therapeutic strategy against cancer, methyltransferase-independent oncogenic functions of EZH2 are also described. Moreover, pharmacological EZH2 methyltransferase inhibition was only variably effective in pre-clinical and clinical studies, suggesting that targeting EZH2 methyltransferase alone may be insufficient. Here, we demonstrate a non-canonical mechanism of EZH2’s oncogenic activity through interactions with inosine monophosphate dehydrogenase 2 (IMPDH2) and downstream promotion of guanosine-5'-triphosphate (GTP) production. Liquid Chromatography-Mass Spectrometry (LC-MS) of EZH2 immunoprecipitates from melanoma cell lines and human patient-derived xenografts (PDXs) revealed EZH2-IMPDH2 interactions that were verified to occur between the N-terminal EED-binding domain of cytosolic EZH2 and the CBS domain of IMPDH2 in a PRC2- and methylation-independent manner. EZH2 silencing reduced cellular GTP, ribosome biogenesis, RhoA-mediated actomyosin contractility and melanoma cell proliferation and invasion by impeding the activity and cytosolic localization of IMPDH2. Guanosine, which replenishes GTP, reversed these effects and thereby promoted invasive and clonogenic cell states even in EZH2 silenced cells. IMPDH2 silencing antagonized the proliferative and invasive effects of EZH2, also in a guanosine-reversible manner. In human melanomas, high cytosolic EZH2 and IMPDH2 expression were associated with nucleolar enlargement, a marker for ribosome biogenesis. We also identified EZH2-IMPDH2 complexes in a range of cancers in which Sappanone A (SA), which inhibits EZH2-IMPDH2 interactions and thereby IMPDH2 tetramerization, was anti-tumorigenic, although notably non-toxic in normal human melanocytes and bone marrow derived blood progenitor cells that lacked observable EZH2-IMPDH2 interactions. These findings illuminate a previously unrecognized, non-canonical, methyltransferase-independent, but GTP-dependent mechanism by which EZH2 regulates tumorigenicity in melanoma and other cancers, opening new avenues for development of anti-EZH2 therapeutics.

The Proteolytic Potential of Normal Human Melanocytes: Comparison With Other Skin Cells and Melanoma Cell Lines

1996 ◽  
Vol 9 (5) ◽  
pp. 255-264 ◽  
Author(s):  
JOZEF BIZIK ◽  
SANDRINE BESSOU ◽  
DIANA FELNEROVA ◽  
ANTTI VAHERI ◽  
ALAIN TAIEB
Keyword(s):  
Cell Lines ◽  
Melanoma Cell ◽  
Skin Cells ◽  
Human Melanocytes ◽  
Normal Human ◽  
Melanoma Cell Lines

scholarly journals The cytosolic role of EZH2-IMPDH2 complex in melanoma progression and metastasis via GTP regulation

2021 ◽  
Author(s):  
Gamze Kuser Abali ◽  
Fumihito Noguchi ◽  
Pacman Szeto ◽  
Youfang Zhang ◽  
Cheng Huang ◽  
...  
Keyword(s):  
Melanoma Cell ◽  
De Novo ◽  
Clinical Samples ◽  
Ribosomal Biogenesis ◽  
Inosine Monophosphate Dehydrogenase ◽  
Methyl Transferase ◽  
Cbs Domain ◽  
Actomyosin Contractility

Although conventional EZH2 enzymatic inhibitors are effective in various tumors, we demonstrated that B-Raf mutant melanoma cells do not respond effectively to both GSK126 and EPZ6438 when used in physiological levels in vitro. In addition, the EZH2 knockdown phenotype (lowered tumorigenesis and metastasis) was rescued by both wild-type EZH2 and methyl-transferase-deficient H689A mutant and cytosolic nuclear localization signal (NLS) deletion-mutant EZH2 overexpression in vitro and in vivo. This clearly indicates a methyl-transferase-independent role of cytosolic EZH2 in melanoma cell tumorigenicity and metastasis. To identify potential methyltransferase-independent mechanisms of EZH2 in melanoma, we performed Liquid Chromatography-Mass Spectrometry (LC-MS) on EZH2 immunoprecipitates from multiple melanoma cell lines and human PDXs. We identified an interacting protein called inosine monophosphate dehydrogenase 2 (IMPDH2), the rate-limiting enzyme in de-novo GTP synthesis. Biochemical studies showed that N-terminal EED-binding domain of cytosolic EZH2 interacts with CBS domain of IMPDH2 in a PRC2- and methylation-independent manner. EZH2 silencing reduces cellular GTP levels by impeding IMPDH2 tetramerization, stability and its cytosolic localization. On the other hand, guanosine, which replenishes GTP, stabilized ribosomal biogenesis and actomyosin contractility and thereby, promoted invasive and clonogenic cell states even in EZH2 silenced cells. In human melanoma clinical samples, high cytosolic EZH2 and IMPDH2 expressions are directly correlated with the nucleolar enlargement in the metastatic melanomas. In addition, IMPDH2 silencing reduces EZH2 overexpression induced proliferation and invasion phenotype that is reversed later by guanosine addition. In addition, EZH2-IMPDH2 complex was also validated across a range of cancers. These results point to a methyltransferase-independent but GTP-dependent non-canonical mechanism of EZH2 regulation in various cancers. Sappanone A (SA), that is shown to inhibit IMPDH2/EZH2 interaction and thereby IMPDH2 tetrametization, is anti-tumorigenic across a range of cancers including melanoma, but not in normal melanocytes or bone marrow progenitor cells. In summary, EZH2 contributes to melanoma tumorigenicity and invasion by upregulating ribosomal biogenesis and actomyosin contractility via IMPDH2-induced GTP synthesis.

scholarly journals LRG1 Promotes Metastatic Dissemination of Melanoma through Regulating EGFR/STAT3 Signalling

Cancers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 3279
Author(s):  
Yuet Ping Kwan ◽  
Melissa Hui Yen Teo ◽  
Jonathan Chee Woei Lim ◽  
Michelle Siying Tan ◽  
Graciella Rosellinny ◽  
...  
Keyword(s):  
Metastatic Melanoma ◽  
Melanoma Cell ◽  
Molecular Mechanisms ◽  
Complex Disease ◽  
Treatment Options ◽  
Melanoma Metastasis ◽  
Dependent Manner ◽  
Promoting Effect ◽  
Human Patient ◽  
Cell Invasiveness

Although less common, melanoma is the deadliest form of skin cancer largely due to its highly metastatic nature. Currently, there are limited treatment options for metastatic melanoma and many of them could cause serious side effects. A better understanding of the molecular mechanisms underlying the complex disease pathophysiology of metastatic melanoma may lead to the identification of novel therapeutic targets and facilitate the development of targeted therapeutics. In this study, we investigated the role of leucine-rich α-2-glycoprotein 1 (LRG1) in melanoma development and progression. We first established the association between LRG1 and melanoma in both human patient biopsies and mouse melanoma cell lines and revealed a significant induction of LRG1 expression in metastatic melanoma cells. We then showed no change in tumour cell growth, proliferation, and angiogenesis in the absence of the host Lrg1. On the other hand, there was reduced melanoma cell metastasis to the lungs in Lrg1-deficient mice. This observation was supported by the promoting effect of LRG1 in melanoma cell migration, invasion, and adhesion. Mechanistically, LRG1 mediates melanoma cell invasiveness in an EGFR/STAT3-dependent manner. Taken together, our studies provided compelling evidence that LRG1 is required for melanoma metastasis but not growth. Targeting LRG1 may offer an alternative strategy to control malignant melanoma.

scholarly journals Molecular and Biochemical Basis of Minocycline-Induced Hyperpigmentation—The Study on Normal Human Melanocytes Exposed to UVA and UVB Radiation

2021 ◽  
Vol 22 (7) ◽  
pp. 3755
Author(s):  
Jakub Rok ◽  
Zuzanna Rzepka ◽  
Justyna Kowalska ◽  
Klaudia Banach ◽  
Artur Beberok ◽  
...  
Keyword(s):  
Uv Radiation ◽  
Therapeutic Potential ◽  
Melanin Synthesis ◽  
Uvb Radiation ◽  
Biochemical Basis ◽  
Skin Hyperpigmentation ◽  
Human Melanocytes ◽  
Anti Cancer ◽  
Normal Human

Minocycline is a drug which induces skin hyperpigmentation. Its frequency reaches up to 50% of treated patients. The adverse effect diminishes the great therapeutic potential of minocycline, including antibacterial, neuroprotective, anti-inflammatory and anti-cancer actions. It is supposed that an elevated melanin level and drug accumulation in melanin-containing cells are related to skin hyperpigmentation. This study aimed to evaluate molecular and biochemical mechanism of minocycline-induced hyperpigmentation in human normal melanocytes, as well as the contribution of UV radiation to this side effect. The experiments involved the evaluation of cyto- and phototoxic potential of the drug using cell imaging with light and confocal microscopes as well as biochemical and molecular analysis of melanogenesis. We showed that minocycline induced melanin synthesis in epidermal melanocytes. The action was intensified by UV irradiation, especially with the UVB spectrum. Minocycline stimulated the expression of microphthalmia-associated transcription factor (MITF) and tyrosinase (TYR) gene. Higher levels of melanin and increased activity of tyrosinase were also observed in treated cells. Moreover, minocycline triggered the supranuclear accumulation of tyrosinase, similar to UV radiation. The decreased level of premelanosome protein PMEL17 observed in all minocycline-treated cultures suggests disorder of the formation, maturation or distribution of melanosomes. The study revealed that minocycline itself was able to enhance melanin synthesis. The action was intensified by irradiation, especially with the UVB spectrum. Demonstrated results confirmed the potential role of melanin and UV radiation minocycline-induced skin hyperpigmentation.

The Role of Nuclear Factor-kappaB and Melanogenesis in Tumor Necrosis Factor-Alpha-Induced Apoptosis of Normal Human Melanocytes

2002 ◽  
Vol 15 (5) ◽  
pp. 321-329 ◽  
Author(s):  
Jing Shang ◽  
Jürgen Eberle ◽  
Christoph C. Geilen ◽  
Amir M. Hossini ◽  
Lothar F. Fecker ◽  
...  
Keyword(s):  
Tumor Necrosis ◽  
Nuclear Factor Kappab ◽  
Nuclear Factor ◽  
Necrosis Factor Alpha ◽  
Human Melanocytes ◽  
Normal Human ◽  
Factor Alpha ◽  
Induced Apoptosis ◽  
Necrosis Factor

E-cadherin is the major mediator of human melanocyte adhesion to keratinocytes in vitro

1994 ◽  
Vol 107 (4) ◽  
pp. 983-992 ◽  
Author(s):  
A. Tang ◽  
M.S. Eller ◽  
M. Hara ◽  
M. Yaar ◽  
S. Hirohashi ◽  
...  
Keyword(s):  
Cell Types ◽  
Melanoma Metastasis ◽  
Normal Keratinocytes ◽  
Human Melanocyte ◽  
Human Melanocytes ◽  
Dependent Cell ◽  
Normal Human ◽  
Pre Treatment ◽  
E Cadherin

E- and P-cadherin are calcium (Ca2+)-dependent cell adhesion molecules important in the morphogenesis and maintenance of skin structure. By use of flow cytometry and specific antibodies, we now show that cultured human melanocytes express E- and P-cadherin on their surfaces, and that these molecules have the same characteristics as reported for other cell types. Specifically, melanocyte cadherins are sensitive to trypsin digestion in the absence of Ca2+ and are protected from trypsin degradation by Ca2+, and are functional at 37 degrees C but not at 4 degrees C. We further show that melanocytes contain mRNA transcripts encoding both E- and P-cadherin. Adhesion of cultured melanocytes to keratinocyte monolayers is abolished by pre-treatment of the melanocytes with trypsin/EDTA, which degrades E- and P-cadherins, is greatly reduced by anti-E-cadherin antibodies and is slightly reduced by antibodies to P-cadherin, alpha 2, alpha 3 and beta 1 integrins. In contrast to normal melanocytes, eight of nine melanoma cell lines lacked E-cadherin (or expressed markedly reduced levels) and five were negative for P-cadherin. Melanoma cells also failed to adhere to keratinocyte monolayers. These results demonstrate that normal human melanocytes express functional E- and P-cadherin and that E-cadherin is primarily responsible for adhesion of human melanocytes to keratinocytes in vitro. In addition, transformed melanocytes express markedly reduced levels of E- and P-cadherin, and exhibit decreased affinity for normal keratinocytes in vitro, suggesting that loss of cadherins may play a role in melanoma metastasis.

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