Microphthalmia-associated Transcription Factor Expression Levels Research Articles

Abstract 5425: MITF/TFE regulatory programs in neural crest migration are co-opted in melanoma metastasis

Abstract Introduction: Microphthalmia-associated transcription factor (MITF) is a critical regulator of melanocyte differentiation and melanoma oncogenesis. Melanoma expression profiling has revealed a strong trend between low MITF expression levels and invasive behavior. However, it is unclear how low levels of MITF are connected to invasive behavior. Preliminary data from our lab has identified transcription factor E3 (TFE3), a MITF paralog, as a transcriptional regulator in MITF-low melanoma states. We hypothesize that in melanoma cells with low MITF levels, TFE3 promotes invasion. To assess the possibility that the antagonistic regulatory interaction between MITF and a paralog was coopted from the embryo, we examine migratory behavior of neural crest cells in zebrafish embryos that are wild-type, mitfa loss-of-function (LOF) mutants, tfec (TF3 ortholog) LOF mutants, or mitfa/tfec double LOF embryos. Methods: We evaluated TFE3 levels by Western blot in a panel of melanoma cell lines known to express a range of MITF expression levels. We mutated TFE3 exon 4, which encodes the DNA binding domain, using a single guide RNA, and assessed cellular invasive potential using an in vitro transwell invasion assay. CUT&RUN sequencing was used to profile TFE3 genomic binding. Zebrafish embryos were generated in which the mitfa promoter drove expression of RNA encoding green fluorescent protein (GFP), and of the genotypes mentioned above. From transgenic wild-type and mitfa LOF mutant embryos we isolated GFP-expressing cells and conducted single cell-RNA sequencing. We assessed migration of GFP-labeled cells by fluorescent microscopy in 20-48 hour post fertilization zebrafish embryos of all genotypes mentioned above. Results: We found that melanoma cell lines with high levels of MITF (SKMEL3 and SKMEL28) had low levels of TFE3 protein, and those with low levels of MITF (A375 and RPMI 7952) had high levels of TFE3 protein. The TFE3-high cell lines were more invasive in vitro than the TFE3-low cell lines. TFE3-high cell lines depleted of TFE3 were less in invasive in vitro than parental cells. CUT&RUN profiling of TFE3 demonstrates that TFE3 binds mesenchymal-like enhancers in MITF-low cell lines. Single cell RNA sequencing revealed that in a melanocyte precursor cluster present in both wild types and in mitfa mutants, expression of tfec was higher in the latter. Finally, migration of GFP-expressing cells was higher in mitfa LOF mutant embryos than in mitfa/tfec double LOF mutant embryos. Conclusion: These data indicate that reduction of MITF expression up-regulates TFE3 expression in melanoma and tfec in zebrafish melanocytes, although the mechanism of this regulation is unclear. They also show that TFE3 and Tfec promote migration of metastatic melanoma and melanocyte precursors, respectively. Because regulatory mechanisms in cancer are often coopted from embryonic cells, studying the embryo may illuminate cancer pathogenesis. Citation Format: Jeremy Chang, Katelyn Campbell, Rachel Moore, Robert Cornell, Colin Kenny. MITF/TFE regulatory programs in neural crest migration are co-opted in melanoma metastasis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5425.

Orcinol Inhibits Melanogenesis in B16F10 Cells via the Upregulation of the MAPK/ERK Signaling Pathway

Background: Orcinol (3,5-dihydroxytoluene) has been reported to demonstrate inhibitory activity against mushroom tyrosinase. This study aims to investigate the inhibitory effect of orcinol on melanogenesis and its mechanism in B16F10 murine melanoma cells. Methods: The effects of orcinol on melanogenesis were determined spectrophotometrically by the intracellular tyrosinase activity and melanin content. The expression of melanogenesis-related gene and signaling pathways was analyzed by Western blot and/or qRT-PCR analyses. Results: Orcinol reduced intracellular tyrosinase activity and melanin content and attenuated the protein expression and mRNA levels of melanogenesis-related genes, such as tyrosinase, tyrosinase-related protein-1, dopachrome tautomerase, and microphthalmia-associated transcription factor (MITF). Orcinol increased the phosphorylation of extracellular signal-regulated kinase (ERK), which decreased MITF expression levels. Conclusion: Orcinol reduces melanogenesis by inhibiting MITF expression, then the ERK signaling pathway, and that orcinol has the potential to become a functional cosmetic compound for skin whitening.

Anti-Melanogenesis Activity of Crocodile (Crocodylus siamensis) White Blood Cell Extract on Ultraviolet B-Irradiated Melanocytes.

Ultraviolet (UV) radiation generates a range of biological effects in the skin, which includes premature skin aging, hyperpigmentation, and cancer. Therefore, the development of new effective agents for UV-related skin damage remains a challenge in the pharmaceutical industry. This study aims to test the inhibitory effect of crocodile white blood cell (cWBC) extract, a rich source of bioactive peptides, on ultraviolet B (UVB)-induced melanocyte pigmentation. The results showed that cWBC (6.25-400 μg/mL) could inhibit tyrosinase without adduct formation by 12.97 ± 4.20% on average. cWBC pretreatment (25-100 μg/mL) had no cytotoxicity and reduced intracellular melanin to 111.17 ± 5.20% compared with 124.87 ± 7.43 for UVB condition. The protective role of cWBC pretreatment against UVB was exhibited by the promotion of cell proliferation and the prevention of UVB-induced morphological change as observed from F actin staining. The decrease of microphthalmia-associated transcription factor expression levels after cWBC pretreatment might be a mechanism by which cWBC suppresses UVB-induced pigmentation. These results suggest that cWBC could be beneficial for the prevention of UVB-induced skin pigmentation.

Promising anti-melanogenic impacts of Portulaca oleracea on B16F1 murine melanoma cell line: An in-vitro vision

Portulaca oleracea (P. oleracea) has been used in folk medicine for treatment of diverse disorders for centuries. In the present study, we aimed to evaluate the anti-melanogenic properties of P. oleracea ethanolic extract on B16F1 murine melanoma cell line. The effect of different concentrations of P. oleracea and arbutin as positive control were investigated on the levels of cell viability, cellular tyrosinase, extracellular and intracellular melanin content as well as tyrosinase, tyrosinase related protein (Trp)-1, Trp-2, and microphthalmia-associated transcription factor (MITF) expression levels using real time-PCR, in B16F1 murine melanoma cell line. All different concentrations of P. oleracea (1–100 μg/ml) and arbutin (10 μM) did not significantly change the viability of B16F1 cells. Our results showed that α−melanocyte-stimulating hormones (α-MSH) (100 nM) significantly increased the levels of tyrosinase activity, extracellular, and intracellular melanin content as well as tyrosinase, Trp-1, Trp-2, and MITF expression levels in B16F1 cells. In contrast, arbutin (10 μM) significantly suppressed these changes following the α-MSH stimulation in B16F1 cells. Moreover, P. oleracea (1–100 μg/ml) remarkably mitigated the levels of tyrosinase activity, extracellular and intracellular melanin content as well as tyrosinase, Trp-1, Trp-2, and MITF expression levels following the α-MSH stimulation in B16F1 cells in a concentration-dependent manner. The plant possessed anti-melanogenic effects through alleviating tyrosinase, TRP-1, TRP-2, and MITF expression levels as well as melanin content and it may be a promising candidate for pigmentation disorders. However, further clinical investigations are required to confirm our results.

Thymocid®, a Standardized Black Cumin (Nigella sativa) Seed Extract, Modulates Collagen Cross-Linking, Collagenase and Elastase Activities, and Melanogenesis in Murine B16F10 Melanoma Cells.

Black cumin (Nigella sativa) seed extract has been shown to improve dermatological conditions, yet its beneficial effects for skin are not fully elucidated. Herein, Thymocid®, a chemically standardized black cumin seed extract, was investigated for its cosmeceutical potential including anti-aging properties associated with modulation of glycation, collagen cross-linking, and collagenase and elastase activities, as well as antimelanogenic effect in murine melanoma B16F10 cells. Thymocid® (50, 100, and 300 µg/mL) inhibited the formation of advanced glycation end-products (by 16.7–70.7%), collagen cross-linking (by 45.1–93.3%), collagenase activity (by 10.4–92.4%), and elastases activities (type I and III by 25.3–75.4% and 36.0–91.1%, respectively). In addition, Thymocid® (2.5–20 µg/mL) decreased melanin content in B16F10 cells by 42.5–61.6% and reduced cellular tyrosinase activity by 20.9% (at 20 µg/mL). Furthermore, Thymocid® (20 µg/mL for 72 h) markedly suppressed the mRNA expression levels of melanogenesis-related genes including microphthalmia-associated transcription factor (MITF), tyrosinase-related protein 1 (TYRP1), and TYRP2 to 78.9%, 0.3%, and 0.2%, respectively. Thymocid® (10 µg/mL) also suppressed the protein expression levels of MITF (by 15.2%) and TYRP1 (by 97.7%). Findings from this study support the anti-aging and antimelanogenic potential of Thymocid® as a bioactive cosmeceutical ingredient for skin care products.

B16F10 Melanoma 세포에서 낙과 배 물 추출물의 멜라닌 생성 저해 효과

This study investigated the water extracts of fallen pear (FPWE) on tyrosinase activity and melanogenesis. In the present study, we examined the effects of FPWE on mushroom tyrosinase activity in vitro, B16F10 melanoma cell tyrosinase activity, melanin contents, and expression of melanogenic enzyme proteins such as tyrosinase. An apparent down-regulatory effect on tyrosinase activity was observed when B16F10 cells were incubated with FPWE. Results of melanin assay using B16F10 cells treated with different concentrations (50, 125, and 250 μg/mL) of FPWE showed a dose-dependent decrease in melanin content. To determine whether or not FPWE indirectly affects tyrosinase activity, we assessed mushroom tyrosinase activity upon treatment with various concentrations (125, 250, 500, and 1,000 μg/mL) of FPWE. In addition, we investigated changes in the protein level of tyrosinase by using Western blotting. Tyrosinase and microphthalmia-associated transcription factor expression levels in B16F10 melanoma cells were reduced in a dose-dependent manner by FPWE. These results suggest that FPWE reduced melanin formation by inhibition of tyrosinase activity. Therefore, we suggest that FPWE could be used an effective whitening agent for skin.

Dysregulated Expression of MITF in Subsets of Hepatocellular Carcinoma and Cholangiocarcinoma.

Cholangiocarcinoma represents the second most common primary liver tumor after hepatocellular carcinoma. Mahanine, a carbazole alkaloid derived from Murraya koenigii (Linn.) Spreng, has been used as folk medicine in Thailand, where the liver fluke-associated cholangiocarcinoma is common. The expression of microphthalmia-associated transcription factor (MITF) is maintained at immunohistochemically undetectable levels in hepatocytes and cholangiocytes. To explore the regulation of MITF expression in the liver, we immunohistochemically analyzed the MITF expression using hepatocellular carcinoma and cholangiocarcinoma specimens of the human liver cancer tissue array. MITF immunoreactivity was detected in subsets of hepatocellular carcinoma (6 out of 38 specimens; 16%) and cholangiocarcinoma (2/7 specimens; 29%). Moreover, immunoreactivity for glioma-associated oncogene 1 (GLI1), a transcription factor of the Hedgehog signaling pathway, was detected in 55% of hepatocellular carcinoma (21/38 specimens) and 86% of cholangiocarcinoma (6/7 specimens). Importantly, MITF was detectable only in the GLI1-positive hepatocellular carcinoma and cholangiocarcinoma, and MITF immunoreactivity is associated with poor prognosis in patients with hepatocellular carcinoma. Subsequently, the effect of mahanine was analyzed in HepG2 human hepatocellular carcinoma and HuCCT1 and KKU-100 human cholangiocarcinoma cells. Mahanine (25 µM) showed the potent cytotoxicity in these hepatic cancer cell lines, which was associated with increased expression levels of MITF, as judged by Western blot analysis. MITF is over-expressed in subsets of hepatocellular carcinoma and cholangiocarcinoma, and detectable MITF immunoreactivity is associated with poor prognosis in patients with hepatocellular carcinoma. MITF expression levels may be determined in hepatic cancer cells by the balance between the Hedgehog signaling and the cellular stress.

Inhibitory effects of ginsenosides on basic fibroblast growth factor-induced melanocyte proliferation

BackgroundUV-B-exposed keratinocytes secrete various paracrine factors. Among these factors, basic fibroblast growth factor (bFGF) stimulates the proliferation of melanocytes. Ginsenosides, the major active compounds of ginseng, are known to have broad pharmacological effects. In this study, we examined the antiproliferative effects of ginsenosides on bFGF-induced melanocyte proliferation. MethodsWe investigated the inhibitory effects of Korean Red Ginseng and ginsenosides from Panax ginseng on bFGF-induced proliferation of melan-a melanocytes. ResultsWhen melan-a melanocytes were treated with UV-B-irradiated SP-1 keratinocytes media, cell proliferation increased. This increased proliferation of melanocytes decreased with a neutralizing anti-bFGF antibody. To elucidate the effects of ginsenosides on melanocyte proliferation induced by bFGF, we tested 15 types of ginsenoside compounds. Among them, Rh3, Rh1, F1, and CK demonstrated antiproliferative effects on bFGF-induced melanocyte proliferation after 72 h of treatment. bFGF stimulated cell proliferation via extracellular signal-regulated kinase (ERK) activation in various cell types. Western blot analysis found bFGF-induced ERK phosphorylation in melan-a. Treatment with Rh3 inhibited bFGF-induced maximum ERK phosphorylation and F1-delayed maximum ERK phosphorylation, whereas Rh1 and CK had no detectable effects. In addition, cotreatment with Rh3 and F1 significantly suppressed bFGF-induced ERK phosphorylation. Western blot analysis found that bFGF increased microphthalmia-associated transcription factor (MITF) protein levels in melan-a. Treatment with Rh3 or F1 had no detectable effects, whereas cotreatment with Rh3 and F1 inhibited bFGF-induced MITF expression levels more strongly than a single treatment. ConclusionIn summary, we found that ginsenosides Rh3 and F1 have a synergistic antiproliferative effect on bFGF-induced melan-a melanocyte proliferation via the inhibition of ERK-mediated upregulation of MITF.

Microphthalmia-associated transcription factor expression levels in melanoma cells contribute to cell invasion and proliferation.

Microphthalmia-associated transcription factor (MITF) is a nodal point in melanoma transcriptional network that regulates dozens of genes with critical functions in cell differentiation, proliferation and survival. Highly variable MITF expression levels exist in tumor cell subpopulations conferring marked heterogeneity and plasticity in the tumor tissue. A model has been postulated whereby lower MITF levels favour cell invasion and suppress proliferation, whereas high levels stimulate differentiation and proliferation. Additionally, MITF is considered to be a prosurvival gene and a lineage addiction oncogene in melanoma. Herein, we review how MITF expression may affect the melanoma phenotype with consequences on the survival, invasion and metastasis of melanoma cells, and we discuss the research challenges.

Reduced MiR-675 in Exosome in H19 RNA-Related Melanogenesis via MITF as a Direct Target

H19 non-coding RNA downregulation stimulates melanogenesis in melasma patients. However, its mechanism is unclear. In this study, the potential role of a H19 microRNA, miR-675, in melanogenesis was examined. Real-time PCR using cultured normal human skin keratinocytes, melanocytes, and fibroblasts with or without H19 knockdown showed accompanying changes between expression levels of H19 and those of miR-675 in keratinocytes. MiR-675 was also detected in concentrated culture supernatants and showed expression levels parallel with those of cell lysates. In addition to RNase resistance, FACS analysis showed anti-CD63-positive exosomes in culture supernatants, suggesting miR-675 could be released extracellularly and delivered to neighboring cells without degradation. In western blot analysis, the miR-675 mimic reduced the expression of microphthalmia-associated transcription factor (MITF) and phosphorylation of cAMP-responsive element-binding protein, extracellular signal-regulated kinase and apoptosis signal-regulating kinase, whereas these expressions were increased by the miR-675 inhibitor. Although H19 was not a miR-675 target, luciferase reporter assay showed a direct binding of miR-675 to 3'-untranslated region of MITF. In addition, localized in vivo miR-675 overexpression in mouse using a cationic polymer transfection reagent showed reduced mRNA expression levels of MITF, tyrosinase, tyrosine-related protein-1 (Trp-1), and Trp-2. Collectively, the results suggest that miR-675 derived from keratinocytes could be involved in H19-stimulated melanogenesis using MITF as a target of miR-675.

Optimization of the method for the culture of melanocyte precursors from hair follicles and their activation by 1,25-dihydroxyvitamin D3

The melanocytes in vitiligo repigmentation are derived predominantly from melanocyte precursors (MPs) present in the outer root sheath (ORS) of hair follicles. The methods currently used for culturing MPs are unstable, and the cultured cells have the capacity to produce melanin. These factors are problematic when conducting in vitro studies to investigate the mechanism of repigmentation. Although 1,25-dihydroxyvitamin D3 (VID) has been demonstrated to be highly effective in the treatment of vitiligo in the clinic, its precise mode of action has yet to be elucidated. In the present study, the method for the culture of MPs from the ORS of hair follicles was optimized and the ability of VID to activate MPs was investigated. The results suggested that the MPs cultured using the optimized method mainly exhibited bipolar morphology. The cells proliferated well and were negative for 3,4-dihydroxy-L-phenylalanine (DOPA) staining. Transmission electron microscopy revealed that the cytoplasm of the MPs contained numerous stage I and stage II melanosomes; however, stage III and IV melanosomes were not observed. Following VID treatment, the MPs showed increased dendritic morphology, the cells stained positive for DOPA and stage III and IV melanosomes appeared in the cells. Western blotting revealed that microphthalmia-associated transcription factor (MITF), tyrosinase (TYR), tyrosinase-related protein-1 (TRP-1) and TRP-2 were expressed in the MPs and that VID increased the expression levels of MITF, TYR and TRP-1. However, the levels of MITF, TYR and TRP-1 in the MPs prior to and following VID treatment were significantly lower compared with those in cultured epidermal melanocytes, while the levels of TRP-2 in these three groups were not significantly different. Subsequent to VID treatment, the TYR activity in the MPs increased significantly, as did the corresponding melanin levels. In conclusion, the present study successfully optimized the method for MP culture. The MPs demonstrated no significant TYR activity or melanin synthesis; therefore, the MP cultures exhibited the features of MPs in vivo. In addition, VID significantly promoted the differentiation of MPs.

Differences in MITF gene expression and histology between albino and normal sea cucumbers (Apostichopus japonicus Selenka)

Albino Apostichopus japonicus occur both in the wild and in captivity. The offspring of albino A. japonicus also suffer from albinism. The formation of melanin in the melanocytes is dependant on microphthalmia-associated transcription factor (MITF). To investigate the role of MITF in controlling albinism, we cloned the full-length MITF cDNA from A. japonicus and compared MITF mRNA expression in albino and normal A. japonicus. In addition, we used light and electron microscopy to compare histological samples of normal and albino A. japonicus. The body wall of albino adults was characterized by significantly lower levels of MITF expression and lower numbers of epidermal melanocytes, which also contained less melanin. In albino juvenile offspring, MITF expression levels were significantly lower 32 d after fertilization and there were fewer, and less developed, epidermal melanocytes. Thus, we conclude that albino A. japonicus have fewer melanocytes and a reduced ability to synthesize melanin, likely because of lower expression of MITF.

TYRO3-mediated regulation of MITF: a novel target in melanoma?

<i>TYRO3</i>-mediated regulation of MITF: a novel target in melanoma?

Modulation of Microphthalmia-associated Transcription Factor Gene Expression Alters Skin Pigmentation

The microphthalmia-associated transcription factor is implicated in melanocyte development and in the regulation of melanogenesis. Microphthalmia-associated transcription factor is thought to bind to the M-box promoter elements of tyrosinase, tyrosinase-related protein-1 and dopachrome tautomerase/tyrosinase-related protein-2 and transactivate these genes, resulting in increased pigmentation. Using a luciferase reporter construct driven by the microphthalmia-associated transcription factor promoter, we identified agents that modulate microphthalmia-associated transcription factor promoter activity. Changes in endogenous microphthalmia-associated transcription factor expression levels upon treatment with these agents were confirmed using northern and western blots, and their pigmentary modulating activities were demonstrated. Ultraviolet B irradiation and traditional Chinese medicine-1, a natural extract used in traditional Chinese medicine, upregulated microphthalmia-associated transcription factor gene expression and enhanced tyrosinase activity in vitro. Dihydrolipoic acid, lipoic acid, and resveratrol reduced microphthalmia-associated transcription factor and tyrosinase promoter activities. These agents also inhibited the forskolin- and ultraviolet B-stimulated promoter activities of these genes and significantly reduced tyrosinase activity in melanocyte cultures, resulting in depigmentation. Overexpressed microphthalmia-associated transcription factor was capable of rescuing the repressive effects of these compounds on the cotransfected tyrosinase promoter. Dark-skinned Yucatan swine treated with these agents showed visible skin lightening, which was confirmed histologically, whereas ultraviolet B-induced tanning of light-skinned swine was inhibited using these agents. Our findings suggest that modulation of microphthalmia-associated transcription factor expression can alter skin pigmentation and further confirm the central role of microphthalmia-associated transcription factor in melanogenesis.