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Project description:MITF regulates SCD and fatty acid saturation to control melanoma phenotypic state.
| PRJNA565361 | ENA
Project description:Phenotypic and metabolic heterogeneity within tumors is a major barrier to effective cancer therapy. How metabolism is implicated in specific phenotypes and whether lineage-restricted mechanisms control key metabolic vulnerabilities remain poorly understood. In melanoma, downregulation of the lineage addiction oncogene microphthalmia-associated transcription factor (MITF) is a hallmark of the proliferative-to-invasive phenotype switch, although how MITF promotes proliferation and suppresses invasion is poorly defined. Here, we show that MITF is a lineage-restricted activator of the key lipogenic enzyme stearoyl-CoA desaturase (SCD) and that SCD is required for MITFHigh melanoma cell proliferation. By contrast MITFLow cells are insensitive to SCD inhibition. Significantly, the MITF-SCD axis suppresses metastasis, inflammatory signaling, and an ATF4-mediated feedback loop that maintains de-differentiation. Our results reveal that MITF is a lineage-specific regulator of metabolic reprogramming, whereby fatty acid composition is a driver of melanoma phenotype switching, and highlight that cell phenotype dictates the response to drugs targeting lipid metabolism.
| S-EPMC7137507 | biostudies-literature
Project description:The ability of cancer cells to switch phenotype in response to a dynamic intra-tumor microenvironment is a major barrier to effective therapy. In melanoma, down-regulation of the lineage addiction oncogene MITF (Microphthalmia-associated transcription factor) is a hallmark of the proliferative-to-invasive phenotype switch. Yet how MITF promotes proliferation and suppresses invasion is poorly understood. Here we show that expression of the key lipogenic enzyme stearoyl-CoA desaturase (SCD) is activated by MITF, but suppressed by the stress-responsive transcription factor ATF4. SCD expression is required for MITF-positive melanoma cell proliferation,. By contrast, MITF-low cells express reduced levels of SCD and are insensitive to its inhibition, indicating that cell phenotype dictates response to drugs targeting lipid metabolism. Since SCD suppresses inflammatory signalling and ATF4 expression, the results identify a positive feedback-loop that can maintain an invasive phenotype, uncover a key role for MITF and ATF4 in metabolic reprograming, and reveal fatty acid composition as a driver of melanoma phenotype-switching.
2019-11-19 | PXD010254 | Pride
Project description:Phenotypic and metabolic heterogeneity within tumors is a major barrier to effective cancer therapy. Yet how metabolism is implicated in specific phenotypes, and whether lineage-restricted mechanisms control key metabolic vulnerabilities remains poorly understood. In melanoma, down-regulation of the lineage addiction oncogene Microphthalmia-associated Transcription Factor (MITF) is a hallmark of the proliferative-to-invasive phenotype switch, though how MITF promotes proliferation and suppresses invasion is poorly defined. Here we show that MITF is a lineage restricted activator of the key lipogenic enzyme stearoyl-CoA desaturase (SCD), and that SCD is required for MITFHigh melanoma cell proliferation. By contrast MITFLow cells are insensitive to SCD inhibition. Significantly, the MITF-SCD axis suppresses metastasis, inflammatory signalling, and an ATF4-mediated feedback-loop that maintains dedifferentiation. Our results reveal that MITF is a lineagespecific regulator of metabolic reprogramming, whereby fatty acid composition is a driver of melanoma phenotype-switching, and highlight that cell phenotype dictates response to drugs targeting lipid metabolism.
2019-10-16 | GSE137390 | GEO
Project description:Lineage-restricted regulation of SCD and fatty acid saturation by MITF controls melanoma phenotypic plasticity
| PRJNA565365 | ENA
Project description:The Microphthalmia associated transcription factor (Mitf) is an important regulator in melanocyte development and has been shown to be involved in melanoma progression. The current model for the role of Mitf in melanoma assumes that the total activity of the protein is tightly regulated in order to secure cell proliferation. Previous research has shown that regulation of Mitf is complex and involves regulation of expression, splicing, protein stability and post-translational modifications. Here we show that microRNAs (miRNAs) are also involved in regulating Mitf in melanoma cells. Sequence analysis revealed conserved binding sites for several miRNAs in the Mitf 3'UTR sequence. Furthermore, miR-148 was shown to affect Mitf mRNA expression in melanoma cells through a conserved binding site in the 3'UTR sequence of mouse and human Mitf. In addition we confirm the previously reported effects of miR-137 on Mitf. Other miRNAs, miR-27a, miR-32 and miR-124 which all have conserved binding sites in the Mitf 3'UTR sequence did not have effects on Mitf. Our data show that miR-148 and miR-137 present an additional level of regulating Mitf expression in melanocytes and melanoma cells. Loss of this regulation, either by mutations or by shortening of the 3'UTR sequence, is therefore a likely factor in melanoma formation and/or progression.
| S-EPMC2904378 | biostudies-other
Project description:Microphthalmia-associated transcription factor (MITF) is a key transcription factor in melanoma development and progression. MITF amplification and downregulation have been observed in a significant proportion of melanoma patients and correlate with clinical outcomes. Here, we have investigated the effect of MITF on melanoma chemokine expression and immune cell attraction. In B16F10 melanoma cells, MITF knockdown reduced expression of CXCL10, with concomitantly decreased attraction of immune cells and accelerated tumor outgrowth. Conversely, overexpression of MITF in YUMM1.1 melanoma cells also led to an increased immune cell attraction in vitro. Subcutaneous YUMM1.1 melanomas overexpressing MITF however showed a reduced immune infiltration of lymphocytes and an increased tumor growth. In human melanoma cell lines, silencing of MITF enhanced chemokine production and immune cell attraction, while overexpression of MITF led to lower immune cell attraction. In summary, our results show that MITF regulates chemokine expression in murine and in human melanoma cells, and affects in vivo immune cell attraction and tumor growth. These results reveal a functional relationship between MITF and immune cell infiltration, which may be exploited for cancer therapy.
| S-EPMC6290759 | biostudies-literature
Project description:The Microphthalmia-associated transcription factor (MITF) is an important regulator of cell-type specific functions in melanocytic cells. MITF is essential for the survival of pigmented cells, but whereas high levels of MITF drive melanocyte differentiation, lower levels are required to permit proliferation and survival of melanoma cells. MITF is phosphorylated by ERK, and this stimulates its activation, but also targets it for degradation through the ubiquitin-proteosome pathway, coupling MITF degradation to its activation. We have previously shown that because ERK is hyper-activated in melanoma cells in which BRAF is mutated, the MITF protein is constitutively down-regulated. Here we describe another intriguing aspect of MITF regulation by oncogenic BRAF in melanoma cells. We show oncogenic BRAF up-regulates MITF transcription through ERK and the transcription factor BRN2 (N-Oct3). In contrast, we show that in melanocytes this pathway does not exist because BRN2 is not expressed, demonstrating that MITF regulation is a newly acquired function of oncogenic BRAF that is not performed by the wild-type protein. Critically, in melanoma cells MITF is required downstream of oncogenic BRAF because it regulates expression of key cell cycle regulatory proteins such as CDK2 and CDK4. Wild-type BRAF does not regulate this pathway in melanocytes. Thus, we show that oncogenic BRAF exerts exquisite control over MITF on two levels. It downregulates the protein by stimulating its degradation, but then counteracts this by increasing transcription through BRN2. Our data suggest that oncogenic BRAF plays a critical role in regulating MITF expression to ensure that its protein levels are compatible with proliferation and survival of melanoma cells. We propose that its ability to appropriate the regulation of this critical factor explains in part why BRAF is such a potent oncogene in melanoma.
| S-EPMC2444043 | biostudies-literature
Project description:Solar ultraviolet B radiation (UVB) is one of the leading causes of various skin conditions, including photoaging, sunburn erythema, and melanoma. As a protective response, the skin has inbuilt defense mechanisms, including DNA repair, cell cycle, apoptosis, and melanin synthesis. Though DNA repair, cell cycle, and apoptosis are clock controlled, the circadian mechanisms associated with melanin synthesis are not well understood. Using human melanocytes and melanoma cells under synchronized clock conditions, we observed that the microphthalmia-associated transcription factor (MITF), a rate-limiting protein in melanin synthesis, is expressed rhythmically with 24-hr periodicity in the presence of circadian clock protein, BMAL1. Furthermore, we demonstrated that BMAL1 binds to the promoter region of MITF and transcriptionally regulates its expression, which positively influences melanin synthesis. Finally, we report that an increase in melanin levels due to BMAL1 overexpression protects human melanoma cells from UVB. In conclusion, our studies provide novel insights into the mechanistic role of the circadian clock in melanin synthesis and protection against UVB-mediated DNA damage and genomic instability.
| S-EPMC8429232 | biostudies-literature
Project description:Fat intake alters mitochondrial lipid composition which can affect function. We used novel methodology to assess bioenergetics, including simultaneous ATP and reactive oxygen species (ROS) production, in liver and heart mitochondria of C57BL/6 mice fed diets of variant fatty acid content and saturation. Our methodology allowed us to clamp ADP concentration and membrane potential (??) at fixed levels. Mice received a control diet for 17–19 weeks, a high-fat (HF) diet (60% lard) for 17–19 weeks, or HF for 12 weeks followed by 6–7 weeks of HF with 50% of fat as menhaden oil (MO) which is rich in n-3 fatty acids. ATP production was determined as conversion of 2-deoxyglucose to 2-deoxyglucose phosphate by NMR spectroscopy. Respiration and ATP production were significantly reduced at all levels of ADP and resultant clamped ?? in liver mitochondria from mice fed HF compared to controls. At given ??, ROS production per mg mitochondrial protein, per unit respiration, or per ATP generated were greater for liver mitochondria of HF-fed mice compared to control or MO-fed mice. Moreover, these ROS metrics began to increase at a lower ?? threshold. Similar, but less marked, changes were observed in heart mitochondria of HF-fed mice compared to controls. No changes in mitochondrial bioenergetics were observed in studies of separate mice fed HF versus control for only 12 weeks. In summary, HF feeding of sufficient duration impairs mitochondrial bioenergetics and is associated with a greater ROS “cost” of ATP production compared to controls. These effects are, in part, mitigated by MO.
| S-EPMC3955408 | biostudies-literature