Project description:The transcription factors PAX3 and MITF are required for the development of the neural crest and melanocyte lineage, and both proteins play important roles in melanoma cell growth and survival. PAX3 transcriptionally activates MITF expression during neural crest development, but the relationship between these transcription factors during melanocyte development and in melanoma cells is currently poorly understood. This study aimed to further our understanding of the interaction between transcriptional networks controlled by PAX3 and MITF by assessing the effect of siRNA-mediated knockdown of PAX3 and MITF in metastatic melanoma cell lines. The goals of this study were to determine (i) if PAX3 is required for maintaining expression of MITF in melanoma and melanocyte cell lines; (ii) whether PAX3 and MITF independently, or redundantly, influence growth and survival in melanoma cell lines; and (iii) to investigate the respective roles of PAX3 and MITF expression in melanoma cell differentiation. Microarrays were used to measure global changes in transcript expression in response to siRNA-mediated knockdown of PAX3 or MITF compared to non-targeting controls in two metastatic melanoma cells lines. RNA was isolated from two different metastatic melanoma cell lines 30 hours after one of four different treaments: (i) transfection with siRNA targeting PAX3; or (ii) transfection with siRNA targeting MITF; or (iii) or transfection with siRNA targeting luciferase (non-targeting negative control); or (iv) treatment with media only (control). Therefore, eight samples were used for gene expression profiling by using GeneChip arrays, with one replicate per cell line per treatment.
Project description:The transcription factors PAX3 and MITF are required for the development of the neural crest and melanocyte lineage, and both proteins play important roles in melanoma cell growth and survival. PAX3 transcriptionally activates MITF expression during neural crest development, but the relationship between these transcription factors during melanocyte development and in melanoma cells is currently poorly understood. This study aimed to further our understanding of the interaction between transcriptional networks controlled by PAX3 and MITF by assessing the effect of siRNA-mediated knockdown of PAX3 and MITF in metastatic melanoma cell lines. The goals of this study were to determine (i) if PAX3 is required for maintaining expression of MITF in melanoma and melanocyte cell lines; (ii) whether PAX3 and MITF independently, or redundantly, influence growth and survival in melanoma cell lines; and (iii) to investigate the respective roles of PAX3 and MITF expression in melanoma cell differentiation. Microarrays were used to measure global changes in transcript expression in response to siRNA-mediated knockdown of PAX3 or MITF compared to non-targeting controls in two metastatic melanoma cells lines.
Project description:MITF plays critical role in development and differentiation of melanocytes and in the context of melanoma, as a lineage survival oncogene. Given its crucial role in melanoma biology, it is very difficult to generate complete knock-out (KO) of MITF and in our hands, those that were generated appear to behave differently than the effect observed using siRNA mediated knock-down, possibly indicative of selection. In order to overcome the limitation of the transient effect of siRNA and study the effect of MITF depletion over a longer period of time, we carried out transcriptomic analyses of Doxycycline inducible shMITF knock down after 8 days in 2 melanoma cell lines MeWo (CVCL_0445) and SkMel 28 (CVCL_0526)
Project description:We analyzed the transcriptional response of the human melanoma cell line MZ7 to TNF-alpha (24 hours) in a dose-dependent manner (TNF-alpha 10U/ml, 100U/ml, 1000U/ml) either transfected with control siRNA (siNT = non-targeting siRNA) or transfected with siRNAs (pool of 4 active and independent siRNAs) against the melanocytic transcription factor and lineage oncogene MITF. (Microphthalmia-associated transcription factor). The experiment was performed as biological duplicate. As MITF is critical for melanoma cell state control, we aimed to explore how MITF expression intersects with inflammation-induced plasticity pathways in melanoma. Total RNA was obtained from siRNA/TNF-treated MZ7 melanoma cell lines at various conditions and global gene expression profiling was done using the Illumina Human HT12 v4 platform.
Project description:To assess the effects of permanent loss of MITF in melanoma cells, we used the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 technique to generate MITF knockout (KO) cell lines in the human hypo-tetraploid SkMel28 melanoma cell line (containing four copies of MITF). We targeted exon 6 (containing the DNA binding domain) of MITF the resulting isogenic cell line is hereafter referred to as ΔMITF-X6. We also performed siRNA mediated transient knock down of MITF along with control siCTRL in 501Mel cells. Furthermore, we used a stable doxycycline inducible over-expression cell line containing FLAG tagged MITF and a control cells with empty vector FLAG in A375P. From our RNA-sequencing studies we found that MITF plays a critical role as a repressor of extracellular matrix gene expression and is actively involved in shaping the microenvironment of melanoma cells in a cell-autonomous manner.
Project description:Ma-Mel-15 human melanoma cell cultures were transiently transfected (RNAiMax, Lipofectamin) with control siRNA, siRNA against MITF (pool of 4 siRNAs), siRNA against c-JUN (pool of 4 siRNAs) or combinations of siMITF and siJUN. Cells were then either treated with TNF-alpha (1000U/ml) for 24 hours or left untreated. The experiment was performed as biological duplicates. We aimed to determine how c-JUN cooperates with acute MITF-loss in human melanoma cells to increase inflammatory responsiveness and cell plasticity. Total RNA was obtained from siRNA/TNF-treated Ma-Mel-15 melanoma cell lines and global gene expression profiling was done using the Illumina Human HT12 v4 platform.
Project description:Background Melanoma cells frequently dedifferentiate in response to inflammation which can increase responses to certain cytokines. Interferon-γ (IFNγ) is an integral part of the anti-tumour immune response and can directly induce both differentiational changes and expression of immunosuppressive proteins in melanoma cells. How the differentiation status of melanoma cells affects IFNγ responses remains unclear. Methods Dedifferentiation of melanoma cells was induced via either siRNA or shRNA mediated MITF knockdown and the cells were subsequently treated with IFNγ. Effects of MITF knockdown and IFNγ treatment on gene expression were evaluated via qPCR and RNA sequencing. A Luminex assay was used to analyse the effects of dedifferentiation and IFNγ treatment on cytokine secretion. Effects on PD-L1 protein expression were analysed via flow cytometry and western blotting. Inhibition of the JAK kinases, NF-κB and STAT3 with small molecule inhibitors, and siRNA mediated knockdown of STAT1 and IRF1 was applied to investigate the molecular mechanism behind IFNγ induced PD-L1 expression in dedifferentiated melanoma cells. The effects of inhibitor treatments and siRNA mediated knockdowns were evaluated via qPCR and western blotting. Bioinformatic analyses of publicly available RNA sequencing data, consisting of 45 patient derived melanoma cell lines, with or without IFNγ treatment, was conducted to assess the generalisability of the in vitro results. Results Dedifferentiation renders 624Mel melanoma cells hypersensitive to IFNγ stimulation in a context-dependent manner, resulting in non-additive upregulation of IFNγ-induced genes, increased PD-L1 protein expression and amplified secretion of CCL2, CXCL10 and IL-10. Furthermore, the intensified PD-L1 protein expression occurs through the JAK-STAT1-IRF1 axis. Lastly, dedifferentiated patient derived melanoma cell lines showed enhanced inflammatory signalling in response to IFNγ compared to differentiated cells, and tended to have higher PD-L1 expression, associated with increased IRF1 expression and activity. Conclusions Together, these findings indicate the existence of a molecular context linking dedifferentiation and IFNγ signalling in melanoma which may lead to immune evasion. Furthermore, these results imply that modulating melanoma differentiation may help shape IFNγ responsiveness.
Project description:The genetic changes underlying metastatic melanoma need to be deciphered to develop new and effective therapeutics. Previously, genome-wide microarray analyses of human melanoma identified two reciprocal gene expression programs, that included expression of mRNAs regulated by either transforming growth factor, beta 1 (TGFB1) pathways or microphthalmia-associated transcription factor (MITF)/SRY-box containing gene 10 (SOX10) pathways. We extend this knowledge to include gene expression analyses of 5 additional human melanoma lines, and show that these lines also fall into either TGFB1 or MITF/SOX10 gene expression groups. These mRNA expression studies were followed up by miRNA expression analyses. Microarray analyses were performed on 5 metastatic melanoma lines in 3 replicates. Standard Affymetrix protocols were used.
Project description:Cellular stress contributes to the capacity of melanoma cells to undergo phenotype switching into highly migratory and drug tolerant dedifferentiated states. Such dedifferentiated melanoma cell states are marked by loss of melanocyte specific gene expression and increase of mesenchymal markers. Two crucial transcription factors, MITF and SOX10, important in melanoma development and progression have been implicated in this process. In this study we describe that loss of MITF is associated with a distinct transcriptional program, MITF promoter hypermethylation and poor patient survival in metastatic melanoma. From a comprehensive collection of melanoma cell lines, we observed that MITF methylated cultures were subdivided in two distinct subtypes. Examining mRNA levels of neural crest associated genes we found that one subtype had lost the expression of several lineage genes including SOX10. Intriguingly, SOX10 loss was associated with SOX10 gene promoter hypermethylation and distinct phenotypic and metastatic properties. Depletion of SOX10 in MITF methylated melanoma cells using CRISPR/Cas9 confirmed these findings. In conclusion, this study describes the significance of melanoma state and the underlying functional properties explaining the aggressiveness of such states.
Project description:We analyzed the transcriptional response of the human melanoma cell line Ma-Mel-15 either transfected with control siRNA (siNT = non-targeting siRNA) or transfected with siRNAs (pool of 4 active and independent siRNAs) directed against the melanocytic transcription factor and lineage oncogene MITF (Microphthalmia-associated transcription factor). The experiment was performed as biological duplicates and RNA was isolated 48 hours after siRNA transfection. We aimed to determine novel markers and pathways of melanoma cell plasticity. Total RNA was obtained from siRNA-treated Ma-Mel-15 melanoma cell lines and global gene expression profiling was done using the Illumina Human HT12 v4 platform.