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- Ji, Zhenyu, et al.
(författare)
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MITF Modulates Therapeutic Resistance through EGFR Signaling.
- 2015
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Ingår i: Journal of Investigative Dermatology. - : Elsevier BV. - 1523-1747 .- 0022-202X. ; 135:7, s. 1863-1872
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Tidskriftsartikel (refereegranskat)abstract
- Response to targeted therapies varies significantly despite shared oncogenic mutations. Nowhere is this more apparent than in BRAF(V600E)-mutated melanomas where initial drug response can be striking and yet relapse is commonplace. Resistance to BRAF inhibitors have been attributed to the activation of various receptor tyrosine kinases (RTKs) though the underlying mechanisms have been largely uncharacterized. Here, we found that EGFR induced vemurafenib resistance is ligand dependent. We then employed whole-genome expression analysis and discovererd that vemurafenib resistance correlated with the loss of MITF, along with its melanocyte lineage program, and with the activation of EGFR signaling. An inverse relationship between MITF, vemurafenib resistance and EGFR was then observed in patient samples of recurrent melanoma and was conserved across melanoma cell lines and patients' tumor specimens. Functional studies revealed that MITF depletion activated EGFR signaling and consequently recapitulated the resistance phenotype. In contrast, forced expression of MITF in melanoma and colon cancer cells inhibited EGFR and conferred sensitivity to BRAF/MEK inhibitors. These findings indicate that an "autocrine drug resistance loop" is suppressed by melanocyte lineage signal(s), such as MITF. This resistance loop modulates drug response and could explain the unique sensitivity of melanomas to BRAF inhibition.Journal of Investigative Dermatology accepted article preview online, 19 March 2015. doi:10.1038/jid.2015.105.
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| 2. |
- Ji, Zhenyu, et al.
(författare)
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Vemurafenib Synergizes with Nutlin-3 to Deplete Survivin and Suppresses Melanoma Viability and Tumor Growth
- 2013
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Ingår i: Clinical Cancer Research. - 1078-0432. ; 19:16, s. 4383-4391
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: For patients with advanced melanoma, primary and secondary resistance to selective BRAF inhibition remains one of the most critically compelling challenges. One rationale argues that novel biologically informed strategies are needed to maximally cripple melanoma cells up front before compensatory mechanisms emerge. As p53 is uncommonly mutated in melanoma, restoration of its function represents an attractive adjunct to selective BRAF inhibition. Experimental Design: Thirty-seven BRAF(V600E)-mutated melanoma lines were subjected to synergy studies in vitro using a combination of vemurafenib and nutlin-3 (Nt-3). In addition, cellular responses and in vivo efficacy were also determined. We also analyzed changes in the levels of canonical apoptotic/survival factors in response to vemurafenib. Results: Dual targeting of BRAF(V600E) and Hdm2 with vemurafenib and Nt-3, respectively, synergistically induced apoptosis and suppressed melanoma viability in vitro and tumor growth in vivo. Suppression of p53 in melanoma cells abrogated Nt-3's effects fully and vemurafenib's effects partially. A survey of canonical survival factors revealed that both vemurafenib and Nt-3 independently attenuated levels of the antiapoptotic protein, survivin. Genetic depletion of survivin reproduces the cytotoxic effects of the combination strategy. Conclusion: These results show preclinical feasibility for overcoming primary vemurafenib resistance by restoring p53 function. Moreover, it identifies survivin as one downstream mediator of the observed synergism and a potential secondary target. (C)2013 AACR.
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| 3. |
- Sanna, Adriana, et al.
(författare)
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DNA promoter hypermethylation of melanocyte lineage genes determines melanoma phenotype
- 2022
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Ingår i: JCI Insight. - : American Society for Clinical Investigation. - 2379-3708. ; 7:19
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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