Project description:Genotype directed anti-cancer therapies such BRAF inhibitor in BRAF mutant melanoma can show remarkable clinical efficacy but resistance limits their benefit. We show that a transposon activation screen efficiently identifies resistance genes to BRAF and captures a number of previously uncharacterized resistance mechanisms, including an E3 ubiquitin ligase NEDD4L and the Hippo pathway effector WWTR1 (TAZ). Resistance can be reversed by combining BRAF inhibition with tyrosine kinase inhibitors as observed previously for other resistance genes. Moreover, an integrative analysis of several gain- and loss-of-function genetic screens performed in the same context reveals smaller functional diversity of resistance mechanisms to MAPK inhibition than suggested by the broad range of resistance genes identified, implying common therapeutic strategies. A375 cells with lentiviral vector controls or WWTR1 cDNA plasmid.
Project description:Genotype directed anti-cancer therapies such BRAF inhibitor in BRAF mutant melanoma can show remarkable clinical efficacy but resistance limits their benefit. We show that a transposon activation screen efficiently identifies resistance genes to BRAF and captures a number of previously uncharacterized resistance mechanisms, including an E3 ubiquitin ligase NEDD4L and the Hippo pathway effector WWTR1 (TAZ). Resistance can be reversed by combining BRAF inhibition with tyrosine kinase inhibitors as observed previously for other resistance genes. Moreover, an integrative analysis of several gain- and loss-of-function genetic screens performed in the same context reveals smaller functional diversity of resistance mechanisms to MAPK inhibition than suggested by the broad range of resistance genes identified, implying common therapeutic strategies.
Project description:Single cell transposon insertion site profiles were generated from A375 xenograft tumors that had aquired BRAF inhibitor resistance in vivo as a consequence of Sleeping Beauty transposon mutagenesis.
Project description:The activation of transcriptional coactivators YAP and its paralog TAZ has been shown to promote resistance to anti-cancer therapies. YAP/TAZ activity is tightly coupled to actin cytoskeleton architecture. However, the influence of actin remodeling on cancer drug resistance remains largely unexplored. Here, we report a pivotal role of actin remodeling in YAP/TAZ-dependent BRAF inhibitor resistance in BRAF V600E mutant melanoma cells. Melanoma cells resistant to BRAF inhibitor PLX4032 exhibit an increase in actin stress fiber formation, which appears to promote the nuclear accumulation of YAP/TAZ. Knockdown of YAP/TAZ overcomes PLX4032 resistance, whereas overexpression of constitutively active YAP induces resistance. Moreover, inhibition of actin polymerization and cytoskeletal tension in melanoma cells suppresses both YAP/TAZ activation and PLX4032 resistance. Our siRNA library screening identifies actin dynamics regulator TESK1 as a novel vulnerable point of the YAP/TAZ-dependent resistance pathway. These results suggest that inhibition of actin remodeling is a promising synthetic lethal strategy to suppress resistance in BRAF inhibitor therapies.
Project description:Somatic transposon mutagenesis in mice is an efficient strategy to investigate the genetic mechanisms of tumorigenesis. The identification of tumor driving transposon insertions traditionally requires the generation of large tumor cohorts to obtain information about common insertion sites. Tumor driving insertions are also characterized by their clonal expansion in tumor tissue, a phenomenon that is facilitated by the slow and evolving transformation process of transposon mutagenesis. We describe here an improved approach for the detection of tumor driving insertions that assesses the clonal expansion of insertions by quantifying the relative proportion of sequence reads obtained in individual tumors. To this end, we have developed a protocol for insertion site sequencing that utilizes acoustic shearing of tumor DNA and Illumina sequencing. We analyzed various solid tumors generated by PiggyBac mutagenesis and for each tumor >10^6 reads corresponding to >10^4 insertion sites were obtained. In each tumor, 9 to 25 insertions stood out by their enriched sequence read frequencies when compared to frequencies obtained from tail DNA controls. These enriched insertions are potential clonally expanded tumor driving insertions, and thus identify candidate cancer genes. The candidate cancer genes of our study comprised many established cancer genes, but also novel candidate genes such as Mastermind-like1 (Mamld1) and Diacylglycerolkinase delta (Dgkd). We show that clonal expansion analysis by high-throughput sequencing is a robust approach for the identification of candidate cancer genes in insertional mutagenesis screens on the level of individual tumors. Solid tumors in mice were generated by somatic transposon mutagenesis with a PiggyBac transposon system. Insertion sites of transposons in 11 tumors and 6 non-cancerous tail controls were determined by Illumina high-throughput sequencing. Insertions were determined both on 5' and 3' sides of the transposon (PB5 and PB3, respectively). Quantitative analysis of read numbers revealed enrichment of certain insertions in tumors, but not in controls, and these enriched insertions identify candidate cancer genes.
Project description:Acquired BRAF/MEK inhibitor resistance in melanoma results in a new transcriptional state associated with increased risk of metastasis. Here, we identified non-canonical EphA2 signaling as a driver of the resistance-associated metastatic state. We used mass spectrometry-based proteomic and phenotypic assays to demonstrate that the expression of active non-canonical EphA2-S897E in melanoma cells led to a mesenchymal-to-amoeboid transition (MAT) driven by Cdc42 activation. The induction of MAT promoted melanoma cell invasion, survival under shear stress, adhesion to endothelial cells under continuous flow conditions, increased permeability of endothelial cell monolayers and stimulated melanoma transendothelial cell migration. In vivo, melanoma cells expressing EphA2-S897E or active Cdc42 showed superior lung retention following tail-vain injection. Analysis of BRAF inhibitor-sensitive and -resistant melanoma cells demonstrated resistance to be associated with an MAT switch, upregulation of Cdc42 activity, increased invasion, and transendothelial migration. The drug resistant metastatic state was dependent upon histone deacetylase 8 (HDAC8) activity. Silencing of HDAC8 lead to inhibition of EphA2 and AKT phosphorylation, reduced invasion and impaired melanoma cell-endothelial cell interactions. In summary, we have demonstrated that the metastatic state associated with acquired BRAF inhibitor resistance is dependent on non-canonical EphA2 signaling, leading to increased melanoma-endothelial cell interactions and enhanced tumor dissemination.
Project description:Acquired BRAF/MEK inhibitor resistance in melanoma results in a new transcriptional state associated with increased risk of metastasis. Here, we identified non-canonical EphA2 signaling as a driver of the resistance-associated metastatic state. We used mass spectrometry-based proteomic and phenotypic assays to demonstrate that the expression of active non-canonical EphA2-S897E in melanoma cells led to a mesenchymal-to-amoeboid transition (MAT) driven by Cdc42 activation. The induction of MAT promoted melanoma cell invasion, survival under shear stress, adhesion to endothelial cells under continuous flow conditions, increased permeability of endothelial cell monolayers and stimulated melanoma transendothelial cell migration. In vivo, melanoma cells expressing EphA2-S897E or active Cdc42 showed superior lung retention following tail-vain injection. Analysis of BRAF inhibitor-sensitive and -resistant melanoma cells demonstrated resistance to be associated with an MAT switch, upregulation of Cdc42 activity, increased invasion, and transendothelial migration. The drug resistant metastatic state was dependent upon histone deacetylase 8 (HDAC8) activity. Silencing of HDAC8 lead to inhibition of EphA2 and AKT phosphorylation, reduced invasion and impaired melanoma cell-endothelial cell interactions. In summary, we have demonstrated that the metastatic state associated with acquired BRAF inhibitor resistance is dependent on non-canonical EphA2 signaling, leading to increased melanoma-endothelial cell interactions and enhanced tumor dissemination.
Project description:Acquired BRAF/MEK inhibitor resistance in melanoma results in a new transcriptional state associated with increased risk of metastasis. Here, we identified non-canonical EphA2 signaling as a driver of the resistance-associated metastatic state. We used mass spectrometry-based proteomic and phenotypic assays to demonstrate that the expression of active non-canonical EphA2-S897E in melanoma cells led to a mesenchymal-to-amoeboid transition (MAT) driven by Cdc42 activation. The induction of MAT promoted melanoma cell invasion, survival under shear stress, adhesion to endothelial cells under continuous flow conditions, increased permeability of endothelial cell monolayers and stimulated melanoma transendothelial cell migration. In vivo, melanoma cells expressing EphA2-S897E or active Cdc42 showed superior lung retention following tail-vain injection. Analysis of BRAF inhibitor-sensitive and -resistant melanoma cells demonstrated resistance to be associated with an MAT switch, upregulation of Cdc42 activity, increased invasion, and transendothelial migration. The drug resistant metastatic state was dependent upon histone deacetylase 8 (HDAC8) activity. Silencing of HDAC8 lead to inhibition of EphA2 and AKT phosphorylation, reduced invasion and impaired melanoma cell-endothelial cell interactions. In summary, we have demonstrated that the metastatic state associated with acquired BRAF inhibitor resistance is dependent on non-canonical EphA2 signaling, leading to increased melanoma-endothelial cell interactions and enhanced tumor dissemination.
Project description:Purpose:To identify resistance mechanisms for the chemotherapeutic drug fludarabine in chronic lymphocytic leukemia (CLL), as innate and acquired resistance to fludarabine-based chemotherapy represents a major challenge for long-term disease control. Methods: We employed piggyBac transposon-mediated mutagenesis, combined with next-generation sequencing, to identify genes that confer resistance to fludarabine in a human CLL cell line. Results: RNA-seq profiling of fludarabine-resistant cells suggested deregulated MAPK signaling as involved in mediating drug resistance in CLL.
Project description:Rapid resistance to BRAF inhibitors in BRAFV600-mutant metastatic melanoma has produced an urgent need for new treatment options. BRAF inhibitor resistance commonly involves reactivation of mitogen-activated protein kinase (MAPK) signaling and yet inhibition of downstream kinases has not circumvented resistance, partly because MAPK is regulated via a complex network of feedback mechanisms that influence pathway rebound. To examine the transcriptome responses of melanoma cells to MAPK inhibition, a panel of 11 BRAFV600-mutant melanoma cell lines were treated with control (DMSO), 100nM dabrafenib alone (i.e BRAF inhibitor monotherapy) or 100nM dabrafenib + 10nM trametinib (i.e combination BRAF + MEK inhibition) for 24h.