Project description:Activation of oncogenes often leads to induction of the DNA damage responses and onset of the cell senescence. Given that DNA damage can also trigger production of type I interferons (IFN) that contribute to senescence development, we sought to determine the role of IFN in the oncogene-induced senescence. Our data in mouse model demonstrate that inactivation of IFN signaling is sufficient for inducing melanomas in melanocytes harboring mutant Braf. Restoration of IFN signaling in IFN-deficient melanoma cells induces cell senescence and suppresses melanoma progression. In addition, data in human patients that received high dose IFN therapy and in mouse transplanted tumor models strongly suggest the importance of the non-cell-autonomous IFN signaling. Suppression of IFN signaling mediated by the downregulation of IFN receptor IFNAR1 invariably occurs during development of mouse melanoma. Mice harboring the IFNAR1 mutant, which is relatively resistant to downregulation, delay melanoma development, suppress the metastatic disease, and better respond to treatment with BRAF or PD1 inhibitors. These results suggest that IFN signaling is an important tumor suppressive pathway that inhibits melanoma development and progression. Accordingly, the inhibition of IFN pathway via IFNAR1 downregulation plays a key role in melanoma pathogenesis. Conversely, these data also argue for targeting IFNAR1 downregulation to prevent the metastatic disease and improve the efficacy of molecularly targeted and immune-targeted therapies. Two genotypes of mice were examined at 2 to 3 times after tamoxifen adminstration, with 2 replicates for each condition, yielding 8 samples in total.
Project description:The development of malignant melanoma is a highly complex process which is still poorly understood despite extensive research. A majority of human melanomas are found to express a handful of oncogenic proteins, such as mutant RAS and BRAF. However, these oncogenes are also found in nevi, and it is now a well-accepted fact that their expression alone leads to senescence. This renders the understanding of senescence escape mechanisms an important criterion to understand tumor development. Here, we describe the ability of the transcription factor MYC to drive the evasion of reactive oxygen stress-induced melanocyte senescence, caused by activated receptor tyrosine kinase signaling. Conversely, MIZ1, the growth suppressing interaction partner of MYC, is involved in mediating melanocyte senescence. Both, MYC overexpression and Miz1 knockdown led to a strong reduction of endogenous reactive oxygen species (ROS), DNA damage and senescence. We identified the cystathionase (CTH) gene product as mediator of the ROS-related MYC and MIZ1 effects. Blocking CTH enzymatic activity in MYC-overexpressing and Miz1 knockdown cells increased intracellular stress and senescence. Importantly, pharmacological inhibition of cystathionase in human melanoma cells also reconstituted senescence in many cell lines, and CTH knockdown reduced tumorigenic effects such as proliferation, H2O2 resistance and soft agar growth. Thus, we identified cystathionase as new MYC target gene with an important function in MYC-mediated senescence evasion. total samples analysed are 4
Project description:Activation of oncogenes often leads to induction of the DNA damage responses and onset of the cell senescence. Given that DNA damage can also trigger production of type I interferons (IFN) that contribute to senescence development, we sought to determine the role of IFN in the oncogene-induced senescence. Our data in mouse model demonstrate that inactivation of IFN signaling is sufficient for inducing melanomas in melanocytes harboring mutant Braf. Restoration of IFN signaling in IFN-deficient melanoma cells induces cell senescence and suppresses melanoma progression. In addition, data in human patients that received high dose IFN therapy and in mouse transplanted tumor models strongly suggest the importance of the non-cell-autonomous IFN signaling. Suppression of IFN signaling mediated by the downregulation of IFN receptor IFNAR1 invariably occurs during development of mouse melanoma. Mice harboring the IFNAR1 mutant, which is relatively resistant to downregulation, delay melanoma development, suppress the metastatic disease, and better respond to treatment with BRAF or PD1 inhibitors. These results suggest that IFN signaling is an important tumor suppressive pathway that inhibits melanoma development and progression. Accordingly, the inhibition of IFN pathway via IFNAR1 downregulation plays a key role in melanoma pathogenesis. Conversely, these data also argue for targeting IFNAR1 downregulation to prevent the metastatic disease and improve the efficacy of molecularly targeted and immune-targeted therapies.
Project description:BRAF inhibitors are widely employed in the treatment of melanoma with the BRAF V600E mutation. However, the development of resistance greatly compromises their therapeutic efficacy. Here, we elucidate the role of polyamine biosynthesis and its regulatory mechanisms in promoting BRAF inhibitor resistance. Leveraging CRISPR-Cas9 screens, we identify AMD1 (S-adenosylmethionine decarboxylase 1), a critical enzyme for polyamine biosynthesis, as a druggable target whose inhibition reverses vemurafenib resistance. Metabolomic and proteomic analyses reveal that polyamine biosynthesis is upregulated in vemurafenib-resistant cancer, resulting in enhanced EIF5A hypusination, translation of mitochondrial proteins and oxidative phosphorylation. We also identify that sustained c-Myc levels in vemurafenib-resistant cancer are responsible for elevated polyamine biosynthesis. Finally, inhibition of polyamine biosynthesis or c-Myc reversed vemurafenib resistance both in vitro and in vivo in a xenograft model. With the polyamine biosynthesis signature correlated with poor prognosis in BRAF mutant melanoma patients, our findings reveal that the polyamine-hypusination-mitochondrial respiration pathway is an effective therapeutic target that can maximize the therapeutic efficacy of existing BRAF inhibitors.
Project description:Recent technological advances in single-cell genomics make it possible to analyze cellular heterogeneity of tumor samples. Here, we applied single-cell RNA-seq to measure the transcriptomes of 307 single cells cultured from three biopsies of three different patients with a BRAF/NRAS wild type, BRAF mutant/NRAS wild type and BRAF wild type/NRAS mutant melanoma metastasis, respectively. Analysis based on self-organizing maps identified sub-populations defined by multiple gene expression modules involved in proliferation, oxidative phosphorylation, pigmentation and cellular stroma. Gene expression modules had prognostic relevance when compared with gene expression data from published melanoma samples and patient survival data. We surveyed kinome expression patterns across sub-populations of the BRAF/NRAS wild type sample and found that CDK4 and CDK2 were consistently highly expressed in the majority of cells, suggesting that these kinases might be involved in melanoma progression. Treatment of cells with the CDK4 inhibitor palbociclib restricted cell proliferation to a similar, and in some cases greater, extent than MAPK inhibitors. Finally, we identified a low abundant sub-population in this sample that highly expressed a module containing ABC transporter ABCB5, surface markers CD271 and CD133, and multiple aldehyde dehydrogenases (ALDHs), as markers for melanoma stem or initiating cells. Patient-derived cultures of the BRAF mutant/NRAS wild type and BRAF wild type/NRAS mutant metastases showed more homogeneous single-cell gene expression patterns with gene expression modules for proliferation and ABC transporters. Taken together, our results describe an intertumor and intratumor heterogeneity in melanoma short-term cultures which might be relevant for patient survival, and suggest promising targets for new treatment approaches in melanoma therapy.
Project description:The development of malignant melanoma is a highly complex process which is still poorly understood despite extensive research. A majority of human melanomas are found to express a handful of oncogenic proteins, such as mutant RAS and BRAF. However, these oncogenes are also found in nevi, and it is now a well-accepted fact that their expression alone leads to senescence. This renders the understanding of senescence escape mechanisms an important criterion to understand tumor development. Here, we describe the ability of the transcription factor MYC to drive the evasion of reactive oxygen stress-induced melanocyte senescence, caused by activated receptor tyrosine kinase signaling. Conversely, MIZ1, the growth suppressing interaction partner of MYC, is involved in mediating melanocyte senescence. Both, MYC overexpression and Miz1 knockdown led to a strong reduction of endogenous reactive oxygen species (ROS), DNA damage and senescence. We identified the cystathionase (CTH) gene product as mediator of the ROS-related MYC and MIZ1 effects. Blocking CTH enzymatic activity in MYC-overexpressing and Miz1 knockdown cells increased intracellular stress and senescence. Importantly, pharmacological inhibition of cystathionase in human melanoma cells also reconstituted senescence in many cell lines, and CTH knockdown reduced tumorigenic effects such as proliferation, H2O2 resistance and soft agar growth. Thus, we identified cystathionase as new MYC target gene with an important function in MYC-mediated senescence evasion.
Project description:We evaluated two matched human cell lines derived from primary melanocytes, termed pmel+BRAF(V600E) and pmel+BRAF(V600E)+MITF. These cells are therefore isogenic with the exception of the expression of MITF. Gene Set Enrichment Analysis of microarray data identified a highly significant induction of oxidative phosphorylation gene set in MITF expressing cells compared to control cells.
Project description:A major contributor to poor sensitivity to anti-cancer kinase inhibitor therapy is drug-induced cellular adaptation, whereby remodeling of signaling and gene regulatory networks permits a drug-tolerant phenotype. Here, we resolve the scale and kinetics of critical subcellular events following oncogenic kinase inhibition and preceding cell cycle re-entry, using mass spectrometry-based phosphoproteomics and RNA sequencing to capture molecular snapshots within the first minutes, hours, and days of BRAF kinase inhibitor exposure in a human BRAF-mutant melanoma model of adaptive therapy resistance. By enriching specific phospho-motifs associated with mitogenic kinase activity, we monitored the dynamics of thousands of growth- and survival-related protein phosphorylation events under oncogenic BRAF inhibition and drug removal. We observed early and sustained inhibition of the BRAF-ERK axis, gradual downregulation of canonical cell cycle-dependent signals, and three distinct and reversible phase transitions toward quiescence. Statistical inference of kinetically-defined regulatory modules revealed a concerted response to oncogenic BRAF inhibition and a dominant compensatory induction of SRC family kinase (SFK) signaling, which we found to be at least partially driven by accumulation of reactive oxygen species via impaired redox homeostasis. This induction sensitized cells to co-treatment with an SFK inhibitor across a panel of patient-derived melanoma cell lines and in an orthotopic mouse xenograft model, underscoring the translational potential for measuring the temporal dynamics of signaling and transcriptional networks under therapeutic challenge.
Project description:Despite the recent remarkable progress of targeted therapies for the clinical management of many cancers, response rates remain lower than desired and long-term response durability is often poor due to drug resistance. A major contributor to treatment failure is drug-induced cellular adaptation to therapy, whereby systems-level reprogramming permits a drug-tolerant phenotype that may gradually lead to cell cycle re-entry and portend relapse. Drug adaptation is known to rapidly implicate complex signaling and transcriptional regulatory networks, but the scale and temporal dynamics of these remodeling events have yet to be fully resolved. Here, we used mass spectrometry-based phosphoproteomics and RNA sequencing to capture molecular snapshots within the first minutes, hours, and days of BRAF kinase inhibitor exposure in a drug-tolerant human BRAF-mutant melanoma model. By enriching specific phospho-motifs associated with mitogenic kinases, we were able to detect and monitor thousands of protein phosphorylation sites over a three-day period of drug treatment, followed by a six-day drug holiday to characterize the plasticity of the adaptive response. We observed early and sustained inhibition of the BRAF-ERK axis, gradual downregulation of canonical cell cycle-dependent phosphorylation events, and a clear delineation between three distinct phase transitions toward drug tolerance, which was almost completely reversible following drug removal. Through measuring the time evolution of large-scale networks, we were able to exploit phosphoproteome and transcriptome dynamics to infer kinetically-defined regulatory modules, revealing a concerted response to oncogenic BRAF inhibition involving cellular metabolism, RNA processing, and mitogenic signaling that demonstrated strong agreement with prior knowledge. The adaptive response to BRAF inhibition was dominated by a compensatory induction of SRC-family kinase (SFK) signaling, which we found to be at least partially driven by impaired redox homeostasis and accumulation of reactive oxygen species – providing a fine degree of temporal, mechanistic, and phosphorylation site-specific context to an important axis in tumor cell survival. This induction sensitized cells to co-treatment with an SFK inhibitor, and combination therapy significantly outperformed single-agent BRAF inhibition across a panel of patient-derived melanoma cell lines and in an orthotopic mouse xenograft model, underscoring the high translational potential for measuring the temporal dynamics of signaling and transcription networks under therapeutic challenge.