Project description:The protein tyrosine phosphatase SHP2 is crucial for oncogenic transformation of acute myeloid leukemia (AML) cells expressing mutated receptor tyrosine kinases (RTKs), as it is required for full RAS-ERK activation to promote cell proliferation and survival programs. SHP2 allosteric inhibitors act by stabilizing SHP2 in its auto-inhibited conformation and they are currently being tested in clinical trials for tumors with over-activation of the RAS/ERK pathway, alone and in various drug combinations. Using in vitro models, we established acquired resistant cell lines to the allosteric SHP2 inhibitor SHP099 from two FLT3-ITD-positive AML cell lines. We performed both label-free and isobaric labeling quantitative mass spectrometry-based phosphoproteomics to reveal that AML cells can restore phosphorylated ERK (pERK) in presence of SHP099, thus developing adaptive resistance. Mechanistically, SHP2 inhibition induces the tyrosine phosphorylation and feedback-activation of the FLT3 receptor, which in turn phosphorylates SHP2 on Tyrosine 62. This phosphorylation stabilizes SHP2 in its open conformation, preventing SHP099 binding, thus resulting in resistance. Combinatorial inhibition of SHP2 and MEK or SHP2 and FLT3 prevents pERK rebound and resistant cell growth. We observed the same mechanism in a FLT3-mutated B-ALL cell line and in the inv(16)/KITD816Y AML mouse model. Finally, we show that allosteric SHP2 inhibition does not impair the clonogenic ability of normal bone marrow progenitors, supporting its future use for clinical applications.
Project description:Acute Myeloid Leukemia (AML) is the most common and aggressive form of acute leukemia, with a 5-year survival rate of just 24%. Over a third of all AML patients harbor activating mutations in kinases, such as the receptor tyrosine kinases FLT3 and KIT. FLT3 and KIT mutations are associated with poor clinical outcomes and lower remission rates in response to standard-of-care chemotherapy. We have recently identified that the core kinase of the non-homologous end joining DNA repair pathway, DNA-PK, is activated downstream of FLT3; and targeting DNA-PK sensitized FLT3-mutant AML cells to standard-of-care therapies. Herein, we investigated DNA-PK as a possible therapeutic vulnerability in KIT mutant AML, using isogenic FDC-P1 myeloid progenitor cell lines transduced with an empty vector or oncogenic mutant KIT (V560G, D816V). Targeted quantitative phosphoproteomic profiling identified phosphorylation of DNA-PK at threonine 2599 in KIT mutant cells, indicative of DNA-PK activation. Accordingly, proliferation assays revealed that KIT mutant FDC-P1 cells were more sensitive to the DNA-PK inhibitors M3814 or NU7441, compared to empty vector controls. DNA-PK inhibition combined with inhibition of KIT signaling via using the kinase inhibitors dasatinib or ibrutinib, or the protein phosphatase 2A activators FTY720 or AAL(S), led to synergistic cell death. Discovery phosphoproteomic analysis of KIT-D816V cells revealed that dasatinib single-agent treatment inhibited ERK1 activity, and M3814 single-agent treatment inhibited Akt/mTOR activity. The combination of dasatinib and M3814 treatment inhibited both ERK/MAPK and Akt/mTOR activity, and induced synergistic inhibition of phosphorylation of transcription regulators including MYC and MYB. This study provides insight into the oncogenic pathways regulated by DNA-PK beyond its canonical role in DNA repair, and demonstrates that DNA-PK is a promising novel therapeutic target for KIT mutant cancers.
Project description:Oncogenic transformation of individual cell fates by developmental signaling cascades and transcription factors triggers diverse cancer types. Chordoma is a rare, aggressive tumor arising from transformed notochord remnants. Various potentially oncogenic factors have been found deregulated in chordoma and its metastases, yet clear causation remains uncertain. In particular, expression of the notochord-controlling transcription factor Brachyury is hypothesized as key molecular driver in chordoma formation, yet an in vivo model to causally test its oncogenic potential in the notochord is missing. Here, we apply a zebrafish model of chordoma onset to identify the notochord-transforming potential of tumor-implicated candidate genes in vivo. We find that overexpression of human and zebrafish Brachyury, including a version with augmented transcriptional activity, is insufficient to initiate notochord hyperplasia in vivo. In contrast, the repeatedly chordoma-implicated receptor tyrosine kinase (RTK) genes EGFR and KDR/VEGFR2 are sufficient to transform developmental notochord cells, akin to direct activation of Ras. Analysis of transcriptome and sub-cellular organization from transformed notochords suggests that aberrant activation of RTK/Ras signaling attenuates processes required for the differentiation of notochord cells. Taken together, our results provide first in vivo indication for a lack of tumor-initiating potential of Brachyury expression in the notochord, and suggest activated RTK signaling as potent hyperplasia-initiating event in chordoma.
Project description:Granulocyte-colony stimulating factor receptor (G-CSFR) controls myeloid progenitor proliferation and differentiation to neutrophils. Mutations in CSF3R (encoding G-CSFR) have been reported in patients with chronic neutrophilic leukemia (CNL) and acute myeloid leukemia (AML); however, despite years of research, the malignant downstream signaling of the mutated G-CSFRs is not well understood. Here, we utilized a quantitative phospho-tyrosine analysis to generate a comprehensive signaling map of G-CSF induced tyrosine phosphorylation in the normal versus mutated (proximal: T618I and truncated: Q741x) G-CSFRs. Unbiased clustering and kinase enrichment analysis identified rapid induction of phospho-proteins associated with endocytosis by the wild-type G-CSFR only; while G-CSFR mutants showed abnormal kinetics of canonical STAT3, STAT5 and MAPK phosphorylation, and aberrant activation of Bruton’s Tyrosine Kinase (Btk). Mutant-G-CSFR-expressing cells displayed enhanced sensitivity (5-fold lower IC50) for Ibrutinib-based chemical inhibition of Btk. Finally, primary murine progenitor cells from G-CSFR-d715x knock-in mice validate activation of Btk by the mutant receptor, and display enhanced sensitivity to Ibrutinib. Together, these data demonstrate the strength of unsupervised proteomics analyses in dissecting oncogenic pathways, and suggest repositioning Ibrutinib for therapy of myeloid leukemia bearing CSF3R mutations.
Project description:Glutamine is a key nutrient for tumor cells that supports nucleotide and amino acid biosynthesis, replenishes the TCA cycle intermediates and contributes to redox metabolism. We identified oncogenic KRAS as a critical regulator of the response to glutamine deprivation in NSCLC. Full activation of the ATF4 stress response pathway is dependent on expression of NRF2 downstream of oncogenic KRAS in NSCLC. Through this mechanism, KRAS alters amino acid uptake and metabolism and sustains mTORC1 signaling during nutrient stress. Furthermore, we identified regulation of asparagine synthetase (ASNS) as a key effect of oncogenic KRAS signaling via ATF4 during glutamine deprivation, and a potential therapeutic target in KRAS mutant NSCLC.
Project description:Glutamine is a key nutrient for tumor cells that supports nucleotide and amino acid biosynthesis, replenishes the TCA cycle intermediates and contributes to redox metabolism. We identified oncogenic KRAS as a critical regulator of the response to glutamine deprivation in NSCLC. Full activation of the ATF4 stress response pathway is dependent on expression of NRF2 downstream of oncogenic KRAS in NSCLC. Through this mechanism, KRAS alters amino acid uptake and metabolism and sustains mTORC1 signaling during nutrient stress. Furthermore, we identified regulation of asparagine synthetase (ASNS) as a key effect of oncogenic KRAS signaling via ATF4 during glutamine deprivation, and a potential therapeutic target in KRAS mutant NSCLC.
Project description:Glutamine is a key nutrient for tumor cells that supports nucleotide and amino acid biosynthesis, replenishes the TCA cycle intermediates and contributes to redox metabolism. We identified oncogenic KRAS as a critical regulator of the response to glutamine deprivation in NSCLC. Full activation of the ATF4 stress response pathway is dependent on expression of NRF2 downstream of oncogenic KRAS in NSCLC. Through this mechanism, KRAS alters amino acid uptake and metabolism and sustains mTORC1 signaling during nutrient stress. Furthermore, we identified regulation of asparagine synthetase (ASNS) as a key effect of oncogenic KRAS signaling via ATF4 during glutamine deprivation, and a potential therapeutic target in KRAS mutant NSCLC.
Project description:Scaffold proteins such as CNK1 are hubs for coordinating signalling pathways. Here, we demonstrate that CNK1 is a crucial transducer of growth factor-stimulated and oncogenic signalling. Activation of CNK1 depends on its dimerization executed by the N-terminal sterile motif alpha (SAM) domain. Accordingly, a CNK1 mutant lacking the SAM domain prevents CNK1-driven cell proliferation and matrix metalloproteinase 14 promoter activation. We identified phosphorylation of Ser22 by AKT as trigger for CNK1 dimerisation. Consistently, the mutant CNK1S22D mimicking constitutive phosphorylation stimulates CNK1 signalling, whereas the phosphoylation-dead mutant CNK1S22A does not. Searching the COSMIC database revealed Ser22 as target for oncogenic activation of CNK1. The mutant CNK1S22D and the oncogenic mutant CNK1S22F form clusters in serum-starved cells comparable to clusters of CNK1 in growth factor stimulated cells. Light-activatable CNK1, optoCNK1, based on the light-induced oligomerisation of cryptochrome 2 confirms that dimerization is the trigger for CNK1 activation. CNK1 dimers induced by activating Ser22 mutants or by light enhance cell invasion and ADP ribosylation factors 1 signalling associated with tumour formation. Positive and negative feedback mechanisms regulates CNK1 dimerisation and in this way its activity. Oncogenic mutants of CNK1 support the positive feedback while escape from negative feedback regulation.
Project description:Scaffold proteins such as CNK1 are hubs for coordinating signalling pathways. Here, we demonstrate that CNK1 is a crucial transducer of growth factor-stimulated and oncogenic signalling. Activation of CNK1 depends on its dimerization executed by the N-terminal sterile motif alpha (SAM) domain. Accordingly, a CNK1 mutant lacking the SAM domain prevents CNK1-driven cell proliferation and matrix metalloproteinase 14 promoter activation. We identified phosphorylation of Ser22 by AKT as trigger for CNK1 dimerisation. Consistently, the mutant CNK1S22D mimicking constitutive phosphorylation stimulates CNK1 signalling, whereas the phosphoylation-dead mutant CNK1S22A does not. Searching the COSMIC database revealed Ser22 as target for oncogenic activation of CNK1. The mutant CNK1S22D and the oncogenic mutant CNK1S22F form clusters in serum-starved cells comparable to clusters of CNK1 in growth factor stimulated cells. Light-activatable CNK1, optoCNK1, based on the light-induced oligomerisation of cryptochrome 2 confirms that dimerization is the trigger for CNK1 activation. CNK1 dimers induced by activating Ser22 mutants or by light enhance cell invasion and ADP ribosylation factors 1 signalling associated with tumour formation. Positive and negative feedback mechanisms regulates CNK1 dimerisation and in this way its activity. Oncogenic mutants of CNK1 support the positive feedback while escape from negative feedback regulation.
Project description:Somatic mutations in calreticulin (CALR) are present in approximately 40% of patients with myeloproliferative neoplasms (MPN). However, the mechanism by which mutant CALR is oncogenic is unknown. Here, we demonstrate that a megakaryocytic-specific MPN phenotype is induced when mutant CALR is over-expressed in mice and that the thrombopoietin receptor, MPL is required for mutant CALR driven transformation. Whole transcriptome analysis reveals enrichment of STAT signatures in mutant CALR transformed cells and JAK2 inhibitor treatment abrogates STAT activation. Employing extensive mutagenesis-based structure-function analysis we demonstrate that the positively charged amino acids within the mutant CALR C-terminus are required for cellular transformation through facilitating physical interaction between mutant CALR and MPL. Together, our findings elucidate a novel mechanism of cancer pathogenesis.