Biology subjects

Pomilio, G.

Publications and source records attributed to Pomilio, G..

3 recordsLinked to original sources

bioRxiv2022

Genome-wide in vivo CRISPR screens identify GATOR1 as a TP53 induced tumour suppressor

Identifying tumor suppressor genes is predicted to inform on the development of novel strategies for cancer therapy. To identify new lymphoma driving processes that cooperate with oncogenic MYC (which is abnormally highly expressed in [~]70% of human cancers) we have used a genome-wide CRISPR knockout screen in E{micro}-Myc;Cas9 transgenic hematopoietic stem and progenitor cells in vivo. We discovered that loss of any of the GATOR1 complex components - NPRL3, DEPDC5, NPRL2 - significantly accelerated c-MYC-driven lymphoma development in mice. Low expression of the GATOR1 complex genes correlated with poor survival outcomes for human patients with high MYC- expressing cancers. Murine lymphomas lacking GATOR1 were highly sensitive to mTOR inhibitors as a single agent therapy, both in vitro and in vivo. These findings identify inhibition of mTORC1 as a potent tumor suppressive mechanism in c-MYC-driven lymphomagenesis and suggest a new avenue for therapeutic intervention in GATOR1-deficient lymphomas through mTOR inhibition. Key PointsO_LIIn vivo CRISPR/Cas9 whole genome knockout screens identified the GATOR1 complex as a potent suppressor of c-MYC-driven lymphomagenesis. C_LIO_LIGATOR1 deficiency in MYC-driven lymphomas confers sensitivity to mTOR inhibition, suggesting a novel therapeutic approach. C_LI

cancer biology↗

bioRxiv2021

The cytosolic role of EZH2-IMPDH2 complex in melanoma progression and metastasis via GTP regulation

The enhancer of zeste homolog 2 (EZH2) oncoprotein is a histone methyltransferase that functions canonically as a catalytic subunit of the polycomb repressive complex 2 (PRC2) to tri-methylate histone H3 at Lys 27 (H3K27me3). Although targeting EZH2 methyltransferase is a promising therapeutic strategy against cancer, methyltransferase-independent oncogenic functions of EZH2 are described. Moreover, pharmacological EZH2 methyltransferase inhibition was only variably effective in pre-clinical and clinical studies, suggesting that targeting EZH2 methyltransferase alone may be insufficient. Here, we demonstrate a non-canonical mechanism of EZH2s oncogenic activity characterized by interactions with inosine monophosphate dehydrogenase 2 (IMPDH2) and downstream promotion of guanosine-5-triphosphate (GTP) production. EZH2-IMPDH2 interactions identified by Liquid Chromatography-Mass Spectrometry (LC-MS) of EZH2 immunoprecipitates from melanoma cells were verified to occur between the N-terminal EED-binding domain of cytosolic EZH2 and the CBS domain of IMPDH2 in a methyltransfersase-independent manner. EZH2 silencing reduced cellular GTP, ribosome biogenesis, RhoA-mediated actomyosin contractility and melanoma cell proliferation and invasion by impeding the activity of IMPDH2. Guanosine, which replenishes GTP, reversed these effects and thereby promoted invasive and clonogenic cell states even in EZH2 silenced cells. IMPDH2 silencing antagonized the proliferative and invasive effects of EZH2, also in a guanosine-reversible manner. In human melanomas, high cytosolic EZH2 and IMPDH2 expression were associated with nucleolar enlargement, a marker of ribosome biogenesis. EZH2-IMPDH2 complexes were also observed in a range of cancers in which Sappanone A (SA), which inhibits EZH2-IMPDH2 interactions, was anti-tumorigenic, although notably non-toxic in normal cells. These findings illuminate a previously unrecognized, non-canonical, methyltransferase-independent, and GTP-dependent mechanism by which EZH2 regulates tumorigenicity in melanoma and other cancers, opening new avenues for development of anti-EZH2 therapeutics. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=157 SRC="FIGDIR/small/467024v2_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@153dd35org.highwire.dtl.DTLVardef@dfeb43org.highwire.dtl.DTLVardef@ce8148org.highwire.dtl.DTLVardef@189d8da_HPS_FORMAT_FIGEXP M_FIG Graphical Abstract C_FIG HighlightsO_LIEZH2 has non-canonical methyltransferase-independent and GTP-dependent tumorigenic and metastatic functions in melanoma. C_LIO_LIThe N-terminal EED-binding domain of EZH2 interacts with the CBS domain of IMPDH2 in a polycomb repressive complex 2- (PRC2-) and methylation-independent manner. C_LIO_LIEZH2 accumulates with IMPDH2 in the cytoplasm and increases IMPDH2s tetramerization-mediated activity independently of EZH2 methyltransferase. C_LIO_LIEZH2 upregulates GTP synthesis by IMPDH2 activation and thereby activates ribosome biogenesis via rRNA synthesis and actomyosin contractility via RhoA GTPase. C_LIO_LISappanone A (SA) inhibits IMPDH2-EZH2 interactions and is anti-proliferative across a range of cancers including melanoma, but not in normal cells. C_LI

cancer biology↗

bioRxiv2020

Reprogramming of serine metabolism is an actionable vulnerability in FLT3-ITD driven acute myeloid leukaemia

Activating FMS-like tyrosine kinase 3 (FLT3) mutations occur in approximately 30% of all acute myeloid leukaemias (AMLs) and are associated with poor prognosis. The limited clinical efficacy of FLT3 inhibitor monotherapy has highlighted the need for alternative therapeutic targets and treatments for FLT3-mutant AML. Using human and murine models of MLL-rearranged AML harbouring FLT3 internal tandem duplication (FLT3-ITD) and primary patient samples, we have demonstrated that FLT3-ITD promotes serine uptake and serine synthesis via transcriptional regulation of neutral amino acid transporters (SLC1A4 and SLC1A5) and genes in the de novo serine synthesis pathway (PHGDH and PSAT1). Mechanistically, dysregulation of serine metabolism in FLT3-mutant AML is dependent on the mTORC1-ATF4 axis, that drives RNA-Pol II occupancy at PHGDH, PSAT1, SLC1A4 and SLC1A5. Genetic or pharmacological inhibition of the de novo serine synthesis pathway selectively inhibited the proliferation of FLT3-ITD AML cells, and this was potentiated by withdrawal of exogenous serine. Purine supplementation effectively rescued the antiproliferative effect of inhibiting de novo serine synthesis, consistent with the idea that serine fuels purine nucleotide synthesis in FLT3-mutant AML. Pharmacological inhibition of the de novo serine synthesis pathway, using the PHGDH inhibitor WQ-2101, sensitises FLT3-mutant AML cells to the standard of care chemotherapy agent cytarabine via exacerbation of DNA damage. Collectively, these data reveal new insights as to how FLT3 mutations reprogram metabolism in AML, and reveal a combination therapy strategy to improve the treatment of FLT3-mutant AML. Statement of SignificanceFLT3 mutations are common in AML and are associated with poor prognosis. We show that FLT3-ITD stimulates serine metabolism, thereby rendering FLT3-ITD leukemias dependent on serine for proliferation and survival. This metabolic dependency can be exploited pharmacologically to sensitize FLT3-mutant AML to chemotherapy.

cancer biology↗