NOTCH1 activation in breast cancer confers sensitivity to inhibition of SUMOylation
Ontology highlight
ABSTRACT: Breast cancer is genetically heterogeneous, and recent studies have underlined a prominent contribution of epigenetics to the development of this disease. To uncover new synthetic lethalities with known breast cancer oncogenes, we screened an epigenome-focused short hairpin RNA library on a panel of engineered breast epithelial cell lines. Here we report a selective interaction between the NOTCH1 signaling pathway and the SUMOylation cascade. Knockdown of the E2-conjugating enzyme UBC9 (UBE2I) as well as inhibition of the E1-activating complex SAE1/UBA2 using ginkgolic acid impairs the growth of NOTCH1-activated breast epithelial cells. We show that upon inhibition of SUMOylation NOTCH1-activated cells proceed slower through the cell cycle and ultimately enter apoptosis. Mechanistically, activation of NOTCH1 signaling depletes the pool of unconjugated small ubiquitin-like modifier 1 (SUMO1) and SUMO2/3 leading to increased sensitivity to perturbation of the SUMOylation cascade. Depletion of unconjugated SUMO correlates with sensitivity to inhibition of SUMOylation also in patient-derived breast cancer cell lines with constitutive NOTCH pathway activation. Our investigation suggests that SUMOylation cascade inhibitors should be further explored as targeted treatment for NOTCH-driven breast cancer.
Project description:Breast cancer is genetically heterogeneous, and recent studies have underlined a prominent contribution of epigenetics to the development of this disease. To uncover new synthetic lethalities with known breast cancer oncogenes, we screened an epigenome-focused short hairpin RNA library on a panel of engineered breast epithelial cell lines. Here we report a selective interaction between the NOTCH1 signaling pathway and the SUMOylation cascade. Knockdown of the E2-conjugating enzyme UBC9 (UBE2I) as well as inhibition of the E1-activating complex SAE1/UBA2 using ginkgolic acid impairs the growth of NOTCH1-activated breast epithelial cells. We show that upon inhibition of SUMOylation NOTCH1-activated cells proceed slower through the cell cycle and ultimately enter apoptosis. Mechanistically, activation of NOTCH1 signaling depletes the pool of unconjugated small ubiquitin-like modifier 1 (SUMO1) and SUMO2/3 leading to increased sensitivity to perturbation of the SUMOylation cascade. Depletion of unconjugated SUMO correlates with sensitivity to inhibition of SUMOylation also in patient-derived breast cancer cell lines with constitutive NOTCH pathway activation. Our investigation suggests that SUMOylation cascade inhibitors should be further explored as targeted treatment for NOTCH-driven breast cancer. We treated MCF10A and NOTCH1 cells with either DMSO or ginkgolic acid 30 uM for 3 days. Two replicates have been analysed for each condition.
Project description:UBC9 is the sole conjugating enzyme E2 in the sumoylation and plays a pivotal role in maintaining homeostasis and restraining stress reaction. Targeting UBC9 is emerging as a novel strategy for cancer therapy. However, the role of UBC9 in bladder cancer is not clear. Here, we sought to determine the alterations of trancriptome after shRNA-mediated knockdown UBC9 in T24 cell lines.
Project description:Purpose: To determine H3K4me3 chromatin profile in UBC9WT and UBC9KO BMDC before and after LPS stimulation. Methods: H3K4me3 chromatin profile was determined by sequencing UBC9 WT and UBC9 KO BMDC chromatin immunoprecipitated with antibody specific for H3K4me3. Results: We show differential chromatin profile for H3K4me3 on the ifnb1 locus between UBC9 KO cells and UBC9 WT. Conclusions: Loss of SUMOylation causes a deregulation of ifnb1 transcription activation mark. A study of H3K4me3 chromatin profile in UBC9 WT and UBC9 KO Bone Marrow derived Dendritic Cells.
Project description:Foxp3-expressing regulatory T (Treg) cells are essential regulators in the immune system; molecular mechanisms underlying Treg cell expansion and function are still not well understood. SUMOylation is an important post-translational modification characterized by covalent attachment of SUMO moieties to lysine within proteins. UBC9 is the only E2 conjugation enzyme involved in this process and loss of UBC9 completely impairs the SUMOylation pathway. Here we report that selective deletion of Ubc9 within the Treg cell lineage resulted in fatal early-onset autoimmunity as the Foxp3 mutant mice. Ubc9-deficient Treg cells exhibited severe defects in TCR-driven homeostatic proliferation, accompanied by impaired activation and compromised suppressor function. Importantly, TCR-enhanced SUMOylation of IRF4, a critical regulator of Treg cell function downstream of TCR signals, regulates its stability in Treg cells. Our data thus have demonstrated an essential role of SUMOylation in the expansion and function of Treg cells.
Project description:Coordination of signaling pathways is essential for tissue homeostasis and for preventing cancer development. Here, we show that the E3 ligase Rnf8, an important component of the DNA double-strand break (DSB) signaling, is critical for cell-fate commitment of the mammary epithelial progenitors. Furthermore, we provide evidence that deficiency of Rnf8 predisposes mouse models for mammary tumorigenesis while low expression levels in breast cancer associates with poor patient prognosis. RNF8 mediates these novel functions through ubiquitylation and degradation of the activated form of NOTCH1, and thereby fine-tuning of NOTCH signaling. Accordingly, RNF8 level negatively correlates with the expression of NOTCH targets in mouse mammary and human breast tumors. Consistent with these findings, Rnf8-deficient mammary tumors are highly sensitive to pharmacological inhibition of NOTCH. Therefore, RNF8 inhibits breast cancer on two fronts, maintaining genomic stability through DSB signaling and regulating growth and differentiation through inhibition of the NOTCH pathway.
Project description:Most human cancers present hyperactivated sumoylation, and cancer cell lines are usually highly sensitive to the lack of it, supporting potential application of sumoylation chemical inhibitors in cancer therapy. Here, we explored the impact of hyposumoylation (Ubc9 haploinsufficiency) on cancer development in mice using Apc loss-driven intestinal tumorigenesis model. We used microarrays to compare the global program of gene expression in intestinal polyps and normal tissue from mice homozygous (+/+) and heterozygous (+/-) for Ubc9, which encodes the unique SUMO E2-conjugating enzyme. This analysis was performed in the context of a conditional ablation of tumor suppressor Apc all along the crypt-villus axis through expresion of Cre recombinase driven by the intestinal specific promoter Villin
Project description:NOTCH activation has been recently implicated in human basal-like breast cancers associated with a poor prognosis. To address the role of Notch1 in mammary transformation and mammary tumor initiating cell activity, we developed a doxycycline-regulated model of Notch1-mediated mammary transformation. These mice develop mammary adenocarcinomas that express cytokeratin (CK) 8/18 and contain rare cells that also express keratin 14. In vivo limiting dilution analyses reveal that these mammary tumors exhibit functional heterogeneity and harbor a rare (1/2978) mammary tumor initiating cell population. Using this dox-regulated Notch1 mammary tumor model, we demonstrate that Notch1 inhibition results in mammary tumor regression in vivo and prevents disease recurrence in 4 of 6 tumors tested. Consistent with the in vivo data, Notch1 inhibition reduces mammary tumorsphere forming activity in vitro. Using doxycycline-responsive tumor derived cell lines, we also identify the embryonic stem cell transcription factor Nanog as a novel Notch1-regulated gene in mammospheres. These data indicate that Notch1 contributes to mammary tumor initiating activity and raises the possibility that NOTCH therapeutics may have efficacy in human basal-like breast cancers associated with NOTCH activation.
Project description:Foxp3-expressing regulatory T (Treg) cells are essential regulators in the immune system; molecular mechanisms underlying Treg cell expansion and function are still not well understood. SUMOylation is an important post-translational modification characterized by covalent attachment of SUMO moieties to lysine within proteins. UBC9 is the only E2 conjugation enzyme involved in this process and loss of UBC9 completely impairs the SUMOylation pathway. Here we report that selective deletion of Ubc9 within the Treg cell lineage resulted in fatal early-onset autoimmunity as the Foxp3 mutant mice. Ubc9-deficient Treg cells exhibited severe defects in TCR-driven homeostatic proliferation, accompanied by impaired activation and compromised suppressor function. Importantly, TCR-enhanced SUMOylation of IRF4, a critical regulator of Treg cell function downstream of TCR signals, regulates its stability in Treg cells. Our data thus have demonstrated an essential role of SUMOylation in the expansion and function of Treg cells. RNA-seq library was generated using mRNA of CD4+ YFP+ Treg cells sorted from lymph nodes and spleen of Foxp3cre/wtUbc9fl/wt or Foxp3cre/wtUbc9fl/fl mice, each sample contained pooled Treg cells from 5~10 mice.
Project description:Ageing and mutations of transthyretin (TTR), the thyroid hormones and retinol transporting protein lead to amyloidosis by destabilizing the structure of TTR. Because protein structure is regulated through posttranslational modifications, we investigated the Small Ubiquitin-like Modifier (SUMO)ylation of TTR. We chose the widely used Ubc9 fusion-directed SUMOylation system, which is based on a fusion of the SUMOylation substrate of interest with Ubc9, a sole SUMO conjugating enzyme. Surprisingly, despite our presumptions, we found that Ubc9 fused to TTR was SUMOylated at a unique set of lysine residues. Three unknown SUMOylation sites of Ubc9—K154, K18 and K65—were revealed by mass spectrometry (MS). The previously reported SUMOylation at K49 of Ubc9 was also observed. SUMOylation of the lysine residues of TTR fused to Ubc9 was hardly detectable. However, non-fused TTR was SUMOylated via trans-SUMOylation by Ubc9 fused to TTR. Interestingly, mutating the catalytic residue of Ubc9 fused to TTR did not result in complete loss of the SUMOylation signal, suggesting that Ubc9 linked to TTR is directly cross-SUMOylated by the SUMO-activating enzyme E1. Ubc9, TTR or fusion proteins composed of TTR and Ubc9 specifically affected the global SUMOylation of cellular proteins. TTR or Ubc9 alone increased global SUMOylation, whereas TTR and Ubc9 together decreased the amount of high-molecular weight (HMW) SUMO conjugates. Our data suggest that TTR may influence the SUMOylation of Ubc9, thereby altering signalling pathways in the cell.