USP7 deubiquitinates and stabilizes NOTCH1 in T-cell acute lymphoblastic leukemia

Abstract

T-cell acute lymphoblastic leukemia (T-ALL) is a highly aggressive leukemia that is primarily caused by aberrant activation of the NOTCH1 signaling pathway. Recent studies have revealed that posttranslational modifications, such as ubiquitination, regulate NOTCH1 stability, activity, and localization. However, the specific deubiquitinase that affects NOTCH1 protein stability remains unestablished. Here, we report that ubiquitin-specific protease 7 (USP7) can stabilize NOTCH1. USP7 deubiquitinated NOTCH1 in vivo and in vitro, whereas knockdown of USP7 increased the ubiquitination of NOTCH1. USP7 interacted with NOTCH1 protein in T-ALL cells, and the MATH and UBL domains of USP7 were responsible for this interaction. Depletion of USP7 significantly suppressed the proliferation of T-ALL cells in vitro and in vivo, accompanied by downregulation of the NOTCH1 protein level. Similarly, pharmacologic inhibition of USP7 led to apoptosis of T-ALL cells. More importantly, we found that USP7 was significantly upregulated in human T-ALL cell lines and patient samples, and a USP7 inhibitor exhibited cell cytotoxicity toward primary T-ALL cells, indicating the clinical relevance of these findings. Overall, our results demonstrate that USP7 is a novel deubiquitinase that stabilizes NOTCH1. Therefore, USP7 may be a promising therapeutic target in the currently incurable T-ALL.

Precision medicine for human cancers with Notch signaling dysregulation (Review)

“…NIcds undergo posttranslational modifications such as phosphorylation, ubiquitination and PARylation. cyclin-dependent kinase (cdK)8-dependent phosphorylation of the NOTcH1 intracellular domain (NIcd1) within the intracellular proline-, glutamate-, serine-and threonine-rich region leads to F-box/Wd repeat-containing protein 7 (FBXW7)-mediated ubiquitination and proteasomal degradation (24,25), whereas ubiquitin carboxyl-terminal hydrolase 7-mediated deubiquitination stabilizes NOTcH1 receptors (26). SRc-dependent phosphorylation of NIcd1 within the intracellular ankyrin repeat region represses Notch signaling through blockade of the NIcd1-MAML interaction and degradation of NIcd1 (27).…”

USP7 Is a Master Regulator of Genome Stability

“…Although outside the scope of this review, USP7 likely also contributes to carcinogenesis by regulating a number of tumor suppressors and oncogenes with roles outside of direct genome stability maintenance ( Bhattacharya et al, 2018 ). These include the tumor suppressors PTEN ( Song et al, 2008a ), NOTCH1 ( Shan et al, 2018 ), the Foxo proteins ( van der Horst et al, 2006 ) and the retinoblastoma protein ( Bhattacharya and Ghosh, 2014 ), as well the oncoproteins c-Myc ( Bhattacharya and Ghosh, 2015 ), the REST transcription factor ( Huang et al, 2011 ) and β-catenin ( Novellasdemunt et al, 2017 ). Together, these data demonstrate that USP7 has context-dependent tumor suppressor and oncogenic roles and that up- or down-regulation can contribute to carcinogenesis.…”

Biomimetic, Hypoxia‐Responsive Nanoparticles Overcome Residual Chemoresistant Leukemic Cells with Co‐Targeting of Therapy‐Induced Bone Marrow Niches

“…NALM‐6 cells in BM were also sorted out by flow cytometry and the intracellular p‐Smad3 were examined using immunofluorescence staining. The leukemic cells in peripheral blood were detected through Wright's stain . Major organs (heart, liver, spleen, lung, and kidney) and femurs of the mice were processed H&E staining or rabbit anti‐firefly luciferase antibody (Abcam) and goat anti‐rabbit IgG H&L (HRP) (Beyotime Biotechnology, Shanghai, China) immunohistochemistry staining to identify the invasion of leukemic cells.…”