Anti-UBE2O monoclonal antibody Made to order

Ubiquitin-conjugating enzyme E2O (UBE2O) is a large E2 ubiquitin-conjugating enzyme that possesses both E2 and E3 ligase activities. Ectopic UBE2O overexpression is associated with a variety of human diseases, especially cancers. However, the expression profile and functional biology of UBE2O in human breast cancer (BC) remain unclear. In this study, we found that UBE2O was significantly overexpressed in human BC tissues and cells. Patients with high UBE2O expression tended to have a high risk of metastasis and poor prognosis. In vitro assays revealed that UBE2O promoted BC cell proliferation and epithelial-mesenchymal transformation (EMT) and endowed BC cells with cancer stemness properties (CSPs). UBE2O knockdown in MDA-MB-231 cells suppressed tumour growth and lung metastasis in MDA-MB-231 xenograft mouse models. Mechanistically, UBE2O functioned as a ubiquitin enzyme of AMPK alpha 2, promoting its ubiquitination and degradation and thus activating the mTORC1 signal pathway and contributing to BC oncogenesis and metastasis. Furthermore, as a downstream factor of the UBE2O/AMPK alpha 2/mTORC1 axis, the oncoprotein MYC transcriptionally promoted UBE2O and formed a positive feedback loop in human BC. Collectively, our study demonstrated that UBE2O/AMPK alpha 2/mTORC1-MYC forms a positive feedback loop in human BC cells that regulates BC cell proliferation and EMT and endows BC cells with CSPs.

Background: UBE2O is proposed as a ubiquitin-conjugating enzyme, but its function was largely unknown. Methods: Mass spectrometry was applied to identify c-Maf ubiquitination-associated proteins. Immunoprecipitation was applied for c-Maf and UBE2O interaction. Immunoblotting was used for Maf protein stability. Luciferase assay was used for c-Maf transcriptional activity. Lentiviral infections were applied for UBE2O function in multiple myeloma (MM) cells. Flow cytometry and nude mice xenografts were applied for MM cell apoptosis and tumor growth assay, respectively. Results: UBE2O was found to interact with c-Maf, a critical transcription factor in MM, by the affinity purification/tandem mass spectrometry assay and co-immunoprecipitation assays. Subsequent studies showed that UBE2O mediated c-Maf polyubiquitination and degradation. Moreover, UBE2O downregulated the transcriptional activity of c-Maf and the expression of cyclin D2, a typical gene modulated by c-Maf. DNA microarray revealed that UBE2O was expressed in normal bone marrow cells but downregulated in MGUS, smoldering MM and MM cells, which was confirmed by RT-PCR in primary MM cells, suggesting its potential role in myeloma pathophysiology. When UBE2O was restored, c-Maf protein in MM cells was significantly decreased and MM cells underwent apoptosis. Furthermore, the human MM xenograft in nude mice showed that re-expression of UBE2O delayed the growth of myeloma xenografts in nude mice in association with c-Maf downregulation and activation of the apoptotic pathway. Conclusions: UBE2O mediates c-Maf polyubiquitination and degradation, induces MM cell apoptosis, and suppresses myeloma tumor growth, which provides a novel insight in understanding myelomagenesis and UBE2O biology.