biostudies-literatureEdelmann JCancer Research UKBarts CharityNCI NIH HHS102089https://www.ebi.ac.uk/biostudies/studies/S-EPMC7878992biostudies-literatureUnknown24(2)The anti-CD20 monoclonal antibodies rituximab and obinutuzumab differ in their mechanisms of action, with obinutuzumab evoking greater direct B cell death. To characterize the signaling processes responsible for improved B cell killing by obinutuzumab, we undertook a phosphoproteomics approach and demonstrate that rituximab and obinutuzumab differentially activate pathways downstream of the B cell receptor. Although both antibodies induce strong ERK and MYC activation sufficient to promote cell-cycle arrest and B cell death, obinutuzumab exceeds rituximab in supporting apoptosis induction by means of aberrant SYK phosphorylation. In contrast, rituximab elicits stronger anti-apoptotic signals by activating AKT, by impairing pro-apoptotic BAD, and by releasing membrane-bound NOTCH1 to up-regiScienceRituximab and obinutuzumab differentially hijack the B cell receptor and NOTCH1 signaling pathways.PMC7878992P01 CA081534MRD020324721Holzmann KKlymenko TGribben JGCutillas PDokal ADBraun AVilventhraraja EEdelmann JBritton DCragg MDohner HfalseRituximab and obinutuzumab differentially hijack the B cell receptor and NOTCH1 signaling pathways.The anti-CD20 monoclonal antibodies rituximab and obinutuzumab differ in their mechanisms of action, with obinutuzumab evoking greater direct B cell death. To characterize the signaling processes responsible for improved B cell killing by obinutuzumab, we undertook a phosphoproteomics approach and demonstrate that rituximab and obinutuzumab differentially activate pathways downstream of the B cell receptor. Although both antibodies induce strong ERK and MYC activation sufficient to promote cell-cycle arrest and B cell death, obinutuzumab exceeds rituximab in supporting apoptosis induction by means of aberrant SYK phosphorylation. In contrast, rituximab elicits stronger anti-apoptotic signals by activating AKT, by impairing pro-apoptotic BAD, and by releasing membrane-bound NOTCH1 to up-reg2021-01-01T00:00:00Z2021 Feb2026-05-01T11:23:48.135Z2021-02-21T11:42:00ZS-EPMC78789923361519710.1016/j.isci.2021.102089