BCR and MYD88 signaling pathways and potential targets. (A) Signaling through BCR leads to downstream activation of the NF-κB transcription factor, which is a driver pathway in ABC DLBCL. Signaling also activates the AKT/MTOR and MAP kinase pathways. Constitutive MYD88 signaling is an alternative pathway leading to NF-κB activation. (B) Inhibition of Btk by ibrutinib is toxic in ABC, but not in GCB DLBCL cell lines, providing evidence for the clinical relevance of the BCR signaling pathway.