Kinobead Profiling Reveals Reprogramming of B-cell Receptor Signaling in Response to Therapy Within Primary Chronic Lymphocytic Leukemia Cells.

Signaling via the B-cell receptor (BCR) is critical for driving CLL pathobiology, promoting both malignant cell survival and disease progression. However, understanding of this pathway is limited, particularly in relation to potential changes in response to therapy. Here, we describe a kinobead-based protocol, used in conjunction with mass-spectrometry to study surface-IgM signaling in primary CLL cells. We identified a fingerprint of over 30 kinases which displayed unique, patientspecific response following sIgM stimulation. Matched analysis of CLL cells in samples taken from clinical trials showed that BCR-induced kinome responses altered between baseline and disease progression in patients who relapsed from chemoimmunotherapy. Moreover, adaptive changes to BCR signaling were also observed in CLL cells from clinical trial patients receiving ibrutinib; longitudinal profiling revealed increased signaling despite BTK inhibition. Collectively, these data comprise the first comprehensive investigation into BCR signaling response within CLL where kinobead profiling reveals unique evidence of adaptive reprogramming in response to therapy.