Thus, many BCR‐related proteins were found to be phosphorylated in all or the majority of samples (LYN, SYK, PI3K, BTK, ZAP70, PLCG3, ERK, NFAT, CD19, PRKCB, NF‐Kβ, JNK, and VAV) [82, 83, 84, 85, 86, 87], suggesting that BCR signaling plays a critical role in the maintenance/survival of CLL/MBL tumor cells (Fig. 5). The gene discussed is BTK; the disease is B-cell chronic lymphocytic leukemia.