The BCR signaling can be targeted with small molecular inhibitors directed against Bruton's tyrosine kinase (Btk), spleen tyrosine kinase (Syk), or phosphoinositide 3′-kinase (PI3K) isoform p110δ (PI3Kδ), all being efficient in the treatment of CLL [125]. This evidence concerns the gene PIK3CD and B-cell chronic lymphocytic leukemia.