This induces activation of Bruton's tyrosine kinase (BTK), phosphoinositide 3- kinase (PI3K), and Ras- dependent extracellular signal-regulated kinase (ERK) (197), which ultimately leads to the upregulation of NFκB which promotes CLL-B cell survival (198). This evidence concerns the gene NFKB1 and B-cell chronic lymphocytic leukemia.