In particular, CD40-CD40L interactions between CLL cells and follicular T-helper cells in the LN promote NF-κB and mTOR activation, resulting in CLL survival and drug resistance by upregulation of anti-apoptotic Bcl-2 family members Bcl-XL, Mcl-1 and Bfl-1 [2–5]. Here, MCL1 is linked to B-cell chronic lymphocytic leukemia.