Surprisingly, the BTK/PI3K inhibitors had a mild effect on CLL cell proliferation in HS5-CD40L-IL4-IL21 co-cultures (limited to some samples), while inhibitors of wild-type RAF (LY3009120 and naporafenib) inhibited proliferation in all cases (≥50% proliferation reduction, P < 0.001; Fig. 3C). Here, IL21 is linked to B-cell chronic lymphocytic leukemia.