Effect of sorafenib, PI3K, Raf, and MEK inhibitors on the viability and signaling pathways in primary human CLL cells. (A) CLL B cells purified from freshly isolated or freeze-thawed PBMCs from CLL patient samples were treated with 0.1 to 5 µM of the PI3K inhibitor AS605240 for 24 hours, and cell survival was determined by flow cytometry (mean ± SEM, n = 4). (B) CLL B cells were treated with a single dose of 10 µM sorafenib, Plexxikon 4720 (PLX), or the Mek-Inhibitor U01206 for 24 hours, and cell survival was determined by flow cytometry (mean ± SEM, n = 10). (C) CLL B cells were treated with a single dose of 10 µM sorafenib, PLX, or U01206 and immunoblotted for Erk phosphorylation and expression. One representative result from 4 independent experiments is shown. (D) Healthy B cells or CLL B cells purified from freshly isolated or freeze-thawed PBMCs from CLL patient samples were lysed and immunoblotted for Ras expression. Four representative samples from 8 donor-derived lysates from each group are shown. n.s., not statistically significant.