siRNA-mediated knockdown of IGF1R leads to enhanced cell death of primary human CLL cells and is associated with downregulation of pErk. IGF1R inhibition overcomes prosurvival effects of the microenvironment. (A) CLL B cells were transfected with IGF1R-specific siRNA and analyzed by flow cytometry for receptor expression (mean ± SEM, n = 5). (B) CLL B cells were transfected with IGF1R-specific siRNA and analyzed by flow cytometry for cell survival (mean ± SEM, n = 5). (C) Downregulation of IGF1R and implicated downstream targets were analyzed by immunoblotting. A representative example from 5 independent experiments is shown. (D) CLL B cells were cocultured with the stromal cell line M2-10B4 or treated with CXCL12, anti-CD49d, or ICAM for 24 hours, and cell survival was determined by flow cytometry (mean ± SEM, n = 4). (E) CLL B cells were treated with a single dose of 15 µM AG1024 in the absence or presence of stroma cells, CXCL12, anti-CD49d, or ICAM for 24 hours, and cell survival was determined by flow cytometry (mean ± SEM, n = 4).