Abstract A70: A genome‐wide siRNA screen for modulators of cell death induced by the proteasome inhibitor bortezomib

Multiple pathways have been proposed as the mechanism by which proteasome inhibition induces cell death. To clarify their relative importance, we performed a genome‐wide siRNA screen to evaluate the genetic determinants that confer sensitivity of the HCT‐116 colon cancer cell line to bortezomib (VELCADE®, PS‐341). The screen identified 100 genes whose knock‐down affects the lethality of bortezomib. From this list, the accumulation of the proteins ASF1B, Myc, ODC1, PMAIP1 (Noxa), BNIP3, Gadd45α, p‐SMC1A, SREBF1, and p53 by proteasome inhibition was linked to the induction of cell death. Fifty‐nine genes in the A375 melanoma cell line and 56 genes in the HeLa cervical cancer cell line showed similar interactions with bortezomib to those seen in HCT‐116 and a subset of 39 genes were common to all three cell lines. Finally, knockdown of these 100 genes in HCT‐116 cells similarly affected their responsiveness to a structurally diverse set of proteasome inhibitors. Our results suggest that proteasome inhibition promotes cell death primarily by dysregulating Myc and polyamines, interfering with protein translation, and disrupting essential DNA damage repair pathways, leading to programmed cell death. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A70.