'Seed' Analysis of Off-Target siRNAs Reveals an Essential Role of Mcl-1 in Resistance to the Small-Molecule Bcl-2/Bcl-XL Inhibitor ABT-737

Oncogene. 2007 Jun 7;26(27):3972-9. doi: 10.1038/sj.onc.1210166. Epub 2006 Dec 18.

Abstract

ABT-737 is a subnanomolar inhibitor of the antiapoptotic proteins Bcl-2, Bcl-X(L) and Bcl-w. Although ABT-737 triggers extensive cell death in many small-cell lung carcinoma (SCLC) cell lines, some of the SCLC cell lines and the majority of the cancer cell lines derived from other solid tumors were found to be resistant to ABT-737. To better understand the mechanism of resistance to ABT-737, we screened a short interfering RNA library consisting of short interfering RNA against 4000 'druggable' targets in an SCLC-derived cell line, NCI-H196. By comparing the knockdowns with phenotypes, all of the three top 'hits' from the screen were found to result from off-target gene silencing. Interestingly, the three off-target siRNAs were found to knock down an antiapoptotic Bcl-2 family protein Mcl-1 owing to the complementation between their seed regions with the 3' untranslated region (3' UTR) of Mcl-1. Furthermore, reducing the level of Mcl-1 using siRNAs or the small-molecule compounds Bay43-9006 and Seliciclib was sufficient to overcome the resistance to ABT-737 in the resistant SCLC cell line and cancer cell lines derived from other solid tumors. These results provide further evidence that Mcl-1 is the major factor that causes resistance to ABT-737 in cancer cells derived from diverse solid tumors, and the combination of Mcl-1 downregulating agents with ABT-737 could be potent therapeutic regimens for patient with ABT-737-resistant SCLC and many other types of solid tumors.

MeSH terms

  • 3' Untranslated Regions / genetics
  • Antineoplastic Agents / pharmacology
  • Base Sequence
  • Benzenesulfonates / pharmacology
  • Biphenyl Compounds / pharmacology*
  • Blotting, Western
  • Carcinoma, Small Cell / drug therapy
  • Carcinoma, Small Cell / genetics
  • Carcinoma, Small Cell / pathology
  • Cell Line, Tumor
  • Cell Survival / drug effects
  • Cell Survival / genetics
  • Cell Survival / physiology
  • DNA-Binding Proteins / genetics
  • Drug Resistance, Neoplasm / drug effects
  • Drug Resistance, Neoplasm / genetics
  • Humans
  • Lung Neoplasms / drug therapy
  • Lung Neoplasms / genetics
  • Lung Neoplasms / pathology
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism
  • Neoplasm Proteins / physiology*
  • Niacinamide / analogs & derivatives
  • Nitrophenols / pharmacology*
  • Phenylurea Compounds
  • Piperazines / pharmacology
  • Proto-Oncogene Proteins c-bcl-2 / antagonists & inhibitors
  • Proto-Oncogene Proteins c-bcl-2 / genetics
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Proto-Oncogene Proteins c-bcl-2 / physiology*
  • Purines / pharmacology
  • Pyridines / pharmacology
  • RNA Interference
  • RNA, Small Interfering / genetics*
  • Receptor, Fibroblast Growth Factor, Type 2
  • Roscovitine
  • Sorafenib
  • Sulfonamides / pharmacology*
  • Transmembrane Activator and CAML Interactor Protein / genetics
  • Zinc Fingers / genetics
  • bcl-X Protein / antagonists & inhibitors

Substances

  • 3' Untranslated Regions
  • ABT-737
  • Antineoplastic Agents
  • Benzenesulfonates
  • Biphenyl Compounds
  • DNA-Binding Proteins
  • Myeloid Cell Leukemia Sequence 1 Protein
  • Neoplasm Proteins
  • Nitrophenols
  • Phenylurea Compounds
  • Piperazines
  • Proto-Oncogene Proteins c-bcl-2
  • Purines
  • Pyridines
  • RNA, Small Interfering
  • Sulfonamides
  • TNFRSF13B protein, human
  • Transmembrane Activator and CAML Interactor Protein
  • bcl-X Protein
  • Roscovitine
  • Niacinamide
  • Sorafenib
  • FGFR2 protein, human
  • Receptor, Fibroblast Growth Factor, Type 2