A Chemical Screen Identifies the Chemotherapeutic Drug Topotecan as a Specific Inhibitor of the B-MYB/MYCN Axis in Neuroblastoma

Oncotarget. 2012 May;3(5):535-45. doi: 10.18632/oncotarget.498.

Abstract

The transcription factor MycN is the prototypical neuroblastoma oncogene and a potential therapeutic target. However, its strong expression caused by gene amplification in about 30% of neuroblastoma patients is a considerable obstacle to the development of therapeutic approaches aiming at eliminating its tumourigenic activity. We have previously reported that B-Myb is essentially required for transcription of the MYCN amplicon and have also shown that B-MYB and MYCN are engaged in a feed forward loop promoting the survival/proliferation of neuroblastoma cells. We postulated that pharmacological strategies breaking the B-MYB/MYCN axis should result in clinically desirable effects. Thus, we implemented a high throughput chemical screen, using a curated library of ~1500 compounds from the National Cancer Institute, whose endpoint was the identification of small molecules that inhibited B-Myb. At the end of the screening, we found that the compounds pinafide, ellipticine and camptothecin inhibited B-Myb transcriptional activity in luciferase assays. One of the compounds, the topoisomerase-1 inhibitor camptothecin, is of considerable clinical interest since its derivatives topotecan and irinotecan are currently used as first and second line treatment agents for various types of cancer, including neuroblastoma. We found that neuroblastoma cells with amplification of MYCN are more sensitive than MYCN negative cells to camptothecin and topotecan killing. Campothecin and topotecan caused selective down-regulation of B-Myb and MycN expression in neuroblastoma cells. Notably, forced overexpression of B-Myb could antagonize the killing effect of topotecan and camptothecin, demonstrating that the transcription factor is a key target of the drugs. These results suggest that camptothecin and its analogues should be more effective in patients whose tumours feature amplification of MYCN and/or overexpression of B-MYB.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis / drug effects
  • Apoptosis / genetics
  • Camptothecin / analogs & derivatives
  • Camptothecin / chemistry
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / metabolism*
  • Cell Line, Tumor
  • High-Throughput Screening Assays
  • Humans
  • N-Myc Proto-Oncogene Protein
  • Neuroblastoma / drug therapy*
  • Neuroblastoma / pathology
  • Nuclear Proteins / metabolism*
  • Oncogene Proteins / metabolism*
  • Protein Binding / drug effects
  • Protein Binding / genetics
  • Small Molecule Libraries
  • Topoisomerase I Inhibitors / chemistry
  • Topoisomerase I Inhibitors / pharmacology*
  • Topoisomerase I Inhibitors / therapeutic use
  • Topotecan / chemistry
  • Topotecan / pharmacology*
  • Topotecan / therapeutic use
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*
  • Transcriptional Activation / drug effects
  • Transcriptional Activation / genetics
  • Transgenes / genetics

Substances

  • Cell Cycle Proteins
  • MYBL2 protein, human
  • MYCN protein, human
  • N-Myc Proto-Oncogene Protein
  • Nuclear Proteins
  • Oncogene Proteins
  • Small Molecule Libraries
  • Topoisomerase I Inhibitors
  • Trans-Activators
  • Topotecan
  • Camptothecin