The combination of BH3-mimetic ABT-737 with the alkylating agent temozolomide induces strong synergistic killing of melanoma cells independent of p53

PLoS One. 2011;6(8):e24294. doi: 10.1371/journal.pone.0024294. Epub 2011 Aug 29.

Abstract

Metastatic melanoma has poor prognosis and is refractory to most conventional chemotherapies. The alkylating agent temozolomide (TMZ) is commonly used in treating melanoma but has a disappointing response rate. Agents that can act cooperatively with TMZ and improve its efficacy are thus highly sought after. The BH3 mimetic ABT-737, which can induce apoptosis by targeting pro-survival Bcl-2 family members, has been found to enhance the efficacy of many conventional chemotherapeutic agents in multiple cancers. We found that combining TMZ and ABT-737 induced strong synergistic apoptosis in multiple human melanoma cell lines. When the drugs were used in combination in a mouse xenograft model, they drastically reduced tumor growth at concentrations where each individual drug had no significant effect. We found that TMZ treatment elevated p53 levels, and that the pro-apoptotic protein Noxa was elevated in TMZ/ABT-737 treated cells. Experiments with shRNA demonstrated that the synergistic effect of TMZ and ABT-737 was largely dependent on Noxa. Experiments with nutlin-3, a p53 inducer, demonstrated that p53 induction was sufficient for synergistic cell death with ABT-737 in a Noxa-dependent fashion. However, p53 was not necessary for TMZ/ABT-737 synergy as demonstrated by a p53-null line, indicating that TMZ and ABT-737 together induce Noxa in a p53-independent fashion. These results demonstrate that targeting anti-apoptotic Bcl-2 members is a promising method for treating metastatic melanoma, and that clinical trials with TMZ and Bcl-2 inhibitors are warranted.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Alkylating Agents / pharmacology*
  • Animals
  • Apoptosis / drug effects*
  • Biomimetic Materials / pharmacology*
  • Biphenyl Compounds / pharmacology*
  • Cell Line, Tumor
  • Dacarbazine / analogs & derivatives*
  • Dacarbazine / pharmacology
  • Drug Synergism
  • Female
  • Gene Expression Regulation, Neoplastic / drug effects
  • Humans
  • Melanoma / pathology*
  • Mice
  • Nitrophenols / pharmacology*
  • Piperazines / pharmacology
  • Protein Structure, Tertiary
  • Proto-Oncogene Proteins c-bcl-2 / metabolism
  • Sulfonamides / pharmacology*
  • Temozolomide
  • Time Factors
  • Tumor Suppressor Protein p53 / metabolism
  • Xenograft Model Antitumor Assays

Substances

  • ABT-737
  • Alkylating Agents
  • Biphenyl Compounds
  • Nitrophenols
  • PMAIP1 protein, human
  • Piperazines
  • Proto-Oncogene Proteins c-bcl-2
  • Sulfonamides
  • Tumor Suppressor Protein p53
  • Dacarbazine
  • Temozolomide