Microphthalmia-associated transcription factor is a critical transcriptional regulator of melanoma inhibitor of apoptosis in melanomas

Cancer Res. 2008 May 1;68(9):3124-32. doi: 10.1158/0008-5472.CAN-07-6622.

Abstract

Melanoma inhibitor of apoptosis (ML-IAP) is a potent inhibitor of apoptosis, which is highly expressed in melanomas and likely contributes to their resistance to chemotherapeutic treatments. Herein, we show that the lineage survival oncogene microphthalmia-associated transcription factor (MITF) is a critical regulator of ML-IAP transcription in melanoma cells. The ML-IAP promoter contains two MITF consensus sites, and analysis of MITF and ML-IAP mRNA levels revealed a high correlation in melanoma tumor samples and cell lines. In reporter assays, MITF promoted a strong stimulation of transcriptional activity from the ML-IAP promoter, and MITF bound the endogenous ML-IAP promoter in melanoma cells by chromatin immunoprecipitation and electrophoretic mobility shift assay. Strikingly, small interfering RNA (siRNA)-mediated knockdown of MITF in melanoma cells led to a dramatic decrease in ML-IAP mRNA and protein levels, establishing that ML-IAP expression in melanoma cells is MITF dependent. Additionally, cyclic AMP-mediated induction of MITF expression in melanocytes resulted in increased ML-IAP expression, suggesting that melanocytes can express ML-IAP when MITF levels are heightened. Disruption of MITF by siRNA led to a decrease in melanoma cell viability, which could be rescued by ectopic expression of ML-IAP. Collectively, these findings implicate MITF as a major transcriptional regulator of ML-IAP expression in melanomas, and suggest that ML-IAP contributes to the prosurvival activity of MITF in melanoma progression.

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics*
  • Cell Survival / genetics
  • Cells, Cultured
  • Cyclic AMP / metabolism
  • DNA Damage / physiology
  • Gene Expression Regulation*
  • Humans
  • Inhibitor of Apoptosis Proteins / genetics*
  • Melanocytes / metabolism
  • Melanoma / genetics*
  • Microphthalmia-Associated Transcription Factor / metabolism
  • Microphthalmia-Associated Transcription Factor / physiology*
  • Neoplasm Proteins / genetics*
  • Promoter Regions, Genetic
  • Protein Binding
  • Signal Transduction / genetics
  • Transcription, Genetic
  • Transfection
  • Tumor Necrosis Factor-alpha / physiology
  • Wnt Proteins / physiology

Substances

  • Adaptor Proteins, Signal Transducing
  • BIRC7 protein, human
  • Inhibitor of Apoptosis Proteins
  • Microphthalmia-Associated Transcription Factor
  • Neoplasm Proteins
  • Tumor Necrosis Factor-alpha
  • Wnt Proteins
  • Cyclic AMP