Elsevier

Neoplasia

Volume 9, Issue 10, October 2007, Pages 801-811, IN1
Neoplasia

Targeting Antiapoptotic Bcl-2 Family Members with Cell-Permeable BH3 Peptides Induces Apoptosis Signaling, Death in Head, Neck Squamous Cell Carcinoma Cells1,2

https://doi.org/10.1593/neo.07394Get rights and content
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open access

Abstract

Head, neck squamous cell carcinomas (HNSCCs) are frequently characterized by chemotherapy, radiation resistance, by overexpression of Bcl-XL, an antiapoptotic member of the Bcl-2 protein family. In this report, we examined whether cell-permeable peptides derived from the BH3 domains of proapoptotic Bax, Bad, or Bak could be used to target Bcl-XL and/or Bcl-2 in HNSCC cells, induce apoptotic death in these cells. To render the peptides cell-permeable, Antennapedia (Ant) or polyarginine (R8) peptide transduction domain was fused to the amino termini. Fluorescence microscopy of peptide-treated HNSCC cells revealed that the BH3 peptides colocalized with mitochondria, the site of Bcl-XL, Bcl-2 expression. By contrast, a mutant peptide (BaxE BH3) that cannot bind Bcl-XL or Bcl-2 was diffusely localized throughout the cytoplasm. Treatment of three HNSCC cell lines (1483, UM-22A, UM-22B) with the wild-type BH3 peptides resulted in loss of viability, induction of apoptosis, as assessed by 3-(4,5-dimethythiazol-2yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assays, annexin V staining. In general, Ant-conjugated peptides were more potent than R8-conjugated peptides, Bad BH3 peptide was typically more potent than Bax BH3 or Bak BH3. Treatment of purified HNSCC mitochondria with BH3 peptides resulted in robust release of cytochrome c. Thus, the relative apoptosis resistance of HNSCC cells is not due to a deficit in this step of the intrinsic, mitochondrialmediated apoptosis pathway. We conclude that cellpermeable BH3 peptides can be used to target Bcl-XL and/or Bcl-2 in HNSCC, that targeting of these proteins may have therapeutic value in the treatment of this disease.

Keywords

HNSCC
Bcl-XL
Bcl-2
BH3 peptides
apoptosis

Abbreviations

Ant
Antennapedia
DMEM
Dulbecco's modified Eagle's medium
EGFR
epidermal growth factor receptor
FITC
fluorescein isothiocyanate
HNSCC
head, neck squamous cell carcinoma
NF-κB
nuclear factor-kappaB
PARP
poly(ADP)-ribose polymerase
PI
propidium iodide
R8
polyarginine
STAT3
signal transducer, activator of transcription-3

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1

This article refers to supplementary material, which is designated by Figure W1, is available online at www.bcdecker.com.

2

This work was supported by a grant (R01-CA86980) from the National Institutes of Health, by a grant (P50-CA097190) from the University of Pittsburgh Specialized Program of Research Excellence (SPORE) in Head, Neck Cancer.

3

Current address: Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA.