BNIP3 plays a role in hypoxic cell death in human epithelial cells that is inhibited by growth factors EGF and IGF.
Hypoxic regions within solid tumors are often resistant to chemotherapy and radiation. BNIP3 (Bcl-2/E1B 19 kDa interacting protein) is a proapoptotic member of the Bcl-2 family that is expressed in hypoxic regions of tumors. During hypoxia, BNIP3 expression is increased in many cell types and upon forced overexpression BNIP3 induces cell death. Herein, we have demonstrated that blockage of hypoxia-induced BNIP3 expression using antisense oligonucleotides against BNIP3 or blockage of BNIP3 function through expression of a mutant form of BNIP3 inhibits hypoxia-induced cell death in human embryonic kidney 293 cells. We have also determined that hypoxia-mediated BNIP3 expression is regulated by the transcription factor, hypoxia-inducible factor-1alpha (HIF-1alpha) in human epithelial cell lines. Furthermore, HIF-1alpha directly binds to a consensus HIF-1alpha-responsive element (HRE) in the human BNIP3 promoter that upon mutation of this HRE site eliminates the hypoxic responsiveness of the promoter. Since BNIP3 is expressed in hypoxic regions of tumors but fails to induce cell death, we determined whether growth factors block BNIP3-induced cell death. Treatment of the breast cancer cell line MCF-7 cells with epidermal growth factor (EGF) or insulin-like growth factor effectively protected these cells from BNIP3-induced cell death. Furthermore, inhibiting EGF receptor signaling using antibodies against ErbB2 (Herceptin) resulted in increased hypoxia-induced cell death in MCF-7 cells. Taken together, BNIP3 plays a role in hypoxia-induced cell death in human epithelial cells that could be circumvented by growth factor signaling.
Kothari
Shilpa
S
Manitoba Institute of Cell Biology, 675 McDermot Ave., Winnipeg, Canada.
Cizeau
Jeannick
J
McMillan-Ward
Eileen
E
Israels
Sara J
SJ
Bailes
Michelle
M
Ens
Karen
K
Kirshenbaum
Lorrie A
LA
Gibson
Spencer B
SB
D000165:Acridine Orange / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D016466:CHO Cells; D016923:Cell Death; D002455:Cell Division; D002460:Cell Line; D006224:Cricetinae; D004815:Epidermal Growth Factor / Q000378:metabolism*; D004847:Epithelial Cells / Q000378:metabolism*; D005456:Fluorescent Dyes / Q000494:pharmacology; D005799:Genes, Dominant; D017930:Genes, Reporter; D006801:Humans; D000860:Hypoxia; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008565:Membrane Proteins / Q000502:physiology*; D008854:Microscopy, Electron; D009154:Mutation; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011401:Promoter Regions, Genetic; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins; D015398:Signal Transduction; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D014343:Trypan Blue / Q000494:pharmacology; D014407:Tumor Cells, Cultured; D025521:Tumor Suppressor Proteins; D001616:beta-Galactosidase / Q000378:metabolism
C090121:BNIP3 protein, human; C116838:BNIP3L protein, human; D005456:Fluorescent Dyes; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008565:Membrane Proteins; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D004815:Epidermal Growth Factor; D007334:Insulin-Like Growth Factor I; D001616:beta-Galactosidase; D000165:Acridine Orange; D014343:Trypan Blue