IGFBP-3 mediates p53-induced apoptosis during serum starvation.
Insulin-like growth factor binding protein (IGFBP)-3, a p53-response gene, can induce apoptosis in an IGF-independent manner. Here we demonstrate that IGFBP-3 mediates p53-induced apoptosis during serum starvation using two foil neoplastic cell models: one which introduces p53 activity and one which eliminates it. We created a doxycycline-inducible p53 model from the p53-negative PC-3 prostate cancer cell line. Doxycycline treatment increased both p53 and IGFBP-3 levels. It also augmented apoptosis, but not during insulin-like growth factor-I co-treatment. In a second model, lung carcinoma H460 cells expressing fully functional p53 were stably transfected with E6, which targets p53 for degradation. H460-E6 cells contained less p53 and IGFBP-3 than control neo-transfected cells, and proteasome blockade restored both. In serum deprivation, H460-E6 cells had enhanced growth and less apoptosis than did H460-neo cells. Reductions in H460-neo apoptosis, comparable in magnitude to H460-E6, were achieved by adding anti-IGFBP-3-antibody or IGFBP-3 antisense oligomers, but not non-specific immunoglobulin or IGFBP-3 sense oligomers. In summary, turning p53 in two foil neoplastic cell models induced IGFBP-3 expression and increased apoptosis during serum starvation, an effect inhibited by insulin-like growth factor-I treatment and specific IGFBP-3 blockade. This is the first demonstration of inhibition of p53 action by antagonizing IGFBP-3.
Grimberg
Adda
A
Division of Pediatric Endocrinology, The Children's Hospital of Philadelphia, Abramson Research Center, Philadelphia, PA 19104, USA. grimberg@email.chop.edu
Liu
Bingrong
B
Bannerman
Peter
P
El-Deiry
Wafik S
WS
Cohen
Pinchas
P
D017209:Apoptosis; D018287:Carcinoma, Large Cell / Q000378:metabolism*; D002455:Cell Division; D016895:Culture Media, Serum-Free / Q000378:metabolism*; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism*; D019868:Kanamycin Kinase / Q000235:genetics / Q000378:metabolism; D008175:Lung Neoplasms / Q000378:metabolism*; D008297:Male; D018613:Microscopy, Confocal; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism; D011471:Prostatic Neoplasms / Q000378:metabolism*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*
D016895:Culture Media, Serum-Free; C466081:E6 protein, Human papillomavirus type 8; D018972:Insulin-Like Growth Factor Binding Protein 3; D009856:Oncogene Proteins, Viral; D011994:Recombinant Proteins; D016159:Tumor Suppressor Protein p53; D019868:Kanamycin Kinase