Insulin-like growth factor-binding protein-3 modulates expression of Bax and Bcl-2 and potentiates p53-independent radiation-induced apoptosis in human breast cancer cells.
We report that transfection of insulin-like growth factor-binding protein-3 (IGFBP-3) cDNA in human breast cancer cell lines expressing either mutant p53 (T47D) or wild-type p53 (MCF-7) induces apoptosis. IGFBP-3 also increases the ratio of pro-apoptotic to anti-apoptotic members of the Bcl-2 family. In MCF-7, an increase in Bad and Bax protein expression and a decrease in Bcl-x(L) protein and Bcl-2 protein and mRNA were observed. In T47D, Bax and Bad proteins were up-regulated; Bcl-2 protein is undetectable in these cells. As T47D expresses mutant p53 protein, these modulations of pro-apoptotic proteins and induction of apoptosis are independent of p53. The effect of IGFBP-3 on the response of T47D to ionizing radiation (IR) was examined. These cells do not G(1) arrest in response to IR and are relatively radioresistant. Transfection of IGFBP-3 increased the radiosensitivity of T47D and increased IR-induced apoptosis but did not effect a rapid G(1) arrest. IR also caused a much greater increase in Bax protein in IGFBP-3 transfectants compared with vector controls. Thus, IGFBP-3 increases the expression of pro-apoptotic proteins and apoptosis both basally and in response to IR, suggesting it may be a p53-independent effector of apoptosis in breast cancer cells via its modulation of the Bax:Bcl-2 protein ratio.
Butt
A J
AJ
Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, New South Wales 2065, Australia. abutt@med.usyd.edu.au
Firth
S M
SM
King
M A
MA
Baxter
R C
RC
D017209:Apoptosis / Q000528:radiation effects*; D015152:Blotting, Northern; D015153:Blotting, Western; D001943:Breast Neoplasms / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism; D002470:Cell Survival / Q000528:radiation effects; D017077:Culture Media, Conditioned / Q000378:metabolism; D016895:Culture Media, Serum-Free / Q000378:metabolism; D053938:DNA Fragmentation; D018076:DNA, Complementary / Q000378:metabolism; D005434:Flow Cytometry; D016193:G1 Phase / Q000528:radiation effects; D006801:Humans; D020287:In Situ Nick-End Labeling; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism*; D009154:Mutation; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D011836:Radiation Tolerance; D011839:Radiation, Ionizing; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D015854:Up-Regulation; D014965:X-Rays; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein
C494819:BAD protein, human; C494826:BAX protein, human; D002352:Carrier Proteins; D017077:Culture Media, Conditioned; D016895:Culture Media, Serum-Free; D018076:DNA, Complementary; D018972:Insulin-Like Growth Factor Binding Protein 3; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D016159:Tumor Suppressor Protein p53; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein