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Signalling pathways involved in antiproliferative effects of IGFBP-3: a review
1Kolling Institute of Medical Research, University of Sydney, Royal North Shore Hospital, Sydney, NSW 2065, Australia. robaxter@med.usyd.edu.au
Abstract:
Insulin-like growth factor binding protein-3 (IGFBP-3), the major circulating carrier protein for IGFs, is also active in the cellular environment as a potent antiproliferative agent. It appears to function both by cell cycle blockade and the induction of apoptosis. Transfection of p53 negative T47D breast cancer cells to express IGFBP-3 leads to induction of the apoptotic protein bax and an increase in sensitivity to ionising radiation. IGFBP-3 can be transported to the nucleus by an importin beta mediated mechanism, where it has been shown to interact with the retinoid X receptor alpha and possibly other nuclear elements. Expression of oncogenic ras is associated with resistance to exogenous IGFBP-3, the effect being reversible by inhibition of mitogen activated protein (MAP) kinase phosphorylation. IGFBP-3 antiproliferative signalling appears to require an active transforming growth factor beta (TGF-beta) signalling pathway, and IGFBP-3 stimulates phosphorylation of the TGF-beta signalling intermediates Smad2 and Smad3. These recent findings all point to a complex intracellular mode of action of IGFBP-3, which will need to be better understood if anti-cancer treatments are to take advantage of the antiproliferative activity of IGFBP-3.
Insights
Insulin-like growth factor binding protein-3 (IGFBP-3) acts as an antiproliferative agent by inducing apoptosis and cell cycle arrest. Understanding its complex intracellular mechanisms is key for developing novel anti-cancer therapies.
Area of Science:
- Molecular Biology
- Cell Biology
- Cancer Research
Background:
- Insulin-like growth factor binding protein-3 (IGFBP-3) is the primary carrier protein for IGFs.
- IGFBP-3 exhibits potent antiproliferative activity within cells.
- Its mechanisms involve cell cycle blockade and apoptosis induction.
Purpose of the Study:
- To elucidate the complex intracellular mechanisms of IGFBP-3's antiproliferative action.
- To investigate IGFBP-3's role in cancer cell sensitivity to radiation.
- To explore IGFBP-3's interaction with nuclear receptors and signaling pathways.
Main Methods:
- Transfection of p53-negative breast cancer cells (T47D) to express IGFBP-3.
- Assessment of apoptosis-related protein (bax) induction and radiation sensitivity.
- Investigation of nuclear transport via importin beta and interaction with retinoid X receptor alpha.
- Analysis of oncogenic ras expression effects and MAP kinase phosphorylation.
- Evaluation of transforming growth factor beta (TGF-beta) pathway involvement and Smad2/Smad3 phosphorylation.
Main Results:
- IGFBP-3 expression in T47D cells induced bax and increased sensitivity to ionizing radiation.
- IGFBP-3 is transported to the nucleus by importin beta and interacts with retinoid X receptor alpha.
- Oncogenic ras conferred resistance to IGFBP-3, reversible by inhibiting MAP kinase phosphorylation.
- IGFBP-3 requires an active TGF-beta signaling pathway and stimulates Smad2/Smad3 phosphorylation.
Conclusions:
- IGFBP-3 possesses a complex intracellular mode of action.
- Its antiproliferative effects are mediated through cell cycle arrest and apoptosis induction.
- Further understanding of IGFBP-3's intracellular functions is crucial for developing targeted anti-cancer treatments.