Biochemical and Biophysical Research Communications
Effects of a non-IGF binding mutant of IGFBP-5 on cell death in human breast cancer cells
Section snippets
Materials and methods
Materials. Insulin-like growth factor-I (IGF-I), long R3 IGF-I (LR3; analogue of IGF-I that has no affinity for IGFBPs) and non-glycosylated (ng) IGFBP-5 were purchased from Gropep (Adelaide, Australia). Human glycosylated (gly) and non-IGF binding mutant of IGFBP-5 (mut) were prepared as described previously [17]. The ceramide analogue (C2) was obtained from Calbiochem (Nottingham, UK). Tissue culture plastics were purchased from Greiner Labortechnik (Stonehouse, UK). The IGFBP-5 antibody was
Effects of IGFBP-5 on C2-induced apoptosis in IGF-non-responsive Hs578T cells
In the Hs578T cell line, C2 induced a significant (P<0.001) increase in cell death from 7.3% to 56.9%. As demonstrated previously [10], we confirmed that non-glycosylated IGFBP-5 was able to significantly (P<0.01) inhibit C2-induced cell death from 56.9% to 34.6%. We have now demonstrated further that gly and mut IGFBP-5 can also dramatically , respectively) inhibit C2-induced cell death from 56.9% to 26% and 30.5%, respectively (Fig. 1A). We have demonstrated previously [10]
Discussion
We have demonstrated in the Hs578T IGF non-responsive cell line that non-glycosylated, glycosylated, and mutant IGFBP-5 can all confer an identical survival effect against C2-induced cell death, clearly in an IGF-independent manner. Having established that the non-IGF binding mutant of IGFBP-5 maintained its intrinsic actions on cell death, we then examined the effects of this mutant in the IGF responsive MCF-7 cell line. We observed in this model that IGF-I acted as a potent survival factor
Acknowledgements
We thank the Association for International Cancer Research and the Needham Cooper Trust for supporting this work.
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