Background. Many antineoplastic agents cause neurotoxicity, which might be dose limiting or even leading to cessation of the treatment. Established anticancer drugs such as platinum compounds and taxanes are well-known for their neurotoxic side effects, while novel compounds such as epothilones and bortezomib also showed neurotoxicity, although the nature of this toxicity is likely to be different. More insight in the mechanism would help to adapt treatment protocols or design protectors against this toxicity. The aim of this study was to characterize the extent of bortezomib, epothiloneB (epoB) and oxaliplatin (OHP) induced neurotoxicity in PC12 cells (rat pheochromocytoma cell line) and to modify this toxicity specifically. Methods. IC50 and IC80 values of bortezomib, epoB and OHP after 72-h treatment were determined by an SRB assay. PC12 cells were induced to differentiate towards a mature neuronal phenotype with neurite elongation using Nerve Growth Factor. Cells were treated with IC50s (0.95 nM bortezomib, 0.75 nM epoB, 0.07 M OHP) to induce a neurotoxic effect which was evaluated using neurite outgrowth as a marker. In order to evaluate the neuroprotective effect of amifostine, PC12 cells were exposed to the different drugs at IC80 values (2.7 nM bortezomib, 1.9 nM epoB, 0.2 M OHP) simulteneously with 0.5 mM amifostine. The expression of cyclin B2 (CB2) and survivin, two potential markers of neuronal differentiation, was evaluated in PC12 cell line and in the human SH-SY5Y neuroblastoma cells with RealTime-PCR. SH-SY5Y cells are a model system widely used to study peripheral neurotoxicity. These cells can be stimulated by retinoic acid to neurite outgrowth. Results. Treatment of differentiated PC12 cells resulted in a statistically significant decrease of neurite length with respect to control cells. Bortezomib, epoB and OHP at their IC50s reduced the neurite length of 68, 78 and 66% respectively, compared to the control. Also the percentage of neurite forming cells (used to discriminate neurotoxicity from general cytotoxicity) reduced from 70% (control) to 55% (bortezomib), 46% (epoB) and 51% (OHP). Amifostine only neuroprotected OHP induced neurotoxicity and increased the neurite length from 59% (OHP alone) to 74% and the percentage of neurite forming cells from 45% to 60%. Amifostine did not protect against bortezomib and epoB induced neurotoxicity, neither neurite length or the percentage of neurite forming cells. Since quantification of neurite outgrowth is impractical, decrease in CB2 and survivin expression was investigated as a model marker. We tested CB2 and survivin expression in PC12 and in SH-SY5Y cells. The expression of these two genes, evaluated with TaqMan RT-PCR, revealed a 2.7 times decrease in CB2 expression in differentiated PC12 cells with respect to undifferentiated control cells, while survivin was not a good marker for neuronal differentiation. However in SH-SY5Y cells both CB2 and survivin expression was significantly decreased in differentiated cells (1.5 and 3 times respectively) representing good model markers for neuronal differentiation. Conclusions. Our results demonstrate that bortezomib, epoB and OHP are all neurotoxic in our PC12 cells model, in accordance with clinical experience. However, amifostine had a neuroprotective effect only in OHP induced neurotoxicity, demonstrating a different type of neurotoxicity. Our study also showed that CB2 and survivin can be used as potential biomarkers of neuronal differentiation in human SH-SY5Y neuroblastoma cells, while in the rat PC12 cells only CB2 is a good marker of neuronal differentiation.
Ceresa, C., Giovannetti, E., Geldof, A., Cavaletti, G., Peters, G. (2008). Bortezomib, oxaliplatin and epothilone B induced neurotoxicity: characterizationand protection. Intervento presentato a: EORTC Pharmacology and molecular mechanisms group, 29th wintwr meeting, Palermo.
Bortezomib, oxaliplatin and epothilone B induced neurotoxicity: characterizationand protection
CERESA, CECILIA;CAVALETTI, GUIDO ANGELO;
2008
Abstract
Background. Many antineoplastic agents cause neurotoxicity, which might be dose limiting or even leading to cessation of the treatment. Established anticancer drugs such as platinum compounds and taxanes are well-known for their neurotoxic side effects, while novel compounds such as epothilones and bortezomib also showed neurotoxicity, although the nature of this toxicity is likely to be different. More insight in the mechanism would help to adapt treatment protocols or design protectors against this toxicity. The aim of this study was to characterize the extent of bortezomib, epothiloneB (epoB) and oxaliplatin (OHP) induced neurotoxicity in PC12 cells (rat pheochromocytoma cell line) and to modify this toxicity specifically. Methods. IC50 and IC80 values of bortezomib, epoB and OHP after 72-h treatment were determined by an SRB assay. PC12 cells were induced to differentiate towards a mature neuronal phenotype with neurite elongation using Nerve Growth Factor. Cells were treated with IC50s (0.95 nM bortezomib, 0.75 nM epoB, 0.07 M OHP) to induce a neurotoxic effect which was evaluated using neurite outgrowth as a marker. In order to evaluate the neuroprotective effect of amifostine, PC12 cells were exposed to the different drugs at IC80 values (2.7 nM bortezomib, 1.9 nM epoB, 0.2 M OHP) simulteneously with 0.5 mM amifostine. The expression of cyclin B2 (CB2) and survivin, two potential markers of neuronal differentiation, was evaluated in PC12 cell line and in the human SH-SY5Y neuroblastoma cells with RealTime-PCR. SH-SY5Y cells are a model system widely used to study peripheral neurotoxicity. These cells can be stimulated by retinoic acid to neurite outgrowth. Results. Treatment of differentiated PC12 cells resulted in a statistically significant decrease of neurite length with respect to control cells. Bortezomib, epoB and OHP at their IC50s reduced the neurite length of 68, 78 and 66% respectively, compared to the control. Also the percentage of neurite forming cells (used to discriminate neurotoxicity from general cytotoxicity) reduced from 70% (control) to 55% (bortezomib), 46% (epoB) and 51% (OHP). Amifostine only neuroprotected OHP induced neurotoxicity and increased the neurite length from 59% (OHP alone) to 74% and the percentage of neurite forming cells from 45% to 60%. Amifostine did not protect against bortezomib and epoB induced neurotoxicity, neither neurite length or the percentage of neurite forming cells. Since quantification of neurite outgrowth is impractical, decrease in CB2 and survivin expression was investigated as a model marker. We tested CB2 and survivin expression in PC12 and in SH-SY5Y cells. The expression of these two genes, evaluated with TaqMan RT-PCR, revealed a 2.7 times decrease in CB2 expression in differentiated PC12 cells with respect to undifferentiated control cells, while survivin was not a good marker for neuronal differentiation. However in SH-SY5Y cells both CB2 and survivin expression was significantly decreased in differentiated cells (1.5 and 3 times respectively) representing good model markers for neuronal differentiation. Conclusions. Our results demonstrate that bortezomib, epoB and OHP are all neurotoxic in our PC12 cells model, in accordance with clinical experience. However, amifostine had a neuroprotective effect only in OHP induced neurotoxicity, demonstrating a different type of neurotoxicity. Our study also showed that CB2 and survivin can be used as potential biomarkers of neuronal differentiation in human SH-SY5Y neuroblastoma cells, while in the rat PC12 cells only CB2 is a good marker of neuronal differentiation.
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