7-hydroxy-2-(n-n-propyl-n-(3-iodo-2--propenyl)-amino)tetralin and Nerve-Sheath-Neoplasms

Emerging evidence indicates that the dopamine D(3) receptor (D(3)R) mediates protective roles both in neuronal and non-neuronal cell lines. In a previous study we proposed that neurofibromin, a large tumor suppressor protein encoded by the neurofibromatosis type 1 gene (NF1), may increase susceptibility to apoptosis after serum deprivation in malignant peripheral nerve sheath tumor (MPNST) cells, thus acting as a proapoptotic gene. In addition, it has been observed that D(3)Rs are functionally correlated to neurofibromin. In this study, we examined whether 7-OH-PIPAT, a potent dopamine D(3)R agonist, exerts an antiapoptotic role under the same culture conditions and then correlated this effect to changes in NF1 expression. Results showed that serum deprivation caused a significant reduction of cell viability (MTT assay) both after 24 and 48 h (p<0.001). Treatment with increasing concentrations of 7-OH-PIPAT (10(-9)-10(-5) M) induced a progressive increase in cell viability both after 24 and 48 h as compared to vehicle-treated cells, with significant changes at the highest concentrations tested (10(-6) and 10(-5) M). Consistently, at the latter two concentrations, a significant reduction in oligonucleosomes formation was observed, thus suggesting an antiapoptotic role of 7-OH-PIPAT. These results were confirmed by Hoechst 33254 nuclear staining. To investigate whether these effects were correlated to changes in NF1 transcript and protein expression, quantitative real-time PCR, Western blot and immunofluorescence analyses were performed. Results demonstrated that the upregulation of NF1 transcripts and protein levels induced by serum withdrawal were remarkably attenuated by 10(-6) and 10(-5) M agonist treatment within 24 h (p<0.01 and p<0.001, respectively), whereas similar effects were observed already at a lower concentration (10(-7) M) after 48 h treatment (p<0.001). In conclusion, these results suggest that D(3)R might mediate the protective response to serum deprivation in MPNST cells through the inhibition of NF1 gene expression, further underlying a subtle role of these receptors in MPNST development.

Topics: Animals; Apoptosis; Blotting, Western; Cell Line, Tumor; Cell Survival; Cytoprotection; Dopamine Agonists; Dose-Response Relationship, Drug; Fluorescent Antibody Technique; Gene Expression Regulation, Neoplastic; Nerve Sheath Neoplasms; Neurofibromin 1; Rats; Receptors, Dopamine D3; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Serum; Tetrahydronaphthalenes; Time Factors