[Memorandum for the management of clinical trials]

A critical appraisal of the recent legislation on clinical trials is proposed, together with some reflections on the implications on the practice and principles of clinical experimentation. The possible role and contribution of Ethical Committees is discussed.

Effects of 50 Hz electromagnetic field exposure on apoptosis and differentiation in a neuroblastoma cell line

Experiments were carried out to assess whether a magnetic field of 50 Hz and 1 mT can influence apoptosis and proliferation in the human neuroblastoma cell line LAN-5. TUNEL assays and poly-ADP ribose polymerase (PARP) expression analysis were performed to test apoptosis induction, and the WST-1 assay was used to calculate the proliferation index in a long term exposure. No alterations were found in cellular ability to undergo programmed cell death, but a small increase in the proliferation index was evidenced after 7 days of continuous exposure. Also, a slight and transient increase of B-myb oncogene expression was detected after 5 days of exposure. Combined exposures of cells to EMF and to chemical agents which interfere with proliferation, such as the differentiative agent retinoic acid and the apoptotic inducer camptothecin, showed an antagonistic effect of magnetic fields against the differentiation of the LAN-5 cells and a protective effect towards apoptosis.

Expression of insulin-like growth factor-binding protein 5 in neuroblastoma cells is regulated at the transcriptional level by c-Myb and B-Myb via direct and indirect mechanisms

Neuroblastoma (NB), a malignant childhood tumor deriving from the embryonic neural crest, is sensitive to the growth-stimulating effects of insulin-like growth factors (IGFs). Aggressive cases of this disease often acquire autocrine loops of IGF production, but the mechanisms through which the different components of the IGF axis are regulated in tumor cells remain unclear. Upon conditional expression of c-Myb in a NB cell line, we detected up-regulation of IGF1, IGF1 receptor, and insulin-like growth factor-binding protein 5 (IGFBP-5) expression. Analysis of the IGFBP-5 promoter revealed two potential Myb binding sites at position -59 to -54 (M1) and -429 to -424 (M2) from the transcription start site; both sites were bound by c-Myb and B-Myb in vitro and in vivo. Reporter assays carried out using the proximal region of the human IGFBP-5 promoter demonstrated that c-Myb and B-Myb enhanced transcription. However, site-directed mutagenesis and deletion of the Myb binding sites coupled with reporter assays revealed that M2 but not M1 was important for Myb-dependent transactivation of the IGFBP-5 promoter. The double mutant M1/M2 was still transactivated by c-Myb, suggesting the existence of Myb binding-independent mechanisms of IGFBP-5 promoter regulation. A constitutively active AKT transactivated the IGFBP-5 promoter, whereas the phosphatidylinositol 3-kinase inhibitor LY294002 suppressed it. Moreover, the kinase dead dominant negative K179M AKT mutant was able to inhibit transcription from the M2 and M1/M2 IGFBP-5 mutant promoters. Deletion analysis of the IGFBP-5 promoter revealed that the AKT-responsive region lies between nucleotides -334 and -83. Together, these data suggest that the Myb binding-independent transactivation of the IGFBP-5 promoter was due to the activation of the phosphatidylinositol 3-kinase/AKT pathway likely mediated by IGF1 receptor-dependent signals. Finally, IGFBP-5 was able to modulate proliferation of NB cells in a manner dependent on its concentration and on the presence of IGFs.