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Induction of cytotoxicity, apoptosis and cell cycle arrest by 1-t-butyl carbamoyl, 7-methyl-indole-3-ethyl isothiocyanate (NB7M) in nervous system cancer cells

Authors Laurent Brard, Rakesh K Singh, Kyu Kwang Kim, Thilo S Lange, Giselle L Saulier Sholler

Published 9 April 2008 Volume 2008:2 Pages 61—69


Laurent Brard†,1, Rakesh K Singh†,1, Kyu Kwang Kim1, Thilo S Lange1, Giselle L Saulier Sholler2

1Molecular Therapeutics Laboratory, Program in Women’s Oncology, Department of Obstetrics and Gynecology, Women and Infants’ Hospital, Brown University, Providence, RI, USA; 2Department of Pediatrics, University of Vermont College of Medicine, Burlington, VT, USA; These authors contributed equally to the manuscript

Abstract: Our group has recently developed 1-tbutyl carbamoyl, 7-methyl-indole-3-ethyl isothiocyanate (NB7M), a novel indole ethyl isothiocyanate analog. We now describe its selective cytotoxicity in both central nervous system (CNS) and neuroblastoma (NB) cancer cells. In an effort to understand its mechanism of action we examined the effects of NB7M on apoptosis, cell cycle arrest, and pro-survival/mitogen-activated protein kinase (MAPK) signaling in neuroblastoma cells. NB7M proved highly cytotoxic to NB cell lines (SMS-KCNR, SK-NSH, SH-SY5Y, IMR-32) with IC50 values ranging from 1.0–2.0 µM, whereas lung fibroblasts were less affected (IC50 ≥ 10 µM). In the NCI 60 cell screen 1-dose assay, NB7M (10 µM) reduced the growth (−89 to −27 % growth) of CNS cancer cell lines SF-268, SF-295, SNB-75 (glioblastoma), SF-539 (gliosarcoma), and U251 (astroglioma) while SNB-19 glioblastoma cells were relatively resistant (19% growth). Hoechst staining of SMS-KCNR cells treated with NB7M (3 µM) for 24 hrs exhibited significant chromatin condensation and DNA fragmentation, whereas Annexin-v/7AAD staining revealed that the majority of cells accumulated in the early-apoptotic and late-apoptotic/necrotic stages. NB7M treatment of SMS-KCNR and SH-SY5Y cells also led to the cleavage of procaspases-3, and PARP-1 while causing activation of pro-apoptotic MAPKs and down-regulation of pro-survival factors AKT and PI-3K. Furthermore, NB7M treatment caused S-phase arrest in SMSKCNR and G1-phase arrest in SH-SY5Y cells. NB7M is active against CNS cancers and NB.

Keywords: cytotoxicity, apoptosis, cell cycle analysis, MAPK

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