title: Requirement of a carbon spacer in benzyl isothiocyanate-mediated cytotoxicity and MAPK activation in head and neck squamous cell carcinoma.
abstract: Cruciferous vegetable-derived isothiocyanates (ITCs; chemical structure: R-N=C=S) are highly effective in affording protection against chemically induced cancers in animal models. Here, we studied the antitumor effects of benzyl isothiocyanate (BITC; Ph-CH2-N=C=S), the predominant ITC compound in broccoli, on head and neck squamous cell carcinoma (HNSCC) cell lines. Proliferation, apoptosis and immunoblotting assays were used to determine the effects and mechanism of several ITCs on HNSCC cells. The IC50 for BITC (24 h treatment) in two of the HNSCC cell lines was approximately 22 and 17 micro M, respectively. Interestingly, phenyl isothiocyanate (PITC; Ph-N=C=S), which is a close structural analog of BITC but lacks a -CH2- spacer that links the aromatic ring to N=C=S moiety, did not result in significant killing of the HNSCC cells in this dose range. BITC (but not PITC) caused activation of caspase 3 and PARP cleavage. Within 20 min of treatment, BITC (but not PITC) induced a rapid activation of p38 MAPK. In addition, BITC (but not PITC) treatment resulted in the activation of p44/42 MAPK. Co-treatment with a specific p38 MAPK inhibitor, SB203580, or an inhibitor of the MEK/MAPK pathway, U0126, partially rescued cells from BITC-induced killing. Our results show that minor structural differences in ITCs can be crucial for the antiproliferative activity of ITCs and that BITC may be a promising chemopreventive as well as therapeutic agent in HNSCC.
authors.affiliation: Department of Otolaryngology and 2Pharmacology, University of Pittsburgh School of Medicine and the University of Pittsburgh Cancer Institute, Pittsburgh, PA 15213, USA.
authors.forename: Vivian W Y
authors.initials: VW
authors.lastname: Lui
authors.forename: Abbey L
authors.initials: AL
authors.lastname: Wentzel
authors.forename: Dong
authors.initials: D
authors.lastname: Xiao
authors.forename: Karen L
authors.initials: KL
authors.lastname: Lew
authors.forename: Shivendra V
authors.initials: SV
authors.lastname: Singh
authors.forename: Jennifer R
authors.initials: JR
authors.lastname: Grandis
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D002294:Carcinoma, Squamous Cell / Q000378:metabolism*; D053148:Caspase 3; D020169:Caspases / Q000187:drug effects / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006258:Head and Neck Neoplasms / Q000378:metabolism*; D006801:Humans; D015151:Immunoblotting; D017953:Isocyanates / Q000737:chemistry / Q000494:pharmacology; D017879:Isothiocyanates / Q000737:chemistry* / Q000494:pharmacology*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D004791:Enzyme Inhibitors; D017953:Isocyanates; D017879:Isothiocyanates; C025319:phenyl isocyanate; C031403:benzyl isothiocyanate; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases