sulphoraphene and phenethyl-isothiocyanate

Isothiocyanates (ITCs), such as phenethyl isothiocyanate (PEITC) and sulforaphane (SFN), are effective cancer chemopreventive compounds. It is believed that the major mechanism for the cancer preventive activity of ITCs is through the induction of cell cycle arrest and apoptosis. However, the upstream molecular targets of ITCs have been underexplored until recently. To identify proteins that are covalently modified by ITCs, human non-small cell lung cancer A549 cells were treated with (14)C-PEITC and (14)C-SFN, and the cell lysates were extracted for analysis by 2-D gel electrophoresis and mass spectrometry. After superimposing the colloidal Coomassie blue protein staining pattern with the pattern of radioactivity obtained from X-ray films, it was clear that only a small fraction of cellular proteins contained radioactivity, presumably resulting from selective binding with PEITC or SFN via thiocarbamation. More than 30 proteins with a variety of biological functions were identified with high confidence. Here, we report the identities of these potential ITC target proteins and discuss their biological relevance. The discovery of the protein targets may facilitate studies of the mechanisms by which ITCs exert their cancer preventive activity and provide the molecular basis for designing more efficacious ITC compounds.

Topics: Anticarcinogenic Agents; Apoptosis; Cell Cycle Checkpoints; Cell Line, Tumor; Chromatography, Liquid; Electrophoresis, Gel, Two-Dimensional; Humans; Isothiocyanates; Proteasome Endopeptidase Complex; Proteomics; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Tandem Mass Spectrometry; Tubulin

Isothiocyanates have potential chemopreventive and antitumor effects. In the present study, we examined the actions of PEITC and sulphoraphane in modulating the activity of protein kinase C (PKC) and telomerase in cervical cancer cell line HeLa. These tumor markers are highly activated in human cancers. These compound efficiently downregulated the antiapoptotic isoforms (PKC-alpha, -betaII, -epsilon, and -zeta) as well as telomerase, whereas the proapoptotic form (PKC-delta) was upregulated. Studies were performed to measure the degree of apoptotic cell death induced by either isothiocyanates alone, or in combination with adriamycin or etoposide. Apoptosis was evident from mitochondrial cytochrome c release, apoptotic index and caspases 3 and 8 activation. Results showed that pretreatment exhibited better efficacy in sensitizing HeLa cells toward apoptosis by modulating PKCs, telomerase. This effect of isothiocyanates might prove to be of considerable value in synergistic therapy of cancer such that the drug dose level could be minimized.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Doxorubicin; Drug Synergism; Etoposide; Female; Gene Expression Regulation, Enzymologic; HeLa Cells; Humans; Isothiocyanates; Protein Kinase C; Telomerase; Uterine Cervical Neoplasms