The Role of STAT-3 in the Induction of Apoptosis in Pancreatic Cancer Cells by Benzyl Isothiocyanate

Department of Pharmaceutical Sciences and Cancer Biology Center, School of Pharmacy, Texas Tech University Health Sciences Center, Amarillo, TX 79106, USA.
Journal of the National Cancer Institute (Impact Factor: 12.58). 02/2009; 101(3):176-93. DOI: 10.1093/jnci/djn470
Source: PubMed


Benzyl isothiocyanate (BITC), a compound found in cruciferous vegetables, has been reported to have anticancer properties, but the mechanism whereby it inhibits growth of human pancreatic cancer cells is incompletely understood.
Human pancreatic cancer cells (BxPC-3, AsPC-1, Capan-2, MiaPaCa-2, and Panc-1) and immortalized human pancreatic cells (HPDE-6) were treated with vehicle or with BITC at 5-40 microM, cell survival was evaluated by sulforhodamine B assay, and apoptosis by caspase-3 and poly-ADP ribose polymerase cleavage or by a commercial assay for cell death. Total and activated signal transducer and activator of transcription-3 (STAT-3) protein expression in the cells were examined by western blotting, STAT-3 mRNA levels by reverse transcription-polymerase chain reaction, and STAT-3 DNA-binding and transcriptional activity by commercially available binding and reporter assays. The effects of BITC treatment on tumor growth, apoptosis, and STAT-3 protein expression in vivo were studied in xenografts of BxPC-3 pancreatic tumor cells in athymic nude mice. All statistical tests were two-sided.
BITC treatment reduced cell survival and induced apoptosis in BxPC-3, AsPC-1, Capan-2, and MiaPaCa-2 cells, and to a much lesser extent in Panc-1 cells, but not in HPDE-6 cells. It also reduced levels of activated and total STAT-3 protein, and as a result, STAT-3 DNA-binding and transcriptional activities. Overexpression of STAT-3 in BxPC-3 cells inhibited BITC-induced apoptosis and restored STAT-3 activity. In mice that were fed BITC (60 micromol/wk, five mice, 10 tumors per group), growth of BxPC-3 pancreatic tumor xenografts was suppressed compared with control mice (at 6 weeks, mean tumor volume of control vs BITC-treated mice = 334 vs 172 mm3, difference =162 mm3, 95% confidence interval = 118 to 204 mm3; P = .008) and tumors had increased apoptosis and reduced STAT-3 protein expression.
BITC induces apoptosis in some types of pancreatic cancer cells by inhibiting the STAT-3 signaling pathway.

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    • "Cells were fixed using 10% tricholoroacetic acid (Sigma Aldrich Ltd.) and incubated for 1 hour at 4°C. Subsequently, cells were stained with 0.5% Sulforhodamine B solution and the absorbance were measured at 570 nm using a plate reader (BioTek Instruments, Winooski, VT) as described by us previously [12], [13]. "
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    • "Besides its established nuclear transcriptional role, STAT3 plays a distinct role in the mitochondria, where it supports Ras-dependent malignant transformation [4], and ensures the optimal function of the electron transport chain [5]. Because it regulates several pathways important in tumorigenesis [6], STAT3 is recognized as a potential drug target for PC [7]. "
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    • "That is the STAT3 transcriptional factor which activates genes coding antiapoptotic BCL-2 protein, vascular endothelial growth factor (VEGF) or antiapoptotic survivin protein. Finally, it blocks expression of the gene coding P-53 protein, which is a very important effector in the process of apoptosis [35]. "
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