cyclin-d1 and benzyl-isothiocyanate

Benzyl isothiocyanate (BITC), a dietary isothiocyanate derived from cruciferous vegetables, inhibits the proliferation of colorectal cancer cells, most of which overexpress β-catenin as a result of mutations in the genes for adenomatous polyposis coli or mutations in β-catenin itself. Because nuclear factor-κB (NF-κB) is a plausible target of BITC signaling in inflammatory cell models, we hypothesized that it is also involved in BITC-inhibited proliferation of colorectal cancer cells. siRNA-mediated knockdown of the NF-κB p65 subunit significantly decreased the BITC sensitivity of human colorectal cancer HT-29 cells with mutated p53 tumor suppressor protein. Treating HT-29 cells with BITC induced the phosphorylation of IκB kinase, IκB-α and p65, the degradation of IκB-α, the translocation of p65 to the nucleus and the upregulation of NF-κB transcriptional activity. BITC also decreased β-catenin binding to a positive cis element of the cyclin D1 promoter and thus inhibited β-catenin-dependent cyclin D1 transcription, possibly through a direct interaction between p65 and β-catenin. siRNA-mediated knockdown of p65 confirmed that p65 negatively affects cyclin D1 expression. On the other hand, when human colorectal cancer HCT-116 cells with wild-type p53 were treated with BITC, translocation of p65 to the nucleus was inhibited rather than enhanced. p53 knockout increased the BITC sensitivity of HCT-116 cells in a p65-dependent manner, suggesting that p53 negatively regulates p65-dependent effects. Together, these results identify BITC as a novel type of antiproliferative agent that regulates the NF-κB pathway in p53-deficient colorectal cancer cells.

Topics: Antineoplastic Agents, Phytogenic; Apoptosis; beta Catenin; Cell Proliferation; Cyclin D1; Gene Expression Regulation, Neoplastic; HCT116 Cells; HT29 Cells; Humans; I-kappa B Kinase; Isothiocyanates; Phosphorylation; Promoter Regions, Genetic; Protein Transport; RNA, Small Interfering; Signal Transduction; Transcription Factor RelA; Tumor Suppressor Protein p53

Molecular effects of obesity, a well-established risk factor for breast cancer progression, are mediated by adipocytokine leptin. Given the important role of leptin in breast cancer growth and metastasis, novel strategies to antagonize biological effects of this adipocytokine are much desired. We showed previously that benzyl isothiocyanate (BITC), a constituent of edible cruciferous vegetables (e.g. garden cress), confers significant protection against mammary carcinogenesis in a transgenic mouse model. The present study provides first evidence for the efficacy of BITC against oncogenic effects of leptin. The BITC treatment circumvented leptin-induced clonogenicity and anchorage-independent growth of MDA-MB-231 and MCF-7 human breast cancer cells. Leptin-stimulated migration and invasion of these cells was also inhibited in the presence of BITC. Analysis of the underlying molecular mechanisms revealed that BITC treatment suppressed leptin-induced Stat3 phosphorylation and cyclin D1 transactivation. The BITC-mediated inhibition of MDA-MB-231 xenograft growth correlated with a modest yet significant decrease in levels of Tyr705 phosphorylated Stat3. The BITC treatment efficiently inhibited Stat3 and SRC1 recruitment to cyclin D1 promoter in a chromatin immunoprecipitation analysis. Furthermore, overexpression of constitutively active Stat3 imparted significant protection against BITC-mediated inhibition of cyclin D1 transactivation, whereas RNA interference of Stat3 resulted in a significant increase in BITC-mediated inhibition of cyclin D1 transactivation in the presence of leptin. These results indicate that Stat3 plays an important role in BITC-mediated inhibition of leptin-induced cyclin D1 transactivation. In conclusion, BITC could potentially be a rational therapeutic strategy for breast carcinoma in obese patients with high leptin levels.

Topics: Apoptosis; Blotting, Western; Breast Neoplasms; Cell Adhesion; Cell Line, Tumor; Cell Movement; Cell Transformation, Neoplastic; Chromatin Immunoprecipitation; Cyclin D1; Humans; Immunoenzyme Techniques; Isothiocyanates; Leptin; Luciferases; Oncogenes; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Signal Transduction; STAT3 Transcription Factor; Wound Healing

NF-kappaB/p65 is constitutively activated in pancreatic cancers, where it plays a critical role in the transcriptional activation of multiple cell survival genes. We have previously shown the apoptosis-inducing effects of benzyl isothiocyanate (BITC) in pancreatic cancer cells. We hypothesized that inhibition of NF-kappaB/p65 could be the mechanism of BITC-induced apoptosis. Therefore, the effect of BITC on NF-kappaB/p65 was evaluated in BxPC-3, Capan-2, and normal HPDE-6 cells by Western blotting, transcriptional and DNA-binding activity, and immunohistochemistry in the xenografted tumors. Our results reveal a remarkable decrease in the phosphorylation of NF-kappaB/p65 at Ser(536) in both BxPC-3 and Capan-2 cells by BITC treatment. The expression of NF-kappaB/p65 was downregulated significantly in BxPC-3 cells, whereas it remained unchanged in Capan-2 cells. BITC treatment caused a significant decrease in NF-kappaB transcriptional and DNA-binding activity in both BxPC-3 and Capan-2 cells. A drastic decrease was observed in the expression and reporter activity of cyclin D1 in both the cell lines. Moreover, BITC also caused a significant decrease in the expression and activity of histone deacetylase (HDAC) 1 and HDAC3 in BxPC-3 and HDAC3 in Capan-2 cells. Overexpression of HDAC1 or HDAC3 abrogated the effects of BITC. BITC treatment did not cause any change in HDAC expression in normal HPDE-6 cells. Immunohistochemical analysis of tumors from BITC-treated mice showed significantly reduced staining for NF-kappaB, cyclin D1, HDAC1, and HDAC3 compared with control. Our results suggest inhibition of HDAC1/HDAC3 by BITC as a plausible mechanism of NF-kappaB inactivation, resulting in the in vitro and in vivo growth suppression of pancreatic cancer cells.

Topics: Apoptosis; Cell Line, Tumor; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p21; DNA; Down-Regulation; Drug Resistance, Neoplasm; Gene Expression Regulation, Neoplastic; Genes, Reporter; Histone Acetyltransferases; Histone Deacetylase Inhibitors; Histone Deacetylases; Humans; Isothiocyanates; Neoplasm Proteins; NF-kappa B; Pancreatic Neoplasms; Promoter Regions, Genetic; Protein Binding; Transcription Factor RelA; Transcription, Genetic; Xenograft Model Antitumor Assays

Benzyl isothiocyanate (BITC), a cruciferous vegetable-derived compound, has been shown to inhibit chemically induced cancer in animal models. Moreover, epidemiological studies have provided compelling evidence to suggest that cruciferous vegetables may be protective against cancer risk. Here, we report that BITC significantly inhibits growth of human pancreatic cancer BxPC-3 cells in a concentration-dependent manner with an IC(50) of approximately 8 micro M, a concentration that can be generated through dietary intake of cruciferous vegetables. Treatment of BxPC-3 cells with growth suppressive concentrations of BITC resulted in G(2)/M phase cell cycle arrest that was associated with a marked decline in protein levels of G(2)/M regulatory proteins including cyclin-dependent kinase 1 (Cdk1), cyclin B1 and cell division cycle 25B (Cdc25B). Further, BITC-mediated growth inhibition of BxPC-3 cells correlated with apoptosis induction that was characterized by an increase in Bax/Bcl-2 ratio, cleavage of procaspase-3 and poly(ADP-ribose)polymerase (PARP), and an increase in cytoplasmic histone-associated DNA fragmentation. Interestingly, BITC treatment caused inhibition of nuclear factor kappaB (NF-kappaB) activation, which is constitutively activated in human pancreatic cancer. Western blotting revealed concentration-dependent decrease in NF-kappaB/Rel-p65 protein level in BxPC-3 cells upon exposure to BITC. An increase in protein level of inhibitory subunit kappaB (IkappaBa) in association with reduced serine-32 phosphorylation was also observed in BITC-treated BxPC-3 cells. Consistent with these findings, BITC treatment caused a decrease in nuclear translocation of NF-kappaB as reflected by reduced DNA-binding capacity of NF-kappaB. Furthermore, the protein level of cyclin D1, a transcriptional target of NF-kappaB, was reduced significantly in BITC-treated BxPC-3 cells. To the best of our knowledge, this study is the first published report to implicate suppression of NF-kappaB activation as a potential mechanism for anti-proliferative activity of BITC against human pancreatic cancer cells.

Topics: Apoptosis; bcl-2-Associated X Protein; Caspase 3; Caspases; CDC2 Protein Kinase; cdc25 Phosphatases; Cell Cycle; Cell Cycle Proteins; Cyclin B; Cyclin B1; Cyclin D1; Humans; Isothiocyanates; NF-kappa B; Pancreatic Neoplasms; Poly(ADP-ribose) Polymerases; Protein Transport; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Tumor Cells, Cultured