Inhibition of NFκB and Pancreatic Cancer Cell and Tumor Growth by Curcumin Is Dependent on Specificity Protein Down-regulation

Abstract

Curcumin activates diverse anticancer activities that lead to inhibition of cancer cell and tumor growth, induction of apoptosis, and antiangiogenic responses. In this study, we observed that curcumin inhibits Panc28 and L3.6pL pancreatic cancer cell and tumor growth in nude mice bearing L3.6pL cells as xenografts. In addition, curcumin decreased expression of p50 and p65 proteins and NFB-dependent transactivation and also decreased Sp1, Sp3, and Sp4 transcription factors that are overexpressed in pancreatic cancer cells. Because both Sp transcription factors and NFB regulate several common genes such as cyclin D1, survivin, and vascular endothelial growth factor that contribute to the cancer phenotype, we also investigated interactions between Sp and NFB transcription factors. Results of Sp1, Sp3, and Sp4 knockdown by RNA interference demonstrate that both p50 and p65 are Sp-regulated genes and that inhibition of constitutive or tumor necrosis factor-induced NFB by curcumin is dependent on down-regulation of Sp1, Sp3, and Sp4 proteins by this compound. Curcumin also decreased mitochondrial membrane potential and induced reactive oxygen species in pancreatic cancer cells, and this pathway is required for down-regulation of Sp proteins in these cells, demonstrating that the mitochondriotoxic effects of curcumin are important for its anticancer activities.

Triptolide-induced Cell Death in Pancreatic Cancer Is Mediated by O-GlcNAc Modification of Transcription Factor Sp1

“…Recently, Sp1 was reported to be responsible for the transcription of NF-B subunits p50 and p65 (33). In the context of that study, we observed that down-regulation of Sp1 by mithramycin, siRNA, or triptolide resulted in decreased NF-B activity in both cell lines and orthotopic animal models.…”

Mechanism of Metformin-dependent Inhibition of Mammalian Target of Rapamycin (mTOR) and Ras Activity in Pancreatic Cancer

“…This involved down-regulation of specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4 and pro-oncogenic Sp-regulated genes such as bcl2, fatty acid synthase (FAS), survivin, vascular endothelial growth factor (VEGF), and VEGF receptor 1 (VEGFR1) (31). The anticancer activities of metformin are also similar to * This work was supported, in whole or in part, by National Institutes of Health that observed after knockdown of Sp1 or all three Sp proteins by RNA interference in cancer cells, and this includes growth inhibition, induction of apoptosis, reversal of epithelial to mesenchymal transition, and decreased migration/invasion (32)(33)(34)(35)(36). Metformin also inhibits NFB and decreases cyclin D1 and ErbB2 in cancer cell lines (13,20,27,28), and these gene products are also decreased after Sp1, Sp3, and Sp4 silencing by RNAi or by other drugs that down-regulate Sp proteins (32)(33)(34)(35)(36).…”

“…Fig. 2A shows that in Panc28 cells transfected with oligonucleotides targeting Sp1 (iSp1), Sp3 (iSp3), and Sp4 (iSp4), there was specific knockdown of the individual Sp proteins as described previously (35), and this was accompanied by decreased expression of phospho-mTOR and AKT but not total mTOR and AKT proteins. A similar approach was used for L3.6pL cells (Fig.…”

“…siRNA Interference Assay-Panc28, Panc1, and L3.6pL pancreatic cancer cells were seeded (1 ϫ 10 5 /well) in 6-well plates in DMEM/Ham's F-12 medium supplemented with 2.5% charcoal-stripped FBS without antibiotic and left to attach for 24 h. Knockdown of Sp1, Sp3, and Sp4 along with iLamin as control was carried out using Lipofectamine 2000 reagent according to the manufacturer's instructions and as described previously (35). Small inhibitory RNAs were prepared by (Sigma-Aldrich).…”

Targeting Apoptosis Pathways in Cancer—Letter

“…For example, the authors have summarized the effects of various proapoptotic agents that act through two interrelated pathways, namely "mitochondrial-mediated" and "reactive oxygen species (ROS)-mediated" apoptosis because drugs targeting mitochondria often induce ROS. Previous studies in this laboratory have demonstrated that natural products such as curcumin, betulinic acid, phenethyl isothiocyanate (PEITC), piperlongumine, and celastrol, which induce ROS and apoptosis, also downregulate specificity protein (Sp) transcription factors Sp1, Sp3, and Sp4, which are highly expressed in cancer cells (2)(3)(4)(5)(6). For most of these studies, compound-induced apoptosis and compound-induced downregulation of Sp transcription factors were reversed in cancer cells after cotreatment with antioxidants.…”