NF-κB Regulated Gene Products Research Articles

Retraction: Modification of Cysteine Residue in p65 Subunit of Nuclear Factor-κB (NF-κB) by Picroliv Suppresses NF-κB–Regulated Gene Products and Potentiates Apoptosis

Retraction: Modification of Cysteine Residue in p65 Subunit of Nuclear Factor-κB (NF-κB) by Picroliv Suppresses NF-κB–Regulated Gene Products and Potentiates Apoptosis

Pinus Roxburghii essential oil anticancer activity and chemical composition evaluation.

The present study was conducted to appraise the anticancer activity of Pinus roxburghii essential oil along with chemical composition evaluation. MTT assay revealed cytotoxicity induction in colon, leukemia, multiple myeloma, pancreatic, head and neck and lung cancer cells exposed to essential oil. Cancer cell death was also observed through live/dead cell viability assay and FACS analysis. Apoptosis induced by essential oil was confirmed by cleavage of PARP and caspase-3 that suppressed the colony-forming ability of tumor cells and 50 % inhibition occurred at a dose of 25 μg/mL. Moreover, essential oil inhibited the activation of inflammatory transcription factor NF-κB and inhibited expression of NF-κB regulated gene products linked to cell survival (survivin, c-FLIP, Bcl-2, Bcl-xL, c-Myc, c-IAP2), proliferation (Cyclin D1) and metastasis (MMP-9). P. roxburghii essential oil has considerable anticancer activity and could be used as anticancer agent, which needs further investigation to identify and purify the bioactive compounds followed by in vivo studies.

NF-κB Blockers Gifted by Mother Nature: Prospectives in Cancer Cell Chemosensitization.

Despite the significant developments made in the field of diagnosis and treatment modalities of cancer during the last two decades, it still remains one of the most life threatening diseases killing 8.2 million people annually across the globe. It has been well-established that development of chemoresistance in cancer cells is the major cause of failure of chemotherapeutic agents in clinic. Most of the chemotherapeutic agents currently being used activate NF-κB and NF-κB regulated gene products in cancer cells and induce drug resistance. Increasing lines of evidences suggest that NF-κB blockers have high potential in decreasing drug resistance and sensitize cancer cells to chemotherapeutic agents. A through literature search was carried out in pubmed to identify natural NF-κB inhibitors that possess high potential in sensitizing cancer cells. Our literature search retrived a number of NF-κB inhibitors that have been identified during the last several years. Notably, the inhibitors obtained from Mother Nature such as curcumin, tocotrienol, resveratrol, garcinol etc. are found to be highly safe, efficacious and inexpensive. Many preclinical and clinical studies have revealed that these agents can block the activation of NF-κB in cancer cells to overcome drug resistance and make them sensitive to chemotherapeutic agents. Both basic and clinical research revealed that constitutive activation of NF-κB is the prime reason for inducing drug resistance in cancer cells. This comprehensive review scientifically evaluates the chemosensitizing potential of these natural agents which serve as potent NF-κB blockers, based on evidence based literature.

Wenshen Xiaozheng Tang induces apoptosis and inhibits migration of ectopic endometriotic stromal cells

Ethnopharmacological relevanceWenshen Xiaozheng Tang (WXT), a traditional Chinese medicine prescription, exerted a good therapeutic effect on endometriosis. However, the underlying mechanism is unclear. In the present study, we sought to evaluate the effect of WXT on the proliferation and migration of ectopic endometriotic stromal cells and explore the potential molecular mechanism. Materials and methodsPrimary stromal cells derived from ectopic endometriotic lesions of patients with endometriosis were isolated and cultured. The inhibition effect of WXT on cell proliferation was determined by MTT. Apoptosis of ectopic endometriotic cells treated with WXT was analyzed with Annexin V-FITC/7-AAD staining. The activation of caspases was detected by western blot analysis. The influence of WXT on migration of ectopic endometriotic cells was measured by scratch wound healing assay and Transwell assay. The DNA binding activity of NF-κB and the expression of nuclear p65 protein were determined by electrophoretic mobility shift assay and western blot analysis, respectively. The impact of WXT on the expression of NF-κB regulated gene products involved in apoptosis and migration was determined by western blot analysis. ResultsWXT inhibited the proliferation of ectopic endometriotic cells in a time- and dose-dependent manner. In addition, WXT treatment resulted in significant induction of apoptosis through the activation of caspases and inhibition of migration in ectopic endometriotic cells. WXT notably suppressed constitutive NF-κB-DNA-binding activity as well as TNF-α induced nuclear translocation of NF-κB p65 subunit in ectopic endometriotic cells. Moreover, WXT diminished the expression of NF-κB regulated gene products involved in apoptosis and migration, including c-IAP1, c-IAP2, XIAP, survivin, Mcl-1, COX-2 and MMP-9. ConclusionsOur results indicate that WXT induces apoptosis and inhibits migration of ectopic endometriotic stromal cells.

Piperlongumine Suppresses Growth and Sensitizes Pancreatic Tumors to Gemcitabine in a Xenograft Mouse Model by Modulating the NF-kappa B Pathway.

Pancreatic cancer is an aggressive malignancy, which generally respond poorly to chemotherapy. Hence, novel agents that are safe and effective are highly needed. The aim of this study was to investigate whether piperlongumine, a natural product isolated from the fruit of the pepper Piper longum, has any efficacy against human pancreatic cancer when used either alone or in combination with gemcitabine in vitro and in a xenograft mouse model. In vitro, piperlongumine inhibited the proliferation of pancreatic cancer cell lines, potentiated the apoptotic effects of gemcitabine, inhibited the constitutive and inducible activation of NF-κB, and suppressed the NF-κB-regulated expression of c-Myc, cyclin D1, Bcl-2, Bcl-xL, Survivin, XIAP, VEGF, and matrix metalloproteinase-9 (MMP-9). Furthermore, in an in vivo xenograft model, we found piperlongumine alone significantly suppressed tumor growth and enhanced the antitumor properties of gemcitabine. These results were consistent with the downregulation of NF-κB activity and its target genes, decreased proliferation (PCNA and Ki-67), decreased microvessel density (CD31), and increased apoptosis (TUNEL) in tumor remnants. Collectively, our results suggest that piperlongumine alone exhibits significant antitumor effects against human pancreatic cancer and it further enhances the therapeutic effects of gemcitabine, possibly through the modulation of NF-κB- and NF-κB-regulated gene products.

Resveratrol induces chemosensitization to 5-fluorouracil through up-regulation of intercellular junctions, Epithelial-to-mesenchymal transition and apoptosis in colorectal cancer

5-Fluorouracil (5-FU), a common chemotherapeutic agent used for the treatment of colorectal cancer (CRC), by itself has inadequate response rates; highlighting the need for novel and improved treatment regimens for these patients. Resveratrol, a naturally-occurring polyphenol, has been linked with chemosensitizing potential and anticancer properties; however, the underlying mechanisms for these effects remain poorly understood.The effect of resveratrol in parental CRC cell lines (HCT116, SW480) and their corresponding isogenic 5-FU-chemoresistant derived clones (HCT116R, SW480R) was examined by MTT assays, intercellular junction formation and apoptosis by electron- and immunoelectron microscopy, nuclear factor-kappaB (NF-κB) and NF-κB regulated gene products by western blot analysis in a 3D-alginate microenvironment. Resveratrol blocked the proliferation of all four CRC cell lines and synergized the invasion inhibitory effects of 5-FU. Interestingly, resveratrol induced a transition from 5-FU-induced formation of microvilli to a planar cell surface, which was concomitant with up-regulation of desmosomes, gap- and tight junctions (claudin-2) and adhesion molecules (E-cadherin) expression in HCT116 and HCT116R cells. Further, resveratrol significantly attenuated drug resistance through inhibition of epithelial-mesenchymal transition (EMT) factors (decreased vimentin and slug, increased E-cadherin) and down-regulation of NF-κB activation and its translocation to the nucleus and abolished NF-κB-regulated gene end-products (MMP-9, caspase-3). Moreover, this suppression was mediated through inhibition of IκBα kinase and IκBα phosphorylation and degradation. Our results demonstrate that resveratrol can potentiate the anti-tumor effects of 5-FU on CRC cells by chemosensitizing them, inhibiting an EMT phenotype via up-regulation of intercellular junctions and by down-regulation of NF-κB pathway.

Isorhamnetin augments the anti-tumor effect of capeciatbine through the negative regulation of NF-κB signaling cascade in gastric cancer

Development of drug resistance to standard chemotherapy is a common phenomenon that leads to poor prognosis in patients. Thus, novel agents that can attenuate chemoresistance are urgently needed. Therefore, we analyzed whether isorhamnetin (IH), a 3′-O-methylated metabolite of quercetin, can enhance the potential efficacy of capecitabine in gastric cancer. The potential effect of IH on viability was analyzed by MTT assay, apoptosis by flow cytometric analysis, and NF-κB activation by DNA binding as well as Western blot assays. The in vivo effect of IH was also examined on the growth of subcutaneously implanted tumors in nude mice. IH inhibited the viability, potentiated the apoptotic effects of capecitabine, abrogated NF-κB activation, and suppressed the expression of various NF-κB regulated gene products in tumor cells. In a gastric cancer xenograft model, administration of IH alone (1 mg/kg body weight, i.p.) significantly suppressed the tumor growth alone as well as in combination with capecitabine. IH further reduced NF-κB activation and the expression of various proliferative and oncogenic biomarkers in tumor tissues. Overall, our results demonstrate that IH can significantly enhance the anti-tumor effects of capecitabine through the negative regulation of NF-κB regulated oncogenic genes.

Thymoquinone overcomes chemoresistance and enhances the anticancer effects of bortezomib through abrogation of NF-κB regulated gene products in multiple myeloma xenograft mouse model

Multiple myeloma (MM) is a B cell malignancy characterized by clonal proliferation of plasma cells in the bone marrow. With the advent of novel targeted agents, the median survival rate has increased to 5 -7 years. However, majority of patients with myeloma suffer relapse or develop chemoresistance to existing therapeutic agents. Thus, there is a need to develop novel alternative therapies for the treatment of MM. Thus in the present study, we investigated whether thymoquinone (TQ), a bioactive constituent of black seed oil, could suppress the proliferation and induce chemosensitization in human myeloma cells and xenograft mouse model. Our results show that TQ inhibited the proliferation of MM cells irrespective of their sensitivity to doxorubicin, melphalan or bortezomib. Interestingly, TQ treatment also resulted in a significant inhibition in the proliferation of CD138+ cells isolated from MM patient samples in a concentration dependent manner. TQ also potentiated the apoptotic effects of bortezomib in various MM cell lines through the activation of caspase-3, resulting in the cleavage of PARP. TQ treatment also inhibited chemotaxis and invasion induced by CXCL12 in MM cells. Furthermore, in a xenograft mouse model, TQ potentiated the antitumor effects of bortezomib (p<0.05, vehicle versus bortezomib + TQ; p<0.05, bortezomib versus bortezomib + TQ), and this correlated with modulation of various markers for survival and angiogenesis, such as Ki-67, vascular endothelial growth factor (VEGF), Bcl-2 and p65 expression. Overall, our results demonstrate that TQ can enhance the anticancer activity of bortezomib in vitro and in vivo and may have a substantial potential in the treatment of MM.

Bortezomib inhibits proteasomal degradation of IκBα and induces mitochondrial dependent apoptosis in activated B-cell diffuse large B-cell lymphoma

Activated B-cell type lymphoma (ABC), a subgroup of diffuse large B-cell lymphoma (DLBCL), has a worse survival after upfront chemotherapy and is characterized by constitutive activation of the anti-apoptotic nuclear factor-κB (NFκB) pathway. The implication of NFκB inhibition in ABC has not yet been fully explored as a potential therapeutic target. Therefore, a panel of ABC cell lines was used to examine the effect of bortezomib, a proteasome inhibitor which blocks degradation of IκBα and consequently inhibits NFκB activity. Our data showed that bortezomib caused a dose-dependent growth inhibition and induction of apoptosis in all cell lines studied. We next determined the status of the NFκB pathway following bortezomib treatment and found that there was accumulation of IκBα without affecting its phosphorylation status at an early time point. Electrophoretic mobility shift assay showed that bortezomib treatment inhibited constitutive nuclear NFκB in ABC cell lines. Furthermore, treatment of ABC cell lines with bortezomib for 48 h also down-regulated the expression of NFκB-regulated gene products, such as IκBα, Bcl-2, Bcl-Xl, XIAP and survivin, leading to apoptosis via the mitochondrial apoptotic pathway. Altogether, these results suggest that NFκB may be a potential target for therapeutic intervention in DLBCL using proteasomal inhibitors such as bortezomib.

Curcumin Enhances the Effect of Chemotherapy against Colorectal Cancer Cells by Inhibition of NF-κB and Src Protein Kinase Signaling Pathways

ObjectiveDevelopment of treatment resistance and adverse toxicity associated with classical chemotherapeutic agents highlights the need for safer and effective therapeutic approaches. Herein, we examined the effectiveness of a combination treatment regimen of 5-fluorouracil (5-FU) and curcumin in colorectal cancer (CRC) cells.MethodsWild type HCT116 cells and HCT116+ch3 cells (complemented with chromosome 3) were treated with curcumin and 5-FU in a time- and dose-dependent manner and evaluated by cell proliferation assays, DAPI staining, transmission electron microscopy, cell cycle analysis and immunoblotting for key signaling proteins.ResultsThe individual IC50 of curcumin and 5-FU were approximately 20 µM and 5 µM in HCT116 cells and 5 µM and 1 µM in HCT116+ch3 cells, respectively (p<0.05). Pretreatment with curcumin significantly reduced survival in both cells; HCT116+ch3 cells were considerably more sensitive to treatment with curcumin and/or 5-FU than wild-type HCT116 cells. The IC50 values for combination treatment were approximately 5 µM and 1 µM in HCT116 and 5 µM and 0.1 µM in HCT116+ch3, respectively (p<0.05). Curcumin induced apoptosis in both cells by inducing mitochondrial degeneration and cytochrome c release. Cell cycle analysis revealed that the anti-proliferative effect of curcumin and/or 5-FU was preceded by accumulation of CRC cells in the S cell cycle phase and induction of apoptosis. Curcumin potentiated 5-FU-induced expression or cleavage of pro-apoptotic proteins (caspase-8, -9, -3, PARP and Bax), and down-regulated anti-apoptotic (Bcl-xL) and proliferative (cyclin D1) proteins. Although 5-FU activated NF-κB/PI-3K/Src pathway in CRC cells, this was down-regulated by curcumin treatment through inhibition of IκBα kinase activation and IκBα phosphorylation.ConclusionsCombining curcumin with conventional chemotherapeutic agents such as 5-FU could provide more effective treatment strategies against chemoresistant colon cancer cells. The mechanisms involved may be mediated via NF-κB/PI-3K/Src pathways and NF-κB regulated gene products.

Abstract 2589: Novel chemopreventive combinatorial regimen significantly suppresses NF-kB and PI3-kinase/Akt pathways in the Syrian golden hamster pancreatic cancer model

Abstract Pancreatic cancer caused 40,000 deaths in 2010 and is currently ranked as the fourth leading cause of deaths in the United States. Due to poor prognosis of this disease, it is imperative that chemopreventive strategies be developed to control the formation of the initial neoplastic lesions. We have previously reported the effectiveness of a low dose combination regimen of aspirin, curcumin and sulforaphane (ACS) on MIA-PaCa-2 and Panc-1 pancreatic cancer cell lines. The objective of the current study was to use the ACS combination regimens in vivo to demonstrate the molecular targets responsible for prevention of pancreatic cancer in N-nitrosobis(2-oxopropyl) amine (BOP) carcinogen treated Syrian golden hamsters. BOP treated Syrian golden hamsters (n=6/group) were sacrificed after 24 weeks of treatment with a low (20+45+1.6), medium (67+150+5) and high (200+450+16) doses (in mg/kg) of ACS, respectively. Saline and BOP controls were included in the study. The pancreatic tissues were processed for isolation of nuclear and cytoplasmic proteins, and 20 mg of tissue was used for isolation of total RNA. Results from the Western blot show that low dose of ACS combined regimen down-regulated active NF-κB by inhibiting phosphorylation of IαBβ and p65. Low dose ACS also inhibited phosphorylation of Akt, needed for IKK activation. Consequently at the transcription level, low dose ACS significant down-regulated NF-κB regulated gene products TNFα, IL1α and IL6 compared to BOP controls (p&amp;lt;0.05). Thus, low dose ACS inhibited the translocation of NF-κB into the nucleus by inhibiting the phosphorylation of IαBβ and p65. In addition, RT qPCR analysis of proliferation markers such as proliferating cell nuclear antigen (PCNA) and cyclin D1 show &amp;gt;2 fold down-regulation in low dose regimen compared to BOP controls. With the high and medium doses, a trend similar to the low dose ACS was evident, whereby the effects were more significant at higher doses (p&amp;lt;0.001), thus demonstrating a dose-dependent response. The significance of this work is in the demonstration of the effectiveness in gene regulation of ACS even at the low-dose level which shows its potential as a powerful combinatorial regimen for pancreatic cancer prevention. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2589. doi:1538-7445.AM2012-2589

Curcumin and EGCG Suppress Apurinic/Apyrimidinic Endonuclease 1 and Induce Complete Remission in B-cell Non-Hodgkin's lymphoma Patients

Background: Follicular lymphoma (FL) is the most common subtype of indolent lymphoma. FL is still considered to be an incurable disease and palliation of symptoms is an acceptable approach to the expected pattern of repeated relapses due to developing resistance to chemotherapy agents. Apurinic/apyrimidinic endonuclease/redox factor-1 (APE1/Ref-1) is a multifunctional protein involved in DNA base excision repair (BER) of oxidative DNA damage and in redox regulation of a number of transcription factors. It was observed that cytoplasmic APE1 induced COX-2 expression through NF-κB activation. It has been shown that chemopreventive agents potentiate the efficacy of chemotherapy through the regulation of multiple signaling pathways, including NF-κB, c-Myc, cyclooxygenase-2, apoptosis, and others, suggesting a multitargeted nature of chemopreventive agents. We hypothesized that curcumin, a polyphenolic antioxidant derived from the spice turmeric, and epigallocatechin gallate (EGCG) from green tea would potentiate the effect of chemotherapy in B-cell lymphoma.Objective: We examined the role of human apurinic/apyrimidinic endonuclease 1 (APE1) in resistance and prognosis in patients with FL. Our major objective was to update the safety and efficacy results of the antitumor effect of combination of curcumin and EGCG therapy in relapsed or resistant indolent or transformed non-Hodgkin follicular lymphoma patients and their peripheral blood mononuclear cells (PBMCs) compared with healthy donors’ controls. Methods: Thirty patients with FL with over-expression of constitutive active NF-κB in their PBMCs received regular CHOP and consumed capsules compatible with curcumin doses between 0.9 and 5.4 g daily for up to 9 months and 9.0 g/day green tea whole extract "1000 mg tablets of green tea whole extract containing 200 mg EGCG. We designed a dose-escalation study to explore the efficacy of CHOP in combination with curcumin and the green tea extract epigallocatechin-3 gallate (EGCG) on the viability of patients’ peripheral blood mononuclear cells (PBMCs) lymphocytes. Results: Treatment of patients with the combination of curcumin and EGCG, significantly lower cytoplasmic APE1 and the levels of the transcription factor were lower than those predicted from the effects of the CHOP agents (cyclophosphamide, doxorubicin, vincristine, and prednisone) alone, especially with a blunting of the remarkable increases in NF- κB activation induced by CHOP. Eighteen of the patients had a CR (18/30), and twelve patients had PR (12/30) within 9 month treatment and followed up to 12 months. They remain disease-free a mean of 8.6 y (range, 7.9–9.2 y) after this combination therapy.Conclusion: Optimal patient benefit might be obtained in follicular lymphoma when administering curcumin up-front in combination with chemotherapy and EGCG treatment. The combination of curcumin with EGCG resulted in a synergistic antitumor activity and that with CHOP agents in additivity or sub-additivity, down-regulated the expression of all NF-κB regulated gene products, leading to the suppression of angiogenesis, metastasis and entering in complete remission as indicated by β2-microglobulin and lactate dehydrogenase (LDH) levels. Key words: Curcumin, EGCG, B- cell NHL, NF-κB, VEGF, APE1, lymphoma

C086, a novel analog of curcumin, induces growth inhibition and down-regulation of NFκB in colon cancer cells and xenograft tumors

New analogues of curcumin with improved properties are needed to meet therapeutic requirements. In this study, the effects of C086 on growth inhibition and NFκB pathway regulation were investigated in colon cancer cells and xenograft tumors. C086 exhibited potent antiproliferative activity in all 6 colon cancer cell lines. In a xenograft model of SW480 cells in nude mice, the oral administration of C086 showed significant growth suppression of SW480 tumors, and both Western blot and immunohistochemistry analyses showed decreased NFκB (p65) expression in tumor tissues. Using TNF-α to induce NFκB activation in SW480 cells, it was revealed that C086 inhibited IκBα phosphorylation and its subsequent degradation, and suppressed the nuclear translocation and DNA binding activity of NFκB. C-Myc, cyclin D1, and Bcl-2, NFκB-regulated gene products involving in cellular proliferation and antiapoptosis, were decreased in the C086 treated groups. This effect was accompanied by pro-apoptosis of C086 in colon cancer cells and lower expression of PCNA in C086 treated colon cancer xenografts. Immunostaining for CD31 showed that there were fewer microvessels in C086 treated SW480 tumors, and NFκB-targeted gene products involved in angiogenesis (i.e., vascular endothelial growth factor, matrix metalloproteinase-9) were also downregulated. C086 also inhibited bovine aortic endothelial cell (BAEC) proliferation and tube formation in Matrigel. Overall, our results suggest that C086 is a potent antitumor agent and has promising future in colon cancer. C086 suppressed NFκB activation through inhibition of IκBα phosphorylation. Downregulation of NFκB-regulated gene products contributed to the antiproliferation, pro-apoptosis, and antiangiogenesis effect of C086.

Genistein potentiates the effect of arsenic trioxide against human hepatocellular carcinoma: Role of Akt and nuclear factor-κB

Hepatocellular carcinoma (HCC) is a highly lethal malignancy mostly because of de novo and acquired resistance to conventional chemotherapy. Constitutive activation of Akt and nuclear factor-κB (NF-κB) represent major cellular abnormalities associated with both the pathogenesis and therapeutic resistance of HCC. The aim of the present study was to determine whether genistein, a natural Akt/NF-κB inhibitor, could enhance the anti-HCC efficacy of ATO both in vitro and in vivo. Our results demonstrated that genistein not only potentiated the proliferation-inhibiting and apoptosis-inducing effect of ATO on human HCC cell lines in vitro, but also dramatically augmented its suppressive effect on both tumor growth and angiogenesis in nude mice. The mechanism is at least partially due to the suppressive effect of genistein both on the proper and ATO-induced Akt activation, and on the activity of NF-κB, and the latter correlated with the suppression of NF-κB regulated gene products, including cyclin D1, Bcl-xL, Bcl-2, c-myc, COX-2, and VEGF. These data suggest that the combination of ATO with genistein presents a promising therapeutic approach for the treatment of HCC.

Thiocolchicoside Exhibits Anticancer Effects through Downregulation of NF-κB Pathway and Its Regulated Gene Products Linked to Inflammation and Cancer

The discovery of new uses for older, clinically approved drugs is one way to expedite drug development for cancer. Thiocolchicoside, a semisynthetic colchicoside from the plant Gloriosa superba, is a muscle relaxant and used to treat rheumatologic and orthopedic disorders because of its analgesic and anti-inflammatory mechanisms. Given that activation of the transcription factor NF-κB plays a major role in inflammation and tumorigenesis, we postulated that thiocolchicoside would inhibit NF-κB and exhibit anticancer effects through the modulation of NF-κB-regulated proteins. We show that thiocolchicoside inhibited proliferation of leukemia, myeloma, squamous cell carcinoma, breast, colon, and kidney cancer cells. Formation of tumor colonies was also suppressed by thiocolchicoside. The colchicoside induced apoptosis, as indicated by caspase-3 and poly(ADP-ribose) polymerase cleavage, and suppressed the expression of cell survival [e.g., Bcl-2, X-linked inhibitor of apoptosis (XIAP), MCL-1, bcl-xL, cIAP-1, cIAP-2, and cFLIP] proteins. Cell proliferation biomarkers such as c-MYC and phosphorylation of phosphoinositide 3-kinase and glycogen synthase kinase 3β were also blocked by thiocolchicoside. Because most cell survival and proliferation gene products are regulated by NF-κB, we studied the effect of thiocolchicoside on this transcription factor and found that thiocolchicoside inhibited NF-κB activation, degradation of inhibitory κBα (IκBα), IκBα ubiquitination, and phosphorylation, abolished the activation of IκBα kinase, and suppressed p65 nuclear translocation. This effect of thiocolchicoside on the NF-κB pathway led to inhibition of NF-κB reporter activity and cyclooxygenase-2 promoter activity. Our results indicate that thiocolchicoside exhibits anticancer activity through inhibition of NF-κB and NF-κB-regulated gene products, which provides novel insight into a half-century old drug.

γ-Tocotrienol Inhibits Pancreatic Tumors and Sensitizes Them to Gemcitabine Treatment by Modulating the Inflammatory Microenvironment

Pancreatic cancers generally respond poorly to chemotherapy, prompting a need to identify agents that could sensitize tumors to treatment. In this study, we investigated the response of human pancreatic cells to γ-tocotrienol (γ-T3), a novel, unsaturated form of vitamin E found in palm oil and rice bran oil, to determine whether it could potentiate the effects of gemcitabine, a standard of care in clinical treatment of pancreatic cancer. γ-T3 inhibited the in vitro proliferation of pancreatic cancer cell lines with variable p53 status and potentiated gemcitabine-induced apoptosis. These effects correlated with an inhibition of NF-κB activation by γ-T3 and a suppression of key cellular regulators including cyclin D1, c-Myc, cyclooxygenase-2 (COX-2), Bcl-2, cellular inhibitor of apoptosis protein, survivin, vascular endothelial growth factor (VEGF), ICAM-1, and CXCR4. In an orthotopic nude mouse model of human pancreatic cancer, p.o. administration of γ-T3 inhibited tumor growth and enhanced the antitumor properties of gemcitabine. Immunohistochemical analysis indicated a correlation between tumor growth inhibition and reduced expression of Ki-67, COX-2, matrix metalloproteinase-9 (MMP-9), NF-κB p65, and VEGF in the tissue. Combination treatment also downregulated NF-κB activity along with the NF-κB-regulated gene products, such as cyclin D1, c-Myc, VEGF, MMP-9, and CXCR4. Consistent with an enhancement of tumor apoptosis, caspase activation was observed in tumor tissues. Overall, our findings suggest that γ-T3 can inhibit the growth of human pancreatic tumors and sensitize them to gemcitabine by suppressing NF-κB-mediated inflammatory pathways linked to tumorigenesis.

Modification of the cysteine residues in IκBα kinase and NF-κB (p65) by xanthohumol leads to suppression of NF-κB–regulated gene products and potentiation of apoptosis in leukemia cells

Xanthohumol (XN), a prenylated chalcone isolated from hop plant, exhibits anti-inflammatory, antiproliferative, and antiangiogenic properties through an undefined mechanism. Whether examined by intracellular esterase activity, phosphatidylserine externalization, DNA strand breaks, or caspase activation, we found that XN potentiated tumor necrosis factor-induced apoptosis in leukemia and myeloma cells. This enhancement of apoptosis correlated with down-regulation of nuclear factor-kappaB (NF-kappaB) survivin, bcl-xL, XIAP, cIAP1, cIAP2, cylin D1, and c-myc. XN down-regulated both constitutive and inducible NF-kappaB activation, inhibition of phosphorylation and degradation of IkappaBalpha, suppression of p65 nuclear translocation, and NF-kappaB-dependent reporter gene transcription. XN directly inhibited tumor necrosis factor-induced IkappaBalpha kinase (IKK) activation and a reducing agent abolished this inhibition, indicating the role of cysteine residue. XN had no effect on the IKK activity when cysteine residue 179 of IKK was mutated to alanine. XN also directly inhibited binding of p65 to DNA, a reducing agent reversed this effect, and mutation of cysteine residue 38 to serine of p65 abolished this effect. Thus, our results show that modification of cysteine residues of IKK and p65 by XN leads to inhibition of the NF-kappaB activation pathway, suppression of antiapoptotic gene products, and potentiation of apoptosis in leukemia cells.

Modification of Cysteine Residue in p65 Subunit of Nuclear Factor-κB (NF-κB) by Picroliv Suppresses NF-κB–Regulated Gene Products and Potentiates Apoptosis

Picroliv, an iridoid glycoside derived from the plant Picrorhiza kurroa, is used traditionally to treat fever, asthma, hepatitis, and other inflammatory conditions. However, the exact mechanism of its therapeutic action is still unknown. Because nuclear factor-kappaB (NF-kappaB) activation plays a major role in inflammation and carcinogenesis, we postulated that picroliv must interfere with this pathway by inhibiting the activation of NF-kappaB-mediated signal cascade. Electrophoretic mobility shift assay showed that pretreatment with picroliv abrogated tumor necrosis factor (TNF)-induced activation of NF-kappaB. The glycoside also inhibited NF-kappaB activated by carcinogenic and inflammatory agents, such as cigarette smoke condensate, phorbol 12-myristate 13-acetate, okadaic acid, hydrogen peroxide, lipopolysaccharide, and epidermal growth factor. When examined for the mechanism of action, we found that picroliv inhibited activation of IkappaBalpha kinase, leading to inhibition of phosphorylation and degradation of IkappaBalpha. It also inhibited phosphorylation and nuclear translocation of p65. Further studies revealed that picroliv directly inhibits the binding of p65 to DNA, which was reversed by the treatment with reducing agents, suggesting a role for a cysteine residue in interaction with picroliv. Mutation of Cys(38) in p65 to serine abolished this effect of picroliv. NF-kappaB inhibition by picroliv leads to suppression of NF-kappaB-regulated proteins, including those linked with cell survival (inhibitor of apoptosis protein 1, Bcl-2, Bcl-xL, survivin, and TNF receptor-associated factor 2), proliferation (cyclin D1 and cyclooxygenase-2), angiogenesis (vascular endothelial growth factor), and invasion (intercellular adhesion molecule-1 and matrix metalloproteinase-9). Suppression of these proteins enhanced apoptosis induced by TNF. Overall, our results show that picroliv inhibits the NF-kappaB activation pathway, which may explain its anti-inflammatory and anticarcinogenic effects.

Berberine Modifies Cysteine 179 of IκBα Kinase, Suppresses Nuclear Factor-κB–Regulated Antiapoptotic Gene Products, and Potentiates Apoptosis

Berberine, an isoquinoline alkaloid derived from a plant used traditionally in Chinese and Ayurvedic medicine, has been reported to exhibit chemopreventive and anti-inflammatory activities through unknown mechanism. Because of the critical role of the transcription factor nuclear factor-kappaB (NF-kappaB) in these processes, we investigated the effect of berberine on this pathway. We found that berberine suppressed NF-kappaB activation induced by various inflammatory agents and carcinogens. This alkaloid also suppressed constitutive NF-kappaB activation found in certain tumor cells. Suppression of NF-kappaB activation occurred through the inhibition of phosphorylation and degradation of IkappaBalpha by the inhibition of IkappaB kinase (IKK) activation, leading to suppression of phosphorylation and nuclear translocation of p65, and finally to inhibition of NF-kappaB reporter activity. Inhibition of IKK by berbeine was direct and could be reversed by reducing agents. Site-specific mutagenesis suggested the involvement of cysteine residue 179 in IKK. Berberine also suppressed the expression of NF-kappaB-regulated gene products involved in antiapoptosis (Bcl-xL, Survivin, IAP1, IAP2, and cFLIP), proliferation (cyclin D1), inflammation (cyclooxygenase-2), and invasion (matrix metalloproteinase-9). Suppression of antiapoptotic gene products correlated with enhancement of apoptosis induced by tumor necrosis factor (TNF)-alpha and chemotherapeutic agents and with inhibition of TNF-induced cellular invasion. Overall, our results indicate that chemopreventive, apoptotic, and anti-inflammatory activities displayed by berberine may be mediated in part through the suppression of the NF-kappaB activation pathway. This may provide the molecular basis for the ability of berberine to act as an anticancer and anti-inflammatory agent.

Curcumin Sensitizes Human Colorectal Cancer Xenografts in Nude Mice to γ-Radiation by Targeting Nuclear Factor-κB–Regulated Gene Products

How colorectal cancer develops resistance to gamma-radiation is not fully understood, but the transcription factor nuclear factor-kappaB (NF-kappaB) and NF-kappaB-regulated gene products have been proposed as mediators. Because curcumin, a component of turmeric (Curcuma longa), has been shown to suppress NF-kappaB activation, whether it can sensitize the colorectal cancer to gamma-radiation was investigated in colorectal cancer xenografts in nude mice. We established HCT 116 xenograft in nude mice, randomized into four groups, and treated with vehicle (corn oil), curcumin, gamma-radiation, and curcumin in combination with gamma-radiation. NF-kappaB modulation was ascertained using electrophoretic mobility shift assay and immunohistochemistry. Markers of proliferation, angiogenesis, and invasion were monitored by immunohistochemistry and Western blot analysis. Curcumin significantly enhanced the efficacy of fractionated radiation therapy by prolonging the time to tumor regrowth (P=0.02) and by reducing the Ki-67 proliferation index (P<0. 001). Moreover, curcumin suppressed NF-kappaB activity and the expression of NF-kappaB-regulated gene products (cyclin D1, c-myc, Bcl-2, Bcl-xL, cellular inhibitor of apoptosis protein-1, cyclooxygenase-2, matrix metalloproteinase-9, and vascular endothelial growth factor), many of which were induced by radiation therapy and mediate radioresistance. The combination of curcumin and radiation therapy also suppressed angiogenesis, as indicated by a decrease in vascular endothelial growth factor and microvessel density (P=0.002 versus radiation alone). Collectively, our results suggest that curcumin potentiates the antitumor effects of radiation therapy in colorectal cancer by suppressing NF-kappaB and NF-kappaB-regulated gene products, leading to inhibition of proliferation and angiogenesis.