Paclitaxel sensitivity of breast cancer cells with constitutively active NF-kappaB is enhanced by IkappaBalpha super-repressor and parthenolide

BCL2 and CASP8 regulation by NF-kappaB differentially affect mitochondrial function and cell fate in antiestrogen-sensitive and -resistant breast cancer cells

Resistance to endocrine therapies remains a major problem in the management of estrogen receptor-alpha (ER)-positive breast cancer. We show that inhibition of NF-kappaB (p65/RELA), either by overexpression of a mutant IkappaB (IkappaBSR) or a small-molecule inhibitor of NF-kappaB (parthenolide; IC(50)=500 nM in tamoxifen-resistant cells), synergistically restores sensitivity to 4-hydroxytamoxifen (4HT) in resistant MCF7/RR and MCF7/LCC9 cells and further sensitizes MCF-7 and MCF7/LCC1 control cells to 4HT. These effects are independent of changes in either cell cycle distribution or in the level of autophagy measured by inhibition of p62/SQSTM1 expression and cleavage of LC3. NF-kappaB inhibition restores the ability of 4HT to decrease BCL2 expression, increase mitochondrial membrane permeability, and induce a caspase-dependent apoptotic cell death in resistant cells. Each of these effects is reversed by a caspase 8 (CASP8)-specific inhibitor that blocks enzyme-substrate binding. Thus, increased activation of NF-kappaB can alter sensitivity to tamoxifen by modulating CASP8 activity, with consequent effects on BCL2 expression, mitochondrial function, and apoptosis. These data provide significant new insights into how molecular signaling affects antiestrogen responsiveness and strongly suggest that a combination of parthenolide and tamoxifen may offer a novel therapeutic approach to the management of some ER-positive breast cancers.

A phase II study of isoflavones, erlotinib, and gemcitabine in advanced pancreatic cancer

BACKGROUND

The EGFR/Akt/NF-κB signalling pathway is frequently deregulated in pancreatic cancer and contributes to cell growth, metastasis and chemoresistance. An isoflavone, genistein, inactivates Akt and NF-κB and enhances the anti-tumor activity of erlotinib and gemcitabine in experimental systems of pancreas cancer. This phase II study was undertaken to determine the effects of adding isoflavone to a regimen of gemcitabine and erlotinib on survival in patients with advanced pancreatic cancer.

METHODS

Eligibility included previously untreated patients with advanced pancreatic adenocarcinoma. Patients received gemcitabine 1,000 mg/m² on days 1, 8, and 15, and erlotinib 150 mg once daily P.O. on day 1 to day 28. Soy isoflavones (Novasoy®) were administered at a dose of 531 mg twice daily P.O. starting day -7 until the end of study participation.

RESULTS

Twenty patients with advanced pancreas cancer were enrolled (median age 57.9 years). Sixteen patients had stage IV disease. The median number of cycles was 2 per patient. The median survival time was 5.2 months (95% CI, 4.6-N/A months). The probability of survival at 6 months was 50% (95% CI, 32-78%).

CONCLUSIONS

The addition of soy isoflavones to gemcitabine and erlotinib did not appear to increase the survival of patients with advanced pancreatic cancer.

Retinoic acid protects human breast cancer cells against etoposide-induced apoptosis by NF-kappaB-dependent but cIAP2-independent mechanisms

Background

Retinoids, through their cognate nuclear receptors, exert potent effects on cell growth, differentiation and apoptosis, and have significant promise for cancer therapy and chemoprevention. These ligands can determine the ultimate fate of target cells by stimulating or repressing gene expression directly, or indirectly through crosstalking with other signal transducers.

Results

Using different breast cancer cell models, we show here that depending on the cellular context retinoids can signal either towards cell death or cell survival. Indeed, retinoids can induce the expression of pro-apoptotic (i.e. TRAIL, TNF-Related Apoptosis-Inducing Ligand, Apo2L/TNFSF10) and anti-apoptotic (i.e. cIAP2, inhibitor of apoptosis protein-2) genes. Promoter mapping, gel retardation and chromatin immunoprecipitation assays revealed that retinoids induce the expression of this gene mainly through crosstalk with NF-kappaB. Supporting this crosstalk, the activation of NF-kappaB by retinoids in T47D cells antagonizes the apoptosis triggered by the chemotherapeutic drugs etoposide, camptothecin or doxorubicin. Notably apoptosis induced by death ligands (i.e. TRAIL or antiFAS) is not antagonized by retinoids. That knockdown of cIAP2 expression by small interfering RNA does not alter the inhibition of etoposide-induced apoptosis by retinoids in T47D cells reveals that stimulation of cIAP2 expression is not the cause of their anti-apoptotic action. However, ectopic overexpression of a NF-kappaB repressor increases apoptosis by retinoids moderately and abrogates almost completely the retinoid-dependent inhibition of etoposide-induced apoptosis. Our data exclude cIAP2 and suggest that retinoids target other regulator(s) of the NF-kappaB signaling pathway to induce resistance to etoposide on certain breast cancer cells.

Conclusions

This study shows an important role for the NF-kappaB pathway in retinoic acid signaling and retinoic acid-mediated resistance to cancer therapy-mediated apoptosis in breast cancer cells, independently of cIAP2. Our data support the use of NF-kappaB pathway activation as a marker for screening that will help to develop novel retinoids, or retinoid-based combination therapies with improved efficacy.

NF-kappaB as a prognostic marker and therapeutic target in chronic lymphocytic leukemia

Chronic lymphocytic leukemia is the most common adult leukemia and is currently incurable with conventional chemotherapeutic agents. Over the last few years, significant discoveries have been made regarding the biology that underpins this disease. These new insights have allowed us to develop more rational prognostic tools and identify promising novel therapeutic targets. In this review, we highlight the importance of both constitutive and inducible DNA binding of the transcription factor NF-kappaB in chronic lymphocytic leukemia. We describe the current knowledge regarding the activity and function of specific NF-kappaB subunits in this disease, and discuss the complex mechanisms that regulate NF-kappaB activation in vivo. In addition, we provide compelling evidence for the utility of the NF-kappaB subunit, Rel A, as a prognostic marker and as a therapeutic target in this disease, and we also describe how this protein may contribute to the drug resistance commonly encountered with this condition.

Id1, inhibitor of differentiation, is a key protein mediating anti-tumor responses of gamma-tocotrienol in breast cancer cells

Gamma-tocotrienol has demonstrated anti-proliferative effect on breast cancer (BCa) cells, but mechanisms involved are largely unknown. This study aimed at deciphering the molecular pathways responsible for its activity. Our results showed that treatment of BCa cells with gamma-tocotrienol resulted in induction of apoptosis as evidenced by activation of pro-caspases, accumulation of sub-G1 cells and DNA fragmentations. Examination of the pro-survival genes revealed that the gamma-tocotrienol-induced cell death was associated with suppression of Id1 and NF-kappaB through modulation of their upstream regulators (Src, Smad1/5/8, Fak and LOX). Meanwhile, gamma-tocotrienol treatment also resulted in the induction of JNK signaling pathway and inhibition of JNK activity by specific inhibitor partially blocked the effect of gamma-tocotrienol. Furthermore, synergistic effect was observed when cells were co-treated with gamma-tocotrienol and Docetaxel. Interestingly, in cells that treated with gamma-tocotrienol, alpha-tocopherol or beta-aminoproprionitrile were found to partially restore Id1 expression. Meanwhile, this restoration of Id1 was found to protect the cells from gamma-tocotrienol induced apoptosis. Consistent outcome was observed in cells ectopically transfected with the Id-1 gene. Our results suggested that the anti-proliferative and chemosensitization effect of gamma-tocotrienol on BCa cells may be mediated through downregulation of Id1 protein.

Chemosensitization in non-small cell lung cancer cells by IKK inhibitor occurs via NF-kappaB and mitochondrial cytochrome c cascade

In this study, we demonstrated with mechanistic evidence that parthenolide, a sesquiterpene lactone, could antagonize paclitaxel-mediated NF-kappaB nuclear translocation and activation by selectively targeting I-kappaB kinase (IKK) activity. We also found that parthenolide could target IKK activity and then inhibit NF-kappaB; this promoted cytochrome c release and activation of caspases 3 and 9. Inhibition of caspase activity blocked the activation of caspase cascade, implying that the observed synergy was related to caspases 3 and 9 activation of parthenolide. In contrast, paclitaxel individually induced apoptosis via a pathway independent of the mitochondrial cytochrome c cascade. Finally, exposure to parthenolide resulted in the inhibition of several NF-kappaB transcript anti-apoptotic proteins such as c-IAP1 and Bcl-xl. These data strengthen the rationale for using parthenolide to decrease the apoptotic threshold via caspase-dependent processes for treatment of non-small cell lung cancer with paclitaxel chemoresistance.

Transglutaminase 2 as a cisplatin resistance marker in non-small cell lung cancer

PURPOSE

Recently, it was reported that expression of transglutaminase 2 plays an important role in doxorubicin/cisplatin resistance in breast and ovarian cancer. The aims of this study were to verify the role of transglutaminase 2 in cisplatin response in non-small cell lung cancer (NSCLC) and to study if transglutaminase 2 gene (TGM2) methylation can be a molecular marker for good response to cisplatin.

METHODS

TGM2 promoter methylation was analyzed by sodium bisulfite sequencing. Cisplatin sensitivity was analyzed by treatment of cisplatin in NSCLC cell lines with/without TGM2 or TGM2 siRNA transfection.

RESULTS

In one-third of NSCLC cell lines, TGase 2 gene (TGM2) was silenced by promoter methylation. The TGM2 promoter-methylated cell lines (HCC-95 and HCC-1588) showed relatively higher sensitivity to cisplatin than the TGM2-expressing cell lines (NCI-H1299 and HCC-1195). Down-regulation and over-expression of TGM2 in those NSCLC cells also suggested a positive correlation of cisplatin sensitivity and TGM2 inhibition. With doxorubicin, the relationship was quite similar.

CONCLUSIONS

We showed that good responders of cisplatin in NSCLC could be identified by the promoter methylation of TGM2 and that TGase 2 inhibition appears to be an effective cisplatin-sensitizing modality in NSCLC.

Nuclear factor-kappaB inhibition by parthenolide potentiates the efficacy of Taxol in non-small cell lung cancer in vitro and in vivo

In this study, we have examined the molecular events induced by parthenolide, a sesquiterpene lactone, and explored possible mechanisms of resistance and sensitization of tumor cells to Taxol. We showed that parthenolide could antagonize Taxol-mediated nuclear factor-kappaB (NF-kappaB) nuclear translocation and activation and Bcl-xl up-regulation by selectively targeting I-kappaB kinase activity. In A549 cells, inhibition of nuclear factor-kappaB by parthenolide resulted in activation of the mitochondrial death pathway to promote cytochrome c release and caspase 3 and 9 activation. In contrast, Taxol alone induced apoptosis via a pathway independent of mitochondria cytochrome c cascade. In addition, depletion of Bcl-xl rescued the apoptotic response to Taxol. Moreover, treatment with parthenolide increased the efficacy of the Taxol-induced inhibition of A549 tumor xenografts in mice. This study elucidated the cellular responses induced by parthenolide that decrease the threshold of mitochondria-dependent apoptosis in the treatment of non-small cell lung cancer cells.

Phase I trial of carboplatin/paclitaxel/bortezomib and concurrent radiotherapy followed by surgical resection in Stage III non-small cell lung cancer

INTRODUCTION

Despite advances in Stage III NSCLC, the mortality from the disease remains >70%. Disease recurrence can occur both locally and systemically. Trimodality therapy may improve outcome by maximizing local control. The purpose of this study was to perform a phase I trial of bortezomib (PS-341, Velcade) in addition to chemotherapy with carboplatin AUC=2 and paclitaxel 50mg/m(2) and concurrent radiotherapy (61 Gy) as induction treatment in a trimodality approach.

METHODS

Patients with pathologically documented Stage III a (N2) or selected IIIb (N3) disease were eligible. Bortezomib was administered on days 1, 4, 15, 18 during the 6-week induction chemoradiotherapy. Cohorts of three patients were entered and observed for toxicity during chemoradiotherapy and for 2 weeks afterwards. Surgical resection was attempted in the patients who had mediastinal sterilization. All patients were to receive consolidation chemotherapy with carboplatin AUC=6 and paclitaxel 200mg/m(2).

RESULTS

Twelve patients in three cohorts were enrolled. The addition of bortezomib was well tolerated, with no unexpected toxicities during the induction phase. However, there were three postoperative deaths (two pneumonitis and one from failure of the bronchopulmonary flap). The trial was halted as a consequence of these toxicities.

CONCLUSIONS

While this approach was well tolerated in terms of acute toxicity, the apparently delayed toxicity was severe and unpredictable. It does not appear that bortezomib can be safely administered as part of preoperative chemoradiotherapy for lung cancer. However, there was a high incidence of complete pathologic response and cautious exploration of this agent in the non-operative setting is appropriate.

Suppression of NF-kappaB activity by parthenolide induces X-ray sensitivity through inhibition of split-dose repair in TP53 null prostate cancer cells

We have shown that parthenolide, a sesquiterpene lactone, is a radiation sensitizer for human CGL1 hybrid cells that have constitutively activated NF-kappaB and wild-type p53. Since many malignant cells have nonfunctional p53, we investigated whether parthenolide could alter the X-ray sensitivity of PC-3 prostate cancer cells, a p53 null cell line with constitutively activated NF-kappaB. The addition of 5 microM parthenolide induced non-apoptotic cell death, inhibited PC-3 proliferation, and increased the population doubling time from 23+/-1 h to 49+/-4 h. Parthenolide also inhibited constitutive and radiation-induced NF-kappaB binding activity and enhanced the X-ray sensitivity of these p53 null PC-3 cells by a dose modification factor of 1.7. Cell cycle analysis of PC-3 cells treated with parthenolide showed only small alterations in G1 and G2/M cells, and these appeared to be insufficient to explain the observed radiosensitization. Split-dose studies using clinically relevant 2- and 4-Gy fractions demonstrated that parthenolide completely inhibited split-dose repair in PC-3 cells. We hypothesized that inhibition of NF-kappaB activity by parthenolide was responsible for the observed X-ray sensitization and inhibition of split-dose repair. To test this hypothesis, we knocked down the expression of NF-kappaB p65 protein, an active component of NF-kappaB in both PC-3 and CGL1 cells, by siRNA. Inhibition of NF-kappaB activity by knockdown of p65 increased radiation sensitivity and completely inhibited split-dose repair in both cell lines in a nearly identical manner as parthenolide treatment alone. Treating p65-depleted PC-3 cells with 5 microM parthenolide did not further increase their radiation sensitivity or the inhibition of split-dose repair. We propose that the suppression of radiation-induced NF-kappaB activity by parthenolide leads to X-ray sensitization through inhibition of split-dose repair in p53 null PC-3 prostate cancer cells.

Aminoparthenolides as novel anti-leukemic agents: Discovery of the NF-kappaB inhibitor, DMAPT (LC-1)

A series of aminoparthenolide analogs (6-37) were synthesized and evaluated for their anti-leukemic activity. Eight compounds exhibited good anti-leukemic activity with LD(50)'s in the low microM range (1.5-3.0microM). Compounds 16, 24 and 30 were the most potent compounds in the series, causing greater than 90% cell death at 10microM concentration against primary AML cells in culture, with LD(50) values of 1.7, 1.8 and 1.6microM.

NFkappaB signaling in carcinogenesis and as a potential molecular target for cancer therapy

It has become increasingly clear that deregulation of the NFkappaB signaling cascade is a common underlying feature of many human ailments including cancers. The past two decades of intensive research on NFkappaB has identified the basic mechanisms that govern the functioning of this pathway but uncovering the details of why this pathway works differently in different cellular contexts or how it interacts with other signaling pathways remains a challenge. A thorough understanding of these processes is needed to design better and more efficient therapeutic approaches to treat complex diseases like cancer. In this review, we summarize the literature documenting the involvement of NFkappaB in cancer, and then focus on the approaches that are being undertaken to develop NFkappaB inhibitors towards treatment of human cancers.

NF-kappaB activation through the alternative pathway correlates with chemoresistance and poor survival in extranodal NK/T-cell lymphoma, nasal type

OBJECTIVE

Nuclear factor-kappaB (NF-kappaB) activation has been identified in a variety of solid tumors and lymphoid malignancies. The aim of our study was to determine the expression status and clinical significance of NF-kappaB in extranodal natural killer (NK)/T-cell lymphoma, nasal type.

METHODS

Tumor specimens from 23 patients with previously untreated NK/T-cell lymphoma initially treated with cyclophosphamide, vincristine, doxorubicin and prednisone (CHOP) or CHOP-based chemotherapy were examined by immunohistochemistry for three NF-kappaB subunits (p65, p50 and p52), which are involved in either the canonical or alternative pathway.

RESULTS

None of the cases could be detected with p65 or p50 nuclear staining. On the other hand, 15 (65.2%) cases had p52 nuclear staining, suggesting NF-kappaB activation through the alternative pathway. All major clinical characteristics were balanced between NF-kappaB p52-positive and -negative patients. The objective response rate achieved in NF-kappaB-positive patients was significantly lower than that in negative patients (33.3% vs. 87.5%, P = 0.027). At a median follow-up of 25 months, 8 (53.3%) of 15 NF-kappaB-positive patients had died compared with none of 8 NF-kappaB-negative patients (P = 0.041). In a multivariate analysis, NF-kappaB status and stage were identified to be independent prognostic factors.

CONCLUSIONS

Our results suggest that NF-kappaB activation through the alternative pathway is frequently observed in NK/T-cell lymphoma and associated with chemoresistance and poor survival.

Parthenolide promotes the ubiquitination of MDM2 and activates p53 cellular functions

MDM2 belongs to a class of ring-finger domain-containing ubiquitin ligases that mediate the proteasomal degradation of numerous proteins, including themselves. Arguably, the most important substrate of MDM2 is p53, which controls cell cycle progression and apoptosis. MDM2 and p53 are parts of a feedback regulatory loop whose perturbations are often present in cancer and are targets for anticancer drug development. We found that the natural product, small-molecule anti-inflammatory agent parthenolide (PN), which is actively being investigated as a potential therapeutic for many human cancers, induces ubiquitination of MDM2 in treated cells, resulting in the activation of p53 and other MDM2-regulated tumor-suppressor proteins. Using cells with functional gene deletions and small interfering RNA knockdown studies, we found that these effects required the DNA damage transducer ataxia telangiectasia mutated. The effects of PN on tumor suppressor activation were comparable with that of nutlin-3a, a recently developed small molecule that was designed to interfere with the interaction between MDM2 and p53 but does not promote MDM2 ubiquitination. Our study illustrates an alternative approach for controlling MDM2 and p53 activities and identifies an additional critically important cancer pathway affected by PN.

Ionizing radiation-induced NF-kappaB activation requires PARP-1 function to confer radioresistance

Recent reports implicate poly(ADP-ribose) polymerase-1 (PARP-1) in the activation of nuclear factor kappaB (NF-kappaB). We investigated the role of PARP-1 in the NF-kappaB signalling cascade induced by ionizing radiation (IR). AG14361, a potent PARP-1 inhibitor, was used in two breast cancer cell lines expressing different levels of constitutively activated NF-kappaB, as well as mouse embryonic fibroblasts (MEFs) proficient or deficient for PARP-1 or NF-kappaB p65. In the breast cancer cell lines, AG14361 had no effect on IR-induced degradation of IkappaBalpha or nuclear translocation of p50 or p65. However, AG14361 inhibited IR-induced NF-kappaB-dependent transcription of a luciferase reporter gene. Similarly, in PARP-1(-/-) MEFs, IR-induced nuclear translocation of p50 and p65 was normal, but kappaB binding and transcriptional activation did not occur. AG14361 sensitized both breast cancer cell lines to IR-induced cell killing, inhibited IR-induced XIAP expression and increased caspase-3 activity. However, AG14361 failed to increase IR-induced caspase activity when p65 was knocked down by siRNA. Consistent with this, AG14361 sensitized p65(+/+) but not p65(-/-) MEFs to IR. We conclude that PARP-1 activity is essential in the upstream regulation of IR-induced NF-kappaB activation. These data indicate that potentiation of IR-induced cytotoxicity by AG14361 is mediated solely by inhibition of NF-kappaB activation.

Modulation of DNA methylation by a sesquiterpene lactone parthenolide

Hypermethylation of 5'-cytosine-guanosine islands of tumor suppressor genes resulting in their silencing has been proposed to be a hallmark of various tumors. Modulation of DNA methylation with DNA methylation inhibitors has been shown to result in cancer cell differentiation or apoptosis and represents a novel strategy for chemotherapy. Currently, effective DNA methylation inhibitors are mainly limited to decitabine and 5-azacytidine, which still show unfavorable toxicity profiles in the clinical setting. Thus, discovery and development of novel hypomethylating agents, with a more favorable toxicity profile, is essential to broaden the spectrum of epigenetic therapy. Parthenolide, the principal bioactive sesquiterpene lactone of feverfew, has been shown to alkylate Cys(38) of p65 to inhibit nuclear factor-kappaB activation and exhibit anti-tumor activity in human malignancies. In this article, we report that parthenolide 1) inhibits DNA methyltransferase 1 (DNMT1) with an IC(50) of 3.5 microM, possibly through alkylation of the proximal thiolate of Cys(1226) of the catalytic domain by its gamma-methylene lactone, and 2) down-regulates DNMT1 expression possibly associated with its SubG(1) cell-cycle arrest or the interruption of transcriptional factor Sp1 binding to the promoter of DNMT1. These dual functions of parthenolide result in the observed in vitro and in vivo global DNA hypomethylation. Furthermore, parthenolide has been shown to reactivate tumor suppressor HIN-1 gene in vitro possibly associated with its promoter hypomethylation. Hence, our study established parthenolide as an effective DNA methylation inhibitor, representing a novel prototype for DNMT1 inhibitor discovery and development from natural structural-diversified sesquiterpene lactones.

Ankyrin repeat domain 1, ANKRD1, a novel determinant of cisplatin sensitivity expressed in ovarian cancer

PURPOSE

The standard of care for ovarian cancer includes platinum-based chemotherapy. It is not possible, however, to predict clinical platinum sensitivity or to design rational strategies to overcome resistance. We used a novel approach to identify altered gene expression associated with high sensitivity to cisplatin, to define novel targets to sensitize tumor cells to platins and ultimately improve the effectiveness of this widely used class of chemotherapeutics.

EXPERIMENTAL DESIGN

Using differential display PCR, we identified genes differentially expressed in a mutagenized cell line with unusual sensitivity to cisplatin. The most highly differentially expressed gene was selected, and its role in determining cisplatin sensitivity was validated by gene transfection and small interfering RNA (siRNA) approaches, by association of expression levels with cisplatin sensitivity in cell lines, and by association of tumor expression levels with survival in a retrospective cohort of 71 patients with serous ovarian adenocarcinoma.

RESULTS

The most highly differently expressed gene identified was ANKRD1, ankyrin repeat domain 1 (cardiac muscle). ANKRD1 mRNA levels were correlated with platinum sensitivity in cell lines, and most significantly, decreasing ANKRD1 using siRNA increased cisplatin sensitivity >2-fold. ANKRD1 was expressed in the majority of ovarian adenocarcinomas tested (62/71, 87%), and higher tumor levels of ANKRD1 were found in patients with worse outcome (overall survival, P=0.013).

CONCLUSIONS

These findings suggest that ANKRD1, a gene not previously associated with ovarian cancer or with response to chemotherapy, is associated with treatment outcome, and decreasing ANKRD1 expression, or function, is a potential strategy to sensitize tumors to platinum-based drugs.

Dehydroxymethylepoxyquinomicin, a novel nuclear Factor-kappaB inhibitor, enhances antitumor activity of taxanes in anaplastic thyroid cancer cells

Nuclear factor kappaB (NF-kappaB), as an antiapoptotic factor, crucially affects the outcomes of cancer treatments, being one of the major culprits of resistance to chemotherapy. In this study, we investigated whether dehydroxymethylepoxyquinomicin (DHMEQ), a novel NF-kappaB inhibitor, can enhance antitumor activities of taxanes in anaplastic thyroid cancer (ATC) cells. Taxanes induced NF-kappaB activation in ATC cells, which could compromise the therapeutic effect of the drugs. However, DHMEQ, by inhibiting the nuclear translocation of NF-kappaB, completely suppressed the DNA binding capacities of NF-kappaB and lowered the levels of nuclear NF-kappaB protein. Compared with single treatment (either taxane or DHMEQ), the combined treatment strongly potentiated apoptosis, confirmed by cell survival assay; Western blotting for poly (ADP-ribose) polymerase, caspase 3, X-linked inhibitor of apoptosis, and survivin; and flow cytometry for annexin V. Furthermore, we also demonstrate for the first time that the combined treatment showed significantly greater inhibitory effect on tumor growth in a nude mice xenograft model. These findings suggest that taxanes are able to induce NF-kappaB activation in ATC cells, which could attenuate antitumor activities of the drugs, but inhibition of NF-kappaB by DHMEQ creates a chemosensitive environment and greatly enhances apoptosis in taxanes-treated ATC cells in vitro and in vivo. Thus, DHMEQ may emerge as an attractive therapeutic strategy to enhance the response to taxanes in ATCs.

The fibroblast growth factor-inducible 14 receptor is highly expressed in HER2-positive breast tumors and regulates breast cancer cell invasive capacity

Genomic characterization is beginning to define a molecular taxonomy for breast cancer; however, the molecular basis of invasion and metastasis remains poorly understood. We report a pivotal role for the fibroblast growth factor-inducible 14 (Fn14) receptor in this process. We examined whether Fn14 and its ligand tumor necrosis factor-like weak inducer of apoptosis (TWEAK) were expressed in breast tumors and whether deregulation of Fn14 levels affected malignant behavior of breast cancer cell lines. Analysis of TWEAK and Fn14 in publicly available gene expression data indicated that high Fn14 expression levels significantly correlated with several poor prognostic indicators (P < 0.05). Fn14 expression was highest in the HER2-positive/estrogen receptor-negative (HER2(+)/ER(-)) intrinsic subtype (P = 0.0008). An association between Fn14 and HER2 expression in breast tumors was confirmed by immunohistochemistry. Fn14 levels were elevated in invasive, ER(-) breast cancer cell lines. Overexpression of Fn14 in weakly invasive MCF7 and T47D cells resulted in a marked induction of invasion and activation of nuclear factor-kappaB (NF-kappaB) signaling. Ectopic expression of Fn14tCT, a Fn14 deletion mutant that cannot activate NF-kappaB signaling, was not able to induce invasion. Moreover, ectopic expression of Fn14tCT in highly invasive MDA-MB-231 cells reduced their invasive capability. RNA interference-mediated inhibition of Fn14 expression in both MDA-MB-231 and MDA-MB-436 cells reduced invasion. Expression profiling of the Fn14-depleted cells revealed deregulation of NF-kappaB activity. Our findings support a role for Fn14-mediated NF-kappaB pathway activation in breast tumor invasion and metastasis.

Nuclear factor-kappaB activation: from bench to bedside

Nuclear factor-kappaB (NF-kappaB) is a proinflammatory transcription factor that has emerged as an important player in the development and progression of malignant cancers. NF-kappaB targets genes that promote tumor cell proliferation, survival, metastasis, inflammation, invasion, and angiogenesis. Constitutive or aberrant activation of NF-kappa is frequently encountered in many human tumors and is associated with a resistant phenotype and poor prognosis. The mechanism of such persistent NF-kappaB activation is not clear but may involve defects in signaling pathways, mutations, or chromosomal rearrangements. Suppression of constitutive NF-kappaB activation inhibits the oncogenic potential of transformed cells and thus makes NF-kappaB an interesting new therapeutic target in cancer.

Parthenolide sensitizes cells to X-ray-induced cell killing through inhibition of NF-kappaB and split-dose repair

Human cancers have multiple alterations in cell signaling pathways that promote resistance to cytotoxic therapy such as X rays. Parthenolide is a sesquiterpene lactone that has been shown to inhibit several pro-survival cell signaling pathways, induce apoptosis, and enhance chemotherapy-induced cell killing. We investigated whether parthenolide would enhance X-ray-induced cell killing in radiation resistant, NF-kappaB-activated CGL1 cells. Treatment with 5 microM parthenolide for 48 to 72 h inhibited constitutive NF-kappaB binding and cell growth, reduced plating efficiency, and induced apoptosis through stabilization of p53 (TP53), induction of the pro-apoptosis protein BAX, and phosphorylation of BID. Parthenolide also enhanced radiation-induced cell killing, increasing the X-ray sensitivity of CGL1 cells by a dose modification factor of 1.6. Flow cytometry revealed that parthenolide reduced the percentage of X-ray-resistant S-phase cells due to induction of p21 waf1/cip1 (CDKN1A) and the onset of G1/S and G2/M blocks, but depletion of radioresistant S-phase cells does not explain the observed X-ray sensitization. Further studies demonstrated that the enhancement of X-ray-induced cell killing by parthenolide is due to inhibition of split-dose repair.

The radiosensitization effect of parthenolide in prostate cancer cells is mediated by nuclear factor-kappaB inhibition and enhanced by the presence of PTEN

Parthenolide has been shown to have anti-inflammatory and antitumor properties. However, whether and how parthenolide enhances tumor sensitivity to radiation therapy are unknown. In this study, we show that inhibition of the nuclear factor-kappaB (NF-kappaB) pathway is a common mechanism for the radiosensitization effect of parthenolide in prostate cancer cells LNCaP, DU 145, and PC3. Parthenolide inhibits radiation-induced NF-kappaB DNA-binding activity and the expression of its downstream target sod2, the gene coding for an important antiapoptotic and antioxidant enzyme (manganese superoxide dismutase) in the three prostate cancer cells. Different susceptibilities to parthenolide's effect are observed in two radioresistant cancer cells, DU 145 and PC3, with DU 145 cells showing higher sensitivity. This differential susceptibility to parthenolide is due, in part, to the fact that in addition to NF-kappaB inhibition, parthenolide activates the phosphatidylinositol-3-kinase/Akt prosurvival pathway in both cell lines. However, the activated Akt in DU 145 cells is kept at a relatively low level compared with that in PC3 cells due to the presence of functional PTEN. Transfection of wild-type PTEN into PTEN-null cells, PC3, confers the enhanced radiosensitization effect of parthenolide in PTEN-expressing cells. When PTEN expression is knocked down in DU 145 cells, the cells become more resistant to parthenolide's effect. Taken together, these results suggest that parthenolide inhibits the NF-kappaB pathway and activates the phosphatidylinositol-3-kinase/Akt pathway in prostate cancer cells. The radiosensitization effect of parthenolide is due, in part, to the inhibition of the NF-kappaB pathway. The presence of PTEN enhances the radiosensitization effect of parthenolide, in part, by suppressing the absolute amount of activated p-Akt.

Interferon-gamma sensitizes hepatitis B virus-expressing hepatocarcinoma cells to 5-fluorouracil through inhibition of hepatitis B virus-mediated nuclear factor-kappaB activation

Nuclear factor (NF)-kappaB is important for immune responses and cell survival; however, abnormal activation of NF-kappaB is linked with many types of diseases, including hepatocellular carcinoma (HCC). Our previous report indicated that hepatitis B virus (HBV) induces NF-kappaB activation through NF-kappaB-inducing kinase (NIK), and this can be blocked specifically by interferon (IFN)-gamma. In the present study, we report that HBV expression in HCC cell lines induces drug resistance against 5-fluorouracil (5-FU). This drug resistance was abolished by inhibition of NF-kappaB activation through small interfering RNA-mediated NIK 'knockdown' and IFN-gamma treatment. In addition to the reduced NF-kappaB activation and drug resistance, the upregulated growth arrest- and DNA damage-inducible protein 45beta (Gadd45beta) in HBV-expressing HCC cell lines was downregulated by the small interfering RNA-mediated NIK knockdown and IFN-gamma treatment. The overexpression of Gadd45beta in HCC cell lines also induces drug resistance against 5-FU. Based on our data, we suggest that IFN-gamma treatment might be helpful for chemotherapy in HBV-integrated HCC through inhibition of the NIK-mediated NF-kappaB activation and downregulation of the NF-kappaB target gene Gadd45beta.

Reversal of chemoresistance and enhancement of apoptosis by statins through down-regulation of the NF-kappaB pathway

We recently found that simvastatin can modulate the nuclear factor-kappaB (NF-kappaB) activation pathway, but whether other statins have similar effects to those of simvastatin is unknown. Therefore, we evaluated the effect six different statins on TNF-induced NF-kappaB activation in human myeloid leukemia cells. We then determined whether the combination of statins and standard chemotherapeutic agents could overcome chemoresistance and augment apoptosis. Of the six statins evaluated, only the natural statins (simvastatin, mevastatin, lovastatin, and pravastatin), not the synthetic statins (fluvastatin and atorvastatin), inhibited TNF-induced NF-kappaB activation. Simvastatin suppressed the NF-kappaB activation and potentiated the apoptosis induced by doxorubicin, paclitaxel, and 5-fluorouracil. These results suggest that different statins behave differently from one another and that they may be useful in overcoming chemoresistance.

Indole-3-carbinol-induced modulation of NF-κB signalling is breast cancer cell-specific and does not correlate with cell death

Indole-3-carbinol (I3C), a dietary chemopreventive compound, induces cell death in human breast cancer cells by modulating activities of Src and epidermal growth factor receptor (EGFR). The effect of I3C on NF-kappaB, constitutively activated in breast cancer cells, was investigated. Nuclear extracts of MDA-MB-468, MDA-MB-231 and HBL100 cells contained all of the Rel proteins with similar expression patterns in the latter two. The level of NF-kappaB-regulated reporter gene expression was in the order HBL100 << MDA-MB-468 << MDA-MB-231. Upstream inhibition, using PI3K, EGFR or IKKbeta inhibitors, resulted in cell-specific effects on expression of the NF-kappaB-regulated reporter gene and endogenous genes Bcl-xL, IkappaBalpha and IL-6, as well as on cell viability. The expression patterns of Rel and several NF-kappaB-regulated genes and the response to LY249002 in MDA-MB-468 cells contrasted with those in other cells. I3C induced NF-kappaB-regulated reporter gene expression at 12 h in MDA-MB-468 cells. Conversely, it was reduced at 24 h in HBL100 cells. I3C treatment for 6 h alone or in combination with TNFalpha induced NF-kappaB-regulated reporter gene expression, detected 5 h later, in MDA-MB-468, but not HBL100 cells. I3C induced NF-kappaB p65/p50 DNA binding at 6.5 h, preceded by association of IKKbeta with the Src/EGFR complex and increased phospho-IkappaBalpha in MDA-MB468 cells. TNFalpha increased I3C-induced apoptosis in MDA-MB-468 and MDA-MB-231 cells. It also induced apoptosis, enhanced by I3C, in HBL100 cells. Hence, regulation of constitutive NF-kappaB was cell-specific. I3C influenced the NF-kappaB pathway in a cell-specific manner, which was not related to apoptosis. However, the combination of I3C and TNFalpha increased apoptosis in all cell lines.

Parthenolide induces significant apoptosis and production of reactive oxygen species in high-risk pre-B leukemia cells

We investigated whether parthenolide, the principal bioactive component of the herb feverfew (Tanacetum parthenium) induced apoptosis in pre-B acute lymphoblastic leukemia (ALL) lines, including cells carrying the t(4;11)(q21;q23) chromosomal translocation. Parthenolide induced rapid apoptotic cell death distinguished by loss of nuclear DNA, externalization of cell membrane phosphatidylserine, and depolarization of mitochondrial membranes at concentrations ranging from 5 to 100 microM. Using reactive oxygen species (ROS)-specific dyes, an increase in nitric oxide and superoxide anion was detected in the cells by 4 h after exposure to parthenolide. Parthenolide-induced elevation of hypochlorite anion was observed only in the two t(4;11) lines. These data suggest parthenolide may have potential as a potent and novel therapeutic agent against pre-B ALLs.

Parthenolide, a natural inhibitor of Nuclear Factor-kappaB, inhibits lung colonization of murine osteosarcoma cells

PURPOSE

The transcription factor nuclear factor-kappaB (NF-kappaB) regulates the expression of several genes important for tumor metastasis and is constitutively active in the highly metastatic murine osteosarcoma cell line LM8. Parthenolide, a sesquiterpene lactone, was reported to inhibit the DNA binding of NF-kappaB. The purpose of this study is to investigate the usefulness of parthenolide as target for antimetastatic therapies.

EXPERIMENTAL DESIGN

We examined the effect of parthenolide on metastasis-associated phenotypes in vitro and in murine experimental lung metastasis models by s.c. and i.v. inoculation of LM8 cells.

RESULTS

We found that parthenolide strongly induced apoptosis and inhibited cell proliferation and the expression of vascular endothelial growth factor in vitro. In the in vivo metastasis models, parthenolide treatment suppressed lung metastasis when treatment was initiated concurrently with s.c. or i.v. inoculation of tumor cells, whereas lung metastasis was not reduced when parthenolide was given after the homing of tumor cells. The growth of s.c. tumors that developed at the inoculation site was not suppressed by parthenolide. We also found that the genetic inhibition of NF-kappaB activity by expressing mutant IkappaBalpha suppressed lung metastasis in vivo but not s.c. tumor growth. This supports our notion that the metastasis-preventing effect of parthenolide is mediated at least in part by inhibition of NF-kappaB activity.

CONCLUSIONS

These findings suggested that NF-kappaB is a potential molecular target for designing specific prophylactic interventions against distant metastasis and that parthenolide is a hopeful candidate for an antimetastatic drug.

Nanosized paclitaxel particles from supercritical carbon dioxide processing and their biological evaluation

The rapid expansion of a supercritical solution into a liquid solvent (RESOLV) technique with benign supercritical carbon dioxide was applied to obtain aqueous suspended nanoparticles of the highly potent anticancer drug paclitaxel. The paclitaxel nanoparticles were protected from agglomeration by using a known nontoxic stabilization agent. The aqueous suspended paclitaxel nanoparticles of different average particle sizes were evaluated in vitro against human breast cancer cells. The results suggest that the nanosized paclitaxel particles are effective, with an antineoplastic activity comparable to that of the commercial paclitaxel formulation. The technique should be generally applicable to the processing of nanoparticles from other important drugs with aqueous solubility problems.

The potential of proteasome inhibition in the treatment of colon cancer

Proteasome inhibition is an entirely novel approach to the treatment of malignant disease. By interfering with the ubiquitin-proteasome degradation system, proteasome inhibitors affect numerous cellular processes that are commonly deregulated in cancer cells including gene transcription, cell-cycle regulation, apoptosis, cell migration and DNA repair. This review outlines the physiology of the ubiquitin-proteasome pathway, discusses preclinical and clinical data regarding the activity of proteasome inhibitors against colon cancer and evaluates the rationale for the use of proteasome inhibitors as monotherapy or in combination with other anticancer therapies (i.e., chemotherapy, radiation therapy and other molecular-targeted therapies) in colon cancer.

NF-kappaB as a potential molecular target for cancer therapy

Nuclear factor kappaB (NF-kappaB), a transcription factor, plays an important role in carcinogenesis as well as in the regulation of immune and inflammatory responses. NF-kappaB induces the expression of diverse target genes that promote cell proliferation, regulate apoptosis, facilitate angiogenesis and stimulate invasion and metastasis. Furthermore, many cancer cells show aberrant or constitutive NF-kappaB activation which mediates resistance to chemo- and radio-therapy. Therefore, the inhibition of NF-kappaB activation and its signaling pathway offers a potential cancer therapy strategy. In addition, recent studies have shown that NF-kappaB can also play a tumor suppressor role in certain settings. In this review, we focus on the role of NF-kappaB in carcinogenesis and the therapeutic potential of targeting NF-kappaB in cancer therapy.

Reversal of drug resistance in breast cancer cells by transglutaminase 2 inhibition and nuclear factor-kappaB inactivation

Induction of transglutaminase 2 (TGase 2) by epidermal growth factor (EGF) in human breast cancer cells increases their oncogenic potential and chemoresistance. The role of TGase 2 in the development of these tumor-related phenotypes remains to be elucidated, but it has been shown that expression of a dominant-negative form of TGase 2 reverses EGF-mediated chemoresistance in breast cancer cells. We examined several different breast cancer cell lines, representing both EGF receptor (EGFR)-positive and EGFR-negative breast cancers, and found that doxorubicin-resistant cells had a higher level of TGase 2 compared with doxorubicin-sensitive cells independent of the EGFR expression level. TGase 2 inhibition increased the chemosensitivity of drug-resistant cells, concomitant with a decrease in nuclear factor-kappaB (NF-kappaB) activity. Increasing the level of TGase 2 in drug-sensitive cells by transient transfection reduced the level of inhibitory subunit alpha of NF-kappaB (IkappaBalpha) and increased NF-kappaB activity in these cells. Inhibition of TGase 2 in drug-resistant cells by RNA interference increased the levels of IkappaBalpha, and this correlated with a shift in the accumulation of NF-kappaB from the nucleus to the cytosol. We recently showed that TGase 2 activated NF-kappaB through polymerization and depletion of free IkappaBalpha during inflammation. Therefore, increased expression of TGase 2 and subsequent activation of NF-kappaB may contribute to drug resistance in breast cancer cells independently of EGF signaling.

Preadministration of high-dose salicylates, suppressors of NF-kappaB activation, may increase the chemosensitivity of many cancers: an example of proapoptotic signal modulation therapy

NF-kappaB activity is elevated in a high proportion of cancers, particularly advanced cancers that have been treated previously. Cytotoxic treatment selects for such up-regulation inasmuch as NF-kappaB promotes transcription of a large number of proteins that inhibit both the intrinsic and extrinsic pathways of apoptosis; NF-kappaB also boosts expression of mdr1, which expels many drugs from cells. Indeed, high NF-kappaB activity appears to be largely responsible for the chemo- and radioresistance of many cancers. Thus, agents that suppress NF-kappaB activity should be useful as adjuvants to cytotoxic cancer therapy. Of the compounds that are known to be NF-kappaB antagonists, the most practical for current use may be the nonsteroidal anti-inflammatory drugs aspirin, salicylic acid, and sulindac, each of which binds to and inhibits Ikappa kinase- beta, a central mediator of NF-kappa activation; the low millimolar plasma concentrations of salicylate required for effective inhibition of this kinase in vivo can be achieved with high-dose regimens traditionally used to manage rheumatic disorders. The gastrointestinal toxicity of such regimens could be minimized by using salsalate or enteric-coated sodium salicy-late or by administering misoprostol in conjunction with aspirin therapy. Presumably, best results would be seen if these agents were administered for several days prior to a course of chemo- or radiotherapy, continuing throughout the course. This concept should first be tested in nude mice bearing xenografts of chemoresistant human tumors known to have elevated NF-kappa activity. Ultimately, more complex adjuvant regimens can be envisioned in which salicylates are used in conjunction with other NF-kappa antagonists and/or agents that target other mediators of down-regulated apoptosis in cancer, such as Stat3; coadministration of salicylate and organic selenium may have intriguing potential in this regard. These strategies may also have potential as adjuvants to metronomic chemotherapy, which seeks to suppress angio-genesis by targeting cycling endothelial cells in tumors.

Feverfew: weeding out the root of leukaemia

Malignant stem cells are central to the pathogenesis and perpetuation of acute myelogenous leukaemia (AML). Despite their crucial role, standard chemotherapy often does not target these critical cells and, thus, the 'root' of leukaemic disease is not eradicated. To derive better therapies, unique molecular features of malignant stem cells have been characterised for AML and evaluated with regard to ablation of disease. In the course of such studies, the compound parthenolide, which is derived from the medicinal plant feverfew, has recently been shown to preferentially induce AML stem cells to undergo apoptosis. Importantly, parthenolide had no discernable effect on normal blood cells. Thus, this naturally occurring agent may provide new avenues of investigation for the treatment of leukaemia. In this article, characteristics of parthenolide are reviewed.

Restoring chemotherapy and hormone therapy sensitivity by parthenolide in a xenograft hormone refractory prostate cancer model

BACKGROUND

Nuclear Factor kappa B (NFkappaB) is a eukaryotic transcription factor that is constitutively active in human cancers and can be inhibited by the naturally occurring sesquiterpene lactone, parthenolide (P).

METHODS

The in vitro effects of P were assessed using the androgen independent cell line, CWR22Rv1, and human umbilical endothelial cells (HUVECs). The in vivo activity of P as a single agent and its ability to augment the efficacy of docetaxel and the anti-androgen, bicalutamide, were determined using the CWR22Rv1 xenograft model.

RESULTS

Parthenolide at low micromolar concentration inhibited proliferation of CWR22Rv1 and HUVEC cells, promoted apoptosis and abrogated NFkappaB-DNA binding. Parthenolide downregulated anti-apoptotic genes under NFkappaB control, TRAF 1 and 2, and promoted sustained activation of c-jun-NH2 kinase (JNK). Parthenolide also augmented the in vivo efficacy of docetaxel and restored sensitivity to anti-androgen therapy.

CONCLUSION

These studies demonstrate parthenolide's anti-tumor and anti-angiogenic activity, and its potential to augment the efficacy of chemotherapy and hormonal therapy.

Inhibition of nuclear factor-κB by an antioxidant enhances paclitaxel sensitivity in ovarian carcinoma cell line

The objective of this study was to determine whether paclitaxel and a strong antioxidant, pyrrolidinedithiocarbamate (PDTC), can affect the activation of nuclear factor-kappa B (NF-kappaB) in SKOV-3 human ovarian cancer cell line and the effect of these two agents on the growth and apoptosis of the cancer cells. The cells were treated with various concentrations of paclitaxel and/or PDTC at various time intervals. Following treatments, cell growth and apoptosis were determined by 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulphonyl)-2H-tetrazolium (WST-8) (WST) assay and flow cytometry, respectively. Western blot assay was used to determine the nuclear p65 protein and cytoplasmic IkappaB-alpha protein. High doses of PDTC significantly inhibited the growth of SKOV-3 cells and caused apoptosis. Paclitaxel and lower doses of PDTC combined demonstrated additive inhibition of cell growth and increased levels of apoptosis. Treatment of paclitaxel alone showed increased nuclear p65 protein and decreased cytoplasmic IkappaB-alpha protein expression, while pretreatment of PDTC reversed this function. PDTC blocks the paclitaxel-induced activation of NF-kappaB leading to increased chemosensitivity to paclitaxel and enhanced apoptosis. Combining antioxidants and paclitaxel has significant potential to overcome the risk of paclitaxel resistance.

Induction of apoptosis in estrogen receptor-negative breast cancer cells by natural and synthetic cyclopentenones: role of the IkappaB kinase/nuclear factor-kappaB pathway

Nuclear factor-kappaB (NF-kappaB), a transcription factor with a critical role in promoting inflammation and cell survival, is constitutively activated in estrogen-receptor (ER)-negative breast cancer and is considered a potential therapeutic target for this type of neoplasia. We have previously demonstrated that cyclopentenone prostaglandins are potent inhibitors of NF-kappaB activation by inflammatory cytokines, mitogens, and viral infection, via direct binding and modification of the beta subunit of the IkappaB kinase complex (IKK). Herein, we describe the NF-kappaB-dependent anticancer activity of natural and synthetic cyclopentenone IKK inhibitors. We demonstrate that the natural cyclopentenone 15-deoxy-Delta(12,14)prostaglandin J(2) (15d-PGJ(2)) is a potent inhibitor of constitutive IkappaB-kinase and NF-kappaB activities in chemotherapy-resistant ER-negative breast cancer cells. 15d-PGJ(2)-induced inhibition of NF-kappaB function is rapidly followed by down-regulation of NF-kappaB-dependent antiapoptotic proteins cIAPs 1/2, Bcl-X(L), and cellular FLICE-inhibitory protein, leading to caspase activation and induction of apoptosis in breast cancer cells resistant to treatment with paclitaxel and doxorubicin. We then demonstrate that the cyclopentenone ring structure is responsible for these activities, and we identify a new synthetic cyclopentenone derivative, 3-tert-butyldimethylsilyloxy-5-(E)-iso-propylmethylenecyclopent-2-enone (CTC-35), as a potent NF-kappaB inhibitor with proapoptotic activity in ER-negative breast cancer cells. The results open new perspectives in the search for novel proapoptotic molecules effective in the treatment of cancers presenting aberrant NF-kappaB regulation.

Parthenolide cooperates with NS398 to inhibit growth of human hepatocellular carcinoma cells through effects on apoptosis and G0-G1 cell cycle arrest

Chemotherapy to date has not been effective in the treatment of human hepatocellular carcinoma. More effective treatment strategies may involve combinations of agents with activity against hepatocellular carcinoma. Parthenolide, a nuclear factor-kappaB (NF-kappaB) inhibitor, and NS398, a cyclooxygenase (COX)-2 inhibitor, have been shown to individually suppress the growth of hepatocellular carcinoma cells in vitro. To investigate their effects in combination, three human hepatocellular carcinoma lines (Hep3B, HepG2, and PLC) were treated with parthenolide and/or NS398. Parthenolide (0.1-10 micromol/L) and NS398 (1-100 micromol/L) each caused concentration-dependent growth inhibition in all cell lines. The addition of parthenolide to NS398 reduced the concentration of NS398 required to inhibit hepatocellular carcinoma growth. Because parthenolide and COX-2 inhibitors have been reported to influence NF-kappaB activity, the effects on this pathway were investigated. The combination of parthenolide/NS398 inhibited phosphorylation of the NF-kappaB-inhibitory protein IkappaBalpha and increased total IkappaBalpha levels. NF-kappaB DNA-binding and transcriptional activities were inhibited more by the combination than the single agents in Hep3B and HepG2 cells but not in PLC cells. The response of PLC cells to NS398 was augmented by p65 small interfering RNA to inhibit NF-kappaB p65 protein expression. The combination of parthenolide/NS398 increased apoptosis only in PLC cells, suggesting that the combination may decrease the apoptotic threshold in these cells. In Hep3B and HepG2 cells, combination treatment with NS398/parthenolide altered the cell cycle distribution resulting in more G0-G1 accumulation. Cyclin D1 levels were further decreased by combination treatment in all cell lines, correlating with the cell cycle alterations. Our results suggest that parthenolide may be effective in combination with COX-2 inhibitors for the treatment of hepatocellular carcinoma.

Novel targets in gastric and esophageal cancer

Esophageal cancer (EC) and gastric cancer (GC) constitute a major cause of cancer deaths worldwide. Recent improvements in both surgical techniques and adjuvant/neoadjuvant chemotherapy, radiotherapy or both have increased the survival of patients with loco-regional disease. However, most patients with GC or EC have advanced disease either at diagnosis or during the follow-up, and despite recent advances, these patients still do poorly. Understanding of the molecular pathways that characterize cell growth, cell cycle, apoptosis, angiogenesis and invasion has provided novel targets in cancer therapy. In this review we describe the current status of targeted therapies in the treatment of EC and GC, including EGFR inhibitors, antiangiogenic agents, cell cycle inhibitors, apoptosis promoters and matrix metalloproteinases inhibitors. The emerging data from the clinical development of these compounds has provided novel opportunities in the treatment of EC and GC that will probably translate into clinical benefit for patients with these common malignancies.

A molecular correlate to the Gleason grading system for prostate adenocarcinoma

Adenocarcinomas of the prostate can be categorized into tumor grades based on the extent to which the cancers histologically resemble normal prostate glands. Because grades are surrogates of intrinsic tumor behavior, characterizing the molecular phenotype of grade is of potential clinical importance. To identify molecular alterations underlying prostate cancer grades, we used microdissection to obtain specific cohorts of cancer cells corresponding to the most common Gleason patterns (patterns 3, 4, and 5) from 29 radical prostatectomy samples. We paired each cancer sample with matched benign lumenal prostate epithelial cells and profiled transcript abundance levels by microarray analysis. We identified an 86-gene model capable of distinguishing low-grade (pattern 3) from high-grade (patterns 4 and 5) cancers. This model performed with 76% accuracy when applied to an independent set of 30 primary prostate carcinomas. Using tissue microarrays comprising >800 prostate samples, we confirmed a significant association between high levels of monoamine oxidase A expression and poorly differentiated cancers by immunohistochemistry. We also confirmed grade-associated levels of defender against death (DAD1) protein and HSD17 beta4 transcripts by immunohistochemistry and quantitative RT-PCR, respectively. The altered expression of these genes provides functional insights into grade-associated features of therapy resistance and tissue invasion. Furthermore, in identifying a profile of 86 genes that distinguish high- from low-grade carcinomas, we have generated a set of potential targets for modulating the development and progression of the lethal prostate cancer phenotype.

Attenuation of mitogen- and stress-activated protein kinase-1-driven nuclear factor-kappaB gene expression by soy isoflavones does not require estrogenic activity

We have analyzed in molecular detail how soy isoflavones (genistein, daidzein, and biochanin A) suppress nuclear factor-kappaB (NF-kappaB)-driven interleukin-6 (IL6) expression. In addition to its physiologic immune function as an acute stress cytokine, sustained elevated expression levels of IL6 promote chronic inflammatory disorders, aging frailty, and tumorigenesis. Our results in estrogen-unresponsive fibroblasts, mitogen- and stress-activated protein kinase (MSK) knockout cells, and estrogen receptor (ER)-deficient breast tumor cells show that phytoestrogenic isoflavones can selectively block nuclear NF-kappaB transactivation of specific target genes (in particular IL6), independently of their estrogenic activity. This occurs via attenuation of mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase (MEK) and ERK activity, which further down-regulates MSK-dependent NF-kappaB p65 and histone H3 phosphorylation. As constitutive NF-kappaB and MSK activity are hallmarks of aggressive metastatic ER-deficient breast cancer, the MSK signaling pathway may become an attractive target for chemotherapy.

Isocostunolide, a sesquiterpene lactone, induces mitochondrial membrane depolarization and caspase-dependent apoptosis in human melanoma cells

Isocostunolide is a sesquiterpene lactone isolated from the roots of Inula helenium. Its chemical structure was determined by NMR and FAB-MS spectra. No biological activities of this compound have yet been reported. In this study, we found isocostunolide could effectively induce cytotoxicity in three cancer cell lines (A2058, HT-29, and HepG2), with an IC(50) of 3.2, 5.0, and 2.0 micro g/mL, respectively. DNA flow cytometric analysis indicated that isocostunolide actively induced apoptosis of cancer cells accompanied by a marked loss of G0/G1 phase cells. To address the mechanism of the apoptotic effect of isocostunolide, we analyzed the induction of apoptosis-related proteins in A2058. The levels of pro-caspase-8, Bid, pro-caspase-3, and poly(ADP-ribose) polymerase (PARP) decreased. However, the level of Fas was increased markedly in a dose-dependent manner. Furthermore, this compound markedly induced a depolarization of mitochondrial membranes to facilitate cytochrome c release into cytosol. The findings suggest that isocostunolide may activate a mitochondria-mediated apoptosis pathway. To address this, we found that isocostunolide-induced loss of mitochondrial membrane potential occurred via modulation of the Bcl-2 family proteins. The production of intracellular reactive oxygen species (ROS) in A2058 was not elicited. In summary, for the first time, we have isolated and characterized isocostunolide from I. helenium. This compound induces apoptosis through a mitochondria-dependent pathway in A2058 cells.

Constitutive activation of NF-kappaB in human hepatocellular carcinoma: evidence of a cytoprotective role

Activation of nuclear factor-kappaB (NF-kappaB) can promote or inhibit apoptosis. Oxidative stress is an important mechanism by which certain anticancer drugs kill cancer cells, and is also one of the mechanisms that activate NF-kappaB. We therefore examined hepatic expression of the NF-kappaB monomer p65 in human hepatocellular carcinoma (HCC) tissue samples from eight patients and compared it with their respective samples of surrounding liver tissues. We also studied the effect of NF-kappaB inhibition in human HCC cells exposed to oxidative stress, by infecting HuH7 cells with a recombinant adenovirus carrying mutant IkappaBalpha (mIkappaBalpha). Cultured HuH7 cells were infected with mIkappaBalpha or beta-galactosidase (beta-Gal) for 24 hr followed by treatment with increasing concentrations of H2O2. Cytotoxicity, NF-kappaB translocation, NF-kappaB DNA binding, cell proliferation, and apoptosis were determined. The monomer p65 was overexpressed in six of eight human HCC tissues. In HuH7 cells, introduction of mIkappaBalpha potently inhibited the translocation, activation, and DNA binding of NF- kappaB. In control (beta-Gal-infected) HuH7 cells, exposure to H2O2 produced a dose-dependent increase in apoptosis, regardless of NF-kappaB status. mIkappaBalpha-mediated inhibition of NF-kappaB activation sensitized HuH7 cells to H2O2-induced inhibition of cell growth, and further promoted cell death. Addition of H2O2 (200-500 microM) to control or mIkappaBalpha-infected HuH7 cells enhanced caspase-3 activity and cleavage. Adenovirus-mediated transfer of mIkappaBalpha potently inhibits NF-kappaB activity in HuH7 cells, and this enhances oxidative stress-induced cell killing.

Microtubule stabilizing agents: Their molecular signaling consequences and the potential for enhancement by drug combination

Microtubule stabilization by chemotherapy is a powerful weapon in the war against cancer. Disruption of the mitotic spindle activates a number of signaling pathways, with consequences that may protect the cell or lead to its death via apoptosis. Taxol, the first microtubule stabilizing drug to be identified, has been utilized successfully in the treatment of solid tumors for two decades. Several features, however, make this drug less than ideal, and the search for next generation stabilizing drugs with increased efficacy has been intense and fruitful. Microtubule stabilizing agents (MSAs), including the taxanes, the epothilones, discodermolide, laulimalide, and eleutherobin, form an important and expanding family of chemotherapeutic agents. A strong understanding of their molecular signaling consequences is essential to their value, particularly in regard to their potential for combinatorial chemotherapy - the use of multiple agents to enhance the efficacy of cancer treatment. Here we present a critical review of research on the signaling mechanisms induced by MSAs, their relevance to apoptosis, and their potential for exploitation by combinatorial therapy.

Antiproliferative Activities of Parthenolide and Golden Feverfew Extract Against Three Human Cancer Cell Lines

The medicinal herb feverfew [Tanacetum parthenium (L.) Schultz-Bip.] has long been used as a folk remedy for the treatment of migraine and arthritis. Parthenolide, a sesquiterpene lactone, is considered to be the primary bioactive compound in feverfew having anti-migraine, anti-tumor, and anti-inflammatory properties. In this study we determined, through in vitro bioassays, the inhibitory activity of parthenolide and golden feverfew extract against two human breast cancer cell lines (Hs605T and MCF-7) and one human cervical cancer cell line (SiHa). Feverfew ethanolic extract inhibited the growth of all three types of cancer cells with a half-effective concentration (EC50) of 1.5 mg/mL against Hs605T, 2.1 mg/mL against MCF-7, and 0.6 mg/mL against SiHa. Among the tested constituents of feverfew (i.e., parthenolide, camphor, luteolin, and apigenin), parthenolide showed the highest inhibitory effect with an EC50 against Hs605T, MCF-7, and SiHa of 2.6 microg/mL, 2.8 microg/mL, and 2.7 microg/mL, respectively. Interactions between parthenolide and flavonoids (apigenin and luteolin) in feverfew extract also were investigated to elucidate possible synergistic or antagonistic effects. The results revealed that apigenin and luteolin might have moderate to weak synergistic effects with parthenolide on the inhibition of cancer cell growth of Hs605T, MCF-7, and SiHa.