Cells lacking IKKα show nuclear cyclin D1 overexpression and a neoplastic phenotype: role of IKKα as a tumor suppressor.

The catalytic subunits of IκB kinase (IKK) complex, IKKα and IKKβ, are involved in activation of NF-κB and in mediating a variety of other biological functions. Though these proteins have a high-sequence homology, IKKα exhibits different functional characteristics as compared with IKKβ. Earlier, we have shown that cyclin D1 is overexpressed and predominantly localized in the nucleus of IKKα(-/-) cells, indicating that IKKα regulates turnover and subcellular distribution of cyclin D1, which is mediated by IKKα-induced phosphorylation of cyclin D1.

Soluble and insoluble nickel compounds exert a differential inhibitory effect on cell growth through IKKalpha-dependent cyclin D1 down-regulation.

It is well-known that insoluble nickel compounds possess much more potent carcinogenic activities as compared with soluble nickel compounds. Although it is assumed that the different entry and clearance rate are responsible for the difference, the mechanisms underlying the different carcinogenic activities are still not well understood yet. In the present study, we found that exposure to soluble, but not insoluble nickel compounds, caused a significant inhibition of cell growth and G1/G0 cell cycle arrest, which was concomitant with a marked down-regulation of cylin D1, an essential nuclear protein for controlling G1/S transition, while both soluble and insoluble nickel compounds showed similar effects on NFkappaB activation, HIF-1alpha protein accumulation and TNF-alpha transcription and CAP43 protein expression at same doses range.

Phase I dose escalation study with irinotecan, capecitabine, epirubicin, and granulocyte colony-stimulating factor support for patients with solid malignancies.

Objectives: Preclinical studies using sequences of topoisomerase I and II inhibitors suggested synergism; preliminary clinical studies, resulting in enhanced antitumor responses, confirm this in selected malignancies. This study determined the maximum-tolerated dose (MTD), toxicity, and pharmacokinetics of irinotecan (CPT-11), capecitabine, and epirubicin in patients with metastatic adenocarcinoma of lung, breast, or gastrointestinal tract. Correlation of topoisomerase IIbeta was also done.

Efficacy of sequential treatment of HCT116 colon cancer monolayers and xenografts with docetaxel, flavopiridol, and 5-fluorouracil.

Aim: Clinical treatment of solid tumors with docetaxel, flavopiridol, or 5-fluorouracil (5-FU) often encounters undesirable side effects and drug resistance. This study aims to evaluate the potential role of combination therapy with docetaxel, flavopiridol, or 5-FU in modulating chemosensitivity and better understand how they might be used clinically.

Methods: HCT116 colon cancer cells were treated with docetaxel, flavopiridol, and 5-FU in several different administrative schedules in vitro, either sequentially or simultaneously.

IkappaB kinase alpha regulates subcellular distribution and turnover of cyclin D1 by phosphorylation.

IkappaB kinases (IKKs), IKKalpha and IKKbeta, with a regulatory subunit IKKgamma/NEMO constitute a high molecular weight IKK complex that regulates NF-kappaB activity. Although IKKalpha and IKKbeta share structural and biochemical similarities, IKKalpha has been shown to have distinct biological roles. Here we show that IKKalpha plays a critical role in regulating cyclin D1 during the cell cycle.

Enhanced chemosensitivity to irinotecan by RNA interference-mediated down-regulation of the nuclear factor-kappaB p65 subunit.

In preclinical tumor models, inhibition of nuclear factor-kappaB (NF-kappaB) has been associated with increased sensitivity to chemotherapeutic agents such as irinotecan (CPT-11). This is based on the fact that a variety of chemotherapy agents such as CPT-11 activate NF-kappaB to result in the expression of genes such as c-IAP1 and c-IAP2 that might be responsible for the inhibition of chemotherapy-induced apoptosis. In this study, RNA interference [small interfering RNA (siRNA)] was used to down-regulate the NF-kappaB p65 subunit in the HCT116 colon cancer cell line, and its role, in the presence and absence of CPT-11, was assessed on cell growth and apoptosis.

Nuclear role of I kappa B Kinase-gamma/NF-kappa B essential modulator (IKK gamma/NEMO) in NF-kappa B-dependent gene expression.

The I kappa B kinase (IKK) complex, which is composed of the two kinases IKK alpha and IKK beta and the regulatory subunit IKK gamma/nuclear factor-kappa B (NF-kappa B) essential modulator (NEMO), is important in the cytokine-induced activation of the NF-kappa B pathway. In addition to modulation of IKK activity, the NF-kappa B pathway is also regulated by other processes, including the nucleocytoplasmic shuttling of various components of this pathway and the post-translational modification of factors bound to NF-kappa B-dependent promoters. In this study, we explored the role of the nucleocytoplasmic shuttling of components of the IKK complex in the regulation of the NF-kappa B pathway.

Histone H3 phosphorylation by IKK-alpha is critical for cytokine-induced gene expression.

Cytokine-induced activation of the IkappaB kinases (IKK) IKK-alpha and IKK-beta is a key step involved in the activation of the NF-kappaB pathway. Gene-disruption studies of the murine IKK genes have shown that IKK-beta, but not IKK-alpha, is critical for cytokine-induced IkappaB degradation. Nevertheless, mouse embryo fibroblasts deficient in IKK-alpha are defective in the induction of NF-kappaB-dependent transcription.

Small interfering RNAs directed against beta-catenin inhibit the in vitro and in vivo growth of colon cancer cells.

The beta-catenin and APC genes are key components of the Wnt signaling pathway. Mutation of these genes results in increased levels of the beta-catenin protein, which is associated with enhanced cellular proliferation and the development of both colon polyps and colon cancer. Recently, a technique known as RNA interference has been successfully adapted to mammalian cells so that it is now possible to specifically decrease the expression of cellular genes after transfection of annealed small interfering 21-mer RNAs.

Sulindac enhances tumor necrosis factor-alpha-mediated apoptosis of lung cancer cell lines by inhibition of nuclear factor-kappaB.

Programmed cell death (apoptosis) is induced by certain anticancer therapies, and resistance to apoptosis is a major mechanism by which tumors evade these therapies. The transcription factor nuclear factor (NF)-kappaB, which is frequently activated by treatment of cancer cells with different chemotherapeutic agents, promotes cell survival, whereas its inhibition leads to enhanced apoptosis. Recently, sulindac and other nonsteroidal anti-inflammatory drugs have been shown to inhibit tumor necrosis factor (TNF)-alpha-mediated NF-kappaB activation.