The IKK Inhibitor BMS-345541 Affects Multiple Mitotic Cell Cycle Transitions

FKBP4 integrates FKBP4/Hsp90/IKK with FKBP4/Hsp70/RelA complex to promote lung adenocarcinoma progression via IKK/NF-κB signaling

FKBP4 belongs to the family of immunophilins, which serve as a regulator for steroid receptor activity. Thus, FKBP4 has been recognized to play a critical role in several hormone-dependent cancers, including breast and prostate cancer. However, there is still no research to address the role of FKBP4 on lung adenocarcinoma (LUAD) progression. We found that FKBP4 expression was elevated in LUAD samples and predicted significantly shorter overall survival based on TCGA and our cohort of LUAD patients. Furthermore, FKBP4 robustly increased the proliferation, metastasis, and invasion of LUAD in vitro and vivo. Mechanistic studies revealed the interaction between FKBP4 and IKK kinase complex. We found that FKBP4 potentiated IKK kinase activity by interacting with Hsp90 and IKK subunits and promoting Hsp90/IKK association. Also, FKBP4 promotes the binding of IKKγ to IKKβ, which supported the facilitation role in IKK complex assembly. We further identified that FKBP4 TPR domains are essential for FKBP4/IKK interaction since its association with Hsp90 is required. In addition, FKBP4 PPIase domains are involved in FKBP4/IKKγ interaction. Interestingly, the association between FKBP4 and Hsp70/RelA favors the transport of RelA toward the nucleus. Collectively, FKBP4 integrates FKBP4/Hsp90/IKK with FKBP4/Hsp70/RelA complex to potentiate the transcriptional activity and nuclear translocation of NF-κB, thereby promoting LUAD progression. Our findings suggest that FKBP4 may function as a prognostic biomarker of LUAD and provide a newly mechanistic insight into modulating IKK/NF-κB signaling.

Intra-articular administration of IκBα kinase inhibitor suppresses mouse knee osteoarthritis via downregulation of the NF-κB/HIF-2α axis

Activation of NF-κB signaling promotes osteoarthritis (OA) through the transcriptional induction of Hif-2α and catabolic enzymes. This study sought to examine whether inhibiting IκBα kinase (IKK) could suppress the development of surgically-induced OA of the knee in a mouse model. We employed BMS-345541 (4(2′-aminoethyl) amino-1, 8-dimethylimidazo (1,2-a) quinoxaline) as a selective inhibitor of the subunits of IKK. OA was created by resecting the medial collateral ligament and the medial meniscus in the knees of mice. The mice were then treated with an intra-articular injection of BMS-345541 (50 nM to 500 µM) or vehicle three times a week for 8 weeks. We found that the intra-articular administration of 500 nM and 5 µM BMS-345541 significantly suppressed OA development. In the BMS-345541-treated cartilage, there was a decrease in the phosphorylation of IκBα and the expression of Hif-2α, Mmp13, and Adamts5. In human articular chondrocytes, the IL-1β-enhanced expression of Hif-2α and catabolic factors were decreased by BMS-345541 treatment in dose-dependent manner. We conclude that the intra-articular administration of BMS-345541 at some concentrations may suppress the development of OA by downregulating signaling through the NF-κB–Hif-2α axis.

Phosphorylation of Xenopus p31(comet) potentiates mitotic checkpoint exit

p31^comet plays an important role in spindle assembly checkpoint (SAC) silencing. However, how p31^comet's activity is regulated remains unclear. Here we show that the timing of M-phase exit in Xenopus egg extracts (XEEs) depends upon SAC activity, even under conditions that are permissive for spindle assembly. p31^comet antagonizes the SAC, promoting XEE progression into anaphase after spindles are fully formed. We further show that mitotic p31^comet phosphorylation by Inhibitor of nuclear factor κ-B kinase-β (IKK-β) enhances this role in SAC silencing. Together, our findings implicate IKK-β in the control of anaphase timing in XEE through p31^comet activation and SAC downregulation.

NF-κB and the cell cycle

The NF-κB (nuclear factor κB) transcription factor family is a pleiotropic regulator of many cellular pathways, providing a mechanism for the cell to respond to a wide variety of stimuli and environmental challenges. It is not surprising therefore that an important component of NF-κB's function includes regulation of the cell cycle. However, this aspect of its behaviour is often overlooked and receives less attention than its ability to induce inflammatory gene expression. In the present article, we provide an updated review of the current state of our knowledge about integration of NF-κB activity with cell cycle regulation, including newly characterized direct and indirect target genes in addition to the mechanisms through which NF-κB itself can be regulated by the cell cycle.

The hypoxia-inducible transcription factor ZNF395 is controlled by IĸB kinase-signaling and activates genes involved in the innate immune response and cancer

Activation of the hypoxia inducible transcription factor HIF and the NF-ĸB pathway promotes inflammation-mediated tumor progression. The cellular transcription factor ZNF395 has repeatedly been found overexpressed in various human cancers, particularly in response to hypoxia, implying a functional relevance. To understand the biological activity of ZNF395, we identified target genes of ZNF395 through a genome-wide expression screen. Induced ZNF395 expression led to the upregulation of genes known to play a role in cancer as well as a subset of interferon (IFN)-stimulated genes (ISG) involved in antiviral responses such as IFIT1/ISG56, IFI44 and IFI16. In cells that lack ZNF395, the IFN-α-mediated stimulation of these factors was impaired, demonstrating that ZNF395 is required for the full induction of these antiviral genes. Transient transfections revealed that ZNF395-mediated activation of the IFIT1/ISG56 promoter depends on the two IFN-stimulated response elements within the promoter and on the DNA-binding domain of ZNF395, a so-called C-clamp. We also show that IĸBα kinase (IKK)-signaling is necessary to allow ZNF395 to activate transcription and simultaneously enhances its proteolytic degradation. Thus, ZNF395 becomes activated at the level of protein modification by IKK. Moreover, we confirm that the expression of ZNF395 is induced by hypoxia. Our results characterize ZNF395 as a novel factor that contributes to the maximal stimulation of a subset of ISGs. This transcriptional activity depends on IKK signaling further supporting a role of ZNF395 in the innate immune response. Given these results it is possible that under hypoxic conditions, elevated levels of ZNF395 may support inflammation and cancer progression by activating the target genes involved in the innate immune response and cancer.

Discovery of 6-aryl-7-alkoxyisoquinoline inhibitors of IkappaB kinase-beta (IKK-beta)

The identification and progression of a potent and selective series of isoquinoline inhibitors of IkappaB kinase-beta (IKK-beta) are described. Hit-generation chemistry based on IKK-beta active-site knowledge yielded a weakly potent but tractable chemotype that was rapidly progressed into a series with robust enzyme and cellular activity and significant selectivity over IKK-alpha.

4-Phenyl-7-azaindoles as potent and selective IKK2 inhibitors

The synthesis and SAR of a novel series of IKK2 inhibitors are described. Modification around the hinge binding region of the 7-azaindole led to a series of potent and selective inhibitors with good cellular activity.

IRF6 in development and disease: a mediator of quiescence and differentiation

Post utero development of the mammary gland is a complex developmental process characterized by states of rapid cell proliferation (branching morphogenesis) followed by functional differentiation (lactation) and the consequent apoptosis (involution) of the secretory mammary epithelial cell. This process is cyclical, such that involution returns the mammary gland to a near-virgin-like state capable of responding to morphogenic cues with each consecutive pregnancy. Importantly, many of the regulatory processes which oversee mammary gland development are corrupted or otherwise compromised during the development of breast cancer. For example, Interferon Regulatory Factor 6 (IRF6) is a novel protein with growth inhibitory properties that was initially identified in mammary epithelial cells through its interaction with maspin, a known tumor suppressor in normal breast tissue. Recent findings from our laboratory suggest that IRF6 functions synergistically with maspin to regulate mammary epithelial cell differentiation by acting on the cell cycle. This perspective focuses on the possible involvement of IRF6 in promoting differentiation by regulating exit from the cell cycle and entry into the G(0) phase of cellular quiescence, and how these new findings shed light on normal mammary gland development and the initiation and progression of breast cancer.