ESM-1 regulates cell growth and metastatic process through activation of NF-κB in colorectal cancer

In our previous study, we reported that endothelial cell specific molecule-1 (ESM-1) was increased in tissue and serum from colorectal cancer patients and suggested that ESM-1 can be used as a potential serum marker for early detection of colorectal cancer. The aim of this study was to evaluate the role of ESM-1 as an intracellular molecule in colorectal cancer. ESM-1 expression was knocked down by small interfering RNA (siRNA) in colorectal cancer cells. Expression of ESM-1 siRNA decreased cell survival through the Akt-dependent inhibition of NF-κB/IκB pathway and an interconnected reduction in phospho-Akt, -p38, -ERK1, -RSK1, -GSK-3α/β and -HSP27, as determined by a phospho-MAPK array. ESM-1 silencing induced G(1) phase cell cycle arrest by induction of PTEN, resulting in the inhibition of cyclin D1 and inhibited cell migration and invasion of COLO205 cells. Consistently, ESM-1 overexpression in HCT-116 cells enhanced cell proliferation through the Akt-dependent activation of NF-κB pathway. In addition, ESM-1 interacted with NF-κB and activated NF-κB promoter. This study demonstrates that ESM-1 is involved in cell survival, cell cycle progression, migration, invasion and EMT during tumor invasion in colorectal cancer. Based on our results, ESM-1 may be a useful therapeutic target for colorectal cancer.     

The IκB kinase complex in NF-κB regulation and beyond

The IκB kinase (IKK) complex is the signal integration hub for NF-κB activation. Composed of two serine-threonine kinases (IKKα and IKKβ) and the regulatory subunit NEMO (also known as IKKγ), the IKK complex integrates signals from all NF-κB activating stimuli to catalyze the phosphorylation of various IκB and NF-κB proteins, as well as of other substrates. Since the discovery of the IKK complex components about 15 years ago, tremendous progress has been made in the understanding of the IKK architecture and its integration into signaling networks. In addition to the control of NF-κB, IKK subunits mediate the crosstalk with other pathways, thereby extending the complexity of their biological function. This review summarizes recent advances in IKK biology and focuses on emerging aspects of IKK structure, regulation and function.     

Proteasome inhibitor-I enhances tunicamycin-induced chemosensitization of prostate cancer cells through regulation of NF-κB and CHOP expression

Although endoplasmic reticulum (ER) stress induction by some anticancer drugs can lead to apoptotic death of cancer cells, combination therapy with other chemicals would be much more efficient. It has been reported that proteasome inhibitors could induce cancer cell death through ER-stress. Our study, however, showed a differential mechanism of proteasome inhibitor-I (Pro-I)-induced cell death. Pro-I significantly enhanced apoptotic death of PC3 prostate cancer cells pretreated with tunicamycin (TM) while other signaling inhibitors against p38, mitogen activated kinase (MEK) and phosphatidyl-inositol 3-kinase (PI3K) did not, as evidenced by cell proliferation and cell cycle analyses. NF-κB inhibition by Pro-I, without direct effect on ER-stress, was found to be responsible for the TM-induced chemosensitization of PC3 cells. Moreover, TM-induced/enhancer-binding protein (C/EBP) homologous protein (CHOP) expression was enhanced by Pro-I without change in GRP78 expression. CHOP knockdown by siRNA also showed a significant decrease in Pro-I chemosensitization. All these data suggest that although TM could induce both NF-κB activation and CHOP expression through ER-stress, both NF-κB inhibition and increased CHOP level by Pro-I are required for enhanced chemosensitization of PC3 prostate cancer cells. Thus, our study might contribute to the identification of anticancer targets against prostate cancer cells.     

NF-κB in the regulation of epithelial homeostasis and inflammation

The IκB kinase/NF-κB signaling pathway has been implicated in the pathogenesis of several inflammatory diseases. Increased activation of NF-κB is often detected in both immune and non-immune cells in tissues affected by chronic inflammation, where it is believed to exert detrimental functions by inducing the expression of proinflammatory mediators that orchestrate and sustain the inflammatory response and cause tissue damage. Thus, increased NF-κB activation is considered an important pathogenic factor in many acute and chronic inflammatory disorders, raising hopes that NF-κB inhibitors could be effective for the treatment of inflammatory diseases. However, ample evidence has accumulated that NF-κB inhibition can also be harmful for the organism, and in some cases trigger the development of inflammation and disease. These findings suggested that NF-κB signaling has important functions for the maintenance of physiological immune homeostasis and for the prevention of inflammatory diseases in many tissues. This beneficial function of NF-κB has been predominantly observed in epithelial cells, indicating that NF-κB signaling has a particularly important role for the maintenance of immune homeostasis in epithelial tissues. It seems therefore that NF-κB displays two faces in chronic inflammation: on the one hand increased and sustained NF-κB activation induces inflammation and tissue damage, but on the other hand inhibition of NF-κB signaling can also disturb immune homeostasis, triggering inflammation and disease. Here, we discuss the mechanisms that control these apparently opposing functions of NF-κB signaling, focusing particularly on the role of NF-κB in the regulation of immune homeostasis and inflammation in the intestine and the skin.     

Deubiquitinases in the regulation of NF-κB signaling

Nuclear factor-kappa B (NF-κB) is a critical regulator of multiple biological functions including innate and adaptive immunity and cell survival. Activation of NF-κB is tightly regulated to preclude chronic signaling that may lead to persistent inflammation and cancer. Ubiquitination of key signaling molecules by E3 ubiquitin ligases has emerged as an important regulatory mechanism for NF-κB signaling. Deubiquitinases (DUBs) counteract E3 ligases and therefore play a prominent role in the downregulation of NF-κB signaling and homeostasis. Understanding the mechanisms of NF-κB downregulation by specific DUBs such as A20 and CYLD may provide therapeutic opportunities for the treatment of chronic inflammatory diseases and cancer.     

Expanding role of ubiquitination in NF-κB signaling

Best known for its role in targeting protein degradation by the proteasome, ubiquitin modification has also emerged as an important mechanism that regulates cell signaling through proteasome-independent mechanisms. The role of ubiquitin as a versatile signaling tag is characteristically illustrated in the NF-κB pathways, which regulate a variety of physiological and pathological processes in response to diverse stimuli. Here, we review the role of ubiquitination in different steps of the NF-κB signaling cascades, focusing on recent advances in understanding the mechanisms of protein kinase activation by polyubiquitin chains in different pathways that converge on NF-κB.     

Anti-proliferative effect of chalcone derivatives through inactivation of NF-κB in human cancer cells

To investigate the anti-proliferative effect of NF-κB inhibitor, a series of analogs of (E)-1-(2-hydroxy-6-(isopentyloxy)phenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one (5a) were prepared and evaluated for their NF-κB inhibition and anti-proliferative activity against various human cancer cell lines. Compounds (E)-1-(2-(3,3-dimethylbutoxy)-6-hydroxyphenyl)-3-(4-hydroxyphenyl)prop-2-en-1-one (5e) and (E)-4-(3-(2-(3,3-dimethylbutoxy)-6-hydroxyphenyl)-3-oxoprop-1-enyl)benzenesulfonamide (5p) showed good NF-κB inhibition as well as potent anti-proliferative activity. SAR studies showed that all the compounds with potent or moderate NF-κB inhibition displayed good anti-proliferative activity. All the analogs (5b–r) maintained a good correlation between their NF-κB inhibition and anti-proliferative activity though the extent is not directly proportional to each other.     

NF-κB inhibitory action of resveratrol: A probable mechanism of neuroprotection in experimental diabetic neuropathy

Resveratrol has shown array of biological actions, and is under clinical development for various disease conditions. The etiology of diabetic neuropathy revolves around oxidative stress, AGE formation, lipid peroxidation etc. All these stimulate inflammatory processes and NF-κB cascade is considered as one of the major players of inflammatory response. Activation of NF-κB results in elevated levels of inflammatory mediators. COX-2 and TNF-α activity have also been correlated with inflammatory damage in the pathophysiology of diabetic neuropathy (DN). Therefore we investigated the effect of resveratrol on NF-κB inflammatory cascade, COX-2, TNF-α and IL-6 levels in experimental DN.We found that resveratrol protected against various functional and behavioral deficits in diabetic neuropathy in line with our earlier published reports. In this study we found that the resveratrol treatment decreased the expression of p65 and IκB-α in treated rats. Treatment also ameliorated the elevated levels of TNF-α, IL-6 and COX-2. Resveratrol treatment produced significant decrease in nerve MDA levels in treated animals which may also be contributing to reduction in neuro-inflammation. This study confirms the NF-κB inhibitory activity and anti-inflammatory activity of resveratrol which may contribute to neuroprotection in diabetic neuropathy apart from its antioxidant effect.     

Activation of EMT in colorectal cancer by MTDH/NF-κB p65 pathway

Molecular and Cellular Biochemistry - Epithelial-mesenchymal transition (EMT) leads to tumor dissemination and metastasis. Metadherin (MTDH) is an oncogene that plays an important role in...     

Mechanism of NF-κB signaling pathway and autophagy in the regulation of osteoblast differentiation

Objective: The objective of the present work was to investigate a possible mechanism of NF-κB signaling pathway and autophagy in the regulation of osteoblast differentiation, and provide experimental basis for the study of tooth eruption disorder.

Methods: Mouse osteoblast-like (MC3T3-E1) cells were inoculated with a cell density of 70%. According to the grouping experimental design, Western blot and monodansylcadaverine (MDC) detection were conducted after dosing for 24?h. The cells were divided into the following five groups: blank control group; 6.25?µg/mL SN50 group; 12.5?µg/mL SN50 group; 25?µg/mL SN50 group and 50?µg/mL SN50 group.

Results: Western blot analysis revealed that the expression of LC3 protein was present in the blank control group; 6.25?µg/mL SN50 group; 12.5?µg/mL SN50 group and 50?µg/mL SN50 group, with no significant differences among these groups. However, the expression of LC3 protein was significantly lower in the 25?µg/mL SN50 group. MDC detection showed that, in the blank control group; 6.25?µg/mL SN50 group; 12.5?µg/mL SN50 group and 50?µg/mL SN50 group, there was obvious green fluorescence in the cytoplasm of the osteoblasts. However, in the 25?µg/mL SN50 group, it was found that there were significantly fewer green fluorescent particles.

Conclusion: The osteoblast itself had a strong function of autophagy. The appropriate concentration of SN50 in blocking the NF-κB pathway of the osteoblast was associated with the obvious inhibition of autophagy. However, the relationship between NF-κB signaling pathway and autophagy in the process of tooth eruption requires further study.     

Suppression of NF-κB and NF-κB-Regulated Gene Expression by Apigenin through IκBα and IKK Pathway in TRAMP Mice

Aberrant Nuclear Factor-κappaB (NF-κB) activation due to rapid IκBα turnover and high basal IκBα kinase (IKK) activity has been frequently observed in prostate cancer. Apigenin, a naturally occurring plant flavone, exhibits anti-proliferative, anti-inflammatory and anti-carcinogenic activities by inhibiting NF-κB pathway, through a mechanism not fully understood. We found that apigenin feeding in microgram doses (bioavailable in humans) inhibited prostate tumorigenesis in TRAMP mice by interfering with NF-κB signaling. Apigenin feeding to TRAMP mice (20 and 50 μg/mouse/day, 6 days/week for 20 weeks) exhibited significant decrease in tumor volumes of the prostate and completely abolished metastasis, which correlated with inhibition of NF-κB activation and binding to the DNA. Apigenin intake blocked phosphorylation and degradation of IκBα by inhibiting IKK activation, which in turn led to suppression of NF-κB activation. The expression of NF-κB-regulated gene products involved in proliferation (cyclin D1, and COX-2), anti-apoptosis (Bcl-2 and Bcl-xL), and angiogenesis (vascular endothelial growth factor) were also downregulated after apigenin feeding. These events correlated with the induction of apoptosis in tumor cells, as evident by increased cleaved caspase-3 labeling index in the dorsolateral prostate. Our results provide convincing evidence that apigenin inhibits IKK activation and restores the expression of IκBα, preventing it’s phosphorylation in a fashion similar to that elicited by IKK and proteasomal inhibitors through suppression of NF-κB signaling pathway.     

The regulation of the UCH-L1 gene by transcription factor NF-κB in podocytes

In kidney, the ubiquitin carboxy-terminal hydrolase 1 (UCH-L1) is involved in podocyte injury and proteinuria but details of the mechanism underlying its regulation are not known. Activation of NF-κB is thought to be the predominant risk factor for kidney disease; therefore, it is postulated that UCH-L1 may be one of the NF-κB target genes. In this study, we investigated the involvement of NF-κB activation in the regulation of UCH-L1 expression and the function of murine podocytes. Stimulation of podocytes with the cytokines TNF-α and IL-1β up-regulated UCH-L1 expression rapidly at the mRNA and protein levels and the NF-κB-specific inhibitor pyrrolidine dithiocarbamate resulted in down-regulation. NF-κB up-regulates UCH-L1 via binding the ? 300 bp and ? 109 bp sites of its promoter, which was confirmed by the electrophoretic mobility shift assay of DNA–nuclear protein binding. In the renal biopsy from lupus nephritis patients, the expressions of NF-κB and UCH-L1 increased in immunohistochestry staining and were positively correlated. Activation of NF-κB up-regulates UCH-L1 expression following changing of other podocytes molecules, such as nephrin and snail. These results suggest that activation of the NF-κB signaling pathway could be the major pathogenesis to up-regulate UCH-L1 in podocyte injury, followed by the turnover of other molecules, which might result in morphological changes and dysfunction of podocytes. This work help us to understand the effect of NF-κB on specific target molecules of podocytes, and suggest that targeting the NF-κB–UCH-L1 interaction could be a novel therapeutic strategy for the treatment of podocyte lesions and proteinuria.     

Study on anti-proliferative effect of benzoxathiole derivatives through inactivation of NF-κB in human cancer cells

To investigate the anti-proliferative effect of a newly discovered NF-kB inhibitor, 6,6-dimethyl-2-(phenylimino)-6,7-dihydrobenzo[d][1,3]oxathiol-4(5H)-one (1a), a series of its analogs (1b-n) were prepared and evaluated for their NF-κB inhibition and anti-proliferative activity against various human cancer cell lines. Slight variation of hydrophobicity by replacement of dimethyl group of 1a at 6-position with bulky isopropyl group and introduction of para-fluoro substitution on 2-phenyl group showed good NF-κB inhibitory activity and anti-proliferative activity. However, excessive increase in hydrophobicity with 2,4,6-trichloro substituents on phenyl group resulted in the loss of both the activities. From the SAR results, 2-phenylimino-6,7-dihydrobenzo[d][1,3]oxathiol-4(5H)-one was identified as the lead scaffold for investigating new anticancer agent through inactivation of NF-κB.