The IKKα-dependent non-canonical pathway of NF-κB activation is constitutively active and modulates progression-related functions in a subset of human melanomas

Manganese-induced reactive oxygen species activate IκB kinase to upregulate YY1 and impair glutamate transporter EAAT2 function in human astrocytes in vitro

Dysregulation of the astrocytic glutamate transporter excitatory amino acid transporter 2 (EAAT2) is associated with several neurological disorders, including Parkinson's disease, Alzheimer's disease, and manganism, the latter induced by chronic exposure to high levels of manganese (Mn). Mechanisms of Mn-induced neurotoxicity include impairment of EAAT2 function secondary to the activation of the transcription factor Yin Yang 1 (YY1) by nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). However, the upstream mechanisms by which Mn-induced NF-κB activates YY1 remain to be elucidated. In the present study, we used the H4 human astrocyte cell line to test if Mn activates YY1 through the canonical NF-κB signaling pathway, leading to EAAT2 repression. The results demonstrate that Mn exposure induced phosphorylation of the upstream kinase IκB kinase (IKK-β), leading to NF-κB p65 translocation, increased YY1 promoter activity, mRNA/protein levels, and consequently repressed EAAT2. Results also demonstrated that Mn-induced oxidative stress and subsequent TNF-α production were upstream of IKK-β activation, as antioxidants attenuated Mn-induced TNF-α production and IKK-β activation. Moreover, TNF-α inhibition attenuated the Mn-induced activation of IKK-β and YY1. Taken together, Mn-induced oxidative stress and TNF-α mediates activation of NF-κB signaling and YY1 upregulation, leading to repression of EAAT2. Thus, targeting reactive oxygen species (ROS), TNF-α and IKK-β may attenuate Mn-induced YY1 activation and consequent EAAT2 repression.

Tudor-staphylococcal nuclease regulates the expression and biological function of alkylglycerone phosphate synthase via nuclear factor-κB and microRNA-127 in human glioma U87MG cells

Glioma is one of the malignant tumor types detrimental to human health; therefore, it is important to find novel targets and therapeutics for this tumor. The downregulated expression of Tudor-staphylococcal nuclease (SN) and alkylglycerone phosphate synthase (AGPS) can decrease cancer malignancy, and the overexpression of them can the increase viability and migration potential of various tumor cell types; however, the role of AGPS in the proliferation and migration of glioma, and the association of Tudor-SN and AGPS in human glioma is not clear. In the present study, it was determined that AGPS silencing suppressed the proliferation and migration potential of glioma U87MG cells, and suppressed the expression of the circular RNAs circ-ubiquitin-associated protein 2, circ-zinc finger protein 292 and circ-homeodomain-interacting protein kinase 3, and the long non-coding RNAs H19 imprinted maternally expressed transcript (non-protein coding), colon cancer-associated transcript 1 (non-protein coding) and hepatocellular carcinoma upregulated long non-coding RNA. Furthermore, Tudor-SN silencing suppressed the expression of AGPS; however, nuclear factor (NF)-κB and microRNA (miR)-127 retrieval experiments partially reduced the expression of AGPS. Additionally, it was determined that Tudor-SN silencing suppressed the activity of the mechanistic target of rapamycin (mTOR) signaling pathway, and NF-κB and miR-127 retrieval experiments partially reduced the activity of mTOR. Therefore, it was considered that NF-κB and miR-127 may be the mediators of Tudor-SN-regulated AGPS via the mTOR signaling pathway. These results improve on our knowledge of the mechanisms underlying Tudor-SN and AGPS in human glioma.

Targeting IκappaB kinases for cancer therapy

The inhibitory kappa B kinases (IKKs) and IKK related kinases are crucial regulators of the pro-inflammatory transcription factor, nuclear factor kappa B (NF-κB). The dysregulation in the activities of these kinases has been reported in several cancer types. These kinases are known to regulate survival, proliferation, invasion, angiogenesis, and metastasis of cancer cells. Thus, IKK and IKK related kinases have emerged as an attractive target for the development of cancer therapeutics. Several IKK inhibitors have been developed, few of which have advanced to the clinic. These inhibitors target IKK either directly or indirectly by modulating the activities of other signaling molecules. Some inhibitors suppress IKK activity by disrupting the protein-protein interaction in the IKK complex. The inhibition of IKK has also been shown to enhance the efficacy of conventional chemotherapeutic agents. Because IKK and NF-κB are the key components of innate immunity, suppressing IKK is associated with the risk of immune suppression. Furthermore, IKK inhibitors may hit other signaling molecules and thus may produce off-target effects. Recent studies suggest that multiple cytoplasmic and nuclear proteins distinct from NF-κB and inhibitory κB are also substrates of IKK. In this review, we discuss the utility of IKK inhibitors for cancer therapy. The limitations associated with the intervention of IKK are also discussed.