NF-κB Activation In Cancer Research Articles

Targeting TRIM3 deletion-induced tumor-associated lymphangiogenesis prohibits lymphatic metastasis in esophageal squamous cell carcinoma.

Tumor-associated lymphangiogenesis has attracted increasing attention because of its potential contribution to lymph node metastasis. However, the molecular mechanisms underlying lymphangiogenesis in cancer remains elusive. In the current study, we demonstrate that tripartite motif-containing 3 (TRIM3) directly interacts with and induces E3 ligase-dependent proteasomal turnover of importin α3 and α-Actinin-4 (ACTN4), which controls nuclear factor kappa B (NF-κB) activity at a well-ordered level. Heterozygous deletion-mediated TRIM3 downregulation led to NF-κB constitutive activation through disruption of the NF-κB-IκB-α negative feedback loop and enhancement of the p65 DNA-binding affinity and transcriptional activity via promoting symmetrical dimethylarginine modification of NF-κB/p65 at Arg30 and Arg35, which consequently promoted lymphatic metastasis of esophageal squamous cell carcinoma (ESCC) cells. Treatment with Tecfidera, a medication used to treat multiple sclerosis, restored the negative feedback inhibition of NF-κB by reducing the NF-κB/ACTN4 interaction and decreasing symmetrically dimethylated NF-κB levels, resulting in inhibition of ESCC lymphatic metastasis both in vitro and in vivo. Taken together, our results uncover a novel mechanism for constitutive NF-κB activation in cancer and may represent an attractive strategy to treat ESCC lymphatic metastasis.

Evaluating TBK1 as a therapeutic target in cancers with activated IRF3.

TBK1 (TANK-binding kinase 1) is a noncanonical IκB protein kinase that phosphorylates and activates downstream targets such as IRF3 and c-Rel and, mediates NF-κB activation in cancer. Previous reports demonstrated synthetic lethality of TBK1 with mutant KRAS in non-small cell lung cancer (NSCLC); thus, TBK1 could be a novel target for treatment of KRAS-mutant NSCLC. Here, the effect of TBK1 on proliferation in a panel of cancer cells by both genetic and pharmacologic approaches was evaluated. In KRAS-mutant cancer cells, reduction of TBK1 activity by knockdown or treatment with TBK1 inhibitors did not correlate with reduced proliferation in a two-dimensional viability assay. Verification of target engagement via reduced phosphorylation of S386 of IRF3 (pIRF3(S386)) was difficult to assess in NSCLC cells due to low protein expression. However, several cell lines were identified with high pIRF3(S386) levels after screening a large panel of cell lines, many of which also harbor KRAS mutations. Specifically, a large subset of KRAS-mutant pancreatic cancer cell lines was uncovered with high constitutive pIRF3(S386) levels, which correlated with high levels of phosphorylated S172 of TBK1 (pTBK1(S172)). Finally, TBK1 inhibitors dose-dependently inhibited pIRF3(S386) in these cell lines, but this did not correlate with inhibition of cell growth. Taken together, these data demonstrate that the regulation of pathways important for cell proliferation in some NSCLC, pancreatic, and colorectal cell lines is not solely dependent on TBK1 activity. TBK1 has therapeutic potential under certain contexts and phosphorylation of its downstream target IRF3 is a biomarker of TBK1 activity.

C11orf95–RELA fusions drive oncogenic NF-κB signalling in ependymoma

The nuclear factor-κB (NF-κB) family of transcriptional regulators are central mediators of the cellular inflammatory response. Although constitutive NF-κB signaling is present in most human tumours, mutations in pathway members are rare, complicating efforts to understand and block aberrant NF-κB activity in cancer. Here, we show that more than two thirds of supratentorial ependymomas contain oncogenic fusions between RELA, the principal effector of canonical NF-κB signalling, and an uncharacterized gene, C11orf95. In each case, C11orf95-RELA fusions resulted from chromothripsis involving chromosome 11q13.1. C11orf95-RELA fusion proteins translocated spontaneously to the nucleus to activate NF-κB target genes, and rapidly transformed neural stem cells—the cell of origin of ependymoma—to form these tumours in mice. Our data identify the first highly recurrent genetic alteration of RELA in human cancer, and the C11orf95-RELA fusion protein as a potential therapeutic target in supratentorial ependymoma.

NFκB regulates expression of Polo-like kinase 4

Activation of the NFκB signaling pathway allows the cell to respond to infection and stress and can affect many cellular processes. As a consequence, NFκB activity must be integrated with a wide variety of parallel signaling pathways. One mechanism through which NFκB can exert widespread effects is through controlling the expression of key regulatory kinases. Here we report that NFκB regulates the expression of genes required for centrosome duplication, and that Polo-like kinase 4 (PLK4) is a direct NFκB target gene. RNA interference, chromatin immunoprecipitation, and analysis of the PLK4 promoter in a luciferase reporter assay revealed that all NFκB subunits participate in its regulation. Moreover, we demonstrate that NFκB regulation of PLK4 expression is seen in multiple cell types. Significantly long-term deletion of the NFκB2 (p100/p52) subunit leads to defects in centrosome structure. This data reveals a new component of cell cycle regulation by NFκB and suggests a mechanism through which deregulated NFκB activity in cancer can lead to increased genomic instability and uncontrolled proliferation.

Inhibition of IκBα Nuclear Export as an Approach to Abrogate Nuclear Factor-κB–Dependent Cancer Cell Survival

Abstract Deregulation of the transcription factor nuclear factor-κB (NF-κB) leading to its constitutive activation is frequently observed in human cancer. Because altered NF-κB activities often promote the survival of malignant cells, its inhibition is regarded as a promising anticancer strategy. Because activation of the latent cytoplasmic NF-κB complex can be induced by a wide variety of different stimuli, its deregulation may occur by an equally large number of distinct mechanisms. This diversity raises a conundrum in conceptualizing general approaches to attenuate NF-κB activity in cancer. Here, we provide evidence that inhibition of IκBα nuclear export is a viable target to generally abrogate constitutive NF-κB activity in different cancer cell types. We show that inhibition of IκBα nuclear export has an important course of events in cancer cells harboring constitutive NF-κB activity—an initial increase in the pool of stable nuclear NF-κB/IκBα complexes that leads to a reduction of constitutive NF-κB activity and subsequent induction of apoptosis. Importantly, similar effects on multiple different cancer cell types indicate that inhibition of nuclear export of IκBα leads to broad inhibition of constitutive NF-κB activation regardless of various deregulated, upstream events involved.

Secretion of cytokines and growth factors as a general cause of constitutive NFkappaB activation in cancer.

The constitutive activation of nuclear factor kappaB (NFkappaB) helps a variety of tumors to resist apoptosis and desensitizes them to chemotherapy, but the causes are still largely unknown. We have analysed this phenomenon in eight mutant cell lines derived from human 293 cells, selected for NFkappaB-dependent expression of a marker gene, and also in seven tumor-derived cell lines. Conditioned media from all of these cells stimulated the activation of NFkappaB (up to 30-fold) in indicator cells carrying an NFkappaB-responsive reporter. Therefore, secretion of extracellular factors as the cause of constitutive activation seems to be general. The mRNAs encoding several different cytokines and growth factors were greatly overexpressed in the tumor and mutant cells. The pattern of overexpression was distinct in each cell line, indicating that the phenomenon is complex. Two secreted factors whose roles in the constitutive activation of NFkappaB are not well defined were investigated further as pure proteins: transforming growth factor beta2 (TGFbeta2) and fibroblast growth factor 5 (FGF5) were both highly expressed in some mutant clones and tumor cell lines, each activated NFkappaB alone, and the combination was synergistic. Our data indicate that a group of different factors, expressed at abnormally high levels, can contribute singly and synergistically to the constitutive activation of NFkappaB in all of the mutant and tumor cell lines we studied. Since several NFkappaB target genes encode secreted proteins that induce NFkappaB, autocrine loops are likely to be ubiquitously important in the constitutive activation of NFkappaB in cancer. We provide the first evidence of the general, complex, and synergistic activation of NFkappaB in tumor and mutant cell lines through the action of secreted factors and suggest that the same explanation is likely for the constitutive activation of NFkappaB in cancers.

The clinical significance between activation of nuclear factor kappa B transcription factor and overexpression of HER-2/neu oncoprotein in Taiwanese patients with breast cancer

Background: This study investigated the role of nuclear factor-kappa B (NF-κB) activity in human breast cancer with overexpression of HER-2/neu oncoprotein, as well as its role on expression of different histological grades of cancer cells taken from Taiwanese breast cancer patients. Materials and methods: Specimens were collected from 82 female breast cancer patients. The HER-2/neu oncoprotein was measured by immunohistochemistry. NF-κB activity expression was assessed by the electrophoretic mobility shift assay, and confirmed by the supershift technique using anti-P65 antibody in both breast cancer tissue and the adjacent normal tissue. The histological grades were measured by Modified Bloom–Richardson Grading Scheme. Results: Of the 82 cancer specimens, 81 (98.7%) showed higher or equal expressions of NF-κB activity when compared to the adjacent normal tissue. Fifty-five cases (67.1%) had higher levels of NF-κB activity in the cancerous tissue than in the adjacent normal tissue ( p<0.005). With regard to tumor size, steroid receptors, stages, histological types, and node status, there were no statistically significant differences in NF-κB activity between cancerous tissues and adjacent normal tissues. However, significantly higher expressions of NF-κB activity were seen in those cases with positive HER2/neu oncoprotein, poorly differentiated histological grades, high nuclear pleomorphisms, and high mitotic counts ( p<0.05). Positive HER-2/neu overexpression of oncoprotein had higher NF-κB activity (86%) than negative overexpression (60%) ( p<0.05). It has been shown that the NF-κB activity increases in the HER-2/neu oncoprotein overexpression in human breast cancer. Conclusion: Overexpression of HER-2/neu gene could induce NF-κB activity in human breast cancer cells, as has been confirmed in other research on cell lines.

NF-κB activation in cancer: a challenge for ubiquitination- and proteasome-based therapeutic approach

Nuclear factor-kappa B (NF-κB) activation relies primarily on ubiquitin-mediated degradation of its inhibitor IκB. NF-κB plays an important role in many aspects of tumor development, progression, and therapy. Some types of cancer are characterized by constitutive NF-κB activity, whereas in others such activity is induced following chemotherapy. NF-κB-harboring tumors are generally resistant to chemotherapy and their eradication requires NF-κB inhibition. Here we describe the mechanisms of NF-κB activation in normal and tumor cells, review prevalent notions regarding the factor's contribution to tumorigenicity and discuss present and future options for NF-κB inhibition in cancer. The ubiquitination-mediated activation of NF-κB is intersected by another cancer-associated protein, β-catenin. We, therefore, compare the related activation pathways and discuss the possibility of differential targeting of the involved ubiquitination machinery.