Multiple mutations contribute to the oncogenicity of the retroviral oncoprotein v-Rel

Overexpression of TRIM44 mediates the NF-κB pathway to promote the progression of ovarian cancer

BACKGROUND

Ovarian cancer (OC) is the second most commonly seen cancer in the US, and patients with OC are commonly diagnosed in the advanced stage. Research into the molecular mechanisms and potential therapeutic targets of OC is becoming increasingly urgent. In our study, we worked to discover the role of TRIM44 in OC development.

OBJECTIVE

This study explored whether the overexpression of TRIM44 mediates the NF-kB pathway to promote the progression of OC.

METHODS

A TRIM44 overexpression model was constructed in SKOV3 cells, and the proliferation ability of the cells was detected using the CCK-8 assay. The migration healing ability of cells was detected using cell scratch assay. Cell migration and invasion were detected using Transwell nesting. TUNEL was applied to detect apoptosis, and ELISA and western blot were used to detect the expression of NF-κB signaling pathway proteins. The pathological changes of the tumor tissues were observed using HE staining in a mouse ovarian cancer xenograft model. Immunofluorescence double staining, RT-PCR, and western blot were used to determine the expression of relevant factors in tumour tissues.

RESULTS

TRIM44 overexpression promoted the proliferation, migration, and invasion of SKOV3 cells in vitro and inhibited apoptosis while enhancing the growth of tumours in vivo. TRIM44 regulated the NF-κB signaling pathway.

CONCLUSIONS

TRIM44 overexpression can regulate the NF-κB signaling pathway to promote the progression of OC, and TRIM44 may be a potential therapeutic target for OC.

Mutations in the Vicinity of the IRAK3 Guanylate Cyclase Center Impact Its Subcellular Localization and Ability to Modulate Inflammatory Signaling in Immortalized Cell Lines

Interleukin-1 receptor-associated kinase 3 (IRAK3) modulates the magnitude of cellular responses to ligands perceived by interleukin-1 receptors (IL-1Rs) and Toll-like receptors (TLRs), leading to decreases in pro-inflammatory cytokines and suppressed inflammation. The molecular mechanism of IRAK3's action remains unknown. IRAK3 functions as a guanylate cyclase, and its cGMP product suppresses lipopolysaccharide (LPS)-induced nuclear factor kappa-light-chain-enhancer of activated B cell (NFκB) activity. To understand the implications of this phenomenon, we expanded the structure-function analyses of IRAK3 through site-directed mutagenesis of amino acids known or predicted to impact different activities of IRAK3. We verified the capacity of the mutated IRAK3 variants to generate cGMP in vitro and revealed residues in and in the vicinity of its GC catalytic center that impact the LPS-induced NFκB activity in immortalized cell lines in the absence or presence of an exogenous membrane-permeable cGMP analog. Mutant IRAK3 variants with reduced cGMP generating capacity and differential regulation of NFκB activity influence subcellular localization of IRAK3 in HEK293T cells and fail to rescue IRAK3 function in IRAK3 knock-out THP-1 monocytes stimulated with LPS unless the cGMP analog is present. Together, our results shed new light on the mechanism by which IRAK3 and its enzymatic product control the downstream signaling, affecting inflammatory responses in immortalized cell lines.

Biological and Exploitable Crossroads for the Immune Response in Cancer and COVID-19

The outbreak of novel coronavirus disease 2019 (COVID-19) has exacted a disproportionate toll on cancer patients. The effects of anticancer treatments and cancer patients’ characteristics shared significant responsibilities for this dismal outcome; however, the underlying immunopathological mechanisms are far from being completely understood. Indeed, despite their different etiologies, SARS-CoV-2 infection and cancer unexpectedly share relevant immunobiological connections. In the pathogenesis and natural history of both conditions, there emerges the centrality of the immune response, orchestrating the timed appearance, functional and dysfunctional roles of multiple effectors in acute and chronic phases. A significant number (more than 600) of observational and interventional studies have explored the interconnections between COVID-19 and cancer, focusing on aspects as diverse as psychological implications and prognostic factors, with more than 4000 manuscripts published so far. In this review, we reported and discussed the dynamic behavior of the main cytokines and immune system signaling pathways involved in acute vs. early, and chronic vs. advanced stages of SARS-CoV-2 infection and cancer. We highlighted the biological similarities and active connections within these dynamic disease scenarios, exploring and speculating on possible therapeutic crossroads from one setting to the other.

Review: NF-kB activation in canine cancer

Spontaneous tumors in dogs share several environmental, epidemiologic, biologic, clinical and molecular features with a wide variety of human cancers, making this companion animal an attractive model. Nuclear factor kappa B (NF-kB) transcription factor overactivation is common in several human cancers, and there is evidence that similar signaling aberrations also occur in canine cancers including lymphoma, leukemia, hemangiosarcoma, mammary cancer, melanoma, glioma, and prostate cancer. This review provides an overview of NF-kB signaling biology, both in health and in cancer development. It also summarizes available evidence of aberrant NF-kB signaling in canine cancer, and reviews antineoplastic compounds that have been shown to inhibit NF-kB activity used in various types of canine cancers. Available data suggest that dogs may be an excellent model for human cancers that have overactivation of NF-kB.

NF-κB Rel subunit exchange on a physiological timescale

The Rel proteins of the NF-κB complex comprise one of the most investigated transcription factor families, forming a variety of hetero- or homodimers. Nevertheless, very little is known about the fundamental kinetics of NF-κB complex assembly, or the inter-conversion potential of dimerised Rel subunits. Here, we examined an unexplored aspect of NF-κB dynamics, focusing on the dissociation and reassociation of the canonical p50 and p65 Rel subunits and their ability to form new hetero- or homodimers. We employed a soluble expression system to enable the facile production of NF-κB Rel subunits, and verified these proteins display canonical NF-κB nucleic acid binding properties. Using a combination of biophysical techniques, we demonstrated that, at physiological temperatures, homodimeric Rel complexes routinely exchange subunits with a half-life of less than 10 min. In contrast, we found a dramatic preference for the formation of the p50/p65 heterodimer, which demonstrated a kinetic stability of at least an order of magnitude greater than either homodimer. These results suggest that specific DNA targets of either the p50 or p65 homodimers can only be targeted when these subunits are expressed exclusively, or with the intervention of additional post-translational modifications. Together, this work implies a new model of how cells can modulate NF-κB activity by fine-tuning the relative proportions of the p50 and p65 proteins, as well as their time of expression. This work thus provides a new quantitative interpretation of Rel dimer distribution in the cell, particularly for those who are developing mathematical models of NF-κB activity.

NF-κB and Human Cancer: What Have We Learned over the Past 35 Years?

Transcription factor NF-κB has been extensively studied for its varied roles in cancer development since its initial characterization as a potent retroviral oncogene. It is now clear that NF-κB also plays a major role in a large variety of human cancers, including especially ones of immune cell origin. NF-κB is generally constitutively or aberrantly activated in human cancers where it is involved. These activations can occur due to mutations in the NF-κB transcription factors themselves, in upstream regulators of NF-κB, or in pathways that impact NF-κB. In addition, NF-κB can be activated by tumor-assisting processes such as inflammation, stromal effects, and genetic or epigenetic changes in chromatin. Aberrant NF-κB activity can affect many tumor-associated processes, including cell survival, cell cycle progression, inflammation, metastasis, angiogenesis, and regulatory T cell function. As such, inhibition of NF-κB has often been investigated as an anticancer strategy. Nevertheless, with a few exceptions, NF-κB inhibition has had limited success in human cancer treatment. This review covers general themes that have emerged regarding the biological roles and mechanisms by which NF-κB contributes to human cancers and new thoughts on how NF-κB may be targeted for cancer prognosis or therapy.

c-Rel gain in B cells drives germinal center reactions and autoantibody production

Single-nucleotide polymorphisms and locus amplification link the NF-κB transcription factor c-Rel to human autoimmune diseases and B cell lymphomas, respectively. However, the functional consequences of enhanced c-Rel levels remain enigmatic. Here, we overexpressed c-Rel specifically in mouse B cells from BAC-transgenic gene loci and demonstrate that c-Rel protein levels linearly dictated expansion of germinal center B (GCB) cells and isotype-switched plasma cells. c-Rel expression in B cells of otherwise c-Rel-deficient mice fully rescued terminal B cell differentiation, underscoring its critical B cell-intrinsic roles. Unexpectedly, in GCB cells transcription-independent regulation produced the highest c-Rel protein levels among B cell subsets. In c-Rel-overexpressing GCB cells this caused enhanced nuclear translocation, a profoundly altered transcriptional program, and increased proliferation. Finally, we provide a link between c-Rel gain and autoimmunity by showing that c-Rel overexpression in B cells caused autoantibody production and renal immune complex deposition.

Regulation of PD-L1 Expression by NF-κB in Cancer

Immune checkpoints are inhibitory receptor/ligand pairs regulating immunity that are exploited as key targets of anti-cancer therapy. Although the PD-1/PD-L1 pair is one of the most studied immune checkpoints, several aspects of its biology remain to be clarified. It has been established that PD-1 is an inhibitory receptor up-regulated by activated T, B, and NK lymphocytes and that its ligand PD-L1 mediates a negative feedback of lymphocyte activation, contributing to the restoration of the steady state condition after acute immune responses. This loop might become detrimental in the presence of either a chronic infection or a growing tumor. PD-L1 expression in tumors is currently used as a biomarker to orient therapeutic decisions; nevertheless, our knowledge about the regulation of PD-L1 expression is limited. The present review discusses how NF-κB, a master transcription factor of inflammation and immunity, is emerging as a key positive regulator of PD-L1 expression in cancer. NF-κB directly induces PD-L1 gene transcription by binding to its promoter, and it can also regulate PD-L1 post-transcriptionally through indirect pathways. These processes, which under conditions of cellular stress and acute inflammation drive tissue homeostasis and promote tissue healing, are largely dysregulated in tumors. Up-regulation of PD-L1 in cancer cells is controlled via NF-κB downstream of several signals, including oncogene- and stress-induced pathways, inflammatory cytokines, and chemotherapeutic drugs. Notably, a shared signaling pathway in epithelial cancers induces both PD-L1 expression and epithelial–mesenchymal transition, suggesting that PD-L1 is part of the tissue remodeling program. Furthermore, PD-L1 expression by tumor infiltrating myeloid cells can contribute to the immune suppressive features of the tumor environment. A better understanding of the interplay between NF-κB signaling and PD-L1 expression is highly relevant to cancer biology and therapy.

TCA Cycle Rewiring as Emerging Metabolic Signature of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common malignancy. Despite progress in treatment, HCC is still one of the most lethal cancers. Therefore, deepening molecular mechanisms underlying HCC pathogenesis and development is required to uncover new therapeutic strategies. Metabolic reprogramming is emerging as a critical player in promoting tumor survival and proliferation to sustain increased metabolic needs of cancer cells. Among the metabolic pathways, the tricarboxylic acid (TCA) cycle is a primary route for bioenergetic, biosynthetic, and redox balance requirements of cells. In recent years, a large amount of evidence has highlighted the relevance of the TCA cycle rewiring in a variety of cancers. Indeed, aberrant gene expression of several key enzymes and changes in levels of critical metabolites have been observed in many solid human tumors. In this review, we summarize the role of the TCA cycle rewiring in HCC by reporting gene expression and activity dysregulation of enzymes relating not only to the TCA cycle but also to glutamine metabolism, malate/aspartate, and citrate/pyruvate shuttles. Regarding the transcriptional regulation, we focus on the link between NF-κB-HIF1 transcriptional factors and TCA cycle reprogramming. Finally, the potential of metabolic targets for new HCC treatments has been explored.

Quantitative structure-activity relationship and molecular docking studies on human proteasome inhibitors for anticancer activity targeting NF-κB signaling pathway

The abnormal ubiquitin-proteasome is found as an important target in various human diseases, especially in cancer, and recently it has received prevalent attention as a challenging therapeutic target. The current work is designed to derive a predictive two-dimensional quantitative structure-activity relationship model for anticancer human proteasome target of NF-κB signaling pathway. The established 2 D-QSAR is dependent on multiple linear regression approach and validated through leave-One-Out and external test set prediction method. The robust QSAR model showed the r² of 0.83 and q² of 0.80 and pred_r² of 0.77. Three chemical properties, electronegativity count, average potential, and T_2_N_6 were identified as significant descriptors to predict the anticancer activities of the proteasome antagonists. Besides, the predicted top hit compounds were considered to check out the compliance with Rule of five and pharmacokinetic parameters for oral bioavailability in the human body. The molecular docking was accomplished to unravel the molecular mode of action of best-predicted compounds which was compatible with the standard drug. Following this approach, lastly two compounds NP and AP were recognized as the best candidates since these top compounds follow all the standard limit point of entire filters and indicated effective and decent docking score. The outcomes of the study sturdily suggested that the developed model and top hit compound's binding conformation are rational in the exploration of unknown antagonist's anticancer activity. The research would be of great support and is supposed to be of immense significance in the development and designing of drug-like candidates in preliminary drug discovery. Communicated by Ramaswamy H. Sarma.

Clinicopathological significance and prognostic implication of nuclear factor-κB activation in colorectal cancer

OBJECTIVE

The aim of the present study was to evaluate the clinicopathological significance of phosphorylated nuclear factor-κB (pNF-κB) expression, and its impact on epithelial-mesenchymal transition and angiogenesis in colorectal cancer (CRC).

METHODS

We carried out immunohistochemistry of pNF-κB on 261 human CRC tissues, and evaluated nuclear expression, regardless of cytoplasmic expression. We also investigated the correlation between pNF-κB expression and clinicopathological characteristics, survival, and epithelial-mesenchymal transition and angiogenesis-related markers in CRC.

RESULTS

pNF-κB was expressed in the nuclei of 164 of the 261 CRC tissues (62.8%). Furthermore, pNF-κB was significantly correlated with frequent perineural invasion, lymph node metastasis, and higher pTNM stage. However, there was no significant correlation between pNF-κB expression and other clinicopathological parameters. Among the epithelial-mesenchymal transition markers examined, SNAIL expression was significantly correlated with pNF-κB expression (P =  0.001) but E-cadherin expression was not. CRC with pNF-κB expression had significantly higher SIRT1 expression levels and hypoxia-inducible factor-1α expression levels than CRC without pNF-κB expression (P <  0.001 and P <  0.001, respectively). However, there was no correlation between the expression levels of pNF-κB and VEGF. pNF-κB expression was significantly correlated with worse overall and recurrence-free survival rates (P <  0.001 and P <  0.001, respectively).

CONCLUSION

pNF-κB expression was significantly correlated with aggressive tumor behaviors and worse survival rates. Furthermore, pNF-κB expression may affect tumor invasion and progression through SNAIL-related epithelial-mesenchymal transition and SIRT1- and hypoxia-inducible factor-1α-induced angiogenesis.

The Role of the Transcription Factor Nuclear Factor-kappa B in Thyroid Autoimmunity and Cancer

Nuclear factor-kappa B (NF-κB) is a ubiquitous transcription factor that is involved in inflammatory and immune responses, as well as in regulation of expression of many other genes related to cell survival, proliferation, and differentiation. In mammals, NF-κB comprises five subunits that can bind to promoter regions of target genes as homodimers or heterodimers. The most common dimer is the p50/p65 heterodimer. The several combinations of dimers that can be formed contribute to the heterogeneous regulation of NF-κB target genes, and this heterogeneity is further increased by interactions of the NF-κB dimers with other transcription factors, such as steroid hormone receptors, activator protein-1 (AP-1), and cAMP response element binding protein (CREB). In the thyroid, several studies have demonstrated the involvement of NF-κB in thyroid autoimmunity, thyroid cancer, and thyroid-specific gene regulation. The role of NF-κB in thyroid autoimmunity was hypothesized more than 20 years ago, after the finding that the binding of distinct NF-κB heterodimers to the major histocompatibility complex class I gene is hormonally regulated. Further studies have shown increased activity of NF-κB in thyroid autoimmune diseases and in thyroid orbitopathy. Increased activity of NF-κB has also been observed in thyroid cancer, where it correlates with a more aggressive pattern. Of particular interest, mutation of some oncogenes or tumor suppressor genes involved in thyroid carcinogenesis results in constitutive activation of the NF-κB pathway. More recently, it has been shown that NF-κB also has a role in thyroid physiology, as it is fundamental for the expression of the main thyroid-specific genes, such as sodium iodide symporter, thyroid peroxidase, thyroglobulin, Pax8, and TTF-1 (NKX2-1).

CRISPR/Cas9-mediated knockout of c-REL in HeLa cells results in profound defects of the cell cycle

Cervical cancer is the fourth common cancer in women resulting worldwide in 266,000 deaths per year. Belonging to the carcinomas, new insights into cervical cancer biology may also have great implications for finding new treatment strategies for other kinds of epithelial cancers. Although the transcription factor NF-κB is known as a key player in tumor formation, the relevance of its particular subunits is still underestimated. Here, we applied CRISPR/Cas9n-mediated genome editing to successfully knockout the NF-κB subunit c-REL in HeLa Kyoto cells as a model system for cervical cancers. We successfully generated a homozygous deletion in the c-REL gene, which we validated using sequencing, qPCR, immunocytochemistry, western blot analysis, EMSA and analysis of off-target effects. On the functional level, we observed the deletion of c-REL to result in a significantly decreased cell proliferation in comparison to wildtype (wt) without affecting apoptosis. The impaired proliferative behavior of c-REL-/- cells was accompanied by a strongly decreased amount of the H2B protein as well as a significant delay in the prometaphase of mitosis compared to c-REL+/+ HeLa Kyoto cells. c-REL-/- cells further showed significantly decreased expression levels of c-REL target genes in comparison to wt. In accordance to our proliferation data, we observed the c-REL knockout to result in a significantly increased resistance against the chemotherapeutic agents 5-Fluoro-2'-deoxyuridine (5-FUDR) and cisplatin. In summary, our findings emphasize the importance of c-REL signaling in a cellular model of cervical cancer with direct clinical implications for the development of new treatment strategies.

Targeting IKK and NF-κB for Therapy

In addition to regulating immune responses, the NF-κB family of transcription factors also promotes cellular proliferation and survival. NF-κB and its activating kinase, IKK, have become appealing therapeutic targets because of their critical roles in the progression of many diseases including chronic inflammation and cancer. Here, we discuss the conditions that lead to pathway activation, the effects of constitutive activation, and some of the strategies used to inhibit NF-κB signaling.

Regulation of LPS-induced mRNA expression of pro-inflammatory cytokines via alteration of NF-κB activity in mouse peritoneal macrophages exposed to fluoride

F toxicity to immune system, especially to macrophage, has been studied a lot recently. Nuclear factor-kappa B (NF-κB), as a transcription factor, plays a central role in immune and inflammatory responses via the regulation of downstream gene expression. Recent studies indicated that fluoride effect on inflammatory cytokine secretion, however, the molecular mechanism was less understood. In our study, peritoneal macrophages (PMs) were divided several groups and were administrated sodium fluoride (NaF, 50, 100, 200, 400, 800 μM) and/or lipopolysaccharide (LPS, 30 ng/mg). The mRNA expression of p65, inducible nitric oxide synthase (iNOS), tumor necrosis factor alpha (TNF-α) and interleukin-1 beta (IL-1β) in macrophages exposed to fluoride was determined by quantitative real-time RT-PCR respectively. The translocation of NF-κB from cytoplasm to nucleus, which in a way reflects NF-κB activity, was demonstrated by Immunofluorescence and ELISA. Our results showed that fluoride had a dose-dependent effect on NF-κB activity, which coincided with LPS-induced mRNA expression of its downstream genes, iNOS and IL-1β. Fluoride alone causes no effect on gene expression. However, the mRNA expression of TNF-α showed non-NF-κB-dependent manner. Therefore, we come to the conclusion that fluoride can regulate LPS-induced mRNA expression of iNOS and IL-1β via NF-κB pathway in mouse peritoneal macrophages.

The NF-κB subunit c-Rel regulates Bach2 tumour suppressor expression in B-cell lymphoma

The REL gene, encoding the NF-κB subunit c-Rel, is frequently amplified in B-cell lymphoma and functions as a tumour-promoting transcription factor. Here we report the surprising result that c-rel-/- mice display significantly earlier lymphomagenesis in the c-Myc driven, Eμ-Myc model of B-cell lymphoma. c-Rel loss also led to earlier onset of disease in a separate TCL1-Tg-driven lymphoma model. Tumour reimplantation experiments indicated that this is an effect intrinsic to the Eμ-Myc lymphoma cells but, counterintuitively, c-rel-/- Eμ-Myc lymphoma cells were more sensitive to apoptotic stimuli. To learn more about why loss of c-Rel led to earlier onset of disease, microarray gene expression analysis was performed on B cells from 4-week-old, wild-type and c-rel-/- Eμ-Myc mice. Extensive changes in gene expression were not seen at this age, but among those transcripts significantly downregulated by the loss of c-Rel was the B-cell tumour suppressor BTB and CNC homology 2 (Bach2). Quantitative PCR and western blot analysis confirmed loss of Bach2 in c-Rel mutant Eμ-Myc tumours at both 4 weeks and the terminal stages of disease. Moreover, Bach2 expression was also downregulated in c-rel-/- TCL1-Tg mice and RelA Thr505Ala mutant Eμ-Myc mice. Analysis of wild-type Eμ-Myc mice demonstrated that the population expressing low levels of Bach2 exhibited the earlier onset of lymphoma seen in c-rel-/- mice. Confirming the relevance of these findings to human disease, analysis of chromatin immunoprecipitation sequencing data revealed that Bach2 is a c-Rel and NF-κB target gene in transformed human B cells, whereas treatment of Burkitt's lymphoma cells with inhibitors of the NF-κB/IκB kinase pathway or deletion of c-Rel or RelA resulted in loss of Bach2 expression. These data reveal a surprising tumour suppressor role for c-Rel in lymphoma development explained by regulation of Bach2 expression, underlining the context-dependent complexity of NF-κB signalling in cancer.

NF-κB signaling as a driver of ageing

NF-κB signaling exerts essential roles in immunity and cellular stress responses, regulating many functions related with organism innate defense. Besides, NF-κB altered signaling has been causally linked to ageing and diverse pathological conditions. We discuss herein the functional involvement of this signaling pathway in ageing, visiting recent experimental evidence about NF-κB activation in this complex process, its functional consequences and the novel biological functions raised from these works. Moreover, we discuss ageing intervention strategies based on NF-κB inhibition, which have demonstrated to be effective at delaying and even reverting different ageing manifestations in human and mouse models of both normal and accelerated ageing. Altogether, the current evidence supports that NF-κB activation constitutes a driving force of the ageing process and a preferential target for rejuvenation-aimed approaches.

Evidence for an oncogenic modifier role for mutant histone acetyltransferases in diffuse large B-cell lymphoma

Mutations in histone acetyltransferases (HATs) are among the most common mutations in diffuse large B-cell lymphoma (DLBCL). We previously showed that two human DLBCL cell lines, RC-K8 and SUDHL2, express C-terminally truncated, HAT domain-deficient p300 proteins (p300ΔC) that are required for optimal cell proliferation. Microarray analysis of mRNA expression in RC-K8 cells following p300ΔC knockdown shows upregulation of NF-κB and p53 gene expression programs and downregulation of a MYC gene expression program. Experiments indicate that these gene expression changes are due to inhibitory effects of p300ΔC on NF-κB activity and on p53 protein levels and stimulatory effects on MYC protein levels, suggesting that p300ΔC mutants enhance the proliferation of DLBCL cells by adjusting the transcriptional output of cell-specific oncoproteins. We propose that p300/CBP gene truncation represents a new class of oncogenic mutation that optimizes the activity of context-specific oncogenic transcription factors. We propose 'oncogenic modifier' to describe such mutations.

Unexpected functions of nuclear factor-κB during germinal center B-cell development: implications for lymphomagenesis

PURPOSE OF REVIEW

B-cell tumors originating from the transformation of germinal center B cells frequently harbor genetic mutations, leading to constitutive activation of the nuclear factor-κB (NF-κB) signaling pathway. The present review highlights recent insights into the roles of separate NF-κB transcription factors in germinal center B-cell development and discusses implications of the results for germinal center lymphomagenesis.

RECENT FINDINGS

Understanding how aberrant NF-κB activation promotes tumorigenesis requires the understanding of the role of NF-κB in the tumor-precursor cells. Despite extensive knowledge on NF-κB biology, the function of this complex signaling pathway in the differentiation of germinal center B cells is largely unknown. The present review will discuss recent findings that revealed distinct roles of separate NF-κB transcription factors during the germinal center reaction in the context of germinal center lymphomagenesis. Most notably, a single NF-κB subunit, c-REL, was found to be required for the maintenance of the germinal center reaction and was associated with the activation of a metabolic program that promotes cell growth.

SUMMARY

Identifying the biological roles of the separate NF-κB transcription factor subunits in germinal center biology will help to better understand the pathogenic consequences of their constitutive activation in B-cell tumors. This knowledge may be exploited for the development of targeted antitumor therapies aimed at inhibiting selectively those components of aberrant NF-κB activity which contribute to pathogenesis.

NF-κB, an active player in human cancers

NF-κB comprises a family of five transcription factors that form distinct protein complexes, which bind to consensus DNA sequences at promoter regions of responsive genes regulating cellular processes. The past three decades have witnessed remarkable progress in understanding the NF-κB signaling pathway in physiologic and pathologic conditions. The role of NF-κB in human cancer initiation, development, metastasis, and resistance to treatment has drawn particular attention. A significant number of human cancers have constitutive NF-κB activity due to the inflammatory microenvironment and various oncogenic mutations. NF-κB activity not only promotes tumor cells' proliferation, suppresses apoptosis, and attracts angiogenesis, but it also induces epithelial-mesenchymal transition, which facilitates distant metastasis. In certain circumstances, NF-κB activation may also remodel local metabolism and anergize the immune system to favor tumor growth. Suppression of NF-κB in myeloid cells or tumor cells usually leads to tumor regression, which makes the NF-κB pathway a promising therapeutic target. However, because of its vital role in various biologic activities, components of the NF-κB pathway need to be carefully selected and evaluated to design targeted therapies.

Bridging the Gap: A Regulator of NF-κB Linking Inflammation and Cancer

BACKGROUND

A close connection between inflammation and cancer has now been firmly established. While tumor initiation is typically independent of inflammatory events, immune cells infiltrating the tumor microenvironment secrete inflammatory cytokines that enhance the aberrant growth of tumor cells and thus facilitate tumor progression. Therefore, inflammation and tumor growth are usually interpreted as closely related on a systemic level but as distinct, independently regulated processes at a molecular level.

HIGHLIGHT

Recently, we reported that a sub-class of small GTPases, namely κB-Ras1 and κB-Ras2, regulate both inflammation and tumor growth, thereby providing a unique molecular bridge between the two biological processes.

CONCLUSION

Here, we briefly summarize the known contact points between inflammation and cancer, including oral cancers, and put into context the identification of κB-Ras proteins as molecular link between two independent pathways important for tumor growth.

To be an ally or an adversary in bladder cancer: the NF-κB story has not unfolded

Signaling and regulation of transcription factor nuclear factor-kappaB (NF-κB) has been an area of extensive research since its first discovery nearly three decades ago. Members of the NF-κB family have been reported to critically mediate a multitude of responses in normal cells. Therefore, it is not surprising that NF-κB function can go awry and result in pathological conditions including cancer. Despite its critical importance, the functional role of NF-κB has not received the same attention in cancers of all tissue types. In the case of cancer of the urinary bladder, which is the second most common urologic cancer, the involvement of NF-κB in the development of superficial or muscle invasive disease and during cancer recurrence is rudimentary at best. Nuclear expression of p65/RelA is seen in bladder cancer patients and has been found to negatively affect survival of patients with superficial and muscle invasive disease. Despite these observations, the exact mechanism of NF-κB upregulation and function remains unknown. Furthermore, the emergence of a tumor suppressive role for NF-κB in recent years suggests that the family may play the role of a double-edged sword in cancer, which remains unexplored in bladder cancer. The challenge now is to delineate the increasing complexity of this pathway in the development and progression of bladder cancer. Here, we review key aspects of the current knowledge of signaling and regulation by the NF-κB family focusing on its controversial role in cancer and highlight the importance of studying NF-κB in bladder cancer in particular.

NF-κB in cancer therapy

The transcription factor nuclear factor kappa B (NF-κB) has attracted increasing attention in the field of cancer research from last few decades. Aberrant activation of this transcription factor is frequently encountered in a variety of solid tumors and hematological malignancies. NF-κB family members and their regulated genes have been linked to malignant transformation, tumor cell proliferation, survival, angiogenesis, invasion/metastasis, and therapeutic resistance. In this review, we highlight the diverse molecular mechanism(s) by which the NF-κB pathway is constitutively activated in different types of human cancers, and the potential role of various oncogenic genes regulated by this transcription factor in cancer development and progression. Additionally, various pharmacological approaches employed to target the deregulated NF-κB signaling pathway, and their possible therapeutic potential in cancer therapy is also discussed briefly.

Methods for assessing the in vitro transforming activity of NF-κB transcription factor c-Rel and related proteins

Among NF-κB transcription factors, c-Rel and c-Rel-derived proteins, including v-Rel, are the only ones that have shown consistent and frank transforming activity in cell culture. In particular, viral, chicken, mouse, and human Rel proteins can rapidly transform primary chicken spleen and bone marrow cells. Overexpression of a human Rel protein missing a C-terminal transactivation domain can also enhance the transformed state of the human B-lymphoma cell line BJAB. As described in this chapter, these in vitro assays can be used to quantitatively assess the transforming activity of Rel proteins.

Characterization of ATF2 in Rel/NFκB oncogenesis reveals its role in the regulation of Ras signaling

The v-Rel oncoprotein is the acutely transforming member of the Rel/NFκB family of transcription factors. v-Rel transforms cells through the inappropriate activation and suppression of genes normally regulated by cellular Rel/NFκB family members. We have recently demonstrated that activation of Ha-Ras by v-Rel contributes to transformation. Characterization of AP-1 family members in v-Rel-mediated transformation revealed ectopic expression of ATF2 inhibited transformation by blocking Ha-Ras activity. This lack of Ha-Ras activity prevented downstream activation of the Raf-MEK-ERK pathway, a critical pathway for v-Rel-mediated transformation. Microarray analysis of cells treated with an inhibitor to the ERK pathway revealed a relatively small number of genes that are specifically regulated by ERK activity in cells expressing v-Rel. These studies suggest the main contribution of ERK activity is to temper the expression of genes in v-Rel transformed cells. The mechanism by which ATF2 regulates Ras-Raf-MEK-ERK signaling appears to be a context dependent event. The ectopic expression of ATF2 in cells that are not expressing v-Rel results in the activation of Ha-Ras. However, activation of downstream Raf-MEK-ERK signaling pathway is blocked, likely through the recruitment of inhibitory 14-3-3 proteins to c-Raf. These results suggest a diverse role for ATF2 in the regulation of the Ras-Raf-MEK-ERK pathway.

Germinal center B cell maintenance and differentiation are controlled by distinct NF-κB transcription factor subunits

Germinal centers (GCs) are the sites where memory B cells and plasma cells producing high-affinity antibodies are generated during T cell-dependent immune responses. The molecular control of GC B cell maintenance and differentiation remains incompletely understood. Activation of the NF-κB signaling pathway has been implicated; however, the distinct roles of the individual NF-κB transcription factor subunits are unknown. We report that GC B cell-specific deletion of the NF-κB subunits c-REL or RELA, which are both activated by the canonical NF-κB pathway, abolished the generation of high-affinity B cells via different mechanisms acting at distinct stages during the GC reaction. c-REL deficiency led to the collapse of established GCs immediately after the formation of dark and light zones at day 7 of the GC reaction and was associated with the failure to activate a metabolic program that promotes cell growth. Conversely, RELA was dispensable for GC maintenance but essential for the development of GC-derived plasma cells due to impaired up-regulation of BLIMP1. These results indicate that activation of the canonical NF-κB pathway in GC B cells controls GC maintenance and differentiation through distinct transcription factor subunits. Our findings have implications for the role of NF-κB in GC lymphomagenesis.

Microarray analysis of gene expression by microdissected epidermis and dermis in mycosis fungoides and adult T-cell leukemia/lymphoma

The characteristic histopathological feature of mycosis fungoides (MF) and adult T-cell leukemia/lymphoma (ATLL) is epidermotropism. To identify the mechanism for epidermotropism of lymphoma cells, total RNAs were obtained from skin biopsies of epidermis and dermis of MF and ATLL patients by means of laser capture microdissection, and used for subsequent complementary DNA (cDNA) microarray experiments. This procedure has made it possible for us to observe and evaluate the regional environment of MF and ATLL. Hierarchical cluster analysis revealed that the cDNAs could be clearly differentiated into MF and ATLL. CCL27 was expressed in the dermis generated from keratinocytes, CCR4/CCR6/CCR7/CCR10/cutaneous lymphocyte-associated antigen (CLA) lymphoma cells in the dermis, and CCL21 in the extracellular matrix (stroma). Lymphotoxin (LT) β and CCL21 expression was significantly higher and that of CCR10 relatively for MF, while CCR4 and CLA expression was relatively higher for ATLL. In the epithelium, keratinocytes expressed CCL20/CCL27, and lymphoma cells CCR4/CCR6/CCR10, while CCR4, CCR6, CCL20 and CCL27 expression was relatively higher for ATLL than MF. The dermis of MF, but not that of ATLL, showed correlation between CCR7 and CCL21. These findings support the suggestion that chemokines and chemokine receptors are involved in the pathogenesis of MF and ATLL, indicate that cutaneous homing seems to be different for MF and ATLL, and point to the possibility that cutaneous T-cell lymphomas originate in regulatory T cells, especially in the case of ATLL.

6-Shogaol from dried ginger inhibits growth of prostate cancer cells both in vitro and in vivo through inhibition of STAT3 and NF-κB signaling

Despite much recent progress, prostate cancer continues to represent a major cause of cancer-related mortality and morbidity in men. Prostate cancer is the most common nonskin neoplasm and second leading cause of death in men. 6-Shogaol (6-SHO), a potent bioactive compound in ginger (Zingiber officinale Roscoe), has been shown to possess anti-inflammatory and anticancer activity. In the present study, the effect of 6-SHO on the growth of prostate cancer cells was investigated. 6-SHO effectively reduced survival and induced apoptosis of cultured human (LNCaP, DU145, and PC3) and mouse (HMVP2) prostate cancer cells. Mechanistic studies revealed that 6-SHO reduced constitutive and interleukin (IL)-6-induced STAT3 activation and inhibited both constitutive and TNF-α-induced NF-κB activity in these cells. In addition, 6-SHO decreased the level of several STAT3 and NF-κB-regulated target genes at the protein level, including cyclin D1, survivin, and cMyc and modulated mRNA levels of chemokine, cytokine, cell cycle, and apoptosis regulatory genes (IL-7, CCL5, BAX, BCL2, p21, and p27). 6-SHO was more effective than two other compounds found in ginger, 6-gingerol, and 6-paradol at reducing survival of prostate cancer cells and reducing STAT3 and NF-κB signaling. 6-SHO also showed significant tumor growth inhibitory activity in an allograft model using HMVP2 cells. Overall, the current results suggest that 6-SHO may have potential as a chemopreventive and/or therapeutic agent for prostate cancer and that further study of this compound is warranted.

Histone acetyltransferase-deficient p300 mutants in diffuse large B cell lymphoma have altered transcriptional regulatory activities and are required for optimal cell growth

Background

Recent genome-wide studies have shown that approximately 30% of diffuse large B-cell lymphoma (DLBCL) cases harbor mutations in the histone acetyltransferase (HAT) coactivators p300 or CBP. The majority of these mutations reduce or eliminate the catalytic HAT activity. We previously demonstrated that the human DLBCL cell line RC-K8 expresses a C-terminally truncated, HAT-defective p300 protein (p300ΔC-1087), whose expression is essential for cell proliferation.

Methods

Using results from large-scale DLBCL studies, we have identified and characterized a second C-terminally truncated, HAT-defective p300 mutant, p300ΔC-820, expressed in the SUDHL2 DLBCL cell line. Properties of p300ΔC-820 were characterized in the SUDHL2 DLBCL cell line by Western blotting, co-immunoprecipitation, and shRNA gene knockdown, as well by using cDNA expression vectors for p300ΔC-820 in pull-down assays, transcriptional reporter assays, and immunofluorescence experiments. A mass spectrometry-based method was used to compare the histone acetylation profile of DLBCL cell lines expressing various levels of wild-type p300.

Results

We show that the SUDHL2 cell line expresses a C-terminally truncated, HAT-defective form of p300 (p300ΔC-820), but no wild-type p300. The p300ΔC-820 protein has a wild-type ability to localize to subnuclear “speckles,” but has a reduced ability to enhance transactivation by transcription factor REL. Knockdown of p300ΔC-820 in SUDHL2 cells reduced their proliferation and soft agar colony-forming ability. In RC-K8 cells, knockdown of p300ΔC-1087 resulted in increased expression of mRNA and protein for REL target genes A20 and IκBα, two genes that have been shown to limit the growth of RC-K8 cells when overexpressed. Among a panel of B-lymphoma cell lines, low-level expression of full-length p300 protein, which is characteristic of the SUDHL2 and RC-K8 cells, was associated with decreased acetylation of histone H3 at lysines 14 and 18.

Conclusions

The high prevalence of p300 mutations in DLBCL suggests that HAT-deficient p300 activity defines a subtype of DLBCL, which we have investigated using human DLBCL cell lines RC-K8 and SUDHL2. Our results suggest that truncated p300 proteins contribute to DLBCL cell growth by affecting the expression of specific genes, perhaps through a mechanism that involves alterations in global histone acetylation.

Activation of nuclear factor-κB contributes to growth and aggressiveness of papillary thyroid carcinoma

Nuclear factor-κB (NF-κB) is involved in proliferation, angiogenesis, and metastasis in various malignancies; however, the role of NF-κB in papillary thyroid carcinoma (PTC) has not been fully elucidated. The purpose of this study was to elucidate the role and clinicopathological significance of the NF-κB signaling pathway in PTC. We investigated NF-κB RelA expression in 122 patients with conventional PTC by immunohistochemistry, and evaluated the correlation between RelA expression and clinicopathological parameters, including BRAF(V600E) mutation. Nuclear expression of NF-κB RelA, regardless of cytoplasmic expression, was identified in 91 of 122 PTCs (74.6%), and was more frequent in PTCs larger than 1cm (overt PTC) (P=0.001). There were significant differences in clinicopathological parameters, such as extrathyroidal extension (P=0.031), nodal metastasis (P=0.021) and BRAF(V600E) mutation (P=0.039), between NF-κB-positive and negative PTCs. Proliferation index was strongly associated with NF-κB activation (P=0.045) but not with BRAF(V600E) mutation (P=0.141). Taken together, our results suggest that NF-κB RelA activation contributes, at least in part, to tumor growth and aggressiveness of PTC after tumor transformation. The expression pattern of NF-κB may serve as a prognostic marker and a potential therapeutic target.

Dietary phytochemicals as potent chemotherapeutic agents against breast cancer: Inhibition of NF-κB pathway via molecular interactions in rel homology domain of its precursor protein p105

BACKGROUND

Dietary phytochemicals consist of a wide variety of biologically active compounds that are ubiquitous in plants, many of which have been reported to have anti-tumor as well as anti-inflammatory properties.

OBJECTIVE

In the present study, we aimed to validate these findings by using docking protocols and explicate the possible mechanism of action for a dataset of nine phytochemicals namely boswellic acid, 1-caffeoylquinic acid, ellagic acid, emodin, genistein, guggulsterone, quercetin, resveratrol, and sylibinin from different plants against the nuclear factor- kappaB (NF-κB) precursor protein p105, an important transcription factor reported to be overexpressed in breast cancer.

MATERIALS AND METHODS

2-D structures of all phytochemicals were retrieved from PubChem Compound database and their subsequent conversion into 3-D structures was performed by using online software system CORINA. The X-ray crystallographic structure of the NF-κB precursor p105 was extracted from Brookhaven Protein Data Bank. Molecular docking simulation study was carried out by using AutoDock Tools 4.0.

RESULTS

Our results showed significant binding affinity of different phytochemicals with the Rel homology domain of the NF-κB precursor protein p105. Quercetin and 1-caffeoylquinic acid were found to be very effective inhibitors against target molecule as they showed binding energy of -12.11 and -11.50 Kcal/mol, respectively. The order of affinity of other ligands with p105 was found as follows: guggulsterone > sylibinin > emodin > resveratrol > genistein > boswellic acid > ellagic acid.

CONCLUSION

Our in silico study has explored the possible chemopreventive mechanism of these phytochemicals against the NF-κB precursor protein p105 and deciphered that quercetin, 1-caffeoylquinic acid and guggulsterone were the potent inhibitors against target molecule. In addition, large scale preclinical and clinical trials are needed to explore the role of these chemotherapeutic molecules against the NF-κB precursor protein p105 in cure and prevention of breast cancer.

A Novel Herbal Medicine KIOM-MA Exerts an Anti-Inflammatory Effect in LPS-Stimulated RAW 264.7 Macrophage Cells

KIOM-MA was recently reported as a novel herbal medicine effective for atopic dermatitis and asthma. In this study, we have demonstrated the inhibitory effect of KIOM-MA on proinflammatory mediator produced in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. KIOM-MA significantly inhibited the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) as well as nitric oxide (NO) and prostaglandin E₂ (PGE₂). Consistent with the inhibitory effect on PGE₂, KIOM-MA suppresses the LPS-induced migration of macrophages and gelatinase activity and the expression of matrix metalloprotease-9 (MMP-9) in a dose-dependent manner. Additionally, KIOM-MA showed a strong suppressive effect on the inflammatory cytokines production such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). We also found that KIOM-MA inhibits the activation of nuclear factor-κB (NF-κB) and represses the activity of extracellular signal-regulated kinase (ERK), p38, and c-Jun NH₂-terminal kinase (JNK) mitogen-activated protein kinases (MAPKs). Taken together, we elucidated the mechanism of anti-inflammatory effect of KIOM-MA using RAW 264.7 cells stimulated by LPS.

The c-Rel Transcription Factor in Development and Disease

c-Rel is a member of the nuclear factor κB (NF-κB) transcription factor family. Unlike other NF-κB proteins that are expressed in a variety of cell types, high levels of c-Rel expression are found primarily in B and T cells, with many c-Rel target genes involved in lymphoid cell growth and survival. In addition to c-Rel playing a major role in mammalian B and T cell function, the human c-rel gene (REL) is a susceptibility locus for certain autoimmune diseases such as arthritis, psoriasis, and celiac disease. The REL locus is also frequently altered (amplified, mutated, rearranged), and expression of REL is increased in a variety of B and T cell malignancies and, to a lesser extent, in other cancer types. Thus, agents that modulate REL activity may have therapeutic benefits for certain human cancers and chronic inflammatory diseases.

Promising personalized therapeutic options for diffuse large B-cell Lymphoma Subtypes with oncogene addictions

Currently, two major classification systems segregate diffuse large B-cell lymphoma (DLBCL) into subtypes based on gene expression profiles and provide great insights about the oncogenic mechanisms that may be crucial for lymphomagenesis as well as prognostic information regarding response to current therapies. However, these current classification systems primarily look at expression and not dependency and are thus limited to inductive or probabilistic reasoning when evaluating alternative therapeutic options. The development of a deductive classification system that identifies subtypes in which all patients with a given phenotype require the same oncogenic drivers, and would therefore have a similar response to a rational therapy targeting the essential drivers, would significantly advance the treatment of DLBCL. This review highlights the putative drivers identified as well as the work done to identify potentially dependent populations. These studies integrated genomic analysis and functional screens to provide a rationale for targeted therapies within defined populations. Personalizing treatments by identifying patients with oncogenic dependencies via genotyping and specifically targeting the responsible drivers may constitute a novel approach for the treatment of DLBCL.

Musca domestica pupae lectin induces apoptosis in HepG2 cells through a NF-κB/p65-mediated caspase pathway

A new lectin (42 kDa) from Musca domestica pupae (MPL) has been known to inhibit proliferation in tumor cells. In this study, flow cytometry analysis showed that MPL induced HepG2 cells apoptosis significantly and the cells were arrested at S phase. MPL inhibited IκB-α degradation and NF-κB/p65 translocation from cytoplasm into nucleus. Simultaneously, the expressions of FLIP, which is a target gene of NF-κB/p65 were down-regulated and the caspase-8 and caspase-3 were then activated to induce apoptosis. Taken together, these results showed that MPL induced a caspase-dependent apoptosis via NF-κB/p65 pathway in HepG2 cells.

Roles of c-Rel signalling in inflammation and disease

Nuclear factor kappa B (NFκB) is a dimeric transcription factor comprised of five family members RelA (p65), RelB, c-Rel, p50 and p52. NFκB signalling is complex and controls a myriad of normal cellular functions. However, constitutive or aberrant activation of this pathway is associated with disease progression and cancer in multiple organs. The diverse array of biological responses is modulated by many factors, including the activating stimulus, recruitment of co-regulatory molecules, consensus DNA binding sequence, dimer composition and post-translational modifications. Each subunit has very different biological functions and in the context of disease the individual subunits forming the NFκB dimer can have a profound effect, causing a shift in the balance from normal to pathogenic signalling. Here we discuss the role of c-Rel dependant signalling in normal physiology and its contribution to disease both inside and outside of the immune system.

Inhibitory kappa B Kinases as targets for pharmacological regulation

The inhibitory kappa B kinases (IKKs) are well recognized as key regulators of the nuclear factor kappa B (NF-κB) cascade and as such represent a point of convergence for many extracellular agents that activate this pathway. The IKKs generally serve to transduce pro-inflammatory and growth stimulating signals that contribute to major cellular processes but also play a key role in the pathogenesis of a number of human diseases. Therefore, the catalytic IKKs represent attractive targets for intervention with small molecule kinase inhibitors. IKK isoforms are assembled as variable multi-subunit IKK complexes that regulate not only NF-κB dimers, but also protein substrates out-with this cascade. Consequently, close consideration of how these individual complexes transduce extracellular signals and more importantly what impact small molecule inhibitors of the IKKs have on functional outcomes are demanded. A number of adenosine triphosphate (ATP)-competitive IKKβ-selective inhibitors have been developed but have demonstrated a lack of activity against IKKα. A number of these chemicals have also exhibited detrimental outcomes such as cellular toxicity and immuno-suppression. The impact of small molecule inhibitors of IKK catalytic activity will therefore be reappraised, examining the advantages and potential disadvantages to this type of intervention strategy in the treatment of diseases such as arthritis, intestinal inflammation and cancer. Furthermore, we will outline some emerging strategies, particularly the disruption of protein-protein interactions within the IKK complex, as an alternative route towards the development of novel pharmacological agents. Whether these alternatives may negate the limitations of ATP-competitive molecules and potentially avoid the issues of toxicity will be discussed.

The diverse and complex roles of NF-κB subunits in cancer

It is only recently that the full importance of nuclear factor-κB (NF-κB) signalling to cancer development has been understood. Although much attention has focused on the upstream pathways leading to NF-κB activation, it is now becoming clear that the inhibitor of NF-κB kinases (IKKs), which regulate NF-κB activation, have many independent functions in tissue homeostasis and normal immune function that could compromise the clinical utility of IKK inhibitors. Therefore, if the NF-κB pathway is to be properly exploited as a target for both anticancer and anti-inflammatory drugs, it is appropriate to reconsider the complex roles of the individual NF-κB subunits.

Genomics of the NF-κB signaling pathway: hypothesized role in ovarian cancer

OBJECTIVE

We sought to review evidence linking nuclear factor-kappa B (NF-κB) to ovarian cancer and to identify genetic variants involved in NF-κB signaling.

METHODS

PubMed was reviewed to inform on ovarian cancer biology and NF-κB signaling and to identify key genes. Public linkage disequilibrium (LD) data were analyzed to identify informative inherited variants (tagSNPs) using ldSelect.

RESULTS

We identified 319 key NF-κB genes including five NF-κB subunits, 167 activating genes, and 55 inhibiting genes. We found that the 1000 Genomes Project was the most informative LD source for most genes (92.8%), and we identified 13,027 LD bins (r (2) ≥ 0.9, minor allele frequency ≥ 0.05) and 1,018 putative-functional variants worthy of investigation. We also report that reliance on a commonly used genome-wide SNP array and genotype imputation with HapMap Phase II data provides data on only 74% of the common inherited NF-κB SNPs of interest.

CONCLUSIONS

Compelling evidence suggests that NF-κB plays a critical role in ovarian cancer, yet inherited variation in these genes has not been thoroughly assessed in relation to disease risk or outcome. We present a collection of variants in key genes and suggest creation of a custom genotyping array as an optimal approach.

Overexpression of Forkhead Box M1 transcription factor and nuclear factor-κB in laryngeal squamous cell carcinoma: a potential indicator for poor prognosis

The Forkhead Box M1 transcription factor and nuclear factor-κB have been shown to play important roles in the development and progression of human cancers. However, the functional significance of Forkhead Box M1 transcription factor in laryngeal squamous cell carcinoma and the correlation between Forkhead Box M1 transcription factor and nuclear factor-κB remain unclear. In the current study, we have shown that Forkhead Box M1 transcription factor and nuclear factor-κB were significantly overexpressed in laryngeal squamous cell carcinoma tissues and precancerous lesions, compared with adjacent normal tissues (both P < .001). The overexpression of Forkhead Box M1 transcription factor was significantly associated with histologic differentiation (rs = 0.321, P = .002), T stage (rs = 0.276, P = .009), lymph node metastasis (rs = 0.266, P = .012), and clinical stage (rs = 0.272, P = .010); overexpression of nuclear factor-κB was significantly associated with T stage (rs = 0.404, P < .001), lymph node metastasis (rs = 0.293, P = .005), and clinical stage (rs = 0.425, P < .001). Overexpressions of both Forkhead Box M1 transcription factor and nuclear factor-κB were associated with worse overall survival (P = .041 and P < .001, respectively). Multivariate Cox regression analysis showed that T stage, lymph node metastasis, and nuclear factor-κB were independent prognostic factors for laryngeal squamous cell carcinoma (P = .038, P = .014, and P = .005, respectively). Furthermore, a significant correlation was observed between Forkhead Box M1 transcription factor and nuclear factor-κB (rs = 0.683, P < .001), indicating the potential direct or indirect interaction between them. In conclusion, our results suggest that overexpressions of Forkhead Box M1 transcription factor and nuclear factor-κB and the possible interaction between them may play important roles in the development and progression of laryngeal squamous cell carcinoma, and Forkhead Box M1 transcription factor and nuclear factor-κB may serve as useful prognostic markers for laryngeal squamous cell carcinoma.

A rearranged EP300 gene in the human B-cell lymphoma cell line RC-K8 encodes a disabled transcriptional co-activator that contributes to cell growth and oncogenicity

Human diffuse large B-cell lymphoma cell line RC-K8 has an altered EP300 locus that encodes a C-terminally truncated histone acetyltransferase (HAT) protein (p300ΔC). We now show that p300ΔC contains 1047N-terminal amino acids of p300 fused to 25 amino acids encoded by sequences from chromosome 6. Over-expressed p300ΔC localized to nuclear subdomains and interacted with transcription factor REL. p300ΔC did not function as a co-activator for REL-directed transactivation, and blocked the ability of wild-type p300 to enhance transcriptional activation by REL. Knock down of p300ΔC in RC-K8 cells reduced their growth in both liquid culture and soft agar. Truncations of p300 were not found in eight other B-lymphoma cell lines. These results suggest that p300ΔC contributes to the oncogenic state of RC-K8 cells by acting as a defective co-activator.

ERK and JNK activation is essential for oncogenic transformation by v-Rel

v-Rel is the acutely oncogenic member of the NF-κB family of transcription factors. Infection with retroviruses expressing v-Rel rapidly induces fatal lymphomas in birds and transforms primary lymphocytes and fibroblasts in vitro. We have previously shown that AP-1 transcriptional activity contributes to v-Rel-mediated transformation. While v-Rel increases the expression of these factors, their activity may also be induced through phosphorylation by the mitogen-activated protein (MAP) kinases. The expression of v-Rel results in the strong and sustained activation of the ERK and JNK MAPK pathways. This induction is critical for the v-Rel transformed phenotype, as suppression of MAPK activity with chemical inhibitors or siRNA severely impairs colony formation of v-Rel transformed lymphoid cell lines. However, signaling must be maintained within an optimal range in these cells, since strong additional activation of either pathway beyond the levels induced by v-Rel through the expression of constitutively active MAPK proteins attenuates the transformed phenotype. MAPK signaling also plays an important role in the initial transformation of primary spleen cells by v-Rel, although distinct requirements for MAPK activity at different stages of v-Rel-mediated transformation were identified. We also show that the ability of v-Rel to induce MAPK signaling more strongly than c-Rel contributes to its greater oncogenicity.

Cell transformation by v-Rel reveals distinct roles of AP-1 family members in Rel/NF-kappaB oncogenesis

Cell transformation by the v-rel oncogene is mediated by the aberrant expression of genes that are normally tightly regulated by other Rel/NF-κB family members. Although a number of genes inappropriately activated or suppressed by v-Rel have been identified, their contributions to the v-Rel transformation process have been poorly characterized. Here, we examine the role of individual AP-1 proteins in v-Rel-mediated transformation. v-Rel transformed cells exhibit elevated RNA and protein expression of c-Fos, c-Jun, and ATF2 and sustained repression of Fra-2. c-Fos and c-Jun are essential in both the initiation and maintenance of v-Rel-mediated transformation while Fra-2 is dispensable. By employing a c-Jun dimerization mutant, we further identified Fos:Jun heterodimers as major contributors to the v-Rel transformation process. The inability of c-Rel to induce the expression of c-Fos and c-Jun contributes to its weaker oncogenic potential relative to v-Rel. Our studies also demonstrate that v-Rel may induce AP-1 members by directly upregulating gene expression (c-fos and ATF2) and by activating pathways that stimulate AP-1 activity. While elevated expression of ATF2 is also required for v-Rel-mediated transformation, its ectopic overexpression is inhibitory. Investigating the mode of ATF2 regulation revealed a positive feedback mechanism whereby ATF2 induces p38 MAPK phosphorylation to further induce its own activity. In addition, these studies identified Ha-Ras as an effector of v-Rel mediated transformation and reveal a novel role for ATF2 in the inhibition of the Ras-Raf-MEK-ERK signaling pathway. Overall, these studies reveal distinct and complex roles of AP-1 proteins in Rel/NF-κB oncogenesis.