Significance of NF‐κB activation in immortalization of nasopharyngeal epithelial cells

NF‐κB is a key regulator of inflammatory response and is frequently activated in human cancer including the undifferentiated nasopharyngeal carcinoma (NPC), which is common in Southern China including Hong Kong. Activation of NF‐κB is common in NPC and may contribute to NPC development. The role of NF‐κB activation in immortalization of nasopharyngeal epithelial (NPE) cells, which may represent an early event in NPC pathogenesis, is unknown. Examination of NF‐κB activation in immortalization of NPE cells is of particular interest as the site of NPC is often heavily infiltrated with inflammatory cellular components. We found that constitutive activation of NF‐κB signaling is a common phenotype in telomerase‐immortalized NPE cell lines. Our results suggest that NF‐κB activation promotes the growth of telomerase‐immortalized NPE cells, and suppression of NF‐κB activity inhibits their proliferation. Furthermore, we observed upregulation of c‐Myc, IL‐6 and Bmi‐1 in our immortalized NPE cells. Inhibition of NF‐κB downregulated expression of c‐Myc, IL‐6 and Bmi‐1, suggesting that they are downstream events of NF‐κB activation in immortalized NPE cells. We further delineated that EGFR/MEK/ERK/IKK/mTORC1 is the key upstream pathway of NF‐κB activation in immortalized NPE cells. Elucidation of events underlying immortalization of NPE cells may provide insights into early events in pathogenesis of NPC. The identification of NF‐κB activation and elucidation of its activation mechanism in immortalized NPE cells may reveal novel therapeutic targets for treatment and prevention of NPC.     

Antitumor effect of nuclear factor‐κB decoy transfer by mannose‐modified bubble lipoplex into macrophages in mouse malignant ascites

Patients with malignant ascites (MAs) display several symptoms, such as dyspnea, nausea, pain, and abdominal tenderness, resulting in a significant reduction in their quality of life. Tumor‐associated macrophages (TAMs) play a crucial role in MA progression. Because TAMs have a tumor‐promoting M2 phenotype, conversion of the M2 phenotypic function of TAMs would be promising for MA treatment. Nuclear factor‐κB (NF‐κB) is a master regulator of macrophage polarization. Here, we developed targeted transfer of a NF‐κB decoy into TAMs by ultrasound (US)‐responsive, mannose‐modified liposome/NF‐κB decoy complexes (Man‐PEG bubble lipoplexes) in a mouse peritoneal dissemination model of Ehrlich ascites carcinoma. In addition, we investigated the effects of NF‐κB decoy transfection into TAMs on MA progression and mouse survival rates. Intraperitoneal injection of Man‐PEG bubble lipoplexes and US exposure transferred the NF‐κB decoy into TAMs effectively. When the NF‐κB decoy was delivered into TAMs by this method in the mouse peritoneal dissemination model, mRNA expression of the Th2 cytokine interleukin (IL)‐10 in TAMs was decreased significantly. In contrast, mRNA levels of Th1 cytokines (IL‐12, tumor necrosis factor‐α, and IL‐6) were increased significantly. Moreover, the expression level of vascular endothelial growth factor in ascites was suppressed significantly, and peritoneal angiogenesis showed a reduction. Furthermore, NF‐κB decoy transfer into TAMs significantly decreased the ascitic volume and number of Ehrlich ascites carcinoma cells in ascites, and prolonged mouse survival. In conclusion, we transferred a NF‐κB decoy efficiently by Man‐PEG bubble lipoplexes with US exposure into TAMs, which may be a novel approach for MA treatment.     

Comprehensive phenotypic characterization of PTLD reveals potential reliance on EBV or NF‐κB signalling instead of B‐cell receptor signalling

Post‐transplant lymphoproliferative disorders (PTLD) are a major problem in transplant medicine. So far, the insights into pathogenesis and potentially druggable pathways in PTLD remain scarce. We investigated a cohort of PTLD patients, consisting of both polymorphic (n = 3) and monomorphic (n = 19) B‐cell lymphoproliferations. Several signalling pathways, cell of origin of PTLD and their relation to viruses were analysed by immunohistochemistry and in situ hybridization. Most PTLD were of activated B‐cell origin. Two‐thirds of cases showed an Epstein–Barr virus (EBV) infection of the neoplastic cells. NF‐κB signalling components were present in the majority of cases, except for EBV‐infected cases with latency type III lacking CD19 and upstream B‐cell signalling constituents. Proteins involved in B‐cell receptor signalling like Bruton tyrosine kinase were only present in a minority of cases. Phosphoinositide 3‐kinase (PI3K) was expressed in 94% of cases and the druggable PI3K class 1 catalytic subunit p110 in 76%, while proteins of other signalling transduction pathways were expressed only in single cases. Unsupervised cluster analysis revealed three distinct subgroups: (i) related to EBV infection, mainly latency type III and mostly lacking CD19, upstream B‐cell signalling and NF‐κB constituents; (ii) mostly related to EBV infection with expression of the alternative NF‐κB pathway compound RelB, CD10, and FOXP1 or MUM1; and finally, (iii) mostly unrelated to virus infection with expression of the classic NF‐κB pathway compound p65. EBV and NF‐κB are important drivers in PTLD in contrast to B‐cell receptor signalling. The main signal transduction pathway is related to PI3K. This links PTLD to other subgroups of EBV‐related lymphomas, highlighting also new potential treatment approaches. Copyright © 2016 John Wiley & Sons, Ltd.     

Chromosome instability in diffuse large B cell lymphomas is suppressed by activation of the noncanonical NF‐κB pathway

Diffuse large B cell lymphoma (DLBCL) is the most common form of lymphoma in the United States. DLBCL comprises biologically distinct subtypes including germinal center‐like (GCB) and activated‐B‐cell‐like DLBCL (ABC). The most aggressive type, ABC‐DLBCL, displays dysregulation of both canonical and noncanonical NF‐κB pathway as well as genomic instability. Although, much is known about the tumorigenic roles of the canonical NF‐kB pathway, the precise role of the noncanonical NF‐kB pathway remains unknown. Here we show that activation of the noncanonical NF‐κB pathway regulates chromosome stability, DNA damage response and centrosome duplication in DLBCL. Analysis of 92 DLBCL samples revealed that activation of the noncanonical NF‐κB pathway is associated with low levels of DNA damage and centrosome amplification. Inhibiting the noncanonical pathway in lymphoma cells uncovered baseline DNA damage and prevented doxorubicin‐induced DNA damage repair. In addition, it triggered centrosome amplification and chromosome instability, indicated by anaphase bridges, multipolar spindles and chromosome missegregation. We determined that the noncanonical NF‐κB pathway execute these functions through the regulation of GADD45α and REDD1 in a p53‐independent manner, while it collaborates with p53 to regulate cyclin G2 expression. Furthermore, this pathway regulates GADD45α, REDD1 and cyclin G2 through direct binding of NF‐κB sites to their promoter region. Overall, these results indicate that the noncanonical NF‐κB pathway plays a central role in maintaining genome integrity in DLBCL. Our data suggests that inhibition of the noncanonical NF‐kB pathway should be considered as an important component in DLBCL therapeutic approach.     

Capn4 is a marker of poor clinical outcomes and promotes nasopharyngeal carcinoma metastasis via nuclear factor‐κB‐induced matrix metalloproteinase 2 expression

Calpain small subunit 1 (Capn4) plays a key role in tumor migration or invasion. In this study, expression and function of Capn4 was investigated in human nasopharyngeal carcinoma (NPC). Here we report that both mRNA and protein levels of Capn4 were elevated in NPC tissues when compared to normal NP tissues. Similarly, Capn4 was also highly expressed in multiple NPC cell lines, compared to immortalized human nasopharyngeal epithelial cell line NP69. Moreover, expression of Capn4 was significantly correlated with Epstein‐Barr virus infection, advanced stages, and lymph node or distant metastasis (P < 0.001). The patients with NPC displaying higher Capn4 had a significantly shorter overall survival (P = 0.002) and progression‐free survival (P = 0.003). Furthermore, siRNA knockdown of Capn4 suppressed cell migration and invasion in vitro and in vivo. These events resulted from Capn4 downregulation were associated with reduced expression of matrix metalloproteinase 2 (MMP2), Snail, and Vimentin. Finally, we demonstrated that Capn4 upregulated MMP2 via nuclear factor‐κB (NF‐κB) activation, manifested by increased phosphorylation of p65, a subunit of NF‐κB. Together, these findings argue a novel function of Capn4 in invasion and metastasis of NPC, and thereby suggest that Capn4 may represent an independent prognostic factor and a potential therapeutic target in NPC.     

A phosphomimetic mutant of RelA/p65 at Ser536 induces apoptosis and senescence: An implication for tumor‐suppressive role of Ser536 phosphorylation

Hundreds of NF‐κB inhibitors have been developed for cancer therapy, but their clinical efficacy is unsatisfactory. Here we show that the phosphorylation activation at Ser536 of RelA/p65 protein, a main subunit in the NF‐κB family, may play a tumor‐suppressive role. In normal colon mucosa, RelA/p65 phosphorylation at Ser536 was increasingly increased with the maturation and apoptotic shedding of epithelial cells, but the phosphorylation at Ser536 was decreased in colon cancer. In colon (HCT116 p53 wt and p53 ?/?), breast (MCF7), and prostate (LNCaP and DU145) cancer cells, a phosphomimetic mutation of RelA/p65 at Ser536 (named p65/S536D) triggered dramatic apoptosis through affecting expression of a wide range of cell death/survival genes, such as Bim, Puma, Noxa, Bcl‐2 and survivin. In HCT116 cells, p65/S536D mutant upregulated Fas, insulted mitochondrial membrane potential, and triggered cleavage and activation of caspase‐3, 7, 8 and 9. A FasL neutralizing antibody (NOK1) prevented cell death induced by the p65/S536D. A pan inhibitor of caspases, Z‐VAD‐FMK (20 μM), blocked caspase‐mediated mitochondrial membrane depolarization. This p65/S536D also triggered senescence in HCT116 cells through a p16‐dependent pathway, but not in MFC7 due to lack of p16. Intratumoral delivery of the p65/S536D effectively suppressed tumor growth in nude mice. Together our data suggest that the phosphorylation of RelA/p65 at Ser536 may confer it a tumor‐suppressive role by inducing apoptosis and senescence, highlighting the importance of discriminating the function and active status of individual active sites in RelA/p65 when NF‐κB inhibitors are considered for targeted therapy of cancer.     

Oncogenic activity of BIRC2 and BIRC3 mutants independent of nuclear factor‐κB‐activating potential

BIRC2 and BIRC3 are closely related members of the inhibitor of apoptosis (IAP) family of proteins and play pivotal roles in regulation of nuclear factor‐κB (NF‐κB) signaling and apoptosis. Copy number loss for and somatic mutation of BIRC2 and BIRC3 have been frequently detected in lymphoid malignancies, with such genetic alterations being thought to contribute to carcinogenesis through activation of the noncanonical NF‐κB signaling pathway. Here we show that BIRC2 and BIRC3 mutations are also present in a wide range of epithelial tumors and that most such nonsense or frameshift mutations confer direct transforming potential. This oncogenic function of BIRC2/3 mutants is largely independent of their ability to activate NF‐κB signaling. Rather, all of the transforming mutants lack an intact RING finger domain, with loss of ubiquitin ligase activity being essential for transformation irrespective of NF‐κB regulation. The serine‐threonine kinase NIK was found to be an important, but not exclusive, mediator of BIRC2/3‐driven carcinogenesis, although this function was independent of NF‐κB activation. Our data thus suggest that, in addition to the BIRC2/3–NIK–NF‐κB signaling pathway, BIRC2/3–NIK signaling targets effectors other than NF‐κB and thereby contributes directly to carcinogenesis. Identification of these effectors may provide a basis for the development of targeted agents for the treatment of lymphoid malignancies and other cancers with BIRC2/3 alterations.     

E‐cadherin expression increases cell proliferation by regulating energy metabolism through nuclear factor‐κB in AGS cells

β‐Catenin is a central player in Wnt signaling, and activation of Wnt signaling is associated with cancer development. E‐cadherin in complex with β‐catenin mediates cell–cell adhesion, which suppresses β‐catenin‐dependent Wnt signaling. Recently, a tumor‐suppressive role for E‐cadherin has been reconsidered, as re‐expression of E‐cadherin was reported to enhance the metastatic potential of malignant tumors. To explore the role of E‐cadherin, we established an E‐cadherin‐expressing cell line, EC96, from AGS cells that featured undetectable E‐cadherin expression and a high level of Wnt signaling. In EC96 cells, E‐cadherin re‐expression enhanced cell proliferation, although Wnt signaling activity was reduced. Subsequent analysis revealed that nuclear factor‐κB (NF‐κB) activation and consequent c‐myc expression might be involved in E‐cadherin expression‐mediated cell proliferation. To facilitate rapid proliferation, EC96 cells enhance glucose uptake and produce ATP using both mitochondria oxidative phosphorylation and glycolysis, whereas AGS cells use these mechanisms less efficiently. These events appeared to be mediated by NF‐κB activation. Therefore, E‐cadherin re‐expression and subsequent induction of NF‐κB signaling likely enhance energy production and cell proliferation.     

Mutation analysis of the TNFAIP3 (A20) tumor suppressor gene in CLL

Chronic lymphocytic leukemia (CLL) cells show constitutive nuclear factor kappa B (NF‐κB) activation, which may have a pathogenetic role. The mechanisms causing this NF‐κB activity are poorly understood. A20, encoded by the TNFAIP3 gene, is a repressor of the NF‐κB pathway and was recently shown to be frequently inactivated by deletions and/or point mutations in several types of B‐cell lymphomas. Here, we studied 48 CLL, including at least 12 cases with a deletion of one allele of TNFAIP3, for mutations. However, only one case harboured a silent mutation, all other cases were unmutated. Therefore, A20 inactivation plays no significant role in the pathogenesis of CLL, and the recurrent deletion in CLL on 6q21‐23, where TNFAIP3 is located, likely affects other gene(s).     

Endoplasmic reticulum stress pathway PERK‐eIF2α confers radioresistance in oropharyngeal carcinoma by activating NF‐κB

Endoplasmic reticulum stress (ERS) plays an important role in the pathogenesis and development of malignant tumors, as well as in the regulation of radiochemoresistance and chemoresistance in many malignancies. ERS signaling pathway protein kinase RNA‐like endoplasmic reticulum kinase (PERK)‐eukaryotic initiation factor‐2 (eIF2α) may induce aberrant activation of nuclear factor‐κB (NF‐κB). Our previous study showed that NF‐κB conferred radioresistance in lymphoma cells. However, whether PERK‐eIF2α regulates radioresistance in oropharyngeal carcinoma through NF‐κB activation is unknown. Herein, we showed that PERK overexpression correlated with a poor prognosis for patients with oropharyngeal carcinoma (P < 0.01). Meanwhile, the percentage of the high expression level of PERK in oropharyngeal carcinoma patients resistant to radiation was higher than in patients sensitive to radiation (77.7 and 33.3%, respectively; P < 0.05). Silencing PERK and eIF2α increased the radiosensitivity in oropharyngeal carcinoma cells and increased radiation‐induced apoptosis and G2/M phase arrest. PERK‐eIF2α silencing also inhibited radiation‐induced NF‐κB phosphorylation and increased the DNA double strand break‐related proteins ATM phosphorylation. NF‐κB activator TNF‐α and the ATM inhibitor Ku55933 offset the regulatory effect of eIF2α on the expression of radiation‐induced cell apoptosis‐related proteins and the G2/M phase arrest‐related proteins. These data indicate that PERK regulates radioresistance in oropharyngeal carcinoma through NF‐kB activation‐mediated phosphorylation of eIF2α, enhancing X‐ray‐induced activation of DNA DSB repair, cell apoptosis inhibition and G2/M cell cycle arrest.     

Platelet‐type 12‐lipoxygenase induces MMP9 expression and cellular invasion via activation of PI3K/Akt/NF‐κB

Prostate cancer is the most frequently diagnosed cancer and the second leading cause of death in males in the United States. Using human prostate cancer specimens, the authors have previously shown that elevated expression levels of 12‐lipoxygenase (12‐LOX) occurred more frequently in advanced stage, high‐grade prostate cancer, suggesting that 12‐LOX expression is associated with carcinoma progression and invasion. Previous reports from their group and others have shown that 12‐LOX is a positive modulator of invasion and metastasis; however, the mechanism remains unclear. In this work, a new link between 12‐LOX and the matrix metalloproteinase 9 (MMP9) in prostate cancer angiogenesis is reported. This study demonstrated that overexpression of 12‐LOX in prostate cancer PC‐3 cells resulted in elevated expression of MMP9 mRNA, protein and secretion. Exogenous addition of 12(S)‐hydroxy eicosatetraenoic acid, the sole and stable end product of arachidonic acid metabolism by 12‐LOX, is able to increase MMP9 expression in wild‐type PC‐3 cells. Furthermore, using pharmacological and genetic inhibition approaches, it was found that 12‐LOX activates phosphoinositol 3 kinase (PI3K)/Akt, which results in nuclear factor‐kappa B (NF‐κB)‐driven MMP9 expression, ensuing in enhanced chemoattraction of endothelial cells. Specific inhibitors of 12‐LOX, PI3K or NF‐κB inhibited MMP9 expression in 12‐LOX‐expressing PC‐3 cells and resulted in the blockade of the migratory ability of endothelial cells. In summary, the authors have identified a new pathway by which overexpression of 12‐LOX in prostate cancer cells leads to augmented production of MMP9 via activation of PI3K/Akt/NF‐κB signaling. The role of 12‐LOX‐mediated MMP9 secretion in endothelial cell migration may account for the proangiogenic function of 12‐LOX in prostate cancer.     

Curcumin sensitizes human colorectal cancer to capecitabine by modulation of cyclin D1, COX‐2, MMP‐9, VEGF and CXCR4 expression in an orthotopic mouse model

Because of the poor prognosis and the development of resistance against chemotherapeutic drugs, the current treatment for advanced metastatic colorectal cancer (CRC) is ineffective. Whether curcumin (a component of turmeric) can potentiate the effect of capecitabine against growth and metastasis of CRC was investigated. The effect of curcumin on proliferation of CRC cell lines was examined by mitochondrial dye‐uptake assay, apoptosis by esterase staining, nuclear factor‐kappaB (NF‐κB) by electrophoretic mobility shift assay and gene expression by Western blot analysis. The effect of curcumin on the growth and metastasis of CRC was also examined in orthotopically implanted tumors in nude mice. In vitro, curcumin inhibited the proliferation of human CRC cell lines, potentiated capecitabine‐induced apoptosis, inhibited NF‐κB activation and suppressed NF‐κB‐regulated gene products. In nude mice, the combination of curcumin and capecitabine was found to be more effective than either agent alone in reducing tumor volume (p = 0.001 vs. control; p = 0.031 vs. capecitabine alone), Ki‐67 proliferation index (p = 0.001 vs. control) and microvessel density marker CD31. The combination treatment was also highly effective in suppressing ascites and distant metastasis to the liver, intestines, lungs, rectum and spleen. This effect was accompanied by suppressed expression of activated NF‐κB and NF‐κB‐regulated gene products (cyclin D1,c‐myc, bcl‐2, bcl‐xL, cIAP‐1, COX‐2, ICAM‐1, MMP‐9, CXCR4 and VEGF). Overall, our results suggest that curcumin sensitizes CRC to the antitumor and antimetastatic effects of capecitabine by suppressing NF‐κB cell signaling pathway. © 2009 UICC     

Effect of verbascoside on apoptosis and metastasis in human oral squamous cell carcinoma

Despite significant advances in therapy, the 5‐year survival rates for patients with advanced stage oral cancers still remains poor as an appropriate treatment has not been found yet, due to side effects of chemo/radiotherapy. Verbascoside (VB), a major bioactive constituent of the Tsoong herb, displays pharmacological properties by exhibiting anti‐oxidative, anti‐inflammatory and anti‐cancer activities. However, the underlining function and mechanism of VB in human oral squamous cell carcinoma (OSCC) remains unclear. In this study, we show that VB significantly decreased the viability and metastasis of HN4 and HN6 tumor cells, while promoting apoptosis. A xenograft OSCC mouse model further showed that intraperitoneal injection of VB strongly inhibited growth and lung metastasis of implanted tumor cells. Immunoblot analysis confirmed that VB effectively suppressed nuclear factor (NF)‐κB activation and downstream Bcl‐2/Bcl‐XL expression, resulting in increased OSCC cell apoptosis. In addition, VB suppressed mRNA and protein expression of matrix metalloproteinase‐9 via suppression of NF‐κB activation, thereby inhibiting tumor cell metastasis. Inspiringly, compared to cisplatin‐treated group, VB is a biocompatible agent without signficant side effects in vivo. Collectively, our results demonstrate that VB effectively inhibits OSCC tumor cell growth and metastasis via suppression of IκB kinase complex (IKK)/NF‐κB‐related signaling activation, suggesting that VB has potential use as a potent anticancer agent in OSCC therapeutic strategies.     

DCLK1 promotes epithelial‐mesenchymal transition via the PI3K/Akt/NF‐κB pathway in colorectal cancer

Double cortin‐like kinase 1 (DCLK1) plays important roles during the epithelial‐mesenchymal transition (EMT) process in human colorectal cancer (CRC). However, the role of DCLK1 in regulating the EMT of CRC is still poorly understood. In this study, we report evidence that DCLK1 acts as a potent oncogene to drive its extremely malignant character of EMT in an NF‐κB‐dependent manner in CRC cells. Mechanistic investigations showed that DCLK1 induced the NF‐κBp65 subunit expression through the PI3K/Akt/Sp1 axis and activated NF‐κBp65 through the PI3K/Akt/IκBα pathway during the EMT of CRC cells. Moreover, we found that silencing the expression of DCLK1 inhibited the invasion and metastasis of CRC cells in vivo. Collectively, our findings identify DCLK1 as a pivotal regulator of an EMT axis in CRC, thus implicating DCLK1 as a potential therapeutic target for CRC metastasis.