Mammary tissue microenvironment determines T cell‐dependent breast cancer‐associated inflammation

Although the importance of the host tissue microenvironment in cancer progression and metastasis has been established, the spatiotemporal process establishing a cancer metastasis‐prone tissue microenvironment remains unknown. In this study, we aim to understand the immunological character of a metastasis‐prone microenvironment in a murine 4T1 breast tumor model, by using the activation of nuclear factor‐κb (NF‐κB) in cancer cells as a sensor of inflammatory status and by monitoring its activity by bioluminescence imaging. By using a 4T1 breast cancer cell line stably expressing an NF‐κB/Luc2 reporter gene (4T1 NF‐κB cells), we observed significantly increased bioluminescence approximately 7 days after metastasis‐prone orthotopic mammary fat‐pad inoculation but not ectopic s.c. inoculation of 4T1 NF‐κB cells. Such in vivo NF‐κB activation within the fat‐pad 4T1 tumor was diminished in immune‐deficient SCID or nude mice, or T cell‐depleted mice, suggesting the requirement of host T cell‐mediated immune responses. Given the fat‐pad 4T1 tumor expressed higher inflammatory mediators in a T cell‐dependent mechanism compared to the s.c. tumor, our results imply the importance of the surrounding tissue microenvironment for inflaming tumors by collaborating with T cells to instigate metastatic spread of 4T1 breast cancer cells.     

Receptor activator for nuclear factor‐κB ligand signaling promotes progesterone‐mediated estrogen‐induced mammary carcinogenesis

Breast cancer is a leading cause of cancer‐related death in women. Prolonged exposure to the ovarian hormones estrogen and progesterone increases the risk of breast cancer. Although estrogen is known as a primary factor in mammary carcinogenesis, very few studies have investigated the role of progesterone. Receptor activator for nuclear factor‐κB (NF‐κB) ligand (RANKL) plays an important role in progesterone‐induced mammary carcinogenesis. However, the molecular mechanism underlying RANKL‐induced mammary carcinogenesis remains unknown. In our current study, we show that RANKL induces glioma‐associated oncogene homolog 1 (GLI‐1) in estrogen‐induced progesterone‐mediated mammary carcinogenesis. In vivo experiments were carried out using ACI rats and in vitro experiments were carried out in MCF‐7 cells. In ACI rats, mifepristone significantly reduced the incidence of mammary tumors. Likewise, mifepristone also inhibited the proliferation of MCF‐7 cells. Hormone treatments induced RANKL, receptor activator of NF‐κB (RANK), and NF‐κB in a protein kinase B‐dependent manner and inhibited apoptosis by activation of anti‐apoptotic protein Bcl2 in mammary tumors and MCF‐7 cells. Mechanistic studies in MCF‐7 cells reveal that RANKL induced upstream stimulatory factor‐1 and NF‐κB, resulting in subsequent activation of their downstream target GLI‐1. We have identified that progesterone mediates estrogen‐induced mammary carcinogenesis through activation of GLI‐1 in a RANKL‐dependent manner.     

p38 MAPK inhibits breast cancer metastasis through regulation of stromal expansion

p38 MAPK signaling controls cell growth, proliferation and the cell cycle under stress conditions. However, the function of p38 activation in tumor metastasis is still not well understood. We report that p38 activation in breast cancer cells inhibits tumor metastasis but does not substantially modulate primary tumor growth. Stable p38 knockdown in breast cancer cells suppressed NF‐κB p65 activation, inhibiting miR‐365 expression and resulting in increased IL‐6 secretion. The inhibitory effect of p38 signaling on metastasis was mediated by suppression of mesenchymal stem cell (MSC) migration to the primary tumor and sites of metastasis, where MSCs can differentiate into cancer‐associated fibroblasts to promote tumor metastasis. The migration of MSCs to these sites relies on CXCR4‐SDF1 signaling in the tumor microenvironment. Analysis of human primary and metastatic breast cancer tumors showed that p38 activation was inversely associated with IL‐6 and vimentin expression. This study suggests that combination analysis of p38 MAPK and IL‐6 signaling in patients with breast cancer may improve prognosis and treatment of metastatic breast cancer.     

Transglutaminase 2 reprogramming of glucose metabolism in mammary epithelial cells via activation of inflammatory signaling pathways

Aberrant glucose metabolism characterized by high levels of glycolysis, even in the presence of oxygen, is an important hallmark of cancer. This metabolic reprogramming referred to as the Warburg effect is essential to the survival of tumor cells and provides them with substrates required for biomass generation. Molecular mechanisms responsible for this shift in glucose metabolism remain elusive. As described herein, we found that aberrant expression of the proinflammatory protein transglutaminase 2 (TG2) is an important regulator of the Warburg effect in mammary epithelial cells. Mechanistically, TG2 regulated metabolic reprogramming by constitutively activating nuclear factor (NF)‐κB, which binds to the hypoxia‐inducible factor (HIF)?1α promoter and induces its expression even under normoxic conditions. TG2/NF‐κB‐induced increase in HIF‐1α expression was associated with increased glucose uptake, increased lactate production and decreased oxygen consumption by mitochondria. Experimental suppression of TG2 attenuated HIF‐1α expression and reversed downstream events in mammary epithelial cells. Moreover, downregulation of p65/RelA or HIF‐1α expression in these cells restored normal glucose uptake, lactate production, mitochondrial respiration and glycolytic protein expression. Our results suggest that aberrant expression of TG2 is a master regulator of metabolic reprogramming and facilitates metabolic alterations in epithelial cells even under normoxic conditions. A TG2‐induced shift in glucose metabolism helps breast cancer cells to survive under stressful conditions and promotes their metastatic competence.     

The effect of focal adhesion kinase gene silencing on 5‐fluorouracil chemosensitivity involves an Akt/NF‐κB signaling pathway in colorectal carcinomas

Multicellular resistance (MCR) is produced because multicellular spheroids (MCSs) are formed with a broad cell–cell connection when cultured in three‐dimensions, which limits the clinical treatment efficacy in solid tumors. Focal adhesion kinase (FAK) plays an important role in apoptosis, survival and cell adhesion between cells and their extracellular matrix. In this study, we investigated the expressions of FAK, Akt and NF‐κB in human colorectal cancer (CRC), and the effects of FAK gene silencing on MCSs formation and 5‐fluorouracil (5‐FU) chemosensitivity in colon carcinoma MCSs culture cells. In CRC samples, FAK, Akt and NF‐κB were overexpressed. The positive expression of FAK correlated notably with lymph node metastasis and cellular differentiation. Positive expressions of Akt and NF‐κB were significantly related to cellular differentiation and lymph node metastasis, respectively. Furthermore, positive expression of FAK correlated with that of Akt and NF‐κB. The expression of FAK was inhibited significantly by a small hairpin RNA targeting FAK. Knockdown of FAK reversed the formation and aggregation of MCSs, significantly decreased the 50% inhibitory concentration of 5‐FU, and markedly increased MCS culture cells apoptosis. These effects were associated with reduced levels of Akt and NF‐κB. These results indicate that suppressing FAK expression potentiated 5‐FU‐induced cytotoxicity and contributed to its chemosensitizing effect by suppressing Akt/NF‐κB signaling in colon carcinoma MCS culture cells. These data also imply that FAK mediates MCR of CRC through the survival signaling pathway FAK/Akt/NF‐κB.     

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.     

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.     

Involvement of Akt/NF‐κB pathway in N6‐isopentenyladenosine‐induced apoptosis in human breast cancer cells

N⁶‐isopentenyladenosine (i6A) inhibits the tumor cell growth by inducing cell apoptosis in various cancer cell lines. However, little is known regarding the mechanisms by which the drug induces cell apoptosis. In this study, we further explored the molecular mechanisms of i6A as an anticancer agent on a human breast cancer cell line MDA MB 231. Treatment with i6A decreased the cell proliferation of MDA MB 231 cells in a dose‐dependent manner by arresting the cells at G₀/G₁ phase. This effect was strongly associated with concomitant decrease in the level of cyclin D1, cyclin E, cdk2, and increase of p21waf1 and p27kip. In addition i6A also induced apoptotic cell death by increasing the expression of Bax, and decreasing the levels of Bcl‐2 and Bcl‐xL, and subsequently triggered mitochondria apoptotic pathway (release of cytochrome c and activation of caspase‐3). We observed that i6A suppressed the nuclear factor kappaB (NF‐κB) pathway and inhibited the Akt activation. The results of this study indicate that i6A decreases cell proliferation and induces apoptotic cell death in human breast cancer cells, possibly by decreasing signal transduction through the Akt/NF‐κB cell survival pathway. © 2010 Wiley‐Liss, Inc.     

Targeting inhibitor of apoptosis proteins by Smac mimetic elicits cell death in poor prognostic subgroups of chronic lymphocytic leukemia

Inhibitor of apoptosis (IAP) proteins are highly expressed in chronic lymphocytic leukemia (CLL) cells and contribute to evasion of cell death and poor therapeutic response. Here, we report that Smac mimetic BV6 dose‐dependently induces cell death in 28 of 51 (54%) investigated CLL samples, while B‐cells from healthy donors are largely unaffected. Importantly, BV6 is significantly more effective in prognostic unfavorable cases with, e.g., non‐mutated VH status and TP53 mutation than samples with unknown or favorable prognosis. The majority of cases with 17p deletion (10/12) and Fludarabine refractory cases respond to BV6, indicating that BV6 acts independently of p53. BV6 also triggers cell death under survival conditions mimicking the microenvironment, e.g., by adding CD40 ligand or conditioned medium. Gene expression profiling identifies cell death, NF‐κB and redox signaling among the top pathways regulated by BV6 not only in CLL but also in core‐binding factor (CBF) acute myeloid leukemia (AML). Consistently, BV6 stimulates production of reactive oxygen species (ROS), which are contributing to BV6‐induced cell death, since antioxidants reduce cell death. While BV6 causes degradation of cellular inhibitor of apoptosis (cIAP)1 and cIAP2 and nuclear factor‐kappaB (NF‐κB) pathway activation in primary CLL samples, BV6 induces cell death independently of caspase activity, receptor‐interacting protein (RIP)1 activity or tumor necrosis factor (TNF)α, as zVAD.fmk, necrostatin‐1 or TNFα‐blocking antibody Enbrel fail to inhibit cell death. Together, these novel insights into BV6‐regulated cell death in CLL have important implications for developing new therapeutic strategies to overcome cell death resistance especially in poor prognostic CLL subgroups.     

Clinicopathological significance of nuclear factor‐kappa B,HIF‐1 alpha,and vascular endothelial growth factor expression in stage III colorectal cancer

Nuclear factor‐κB (NF‐κB), hypoxia‐inducible factor 1α (HIF‐1α), and vascular endothelial growth factor (VEGF) are involved in cell proliferation, invasion, angiogenesis, and metastases. The principal objective of this study was to assess the prognostic significance of NF‐κB, HIF‐1α, and VEGF expression in stage III colorectal cancer. Tumor tissues from 148 patients with stage III colorectal carcinoma, all of whom underwent potentially curative resection, were immunohistochemically evaluated using monoclonal antibodies against NF‐κB, HIF‐1α, and VEGF. Positivity rates of NF‐κB, HIF‐1α, and VEGF were 47.3%, 42.6%, and 61.5%, respectively. NF‐κB expression in tumor tissues was correlated significantly with HIF‐1α expression (P < 0.001), VEGF expression (P = 0.044), and the presence of vascular invasion (P = 0.013). Univariate analysis demonstrated that NF‐κB expression was associated with poor 5‐year overall survival (55.8 months vs 76.9 months, P = 0.012). Multivariate analysis verified that NF‐κB was independently associated with adverse outcomes (relative risk: 1.92, P = 0.049). However, HIF‐1α and VEGF did not appear to be related to clinical outcomes. NF‐κB expression in tumor tissue is associated with angiogenesis and poor 5‐year overall survival in stage III colorectal cancer patients. (Cancer Sci 2010; 00: 000–000)     

TM‐233, a novel analog of 1′‐acetoxychavicol acetate,induces cell death in myeloma cells by inhibiting both JAK/STAT and proteasome activities

Although the introduction of bortezomib and immunomodulatory drugs has led to improved outcomes in patients with multiple myeloma, the disease remains incurable. In an effort to identify more potent and well‐tolerated agents for myeloma, we have previously reported that 1′‐acetoxychavicol acetate (ACA), a natural condiment from South‐East Asia, induces apoptotic cell death of myeloma cells in vitro and in vivo through inhibition of NF‐κB‐related functions. Searching for more potent NF‐κB inhibitors, we developed several ACA analogs based on quantitative structure–activity relationship analysis. TM‐233, one of these ACA analogs, inhibited cellular proliferation and induced cell death in various myeloma cell lines with a lower IC₅₀ than ACA. Treatment with TM‐233 inhibited constitutive activation of JAK2 and STAT3, and then downregulated the expression of anti‐apoptotic Mcl‐1 protein, but not Bcl‐2 and Bcl‐xL proteins. In addition, TM‐233 rapidly decreased the nuclear expression of NF‐κB and also decreased the accumulation of cytosolic NF‐κB. We also examined the effects of TM‐233 on bortezomib‐resistant myeloma cells that we recently established, KMS‐11/BTZ and OPM‐2/BTZ. TM‐233, but not bortezomib, inhibited cellular proliferation and induced cell death in KMS‐11/BTZ and OPM‐2/BTZ cells. Interestingly, the combination of TM‐233 and bortezomib significantly induced cell death in these bortezomib‐resistant myeloma cells through inhibition of NF‐κB activity. These results indicate that TM‐233 could overcome bortezomib resistance in myeloma cells mediated through different mechanisms, possibly inhibiting the JAK/STAT pathway. In conclusion, TM‐233 might be a more potent NF‐κB inhibitor than ACA, and could overcome bortezomib resistance in myeloma cells.     

Association between activation of atypical NF‐κB1 p105 signaling pathway and nuclear β‐catenin accumulation in colorectal carcinoma

Recent studies have demonstrated that increased expression of coding region determinant‐binding protein (CRD‐BP) in response to β‐catenin signaling leads to the stabilization of β‐TrCP1, a substrate‐specific component of SCF E3 ubiquitin ligase complex, resulting in an accelerated degradation of IκBα and activation of canonical nuclear factor‐κB (NF‐κB) pathway. Here, we show that the noncanonical NF‐κB1 p105 pathway is constitutively activated in colorectal carcinoma specimens, being particularly associated with β‐catenin‐mediated increased expression of CRD‐BP and β‐TrCP1. In the carcinoma tissues exhibiting high levels of nuclear β‐catenin the phospho‐p105 levels were increased and total p105 amounts were decreased in comparison to that of normal tissue indicating an activation of this NF‐κB pathway. Knockdown of CRD‐BP in colorectal cancer cell line SW620 resulted in significantly higher basal levels of both NF‐κB inhibitory proteins, p105 and IκBα. Furthermore decreased NF‐κB binding activity was observed in CRD‐BP siRNA‐transfected SW620 cells as compared with those transfected with control siRNA. Altogether, our findings suggest that activation of NF‐κB1 p105 signaling in colorectal carcinoma might be attributed to β‐catenin‐mediated induction of CRD‐BP and β‐TrCP1. © 2009 Wiley‐Liss, Inc.     

Enhancement of chemotherapeutic agent‐induced apoptosis by inhibition of NF‐κB using ursolic acid

NF‐κB activation is known to reduce the efficiency of chemotherapy in cancer treatment. Ursolic acid, a minimally toxic compound, has shown the capability to inhibit NF‐κB activation in living cells. Here, for the first time, we investigated the effects and mechanisms of NF‐κB inhibition by ursolic acid on chemotherapy treatment (Taxol or cisplatin) of cancer. ASTC‐a‐1 (human lung adenocarcinoma), Hela (human cervical cancer) cells, primary normal mouse cells of lung and liver and mouse in vivo model were used. Activity of signal factors (NF‐κB, Akt, Fas/FasL, BID, Bcl‐2, cytochrome c and caspase‐8, 3) was used to analyze the mechanisms of ursolic acid‐chemo treatment. Ursolic acid‐mediated suppression of NF‐κB drastically reduced the required dosage of the chemotherapeutic agents to achieve identical biological endpoints and enhanced the chemotherapeutic agent‐induced cancer cells apoptosis. Chemosensitization by ursolic acid in cancer cells was dependent on the amplified activation of intrinsic pathway (caspase‐8‐BID‐mitochondria‐cytochrome c‐caspase‐3) by augmentation of BID cleavage and activation of Fas/FasL‐caspase‐8 pathway. Prolonged treatment with relatively low doses of ursolic acid also sensitized cancer cells to the chemotherapeutic agents through suppression of NF‐κB. Chemosensitization by ursolic acid was observed only in cancer cells, but not in primary normal cells. The inhibitive effect of ursolic acid on NF‐κB was reversible, and the reversal was not accompanied by a loss in cells viability. By supplementing chemotherapy with minimally toxic ursolic acid, it is possible to improve the efficacy of cancer treatment by significantly reducing the necessary drug dose without sacrificing the treatment results.