RETRACTED ARTICLE: Platelet-derived growth factor-D contributes to aggressiveness of breast cancer cells by up-regulating Notch and NF-κB signaling pathways

Platelet-derived growth factor-D (PDGF-D) has been linked with several human malignancies; however, its role in breast cancer progression is not known. We found that PDGF-D expressing breast cancer cell lines MDA-MB-231 and SUM-149 are more invasive compared to cell lines with little or no expression of PDGF-D such as MDA-MB-468 and MCF-7 cells. Over-expression of PDGF-D in PDGF-D low expressing MDA-MB-468 and MCF-7 cells by cDNA transfection showed increased cell proliferation while silencing the expression of PDGF-D by siRNA in PDGF-D high expressing MDA-MB-231 and SUM-149 cells showed decreased cell proliferation and increased apoptosis. Moreover, PDGF-D over-expression was positively correlated with the expression of Notch-1 and Jagged-1, and the expression of mesenchymal markers (Vimentin and ZEB-2) with concomitant decreased expression of epithelial marker E-cadherin. Since NF-κB activation plays a crucial role in Notch signaling as well as in epithelial–mesenchymal transition and tumor aggressiveness, we determined the DNA binding activity of NF-κB and our findings are consistent showing that PDGF-D over-expression led to increased DNA binding activity of NF-κB while it was found to be decreased by inactivation of PDGF-D. These results were also consistent with the expression and activity of MMP-9 and VEGF, as well as invasive characteristics. Further, forced expression of Notch-1/Jagged-1 by cDNA transfection de-repressed the effects of PDGF-D silencing on NF-κB activity and invasion. From these results, we conclude that PDGF-D plays an important role in breast tumor aggressiveness and this process is mechanistically linked with the activation of Notch and NF-κB signaling.     

Fibronectin-integrin (alpha5beta1) modulates migration and invasion of murine melanoma cell line B16F10 by involving MMP-9

Cell adhesion to extracellular matrix (ECM) initiates signaling cascade regulated by cell surface integrin receptors, which affects the proliferation and invasion of cells. Cells cultured in the presence of ECM ligand fibronectin (FN) stimulate secretion of matrix metalloproteinases (MMPs), facilitating cancer cell invasion and metastasis. Among all the members of the MMP family, MMP-9 is of crucial importance in tumor invasion and metastasis. The present study aims at studying the effects of integrin receptor alpha5beta1 and its ligand FN on expression of MMP-9 in murine melanoma cell line B16F10 and understanding the molecular mechanism(s) involved. The main experimental methods performed in the study were gelatin zymography, immunoblot, real-time RT-PCR, immunocytochemistry, enzyme linked immunosorbent assay (ELISA), transwell chamber assay, and in vivo metastasis assay in syngenic (C57BL6J) mice. The study reports that FN induces the activity, mRNA, and protein expression of MMP-9 and initiates its proteolytic activation in B16F10 cells. Blockage of the alpha5 receptor abrogated the FN-mediated stimulatory response on MMP-9 in B16F10 cells. Inhibitor studies and immunoblot analysis strongly suggest the involvement of focal adhesion kinase (FAK), extracellular regulated kinase (ERK), and phosphatidylinositol-3-kinase (PI-3K) in the FN-mediated responses. Immunocytochemical analysis showed the nuclear localization of nuclear factor-kappaB (NF-kappaB) might lead to activation of MMP-9 gene upon FN treatment. This study demonstrates that integrin receptor alpha5beta1 and FN interaction induces the invasive potential of B16F10 cells and MMP-9 induction is the downstream effectors in the process. This system serves as a novel model system to understand the molecular mechanism of melanoma growth and invasion.     

Expression of TNF-α leader sequence renders MCF-7 tumor cells resistant to the cytotoxicity of soluble TNF-α

Transmembrane TNF-α (tmTNF-α) contains a leader sequence (LS) that can be phosphorylated and cleaved at its cytoplasmic portion, inducing IL-12 production. We observed that the breast cancer cell line MDA-MB-231 expressing transmembrane TNF-α (tmTNF-α) at high level was resistant to soluble TNF-α (sTNF-α)-induced cytotoxicity, accompanied by constitutive NF-κB activation. In contrast, MCF-7 cells expressing tmTNF-α at very low level were sensitive to sTNF-α-induced cell death and had no detectable NF-κB activation. Consistently, siRNA-mediated tmTNF-α knockdown blocked NF-κB activation and rendered MDA-MB-231 sensitive. To test our hypothesis that TNF-LS may play an important role in determining the sensitivity of tumor cells to sTNF-α, we stably transfected MCF-7 cells with TNF-LS. We found that transfection of TNF-LS or wild-type TNF-α containing LS constitutively activated NF-κB and conferred the cytotoxic resistance of MCF-7 cells, while transfection of a mutant tmTNF-α lacking the cytoplasmic segment of LS neither activated NF-κB nor affected the sensitivity. However, NF-κB inhibitor PDTC suppressed NF-κB activation and reconstituted sensitivity of TNF-LS/MCF-7 cells. To check whether TNF-LS is required to be cleaved or internalized for NF-κB activation to occur, we used signal peptide peptidase inhibitor (Z-LL)₂-ketone and receptor internalization inhibitor MDC to treat cells. Interestingly, both inhibitors increased TNF-LS expression on the cell surface and enhanced NF-κB activation. These results indicate that membrane-anchored TNF-LS contributes to constitutive activation of NF-κB and resistance to sTNF-α-induced cell death. Therefore, TNF-LS appears to be responsible for tmTNF-α-induced resistance in the breast cancer cells. D. Yan and N. Qin have contributed equally to this work.     

Estrogen receptor-α and sex steroid hormones regulate Toll-like receptor-9 expression and invasive function in human breast cancer cells

Toll-like receptor 9 (TLR9) is a cellular DNA-receptor, which is widely expressed in cancer. Synthetic TLR9-ligands induce cancer cell invasion in vitro, but the role of TLR9 in cancer pathophysiology remains unclear. Increased TLR9 expression has been, however, detected in estrogen receptor negative (ER−) breast cancers. In this study, we investigated the effects of ERα expression and sex steroid hormones on TLR9 expression in human ER+ (MCF-7, T47-D) and ER− (MDA-MB-231) breast cancer cell lines in vitro. We also studied TLR9 mRNA expression in archival breast cancer specimens (n = 12) with qRT-PCR, using primer sets that detect only the TLR9A isoform or the isoforms A and B (TLR9A/B). The TLR9 mRNA expression was detected in 10/12 specimens with both primer sets, and in 1/12 with only the TLR9A or the TLR9A/B primer sets. The basal TLR9 mRNA expression levels were significantly lower in the ER+ cell lines as compared with the ER− MDA-MB-231 cells. The transfection of ERα cDNA into MDA-MB-231 cells also resulted in down-regulation of TLR9 expression. While sex steroids had no effect on TLR9 expression in MCF-7 cells, testosterone (10⁻⁸ M) induced TLR9 expression in MDA-MB-231 and T47-D cells. Although bicalutamide blocked this testosterone effect in MDA-MB-231 cells, in T47-D cells bicalutamide increased TLR9 expression and only partially blocked the testosterone effects. Estradiol (10⁻⁸ M) induced TLR9 expression in T47-D cells. The invasive effects of synthetic TLR9-ligands were augmented by testosterone in vitro. This effect was lost in TLR9 siRNA MDA-MB-231 cells and also decreased by over-expression of ERα, which also inhibited NF-κB activation by TLR9-ligands. In conclusion, expression of TLR9 isoforms A and B can be detected in clinical breast cancer specimens. The ERα and sex steroid hormones regulate TLR9 expression and invasive effects in the breast cancer cells. Also, the commonly used hormonal cancer therapy bicalutamide affects TLR9 expression.     

Down-Regulation of Notch1 and NF-κB by Curcumin in Breast Cancer Cells MDA-MB-231

Objective  To test whether the down-regulation of Notch1 gene expression by curcumin could inhibit cell growth and induce apoptosis, which may be associated mechanistically with the down-regulation of NF-κB in breast cancer cells. Methods  Breast cancer cell lines MDA-MB-231 were cultured in vitro and treated with different dosages of curcumin (0, 1.25, 5.0, 20.0μmol/L) for dose-dependent assay and different time (0, 24, 48, 72 h) at the dosage of 5.0μmol/L for time course assay. The changes of the mRNA and protein expression of Notch1 and NF-κB were measured by RT-PCR and Western Blot, and MTT assay was used to measure the change of proliferation. Results  The mRNA and protein levels of Notch1 and NF-κB were decreased significantly in human breast cancer cell line with the increase of dosage of curcumin(P<0.05), and with the extension of time course(P<0.05). These changes suggested a dose- and time-dependent manner. The proliferation rate of cells also was significantly inhibited(P<0.05). Conclusion  The current results show that the Notch-1 signaling pathway is associated mechanistically with NF-κB activity during curcumin-induced cell growth inhibition and apoptosis of breast cancer cells. These results suggest that the down-regulation of Notch signaling by curcumin may be a novel strategy for the treatment of patients with breast cancer.      

Beta-parvin inhibits integrin-linked kinase signaling and is downregulated in breast cancer

We analysed breast tumors and breast cancer cell lines for the expression of beta-parvin (ParvB), an adaptor protein that binds to the integrin-linked kinase (ILK). Quantitative RT-PCR indicated that ParvB mRNA was downregulated, by at least 60%, in four of nine breast tumors, relative to patient-matched normal mammary gland tissue. We also found that ParvB protein levels were reduced by > or =90% in five of seven advanced tumors, relative to matched normal breast tissue. Conversely, ILK protein and kinase activity levels were elevated in these tumors, suggesting that downregulation of ParvB stimulates ILK signaling. Western blot analyses indicated very low levels of ParvB protein in MDA-MB-231 and MCF7 breast cancer cells, facilitating functional studies of the effects of ParvB on ILK signaling. Expression of ParvB in MDA-MB-231 and MCF7 cells increased cell adhesion to collagen. ParvB inhibited ILK kinase activity, anchorage-independent cell growth and in vitro matrigel invasion by MDA-MB-231 cells. EGF-induced phosphorylation of two ILK targets, PKB (Ser473) and glycogen synthase kinase 3beta (Ser9), was also inhibited by ParvB. These results indicated that ParvB inhibits ILK signaling downstream of receptor tyrosine kinases. Our results suggest that loss of ParvB expression is a novel mechanism for upregulating ILK activity in tumors.     

Daintain/AIF-1 promotes breast cancer cell migration by up-regulated TNF-α via activate p38 MAPK signaling pathway

Tumor-associated macrophages can release a vast diversity of growth factors, proteolytic enzymes, cytokines, and inflammatory mediators. Many of these factors are key agents in cancer metastasis. Daintain/AIF-1 is a macrophage-derived inflammatory cytokine which defined a distinct subset of tumor-associated activated macrophages/microglial cells. Previous study demonstrated that daintain/AIF-1 could promote breast cancer proliferation through activating NF-κB/cyclin D1 pathway and facilitate tumor growth. However, the effect of Daintain/AIF-1 on cell migration and cancer metastasis has never been reported. Herein, we used a mimic tumor microenvironment by incubating breast cancer cell lines, MDA-MB-231 and MCF-7 cells, with macrophage-conditioned medium with or without purified daintain/AIF-1 polypeptide to evaluate cell migration. Results indicated that daintain/AIF-1 enhanced the migration of MDA-MB-231 and MCF-7 cells in the manner of TNF-α up-regulation. Further study found that daintain/AIF-1 activates p38 MAPK signaling pathway contributing to up-regulation of TNF-α in MDA-MB-231 and MCF-7 cells. Therefore, this novel daintain/AIF-1-p38-TNF-α pathway and insight into daintain/AIF-1 might have potential benefits in the control of tumor metastasis during cancer therapy.     

PYRROLIDINE DITHIOCARBAMATE INHIBITS NF-KB ACTIVATION AND ENHANCES TNF-INDUCED APOPTOSIS IN HUMAN BREAST CANCER CELLS

Objective: To determine whether pyrrolidine dithio-carbamate(PDTC) enhances TNFα-induced apoptosis in cultured breast cancer cells and explore the role of NF-κB in TNFα-induced apoptosis. Methods: Human breast cancer cell lines MCF-7 and MDA-MB-435s were treated with TNFα, PDTC and combination therapy. Cell survivals were determined by MTT assay. Apoptosis was detected by TUNEL and flow cytometry. NF-κB DNA binding activity was detected using electrophoresis mobility shift assay (EMSA). Western blots were performed to demonstrate IκBα(Inhibitor protein of nuclear factorκB) phosphorylation and degradation. Results: Cell growth was not suppressed by either TNFα(2000 U/ml or less) or PDTC alone. Both cell lines treated with TNFα(2000 U/ml) combined with PDTC(50 μmol/L) showed significant growth inhibition. PDTC inhibited TNFα-induced IκBα phosphorylation and degradation in both cell lines. EMSA showed that PDTC continuously inhibited TNFα induced NF-κB DNA binding activity. TNFα induced apoptosis(TUNEL) was increased significantly when both cells were pretreated with PDTC, and this was confirmed by Flow cytometry. Conclusion: PDTC enhances TNFα-induced apoptosis via inhibiting IκBα phosphorylation and degradation in human breast cancer cells. NF-κB protects against TNFα-induced apoptosis.     

Pim-2 Activates API-5 to Inhibit the Apoptosis of Hepatocellular Carcinoma Cells Through NF-κB Pathway

Pim-2 is proved to be relevant to the tumorigenesis of hepatocellular carcinoma (HCC), but the mechanism is unclear. We studied the relationship among Pim-2, NF-κB and API-5. In our experiment, expression level of the three factors and phosphorylation level of API-5, as well as NF-κB activity, were detected in HCC tissues and the nontumorous controls. Then Pim-2 gene was transfected into nontumorous liver cells L02, and Pim-2 SiRNA was transfected into hepatoblastoma cell line HepG2. Parthenolide was added as NF-κB inhibitor. The same detections as above were repeated in the cells, along with the apoptosis analysis. We found the levels of Pim-2, NF-κB and API-5, as well as NF-κB activity, were significantly higher in HCC tissues. Pim-2 level was increased in L02 cells after the transfection of Pim-2 gene, but decreased in HepG2 cells after the transfection of Pim-2 SiRNA. The levels of NF-κB and API-5, as well as NF-κB activity and API-5 phosphorylation level, were in accordance with Pim-2 level, but could be reversed by Parthenolide. Cell apoptosis rates were negatively correlated with API-5 phosphorylation level. Therefore, we infer that Pim-2 could activate API-5 to inhibit the apoptosis of liver cells, and NF-κB is the key regulator.     

HGF upregulates CXCR4 expression in gliomas via NF-κB: implications for glioma cell migration

Invasion is a hallmark of malignant gliomas and is the main reason for therapeutic failure and recurrence of the tumor. CXCR4 is a key chemokine receptor implicated in glioma cell migration whose expression is regulated by hypoxia. Here, we report that hepatocyte growth factor (HGF) upregulated CXCR4 protein expression in glioma cells. HGF pre-treatment increased migration of U87MG and LN229 glioma cells towards the CXCR4 ligand, stromal cell-derived factor-1α (SDF-1α). AMD3100, a CXCR4 inhibitor, inhibited the increased migration of HGF pre-treated LN229 glioma cells towards SDF-1α. Following exposure to HGF and hypoxia, both cell lines showed nuclear translocation of NF-κB (p65). The HGF- and hypoxia-induced nuclear translocation of NF-κB (p65) involved phosphorylation and degradation of IκB-α. Knock-down of NF-κB expression inhibited the induction of CXCR4 expression in response to HGF, but not to hypoxia. However, knock-down of NF-κB expression inhibited the induction of CXCR4 expression in response to hypoxia in the presence of HGF. NF-κB mediated migration towards SDF-1α in response to HGF. Knock-down of NF-κB expression resulted in decreased migration of HGF pre-treated glioma cells towards SDF-1α. Therefore, HGF upregulates CXCR4 expression via NF-κB and leads to enhanced migration. To our knowledge, this is the first report to show that a crosstalk mediated by NF-κB exists between the SDF-1α/CXCR4 and HGF/c-Met axes relevant to glioma cell migration. These findings imply that effective inhibition of glioma invasion should be directed against several ligand/receptor signaling pathways.     

The nonsteroidal anti-inflammatory drug celecoxib suppresses the growth and induces apoptosis of human glioblastoma cells via the NF-κB pathway

Gliomas are devastating primary tumors of the central nervous system and tend to recur even after standard therapy. Celecoxib, the selective COX-2 nonsteroidal anti-inflammatory drug, has anti-neoplastic activity against several malignancies. Accumulating evidence suggests that several COX-2-independent mechanisms may also be involved in the anti-tumor effects of celecoxib. Deregulation of the NF-κB signaling pathway contributes to enhanced glioma cell survival, proliferation, and chemoresistance. In this study, we examined the efficacy of celecoxib in suppressing the growth of glioblastoma cell lines. We observed that treatment with celecoxib significantly reduced the proliferation of a variety of GBM cell lines in a dose-dependent manner and also induced apoptosis, which was evident from enhanced caspase-3 and 8 activity, PARP cleavage, and TUNEL positive cells. Celecoxib treatment significantly down-regulated TNF-α induced NF-κB nuclear translocation, NF-κB DNA binding activity, and NF-κB-dependent reporter gene expression in U373 and T98G cells in a dose-dependent manner. Furthermore, celecoxib suppressed IκBα degradation and phosphorylation and reduced IKK activity in a dose-dependent manner. This study provides evidence that celecoxib suppresses the growth of GBM cell lines partly by inhibiting the NF-κB signaling pathway.     

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.     

Inhibition of NF-κB signaling commits resveratrol-treated medulloblastoma cells to apoptosis without neuronal differentiation

Resveratrol promotes differentiation and apoptosis of medulloblastoma cells by suppressing STAT3 signaling and a range of cancer-associated gene expression. However, Bcl-2, a common target of STAT3 and NF-κB signaling, is distinctly up-regulated in resveratrol-treated medulloblastoma cells, indicating potential effects of NF-κB in Bcl-2 expression and anti-medulloblastoma efficiency of resveratrol. To clarify this point, the status of NF-κB signaling and the consequence of NF-κB inhibition in UW228-2 and UW228-3 medulloblastoma cells without and with resveratrol treatment were evaluated by several experimental approaches. The results revealed that resveratrol activated NF-κB signaling in both cell lines at the 4-h treatment point, and the treated cells sequentially exhibited Bcl-2 up-regulation, neuronal-like phenotype with synaptophisin expression, and, eventually, apoptosis. Pyrrolidine dithiocarbamate (PDTC) treatment inhibited NF-κB activation and Bcl-2 expression and committed resveratrol-treated cells to apoptosis at the 8-h time point without the step of neuron-oriented differentiation. On the other hand, a single 50 μg/ml lipopolysaccharide (LPS) treatment activated NF-κB signaling accompanied with sustained proliferation and neuron-like differentiation. Tissue microarray-based immunohistochemical staining showed significantly different (P < 0.001) p65 nuclear translocation between the neurons of tumor-surrounding cerebella (10/10; 100%) and medulloblastoma tissues (20/117; 17.09%). Additionally, synaptophysin production was found in 83.64% of p65-positive and in 40.35% of p65-negative medulloblastoma cases. Our in-vitro and in-vivo results thus demonstrate the dual effects of NF-κB signaling on medulloblastoma cells by delaying resveratrol-induced apoptosis by up-regulating Bcl-2 expression or by involvement in neuronal-like differentiation in the absence of resveratrol. Therefore, appropriate inhibition of NF-κB activation may enhance the anti-medulloblastoma efficacy of resveratrol.     

Visfatin promotes cell and tumor growth by upregulating Notch1 in breast cancer

Overexpression of Notch1 has been associated with breast cancer. We recently showed that visfatin stimulates breast cancer cell proliferation and invasion. The present study was undertaken to determine whether Notch1 signaling is affected by visfatin and to characterize the functional role of the visfatin-Notch1 axis in breast cancer. Visfatin and Notch1 were expressed at higher levels in breast tumors than in matched control tissues. Visfatin induced Notch1 expression in MDA-MB-231 breast cancer cell line and in nontransformed MCF10A mammary epithelial cells, whereas visfatin depletion reduced Notch1 mRNA and protein levels. Depletion of Notch1 in MDA-MB-231 cells attenuated cell growth in vitro and in vivo; visfatin depletion produced similar effects, but was less potent. Additionally, Notch1 depletion inhibited cell proliferation induced by visfatin. Analysis of the signaling pathways underlying visfatin-mediated Notch1 upregulation revealed that visfatin activated NF-κB p65. Blockade of NF-κB signaling suppressed the effects of visfatin on Notch1 upregulation and breast cancer cell proliferation. Breast tumors expressing high levels of NF-κB p65 exhibited increased expression of Notch1. Our results demonstrate that the visfatin-Notch1 axis contributes to breast tumor growth through the activation of the NF-κB pathway. Study of the visfatin-Notch1 axis may offer new therapeutic directions for breast cancer.     

The alpha 3 beta 1 integrin is associated with mammary carcinoma cell metastasis, invasion, and gelatinase B (MMP-9) activity

The alpha 3 beta 1 integrin is elevated in several types of metastatic tumor and has been associated with increased migration and invasion. Our analysis of a series of mammary carcinomas of different histotypes and their corresponding metastases demonstrated significantly increased expression of alpha 3 beta 1 in the tumor metastases. We therefore studied alpha 3 beta 1 expression of several human breast carcinoma cell lines and its association with the invasive phenotype. The MDA-MB-231 cell line expressed high levels of the beta1, alpha 2, alpha 3, alpha 5, and alpha 6 integrin subunits along with moderate levels of the alpha v beta 3 integrin. This line was highly migratory and the most invasive using a chemo-invasion assay. In contrast, the other lines tested, MDA-MB-145, MCF-7, and SK-BR-3, showed lower migratory and invasive activity and reduced alpha 3 integrin subunit expression. Metalloproteases capable of degrading collagen IV are necessary for the invasive process. RT-PCR showed that MDA-MB-231 cells expressed MMP-9, but not MMP-2, gelatinase/collagenase IV. Gelatin zymography demonstrated that invading MDA-MB-231 cells released high levels of MMP-9 gelatinase activity. A direct role for this gelatinase in MDA-MB-231 cell invasion was confirmed by inhibition of invasion using the metalloprotease inhibitor Batimastat. Treatment of MDA-MB-231 cells with a function-blocking anti-alpha 3 antibody strongly inhibited migration and invasion. This correlated with a marked reduction in MMP-9 activity produced by MDA-MB-231 cells, suggesting a role for alpha 3 beta 1 ligand binding in cell signaling and regulation of extracellular matrix degradation.