Kruppel-like Factor 6 Promotes Macrophage-mediated Inflammation by Suppressing B Cell Leukemia/Lymphoma 6 Expression.

Macrophages are the predominant innate immune cells recruited to tissues following injury or infection. These early-responding, pro-inflammatory macrophages play an essential role in the amplification of inflammation. However, macrophage pro-inflammatory gene expression should be tightly regulated to avert host tissue damage. In this study, we identify the Kruppel-like transcription factor 6 (KLF6)-B cell leukemia/lymphoma 6 (BCL6) signaling axis as a novel regulator of macrophage inflammatory gene expression and function. Utilizing complementary gain- and loss-of-function studies, we observed that KLF6 is essential for macrophage motility under ex vivo and in vivo conditions. Concordant with these observations, myeloid-specific deficiency of KLF6 significantly attenuates macrophage pro-inflammatory gene expression, recruitment, and progression of inflammation. At the molecular level, KLF6 suppresses BCL6 mRNA and protein expression by elevating PR domain-containing 1 with ZNF domain (PRDM1) levels in macrophages. Interestingly, pharmacological or genetic inhibition of BCL6 in KLF6-deficient macrophages completely abrogated the attenuation of pro-inflammatory cytokine/chemokine expression and cellular motility. Collectively, our observations reveal that KLF6 repress BCL6 to enhance macrophage inflammatory gene expression and function.

Plasminogen promotes macrophage phagocytosis in mice.

The phagocytic function of macrophages plays a pivotal role in eliminating apoptotic cells and invading pathogens. Evidence implicating plasminogen (Plg), the zymogen of plasmin, in phagocytosis is extremely limited with the most recent in vitro study showing that plasmin acts on prey cells rather than on macrophages. Here, we use apoptotic thymocytes and immunoglobulin opsonized bodies to show that Plg exerts a profound effect on macrophage-mediated phagocytosis in vitro and in vivo. Plg enhanced the uptake of these prey by J774A.1 macrophage-like cells by 3.5- to fivefold Plg receptors and plasmin proteolytic activity were required for phagocytosis of both preys. Compared with Plg(+/+) mice, Plg(-/-) mice exhibited a 60% delay in clearance of apoptotic thymocytes by spleen and an 85% reduction in uptake by peritoneal macrophages. Phagocytosis of antibody-mediated erythrocyte clearance by liver Kupffer cells was reduced by 90% in Plg(-/-) mice compared with Plg(+/+) mice. A gene array of splenic and hepatic tissues from Plg(-/-) and Plg(+/+) mice showed downregulation of numerous genes in Plg(-/-) mice involved in phagocytosis and regulation of phagocytic gene expression was confirmed in macrophage-like cells. Thus, Plg may play an important role in innate immunity by changing expression of genes that contribute to phagocytosis.

Kruppel-like transcription factor 6 regulates inflammatory macrophage polarization.

Accumulating evidence supports the importance of macrophage plasticity in a broad spectrum of biological processes operative in health and disease. A major locus of control regulating macrophage polarization is at the transcriptional level, and several major pathways have been elucidated in recent years. In this study, we identify the Kruppel-like transcription factor 6 (KLF6) as a molecular toggle controlling macrophage speciation. KLF6 expression was robustly induced by pro-inflammatory M1 stimuli (e.g. LPS and IFN-γ) and strongly suppressed by M2 stimuli (e.g. IL4 and IL-13) in human and murine macrophages. Gain- and loss-of-function studies suggest that KLF6 is required for optimal LPS-induced pro-inflammatory gene expression, acting cooperatively with NF-κB. Furthermore, KLF6 inhibits anti-inflammatory gene expression by negatively regulating peroxisome proliferator-activated receptor γ expression in macrophages. Collectively, these observations identify KLF6 as a novel transcriptional regulator of macrophage polarization.

Macrophage gene expression and foam cell formation are regulated by plasminogen.

BACKGROUND: Deciphering the molecular and cellular processes that govern macrophage foam cell formation is critical to understanding the basic mechanisms underlying atherosclerosis and other vascular pathologies. METHODS AND RESULTS: Here, we identify a pivotal role of plasminogen (Plg) in regulating foam cell formation. Deficiency of Plg inhibited macrophage cholesterol accumulation on exposure to hyperlipidemic conditions in vitro, ex vivo, and in vivo. Gene expression analysis identified CD36 as a regulated target of Plg, and macrophages from Plg(-/-) mice had decreased CD36 expression and diminished foam cell formation. The Plg-dependent CD36 expression and foam cell formation depended on conversion of Plg to plasmin, binding to the macrophage surface, and the consequent intracellular signaling that leads to production of leukotriene B4. Leukotriene B4 rescued the suppression of CD36 expression and foam cell formation arising from Plg deficiency. CONCLUSIONS: Our findings demonstrate an unanticipated role of Plg in the regulation of gene expression and cholesterol metabolism by macrophages and identify Plg-mediated regulation of leukotriene B4 as an underlying mechanism.

Identification and interpretation of TET2 noncanonical splicing site intronic variants in myeloid neoplasm patients.

Background: DNA hypermethylation and instability due to inactivation mutations in Ten-eleven translocation 2 (TET2) is a key biomarker of hematological malignancies. This study aims at characterizing two intronic noncanonical splice-site variants, c.3954+5_3954+8delGTTT and c.3954+5G>A. Methods: We used in silico prediction tools, reverse transcription (RT)-PCR, and Sanger sequencing on blood/bone marrow-derived RNA specimens to determine the aberrant splicing. Results: In silico prediction of both variants exhibited reduced splicing strength at the TET2 intron 7 splicing donor site. RT-PCR and Sanger sequencing identified a 62-bp deletion at the exon 7, producing a frameshift mutation, p.Cys1298*. Conclusion: This study provides functional evidence for two intronic TET2 variants that cause alternative splicing and frameshift mutation.

So many plasminogen receptors: why?

Plasminogen and plasmin tether to cell surfaces through ubiquitously expressed and structurally quite dissimilar family of proteins, as well as some nonproteins, that are collectively referred to as plasminogen receptors. Of the more than one dozen plasminogen receptors that have been identified, many have been shown to facilitate plasminogen activation to plasmin and to protect bound plasmin from inactivation by inhibitors. The generation of such localized and sustained protease activity is utilized to facilitate numerous cellular responses, including responses that depend on cellular migration. However, many cells express multiple plasminogen receptors and numerous plasminogen receptors are expressed on many different cell types. Furthermore, several different plasminogen receptors can be used to support the same cellular response, such as inflammatory cell migration. Here, we discuss the perplexing issue: why are there so many different Plg-Rs?

Identification of Novel MET Exon 14 Skipping Variants in Non-Small Cell Lung Cancer Patients: A Prototype Workflow Involving in Silico Prediction and RT-PCR.

Background and aims: The MET exon 14 skipping (METex14) is an oncogenic driver mutation that provides a therapeutic opportunity in non-small cell lung cancer (NSCLCs) patients. This event often results from sequence changes at the MET canonical splicing sites. We characterize two novel non-canonical splicing site variants of MET that produce METex14. Materials and Methods: Two variants were identified in three advanced-stage NSCLC patients in a next-generation sequencing panel. The potential impact on splicing was predicted using in silico tools. METex14 mutation was confirmed using reverse transcription (RT)-PCR and a Sanger sequencing analysis on RNA extracted from stained cytology smears. Results: The interrogated MET (RefSeq ID NM_000245.3) variants include a single nucleotide substitution, c.3028+3A>T, in intron 14 and a deletion mutation, c.3012_3028del, in exon 14. The in silico prediction analysis exhibited reduced splicing strength in both variants compared with the MET normal transcript. The RT-PCR and subsequent Sanger sequencing analyses confirmed METex14 skipping in all three patients carrying these variants. Conclusion: This study reveals two non-canonical MET splice variants that cause exon 14 skipping, concurrently also proposes a clinical workflow for the classification of such non-canonical splicing site variants detected by routine DNA-based NGS test. It shows the usefulness of in silico prediction to identify potential METex14 driver mutation and exemplifies the opportunity of routine cytology slides for RNA-based testing.

L-type calcium channel blockers exert an antiinflammatory effect by suppressing expression of plasminogen receptors on macrophages.

L-type Ca(2+) channel (LTCC) blockers, represented by amlodipine and verapamil, are widely used antihypertensive drugs that also have antiinflammatory activities. Plasminogen (Plg) is an important mediator of macrophage recruitment, and this role depends on its interaction with Plg receptors (Plg-Rs). Plg-Rs include histone 2B, alpha-enolase, annexin 2, and p11, all proteins which lack signal sequences for cell surface export. When human or murine monocytoid cells were induced to differentiate into macrophages, their Plg binding and Plg-R expression increased by 4-fold. These changes were suppressed by pretreatment with verapamil and amlodipine. Expression of the Ca(v)1.2 LTCC pore subunit was induced in differentiated macrophages, and siRNA against this subunit suppressed the upregulation of Plg binding and Plg-Rs. In vivo, amlodipine and verapamil suppressed peritoneal macrophage recruitment in response to thioglycollate by >60% at doses that did not affect blood pressure. In drug-treated animals, macrophages migrated into but not through the peritoneal membrane tissue and showed reduced surface expression of Plg-Rs. These findings demonstrate that Plg-R expression on macrophages is dependent on Ca(v)1.2 LTCC subunit expression. Suppression of Plg-Rs may contribute to the antiinflammatory effects of the widely used LTCC blockers.

Plasminogen-induced foam cell formation by macrophages occurs through a histone 2B (H2B)-PAR1 pathway and requires integrity of clathrin-coated pits.

OBJECTIVE: Plasminogen/plasmin is a serine protease system primarily responsible for degrading fibrin within blood clots. Plasminogen mediates its functions by interacting with plasminogen receptors on the cell surface. H2B, one such plasminogen receptor, is found on the surface of several cell types including macrophages. Both basic and clinical studies support the role of plasminogen in the process of foam cell formation (FCF), a hallmark of atherosclerosis. Growing evidence also implicates serine protease-activated receptors (PARs) in atherosclerosis. These receptors are also found on macrophages, and plasmin is capable of activating PAR1 and PAR4. The goal of this study was to determine the extent of H2B's contribution to plasminogen-mediated FCF by macrophages and if PARs are involved in this process. APPROACH AND RESULTS: Treating macrophages with plasminogen increases their oxidized low-density lipoprotein uptake and plasminogen-mediated foam cell formation (Plg-FCF) significantly. The magnitude of Plg-FCF correlates with cell-surface expression of the H2B level. H2B blockade or downregulation reduces Plg-FCF, whereas its overexpression or high endogenous levels increases Plg-FCF. Modulating PAR1 level in mouse macrophages affects Plg-FCF. Activation/overexpression of PAR1 increases and its blockade/knockdown reduces this response. Confocal imaging indicates that both H2B and PAR1 colocalize with clathrin coated pits on the surface of macrophages, and reducing expression of clathrin or interfering with the clathrin-coated pits integrity reduces Plg-FCF. CONCLUSION: Our data indicate that the magnitude of Plg-FCF by macrophages is proportional to the H2B levels and demonstrate for the first time that PAR1 is involved in this process and that the integrity of clathrin-coated pits is required for the full effect of Plg-induced FCF.

CITED2 Restrains Proinflammatory Macrophage Activation and Response.

Macrophages are strategically distributed in mammalian tissues and play an essential role in priming the immune response. However, macrophages need to constantly strike a balance between activation and inhibition states to avoid a futile inflammatory reaction. Here, we identify the CBP/p300-interacting transactivator with glutamic acid/aspartic acid-rich carboxyl-terminal domain 2 (CITED2) as a potent repressor of macrophage proinflammatory activation. Gain- and loss-of-function studies revealed that CITED2 is required for optimal peroxisome proliferator-activated receptor gamma (PPARγ) activation and attendant select anti-inflammatory gene expression in macrophages. More importantly, deficiency of CITED2 resulted in significant attenuation of rosiglitazone-induced PPARγ activity, PPARγ recruitment to target gene promoters, and anti-inflammatory target gene expression in macrophages. Interestingly, deficiency of Cited2 strikingly heightened proinflammatory gene expression through stabilization of hypoxia-inducible factor 1 alpha (HIF1α) protein in macrophages. Further, overexpression of Egln3 or inhibition of HIF1α in Cited2-deficient macrophages completely reversed elevated proinflammatory cytokine/chemokine gene expression. Importantly, mice bearing a myeloid cell-specific deletion of Cited2 were highly susceptible to endotoxin-induced sepsis symptomatology and mortality. Collectively, our observations identify CITED2 as a novel negative regulator of macrophage proinflammatory activation that protects the host from inflammatory insults.

Plasminogen promotes cholesterol efflux by the ABCA1 pathway.

Using genetic and biochemical approaches, we investigated proteins that regulate macrophage cholesterol efflux capacity (CEC) and ABCA1-specific CEC (ABCA1 CEC), 2 functional assays that predict cardiovascular disease (CVD). Macrophage CEC and the concentration of HDL particles were markedly reduced in mice deficient in apolipoprotein A-I (APOA1) or apolipoprotein E (APOE) but not apolipoprotein A-IV (APOA4). ABCA1 CEC was markedly reduced in APOA1-deficient mice but was barely affected in mice deficient in APOE or APOA4. High-resolution size-exclusion chromatography of plasma produced 2 major peaks of ABCA1 CEC activity. The early-eluting peak, which coeluted with HDL, was markedly reduced in APOA1- or APOE-deficient mice. The late-eluting peak was modestly reduced in APOA1-deficient mice but little affected in APOE- or APOA4-deficient mice. Ion-exchange chromatography and shotgun proteomics suggested that plasminogen (PLG) accounted for a substantial fraction of the ABCA1 CEC activity in the peak not associated with HDL. Human PLG promoted cholesterol efflux by the ABCA1 pathway, and PLG-dependent efflux was inhibited by lipoprotein(a) [Lp(a)]. Our observations identify APOA1, APOE, and PLG as key determinants of CEC. Because PLG and Lp(a) associate with human CVD risk, interplay among the proteins might affect atherosclerosis by regulating cholesterol efflux from macrophages.

Plasminogen and its receptors as regulators of cardiovascular inflammatory responses.

In addition to its role in fibrinolysis, plasminogen (Plg) influences inflammatory cell migration and thereby plays a prominent role in cardiovascular pathology. The contribution of Plg to inflammatory cell recruitment depends on its tethering to the surface of responding cells. Plasminogen receptors (Plg-Rs) are heterogeneous and can be classified as tailless, lacking cytoplasmic tails, or tailed (having cytoplasmic tails). In vivo observations implicate several tailless Plg-Rs in inflammatory responses. Tailed Plg-Rs on leukocytes include several integrins, which have also been implicated in Plg-dependent responses. Surface expression of both tailless and tailed Plg-Rs can be modulated in number and/or function. A common mechanism involving intracellular calcium mobilization and calcium channels regulates expression of both classes of Plg-Rs. Data are emerging to indicate that targeting Plg and Plg-Rs may limit inflammation and cardiovascular pathology.

Histone H2B as a functionally important plasminogen receptor on macrophages.

Plasminogen (Plg) facilitates inflammatory cell recruitment, a function that depends upon its binding to Plg receptors (Plg-Rs). However, the Plg-Rs that are critical for cell migration are not well defined. Three previously characterized Plg-Rs (alpha-enolase, annexin 2, and p11) and a recently identified Plg-R (histone H2B [H2B]) were assessed for their contribution to Plg binding and function on macrophages. Two murine macrophage cell lines (RAW 264.7 and J774A.1) and mouse peritoneal macrophages induced by thioglycollate were analyzed. All 4 Plg-Rs were present on the surface of these cells and showed enhanced expression on the thioglycollate-induced macrophages compared with peripheral blood monocytes. Using blocking Fab fragments to each Plg-R, H2B supported approximately 50% of the Plg binding capacity, whereas the other Plg-Rs contributed less than 25%. Anti-H2B Fab also demonstrated a major role of this Plg-R in plasmin generation and matrix invasion. When mice were treated intravenously with anti-H2B Fab, peritoneal macrophage recruitment in response to thioglycollate was reduced by approximately 45% at 24, 48, and 72 hours, with no effect on blood monocyte levels. Taken together, these data suggest that multiple Plg-Rs do contribute to Plg binding to macrophages, and among these, H2B plays a very prominent and functionally important role.

Identification of histone H2B as a regulated plasminogen receptor.

Tethering of plasminogen to cell surfaces controls plasmin formation and, thereby, influences pericellular proteolysis and cell migration. Modulation of cellular plasminogen binding sites provides a mechanism for regulation of these events. In this study, two distinct models, phorbol ester-stimulated adhesion of U937 monocytoid cells and culturing of peripheral blood neutrophils, treatments which modulate plasminogen binding sites, have been examined to determine the molecular basis for the upregulation of plasminogen receptors. Membranes were isolated from cell populations, with and without upregulated plasminogen binding capacities, and analyzed by [(125)I]plasminogen ligand blotting of gel transfers. Approximately 15 different [(125)I]plasminogen-binding proteins were discerned in the membrane fractions, and only relatively minor differences in the intensities of individual bands were noted in the different cell populations. The notable exception was the presence of a 17 kDa band, which was selectively and markedly enhanced in the membranes from cells with enhanced plasminogen binding capacities. The 17 kDa protein was isolated from both cell types, and amino acid sequencing of peptide fragments identified the same protein, histone H2B. Increased expression of histone H2B was observed on stimulated U937 cells and cultured neutrophils by confocal microscopy with an antibody raised to the carboxy-terminal octopeptide sequence of histone H2B. This antibody or its Fab fragments substantially decreased the level of binding of plasminogen to these cultured neutrophils and stimulated U937 cells that exhibited elevated levels of binding but not to nonstimulated cells. Thus, histone H2B represents a regulated plasminogen receptor, which contributes significantly to the plasminogen binding capacity of cells.

Osteopontin: it's role in regulation of cell motility and nuclear factor kappa B-mediated urokinase type plasminogen activator expression.

Cancer progression depends on an accumulation of metastasis supporting cell signaling molecules that target signal transduction pathways and ultimately gene expression. Osteopontin (OPN) is one such chemokine like metastasis gene which plays a key signaling event in regulating the oncogenic potential of various cancers by controlling cell motility, invasiveness and tumor growth. We have reported that OPN stimulates tumor growth and nuclear factor kappaB (NFkappaB)-mediated promatrix metalloproteinase-2 (pro-MMP-2) activation through IkappaBalpha/IKK (IkappaBalpha kinase) signaling pathway in melanoma cells. Urokinase type plasminogen activator (uPA), a widely acting serine protease degrades the ECM components and plays a pivotal role in cancer progression. However, the molecular mechanism by which upstream kinases regulate the OPN-induced NFkappaB activation and uPA secretion in human breast cancer cells is not well defined. Here we report that OPN induces the phosphatidylinositol 3'-kinase (PI 3'-kinase) activity and phosphorylation of Akt/PKB (protein kinase B) in highly invasive (MDA-MB-231) and low invasive (MCF-7) breast cancer cells. The OPN-induced Akt phosphorylation was inhibited when cells were transfected with dominant negative mutant of p85 domain of PI 3'-kinase (Deltap85) indicating that PI 3'-kinase is involved in Akt phosphorylation. OPN enhances the interaction between IkappaBalpha kinase (IKK) and phosphorylated Akt. OPN also induces NFkappaB activation through phosphorylation and degradation of IkappaBalpha by inducing the IKK activity. OPN also enhances uPA secretion, cell motility and ECM-invasion. Furthermore, cells transfected with Deltap85 or super-repressor form of IkappaBalpha suppressed the OPN-induced uPA secretion and cell motility. Pretreatment of cells with PI 3'-kinase inhibitors or NFkappaB inhibitory peptide (SN50) reduced the OPN-induced uPA secretion, cell motility and ECM-invasion. Taken together, OPN induces NFkappaB activity and uPA secretion by activating PI 3'-kinase/Akt/IKK-mediated signaling pathways and further demonstrates a functional molecular link between OPN induced PI 3'-kinase dependent Akt phosphorylation and NFkappaB-mediated uPA secretion, and all of these ultimately control the motility and invasiveness of breast cancer cells.

Tyrosine kinase, p56lck-induced cell motility, and urokinase-type plasminogen activator secretion involve activation of epidermal growth factor receptor/extracellular signal regulated kinase pathways.

We have recently reported that tyrosine kinase, p56(lck) regulates cell motility and nuclear factor kappaB-mediated secretion of urokinase-type plasminogen activator (uPA) through tyrosine phosphorylation of IkappaBalpha following hypoxia/reoxygenation (Mahabeleshwar, G. H., and Kundu, G. C. (2003) J. Biol. Chem. 278, 52598-52612). However, the role of hypoxia/reoxygenation (H/R) on ERK1/2-mediated uPA secretion and cell motility and the involvement of p56(lck) and EGF receptor in these processes in breast cancer cells is not well defined. We provide here evidence that H/R induces Lck kinase activity and Lck-dependent tyrosine phosphorylation of EGF receptor in highly invasive (MDA-MB-231) and low invasive (MCF-7) breast cancer cells. H/R also stimulates MEK-1 and ERK1/2 phosphorylations, and H/R-induced phosphorylations were suppressed by the dominant negative form of Lck (DN Lck, K273R) as well as pharmacological inhibitors of EGF receptor and Lck indicating that EGF receptors and Lck are involved in these processes. Transfection of these cells with wild type Lck or Lck F505 (Y505F) but not with Lck F394 (Y394F) induced phosphorylations of EGF receptor followed by MEK-1 and ERK1/2, suggesting that Lck is upstream of EGF receptor and Tyr-394 of Lck is crucial for these processes. H/R also induced uPA secretion and cell motility in these cells. DN Lck and inhibitors of Lck, EGF receptor, and MEK-1 suppressed H/R-induced uPA secretion and cell motility. To our knowledge, this is the first report that p56(lck) in presence of H/R regulates MEK-1-dependent ERK1/2 phosphorylation and uPA secretion through tyrosine phosphorylation of EGF receptor, and it further demonstrates that all of these signaling molecules ultimately control the motility of breast cancer cells.

Osteopontin induces AP-1-mediated secretion of urokinase-type plasminogen activator through c-Src-dependent epidermal growth factor receptor transactivation in breast cancer cells.

We have recently reported that osteopontin (OPN) stimulates cell motility and nuclear factor kappaB-mediated secretion of urokinase-type plasminogen activator (uPA) through phosphatidylinositol 3-kinase/Akt signaling pathways in breast cancer cells (Das, R., Mahabeleshwar, G. H., and Kundu, G. C. (2003) J. Biol. Chem. 278, 28593-28606). However, the role(s) of OPN on AP-1-mediated uPA secretion and cell motility and the involvement of c-Src/epidermal growth factor receptor (EGFR) in these processes in breast cancer cells are not well defined. In this study we report that OPN induces alpha(v)beta(3) integrin-mediated c-Src kinase activity in both highly invasive (MDA-MB-231) and low invasive (MCF-7) breast cancer cells. Ligation of OPN with alpha(v)beta(3) integrin induces kinase activity and tyrosine phosphorylation of EGFR in MDA-MB-231 and wild type EGFR-transfected MCF-7 cells, and this was inhibited by the dominant negative form of c-Src (dn c-Src) indicating that c-Src kinase plays a crucial role in this process. OPN induces association between alpha(v)beta(3) integrin and EGFR on the cell membrane in a macromolecular form with c-Src. Furthermore, OPN induces alpha(v)beta(3) integrin/EGFR-mediated ERK1/2 phosphorylation and AP-1 activation. Moreover, dn c-Src also suppressed the OPN-induced phosphatidylinositol (PI) 3-kinase activity in these cells indicating that c-Src acts as master switch in regulating MEK/ERK1/2 and phosphatidylinositol 3-kinase/Akt signaling pathways. OPN-induced ERK phosphorylation, AP-1 activation, uPA secretion, and cell motility were suppressed when cells were transfected with dn c-Src or pretreated with alpha(v)beta(3) integrin antibody, c-Src kinase inhibitor (pp2), EGFR tyrosine kinase inhibitor (PD153035), and MEK-1 inhibitor (PD98059). To our knowledge, this is the first report that OPN induces alpha(v)beta(3) integrin-mediated AP-1 activity and uPA secretion by activating c-Src/EGFR/ERK signaling pathways and further demonstrates a functional molecular link between OPN-induced integrin/c-Src-dependent EGFR phosphorylation and ERK/AP-1-mediated uPA secretion, and all of these ultimately control the motility of breast cancer cells.

Osteopontin stimulates cell motility and nuclear factor kappaB-mediated secretion of urokinase type plasminogen activator through phosphatidylinositol 3-kinase/Akt signaling pathways in breast cancer cells.

We have recently reported that osteopontin (OPN) induces nuclear factor kappaB (NFkappaB)-mediated promatrix metalloproteinase-2 activation through IkappaBalpha/IKK signaling pathways and that curcumin (diferulolylmethane) down-regulates these pathways (Philip, S., and Kundu, G. C. (2003) J. Biol. Chem. 278, 14487-14497). However, the molecular mechanism by which upstream kinases regulate the OPN-induced NFkappaB activation and urokinase type plasminogen activator (uPA) secretion in human breast cancer cells is not well defined. Here we report that OPN induces the phosphatidylinositol 3'-kinase (PI 3'-kinase) activity and phosphorylation of Akt in highly invasive MDA-MB-231 and low invasive MCF-7 cells. The OPN-induced Akt phosphorylation was inhibited when cells were transfected with a dominant negative mutant of the p85 domain of PI 3-kinase (Deltap85) and enhanced when cells were transfected with an activated form of PI 3-kinase (p110CAAX), indicating that PI 3'-kinase is involved in Akt phosphorylation. OPN enhances the interaction between IkappaBalpha kinase (IKK) and phosphorylated Akt. OPN also induces NFkappaB activation through phosphorylation and degradation of IkappaBalpha by inducing the IKK activity. However, both pharmacological (wortmannin and LY294002) and genetic (Deltap85) inhibitors of PI 3'-kinase inhibited OPN-induced Akt phosphorylation, IKK activity, and NFkappaB activation through phosphorylation and degradation of IkappaBalpha. OPN also enhances uPA secretion, cell motility, and extracellular matrix invasion. Furthermore, cells transfected with Deltap85 or the super-repressor form of IkappaBalpha suppressed the OPN-induced uPA secretion and cell motility, whereas cells transfected with p110CAAX enhanced these effects. Pretreatment of cells with PI 3-kinase inhibitors or NFkappaB inhibitory peptide (SN-50) reduced the OPN-induced uPA secretion, cell motility, and invasion. To our knowledge, this is first report that OPN induces NFkappaB activity and uPA secretion by activating PI 3'-kinase/Akt/IKK-mediated signaling pathways and further demonstrates a functional molecular link between OPN-induced PI 3'-kinase-dependent Akt phosphorylation and NFkappaB-mediated uPA secretion, and all of these ultimately control the motility of breast cancer cells.