NHE1 mediates MDA-MB-231 cells invasion through the regulation of MT1-MMP

Na⁺/H⁺ exchanger 1 (NHE1), an important regulator of intracellular pH (pH_i) and extracellular pH (pH_e), has been shown to play a key role in breast cancer metastasis. However, the exact mechanism by which NHE1 mediates breast cancer metastasis is not yet well known. We showed here that inhibition of NHE1 activity, with specific inhibitor Cariporide, could suppress MDA-MB-231 cells invasion as well as the activity and expression of MT1-MMP. Overexpression of MT1-MMP resulted in a distinguished increase in MDA-MB-231 cells invasiveness, but treatment with Cariporide reversed the MT1-MMP-mediated enhanced invasiveness. To explore the role of MAPK signaling pathways in NHE1-mediated breast cancer metastasis, we compared the difference of constitutively phosphorylated ERK1/2, p38 MAPK and JNK in non-invasive MCF-7 cells and invasive MDA-MB-231cells. Interestingly, we found that the phosphorylation levels of ERK1/2 and p38 MAPK in MDA-MB-231 cells were higher than in MCF-7 cells, but both MCF-7 cells and MDA-MB-231 cells expressed similar constitutively phosphorylated JNK. Treating MDA-MB-231 cells with Cariporide led to decreased phosphorylation level of both p38 MAPK and ERK1/2 in a time-dependent manner, but JNK activity was not influenced. Supplementation with MAPK inhibitor (MEK inhibitor PD98059, p38 MAPK inhibitor SB203580 and JNK inhibitor SP600125) or Cariporide all exhibited significant depression of MDA-MB-231 cells invasion and MT1-MMP expression. Furthermore, we co-treated MDA-MB-231 cells with MAPK inhibitor and Cariporide. The result showed that Cariporide synergistically suppressed invasion and MT1-MMP expression with MEK inhibitor and p38 MAPK inhibitor, but not be synergistic with the JNK inhibitor. These findings suggest that NHE1 mediates MDA-MB-231 cells invasion partly through regulating MT1-MMP in ERK1/2 and p38 MAPK signaling pathways dependent manner.     

Homophilic interactions of Tetraspanin CD151 up-regulate motility and matrix metalloproteinase-9 expression of human melanoma cells through adhesion-dependent c-Jun activation signaling pathways

The tetraspanin membrane protein CD151 has been suggested to regulate cancer invasion and metastasis by initiating signaling events. The CD151-mediated signaling pathways involved in this regulation remain to be revealed. In this study, we found that stable transfection of CD151 into MelJuSo human melanoma cells lacking CD151 expression significantly increased cell motility, matrix metalloproteinase-9 (MMP-9) expression, and invasiveness. The enhancement of cell motility and MMP-9 expression by CD151 overexpression was abrogated by inhibitors and small interfering RNAs targeted to focal adhesion kinase (FAK), Src, p38 MAPK, and JNK, suggesting an essential role of these signaling components in CD151 signaling pathways. Also, CD151-induced MMP-9 expression was shown to be mediated by c-Jun binding to AP-1 sites in the MMP-9 gene promoter, indicating AP-1 activation by CD151 signaling pathways. Meanwhile, CD151 was found to be associated with alpha(3)beta(1) and alpha(6)beta(1) integrins in MelJuSo cells, and activation of associated integrins was a prerequisite for CD151-stimulated MMP-9 expression and activation of FAK, Src, p38 MAPK, JNK, and c-Jun. Furthermore, CD151 on one cell was shown to bind to neighboring cells expressing CD151, suggesting that CD151 is a homophilic interacting protein. The homophilic interactions of CD151 increased motility and MMP-9 expression of CD151-transfected MelJuSo cells, along with FAK-, Src-, p38 MAPK-, and JNK-mediated activation of c-Jun in an adhesion-dependent manner. Furthermore, C8161 melanoma cells with endogenous CD151 were also shown to respond to homophilic CD151 interactions for the induction of adhesion-dependent activation of FAK, Src, and c-Jun. These results suggest that homophilic interactions of CD151 stimulate integrin-dependent signaling to c-Jun through FAK-Src-MAPKs pathways in human melanoma cells, leading to enhanced cell motility and MMP-9 expression.     

6]-Gingerol inhibits metastasis of MDA-MB-231 human breast cancer cells

Gingerol (Zingiber officinale Roscoe, Zingiberaceae) is one of the most frequently and heavily consumed dietary condiments throughout the world. The oleoresin from rhizomes of ginger contains [6]-gingerol (1-[4′-hydroxy-3′-methoxyphenyl]-5-hydroxy-3-decanone) and its homologs which are pungent ingredients that have been found to possess many interesting pharmacological and physiological activities, such as anti-inflammatory, antihepatotoxic and cardiotonic effects. However, the effects of [6]-gingerol on metastatic processes in breast cancer cells are not currently well known. Therefore, in this study, we examined the effects of [6]-gingerol on adhesion, invasion, motility, activity and the amount of MMP-2 or -9 in the MDA-MB-231 human breast cancer cell line. We cultured MDA-MB-231 cells in the presence of various concentrations of [6]-gingerol (0, 2.5, 5 and 10 μM). [6]-Gingerol had no effect on cell adhesion up to 5 μM, but resulted in a 16% reduction at 10 μM. Treatment of MDA-MB-231 cells with increasing concentrations of [6]-gingerol led to a concentration-dependent decrease in cell migration and motility. The activities of MMP-2 or MMP-9 in MDA-MB-231 cells were decreased by treatment with [6]-gingerol and occurred in a dose-dependent manner. The amount of MMP-2 protein was decreased in a dose-dependent manner, although there was no change in the MMP-9 protein levels following treatment with [6]-gingerol. MMP-2 and MMP-9 mRNA expression were decreased by [6]-gingerol treatment. In conclusion, we have shown that [6]-gingerol inhibits cell adhesion, invasion, motility and activities of MMP-2 and MMP-9 in MDA-MB-231 human breast cancer cell lines.     

Anti-invasive effect of gambogic acid in MDA-MB-231 human breast carcinoma cells

Gambogic acid (GA) has been known to have antitumor activity in vitro and in vivo. In the present study, we investigated the anti-invasive effects of GA in MDA-MB-231 human breast carcinoma cells. The results indicated that GA significantly inhibited the adhesion, migration, and invasion of the cells in vitro tested by the heterotypic adhesion assay, wound migration assay, and chamber invasion assay. Results of Western blotting and immunocytochemistry analysis showed that GA could suppress the expressions of matrix metalloproteinase 2 (MMP-2) and 9 (MMP-9) in MDA-MB-231 cells. Furthermore, gelatin zymography revealed that GA decreased the activities of MMP-2 and MMP-9. Additionally, GA exerted an inhibitory effect on the phosphorylation of ERK1/2 and JNK, while it had no effect on p38. Taken together, our results demonstrated the anti-invasive property of GA for the first time and indicated it could serve as a promising drug for the treatment of cancer metastasis.     

Luteolin 8-C-β-fucopyranoside inhibits invasion and suppresses TPA-induced MMP-9 and IL-8 via ERK/AP-1 and ERK/NF-κB signaling in MCF-7 breast cancer cells

Matrix metalloproteinase 9 (MMP-9) and interleukin-8 (IL-8) play major roles in tumor progression and invasion of breast cancer cells. The present study was undertaken to investigate the inhibitory mechanism of cell invasion by luteolin 8-C-β-fucopyranoside (named as LU8C-FP), a C-glycosylflavone, in human breast cancer cells. We investigated whether LU8C-FP would inhibit MMP-9 activation and IL-8 expression in 12-O-tetradecanoylphorbol-13-acetate (TPA)-treated MCF-7 breast cancer cells. LU8C-FP suppressed TPA-induced MMP-9 and IL-8 secretion and mRNA expression via inhibition of the MAPK signaling pathway and down-regulation of nuclear AP-1 and NF-κB. TPA-induced phosphorylation of ERK 1/2 was suppressed by LU8C-FP, whereas JNK and p38 MAPK phosphorylation were unaffected. In addition, LU8C-FP blocked the ERK 1/2 pathways following expression of MMP-9 and IL-8. These results suggest LU8C-FP may function to suppress invasion of breast cancer cells through the ERK/AP-1 and ERK/NF-κB signaling cascades.     

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.     

JNK1 differentially regulates osteopontin-induced nuclear factor-inducing kinase/MEKK1-dependent activating protein-1-mediated promatrix metalloproteinase-9 activation

We have recently demonstrated that nuclear factor-inducing kinase (NIK) plays a crucial role in osteopontin (OPN)-induced mitogen-activated protein kinase/I kappa B alpha kinase-dependent nuclear factor kappa B (NF kappa B)-mediated promatrix metalloproteinase-9 activation (Rangaswami, H., Bulbule, A., and Kundu, G. C. (2004) J. Biol. Chem. 279, 38921-38935). However, the molecular mechanism(s) by which OPN regulates NIK/MEKK1-dependent activating protein-1 (AP-1)-mediated promatrix metalloproteinase-9 activation and whether JNK1 plays any role in regulating both these pathways that control the cell motility are not well defined. Here we report that OPN induces alpha v beta3 integrin-mediated MEKK1 phosphorylation and MEKK1-dependent JNK1 phosphorylation and activation. Overexpression of NIK enhances OPN-induced c-Jun expression, whereas overexpressed NIK had no role in OPN-induced JNK1 phosphorylation and activation. Sustained activation of JNK1 by overexpression of wild type but not kinase negative MEKK1 resulted in suppression of ERK1/2 activation. But this did not affect the OPN-induced NIK-dependent ERK1/2 activation. OPN stimulated both NIK and MEKK1-dependent c-Jun expression, leading to AP-1 activation, whereas NIK-dependent AP-1 activation is independent of JNK1. OPN also enhanced JNK1-dependent/independent AP-1-mediated urokinase type plasminogen activator (uPA) secretion, uPA-dependent promatrix metalloproteinase-9 (MMP-9) activation, cell motility, and invasion. OPN stimulates tumor growth, and the levels of c-Jun, AP-1, urokinase type plasminogen activator, and MMP-9 were higher in OPN-induced tumor compared with control. To our knowledge this is first report that OPN induces NIK/MEKK1-mediated JNK1-dependent/independent AP-1-mediated pro-MMP-9 activation and regulates the negative crosstalk between NIK/ERK1/2 and MEKK1/JNK1 pathways that ultimately controls the cell motility, invasiveness, and tumor growth.     

Bone morphogenetic protein-4 induced by NDRG2 expression inhibits MMP-9 activity in breast cancer cells

In the current study, we examined the function of N-myc downstream-regulated gene 2 (NDRG2) expression in breast cancer cells, especially focusing on the role of bone morphogenetic protein-4 (BMP-4) induced by NDRG2. NDRG2 expression in MDA-MB-231 cells inhibited the mRNA expression of several matrix metalloproteinases (MMPs) and the gelatinolytic activity of MMP-9. Interestingly, a specific induction of active BMP-4 was exclusively observed in MDA-MB-231-NDRG2 cells but not in MDA-MB-231-mock cells. Neutralization of BMP-4 in MDA-MB-231-NDRG2 cells resulted in the rescue of MMP-9 mRNA expression and migration capacity. In addition, treatment with recombinant BMP-4 dramatically suppressed MMP-9 mRNA expression, gelatinolytic MMP-9 activity, migration, and invasion capacity both in MDA-MB-231 and PMA-treated MCF-7 cells. Collectively, our data show that BMP-4 induced by NDRG2 expression inhibits the metastatic potential of breast cancer cells, especially via suppression of MMP-9 activity.     

Signal transductions induced by bone morphogenetic protein-2 and transforming growth factor-beta in normal human osteoblastic cells

Transforming growth factor beta (TGF-beta) activates Ras/MAPK signaling in many cell types. Because TGF-beta and BMP-2 exert similar effects, we examined if this signaling is stimulated by both factors and analyzed the relationship between this signaling and the Smads in osteoblasts. BMP-2 and TGF-beta stimulated Ras, MAPK, and AP-1 activities. The DNA binding activities of c-Fos, FosB/Delta FosB, Fra-1, Fra-2, and JunB were up-regulated whereas JunD activity was decreased. c-Fos, FosB/Delta FosB, and JunB were associated with Smad4. The stimulation of AP-1 by BMP-2 and TGF-beta was dependent on Smad signaling, and anti-Smad4 antibody interfered with AP-1 activity. Thus, BMP-2 and TGF-beta activate both Ras/MAPK/AP-1 and Smad signaling in osteoblasts with Smads modulating AP-1 activity. To determine the roles of MAPK in BMP-2 and TGF-beta function, we analyzed the effect of ERK and p38 inhibitors on the regulation of bone matrix protein expression and JunB and JunD levels by these two factors. ERK and p38 mediated TGF-beta suppression of osteocalcin and JunD as well as stimulation of JunB. p38 was essential in BMP-2 up-regulation of type I collagen, fibronectin, osteopontin, osteocalcin, and alkaline phosphatase activity whereas ERK mediated BMP-2 stimulation of fibronectin and osteopontin. Thus, ERK and p38 differentially mediate TGF-beta and BMP-2 function in osteoblasts.     

Activated protein C enhances cell motility of endothelial cells and MDA-MB-231 breast cancer cells by intracellular signal transduction

Activated protein C (APC), an anticoagulant serine protease, has been shown to have non-hemostatic functions related to inflammation, cell survival, and cell migration. In this study we investigate the mechanism by which APC promotes angiogenesis and breast cancer invasion using ex vivo and in vitro methods. When proteolytically active, APC promotes cell motility/invasion and tube formation of endothelial cells. Ex vivo aortic ring assays verify the role of APC in promoting angiogenesis, which was determined to be dependent on EGFR and MMP activation. Given the capacity of APC to promote angiogenesis and the importance of this process in cancer pathology, we investigated whether the mechanisms by which APC promotes angiogenesis can also promote motility and invasion in the MDA-MB-231 breast cancer cell line. Our results indicate that, extracellularly, APC engages EPCR, PAR-1, and EGFR in order to increase the invasiveness of MDA-MB-231 cells. APC activation of matrix metalloprotease (MMP) -2 and/or -9 is necessary but not sufficient to increase invasion, and APC does not utilize the endogenous plasminogen activation system to increase invasion. Intracellularly, APC activates ERK, Akt, and NFκB, but not the JNK pathway to promote MDA-MB-231 cell motility. Similar to the hemostatic protease thrombin, APC has the ability to enhance both endothelial cell motility/angiogenesis and breast cancer cell migration.     

The hyaluronan receptors CD44 and Rhamm (CD168) form complexes with ERK1,2 that sustain high basal motility in breast cancer cells

CD44 is an integral hyaluronan receptor that can promote or inhibit motogenic signaling in tumor cells. Rhamm is a nonintegral cell surface hyaluronan receptor (CD168) and intracellular protein that promotes cell motility in culture. Here we describe an autocrine mechanism utilizing cell surface Rhamm-CD44 interactions to sustain rapid basal motility in invasive breast cancer cell lines that requires endogenous hyaluronan synthesis and the formation of Rhamm-CD44-ERK1,2 complexes. Motile/invasive MDA-MB-231 and Ras-MCF10A cells produce more endogenous hyaluronan, cell surface CD44 and Rhamm, an oncogenic Rhamm isoform, and exhibit more elevated basal activation of ERK1,2 than less invasive MCF7 and MCF10A breast cancer cells. Furthermore, CD44, Rhamm, and ERK1,2 uniquely co-immunoprecipitate and co-localize in MDA-MB-231 and Ras-MCF10A cells. Combinations of anti-CD44, anti-Rhamm antibodies, and a MEK1 inhibitor (PD098059) had less-than-additive blocking effects, suggesting the action of all three proteins on a common motogenic signaling pathway. Collectively, these results show that cell surface Rhamm and CD44 act together in a hyaluronan-dependent autocrine mechanism to coordinate sustained signaling through ERK1,2, leading to high basal motility of invasive breast cancer cells. Therefore, an effect of CD44 on tumor cell motility may depend in part on its ability to partner with additional proteins, such as cell surface Rhamm.