Biomedical subjects

Venkateshwar G Keshamouni

Publications and source records attributed to Venkateshwar G Keshamouni.

10 recordsLinked to original sources

PubMed2006

Differential protein expression profiling by iTRAQ-2DLC-MS/MS of lung cancer cells undergoing epithelial-mesenchymal transition reveals a migratory/invasive phenotype.

Transforming growth factor-beta (TGF-beta) induces epithelial-mesenchymal transition (EMT) of epithelial cells in both normal embryonic development and certain pathological contexts. Here, we show that TGF-beta induced-EMT in human lung cancer cells (A549; adenocarcinoma cells) mediates tumor cell migration and invasion phenotypes. To gain insights into molecular events during EMT, we employed a global stable isotope labeled profiling strategy using iTRAQ reagents, followed by 2DLC-MS/MS, which identified a total of 51 differentially expressed proteins during EMT; 29 proteins were up-regulated and 22 proteins were down-regulated. Down-regulated proteins were predominantly enzymes involved in regulating nutrient or drug metabolism. The majority of the TGF-beta-induced proteins (such as tropomyosins, filamin A, B, & C, integrin-beta1, heat shock protein27, transglutaminase2, cofilin, 14-3-3 zeta, ezrin-radixin-moesin) are involved in the regulation of cell migration, adhesion and invasion, suggesting the acquisition of a invasive phenotype.

Adenocarcinoma↗

PubMed2005

Human alpha1 type IV collagen NC1 domain exhibits distinct antiangiogenic activity mediated by alpha1beta1 integrin.

Human noncollagenous domain 1 of the alpha1 chain of type IV collagen [alpha1(IV)NC1], or arresten, is derived from the carboxy terminal of type IV collagen. It was shown to inhibit angiogenesis and tumor growth in vivo; however, the mechanisms involved are not known. In the present study we demonstrate that human alpha1(IV)NC1 binds to alpha1beta1 integrin, competes with type IV collagen binding to alpha1beta1 integrin, and inhibits migration, proliferation, and tube formation by ECs. Also, alpha1(IV)NC1 pretreatment inhibited FAK/c-Raf/MEK/ERK1/2/p38 MAPK activation in ECs but had no effect on the PI3K/Akt pathway. In contrast, alpha1(IV)NC1 did not affect proliferation, migration, or the activation of FAK/c-Raf/MEK1/2/p38/ERK1 MAPK pathway in alpha1 integrin receptor knockout ECs. Consistent with this, alpha1(IV)NC1 elicited significant antiangiogenic effects and tumor growth inhibition in vivo but failed to do the same in alpha1 integrin receptor knockout mice. This suggests a highly specific, alpha1beta1 integrin-dependent antiangiogenic activity of alpha1(IV)NC1. In addition, alpha1(IV)NC1 inhibited hypoxia-induced expression of hypoxia-inducible factor 1alpha and VEGF in ECs cultured on type IV collagen by inhibiting ERK1/2 and p38 activation. This unravels a hitherto unknown function of human alpha1(IV)NC1 and suggests a critical role for integrins in hypoxia and hypoxia-induced angiogenesis. Collectively, the above data indicate that alpha1(IV)NC1 is a potential therapeutic candidate for targeting tumor angiogenesis.

Angiogenesis Inhibitors↗

PubMed2005

Curcumin for malaria therapy.

Malaria remains a major global health concern. New, inexpensive, and effective antimalarial agents are urgently needed. Here we show that curcumin, a polyphenolic organic molecule derived from turmeric, inhibits chloroquine-resistant Plasmodium falciparum growth in culture in a dose dependent manner with an IC(50) of approximately 5 microM. Additionally, oral administration of curcumin to mice infected with malaria parasite (Plasmodium berghei) reduces blood parasitemia by 80-90% and enhances their survival significantly. Thus, curcumin may represent a novel treatment for malarial infection.

Animals↗

PubMed2005

Peroxisome proliferator-activated receptor-{gamma} as a regulator of lung inflammation and repair.

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily that regulate the expression of genes involved in a variety of biological processes, including lipid metabolism and insulin sensitivity. Members of the PPAR family-in particular, PPAR-gamma-have more recently been shown to broadly regulate inflammatory and reparative responses. PPAR-gamma is expressed in both alveolar macrophages and neutrophils, and the ligand-dependent activation of this receptor results in suppression of leukocyte effector responses, including cytokine production, the elaboration of reactive oxygen and nitrogen species, and migratory responses. In addition to antiinflammatory effects, PPAR-gamma regulates diverse processes in lung stromal/parenchymal cells, including cell growth, differentiation, and apoptosis. Studies examining in vivo effects of PPAR-gamma have produced complex and at times conflicting results. However, evidence to date generally suggests that PPAR-gamma functions to dampen inflammation and injury in various animal models of acute lung injury. PPAR-gamma may also play an important role in other inflammatory/immune lung diseases, including ischemia-reperfusion injury, allergic airway inflammation, and cancer. The role of PPAR-gamma in human lung diseases, including acute lung injury, requires further study.

Animals↗

PubMed2005

PPAR-gamma activation inhibits angiogenesis by blocking ELR+CXC chemokine production in non-small cell lung cancer.

Activation of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) results in inhibition of tumor growth in various types of cancers, but the mechanism(s) by which PPAR-gamma induces growth arrest has not been completely defined. In a recent study, we demonstrate that treatment of A549 (human non small cell lung cancer cell line) tumor-bearing SCID mice with PPAR-gamma ligands troglitazone (Tro) and pioglitazone significantly inhibits primary tumor growth. In this study, immunohistochemical analysis of Tro-treated and Pio-treated tumors with factor VIII antibody revealed a significant reduction in blood vessel density compared to tumors in control animals, suggesting inhibition of angiogenesis. Further analysis showed that treatment of A549 cells in vitro with Tro or transient transfection of A549 cells with constitutively active PPAR-gamma (VP16-PPAR-gamma) construct blocked the production of the angiogenic ELR+CXC chemokines IL-8 (CXCL8), ENA-78 (CXCL5), and Gro-alpha (CXCL1). Similarly, an inhibitor of NF-kappa B activation (PDTC) also blocked CXCL8, CXCL5, and CXCL1 production, consistent with their NF-kappa B-dependent regulation. Conditioned media from A549 cells induce human microvascular endothelial cell (HMVEC) chemotaxis. However, conditioned media from Tro-treated A549 cells induced significantly less HMVEC chemotaxis compared to untreated A549 cells. Furthermore, PPAR-gamma activation inhibited NF-kappa B transcriptional activity, as assessed by TransAM reporter gene assay. Collectively, our data suggest that PPAR-gamma ligands can inhibit tumor-associated angiogenesis by blocking the production of ELR+CXC chemokines, which is mediated through antagonizing NF-kappaB activation. These antiangiogenic effects likely contribute to the inhibition of primary tumor growth by PPAR-gamma ligands.

Amino Acid Motifs↗

PubMed2004

Peroxisome proliferator-activated receptor-gamma activation inhibits tumor progression in non-small-cell lung cancer.

The peroxisome proliferator-activated receptor-gamma (PPAR-gamma) is a member of the nuclear hormone receptor superfamily of ligand-activated transcription factors and a crucial regulator of cellular differentiation. Differentiation-inducing and antiproliferative effects of PPAR-gamma suggest that PPAR-gamma agonists might be useful as effective anticancer agents. Few studies have examined the efficacy of these agonists in animal models of tumorigenesis, and their mechanism(s) of action are still not clear. Our studies indicate higher PPAR-gamma expression in primary tumors from non-small-cell lung cancer (NSCLC) patients when compared to normal surrounding tissue. The expression of PPAR-gamma was also observed in several NSCLC lines. The treatment of lung adenocarcinoma cells (A549) with troglitazone (Tro), a PPAR-gamma ligand, enhanced PPAR-gamma transcriptional activity and induced a dose-dependent inhibition of A549 cell growth. The observed growth arrest was predominantly due to the inhibition of cell proliferation without significant induction of apoptosis. Cell cycle analysis of Tro-treated cells revealed a cell cycle arrest at G(0)/G(1) with concomitant downregulation of G(0)/G(1) cyclins D and E. In addition, Tro treatment stimulated sustained Erk1/2 activation in A549 cells, suggesting the activation of a differentiation-inducing pathway. Furthermore, treatment of A549 tumor-bearing SCID mice with Tro or Pio inhibited primary tumor growth by 66.7% and significantly inhibited the number of spontaneous lung metastatic lesions. Collectively, our data demonstrate that activation of PPAR-gamma impedes lung tumor progression and suggest that PPAR-gamma ligands may serve as potential therapeutic agents for NSCLC.

Carcinoma, Non-Small-Cell Lung↗

PubMed2003

Deactivation of murine alveolar macrophages by peroxisome proliferator-activated receptor-gamma ligands.

Peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a member of the nuclear hormone receptor family of ligand-dependent transcription factors, is a critical regulator of adipocyte differentiation and glucose metabolism. The expression, regulation, and functional significance of PPAR-gamma in alveolar macrophages (AMs), the predominant resident immune effector cell within the alveolus, have not been previously examined. In this study, we show that, in contrast to peritoneal macrophages, resident murine AMs constitutively express high levels of PPAR-gamma. Expression was primarily located in the nucleus by immunofluorescence staining. Quantitative real-time RT-PCR demonstrated that the predominant isoform was PPAR-gamma2. Expression of PPAR-gamma was induced by the anti-inflammatory cytokine IL-4. Treatment of murine AMs with PPAR-gamma ligands suppresses PMA-stimulated oxidative burst activity and LPS + IFN-gamma-mediated expression of inducible nitric oxide synthase. In addition, LPS-induced IL-12 mRNA and protein expression was inhibited by PPAR-gamma ligands. These results support an important immunomodulatory role for PPAR-gamma in AM responses.

3T3-L1 Cells↗

PubMed2003

Activation of the pro-survival phosphatidylinositol 3-kinase/AKT pathway by transforming growth factor-beta1 in mesenchymal cells is mediated by p38 MAPK-dependent induction of an autocrine growth factor.

Transforming growth factor-beta1 (TGF-beta1) is a multifunctional cytokine involved in differentiation, growth, and survival of mesenchymal cells while inhibiting growth/survival of most other cell types. The mechanism(s) of pro-survival signaling by TGF-beta1 in mesenchymal cells is unclear. In this report, we demonstrate that TGF-beta1 protects against serum deprivation-induced apoptosis of mesenchymal cells isolated from patients with acute lung injury and of normal human fetal lung fibroblasts (IMR-90). TGF-beta receptor(s)-activated signaling in these cells involves rapid activation of the Smad and p38 MAPK pathways within minutes of TGF-beta1 treatment followed by a more delayed activation of the pro-survival phosphatidylinositol 3-kinase-protein kinase B (PKB)/Akt pathway. Pharmacological inhibition of p38 MAPK with SB203580 or expression of a p38 kinase-deficient mutant protein inhibits TGF-beta1-induced PKB/Akt phosphorylation. Conditioned medium from TGF-beta1-treated cells rapidly induces PKB/Akt activation in an SB203580- and suramin-sensitive manner, suggesting p38 MAPK-dependent production of a secreted growth factor that activates this pro-survival pathway by an autocrine/paracrine mechanism. Inhibition of the phosphatidylinositol 3-kinase-PKB/Akt pathway blocks TGF-beta1-induced resistance to apoptosis. These results demonstrate the activation of a novel TGF-beta1-activated pro-survival/anti-apoptotic signaling pathway in mesenchymal cells/fibroblasts that may explain cell-specific actions of TGF-beta1 and provide mechanistic insights into its pro-fibrotic and tumor-promoting effects.

Apoptosis↗

PubMed2002

MAP kinase/estrogen receptor cross-talk enhances estrogen-mediated signaling and tumor growth but does not confer tamoxifen resistance.

The estrogen receptor alpha (ERalpha) signaling plays an essential role in breast cancer progression and endocrine therapy. Mitogen-activated protein kinase (MAPK/Erk1/2) has been implicated in ligand-independent activation of ER, resulting in the cross-talk between growth factor and ER mediated signaling. In this study, we examined the effect of the cross-talk on estradiol (E(2))-mediated signaling, tumor growth and its effect on anti-estrogen therapy. Our findings demonstrate that expression of constitutively activated mitogen activated kinase kinase (MEK1), an immediate upstream activator of MAPK in estrogen receptor positive MCF-7 breast cancer cells (MEK/MCF-7), showed an increase in ERalpha-driven transcriptional activation. In MEK/MCF-7 cells maximal transactivation levels were achieved in response to treatment with much lower E(2) concentrations (10(-10) M E(2)) when compared to MCF-7 control cells (10(-8) M E(2)). Furthermore, we have seen an increased association between ERalpha and its nuclear coactivators AIB1 or TIF-2, in MEK/MCF-7 cells relative to those seen in MCF-7 control cells. In addition, in vivo studies show that MEK/MCF-7 cell tumors are approximately threefold larger than those of MCF-7 cell, in the presence of E(2). Immunohistochemical staining demonstrates that progesterone receptor (PR) and pS2, two E(2)-regulated gene products, are significantly increased in MEK/MCF-7 cell tumors compared to those of MCF-7 control tumors, suggesting that activation of ERalpha by MAPK enhances the expression of E(2)-regulated genes and accelerates tumor growth. Remarkably, the antiestrogens tamoxifen and ICI 182,780, were shown both in vitro and in vivo studies to efficiently antagonize the stimulatory effects of E(2) on ER regulated transactivation and tumor growth in MEK/MCF-7 as well as MCF-7 cell lines. Taken together, these data suggest that MAPK/ER cross-talk enhances ERalpha-mediated signaling and accelerates E(2)-dependent tumor growth without diminishing sensitivity to the inhibitory effects of anti-estrogens.

Animals↗

PubMed2002

Mechanism of 17-beta-estradiol-induced Erk1/2 activation in breast cancer cells. A role for HER2 AND PKC-delta.

Activation of mitogen-activated protein kinase (Erk/MAPK) is a critical signal transduction event for estrogen (E(2))-mediated cell proliferation. Recent studies from our group and others have shown that persistent activation of Erk plays a major role in cell migration and tumor progression. The signaling mechanism(s) responsible for persistent Erk activation are not fully characterized, however. In this study, we have shown that E(2) induces a slow but persistent activation of Erk in MCF-7 breast carcinoma cells. The E(2)-induced Erk activation is dependent on new protein synthesis, suggesting that E(2)-induced growth factors play a major role in Erk activation. When MCF-7 cells were treated with E(2) in the presence of an anti-HER-2 monoclonal antibody (herceptin), 60-70% of E(2)-induced Erk activation is blocked. In addition, when untreated MCF-7 cells were exposed to conditioned medium from E(2)-treated cells, Erk activity was significantly enhanced. Furthermore Erk activity was blocked by an antibody against HER-2 or by heregulin (HRG) depletion from the conditioned medium through immunoprecipitation. In contrast, epidermal growth factor receptor (Ab528) antibody only blocked 10-20% of E(2)-induced Erk activation, suggesting that E(2)-induced Erk activation is predominantly mediated through the secretion of HRG and activation of HER-2 by an autoctine/paracrine mechanism. Inhibition of PKC-delta-mediated signaling by a dominant negative mutant or the relatively specific PKC-delta inhibitor rottlerin blocked most of the E(2)-induced Erk activation but had no effect on TGF alpha-induced Erk activation. By contrast inhibition of Ras, by inhibition of farnesyl transferase (Ftase-1) or dominant negative (N17)-Ras, significantly inhibited both E(2)- and TGF alpha-induced Erk activation. This evaluation of downstream signaling revealed that E(2)-induced Erk activation is mediated by a HRG/HER-2/PKC-delta/Ras pathway that could be crucial for E(2)-dependent growth-promoting effects in early stages of tumor progression.

Blotting, Western↗