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Nicholas Mitsiades

Publications and source records attributed to Nicholas Mitsiades.

At least 19 recordsLinked to original sources
PubMed2006

Total and high-molecular-weight adiponectin in breast cancer: in vitro and in vivo studies.

BACKGROUND: Obesity is a major risk factor for breast cancer. We hypothesized that obesity-induced decreases in total and/or high-molecular-weight (HMW) adiponectin levels may underlie this association. METHODS: We measured serum total and HMW adiponectin in a hospital-based case-control study of 74 female breast cancer patients and 76 controls. In parallel, expression of adiponectin and its receptors AdipoR1/R2 were measured in tissue samples using RT-PCR, and protein expression of AdipoR1/R2 was localized and quantified using immunohistochemistry. Finally, we documented AdipoR1/R2 expression in several breast cancer cell lines and studied adiponectin signaling and the effect of adiponectin on proliferation in the T47D breast cancer cell line in vitro. RESULTS: Women with the highest adiponectin levels had a 65% reduced risk of breast cancer (P = 0.04). This association became stronger after adjustment for age, body mass index, and hormonal and reproductive factors (P = 0.02). Modeling HMW instead of total adiponectin produced similar results and did not offer any additional predictive value. Breast cancer cells expressed AdipoR1/R2 but not adiponectin. Expression of AdipoR1, but not AdipoR2, was higher in tumor tissue than both adjacent and control tissues. Exposure of T47D cells to adiponectin significantly inhibited the percentage of viable cells to 86% and proliferation to 66% but had no effect on apoptosis. These effects were associated with activation of ERK1/2 but not AMP-activated protein kinase or p38MAPK. CONCLUSION: These studies suggest that adiponectin may act as a biomarker of carcinogenesis and may constitute a molecular link between obesity and breast cancer.

Adiponectin↗
PubMed2006

Targeting mitochondrial factor Smac/DIABLO as therapy for multiple myeloma (MM).

Second mitochondria-derived activator of caspases (Smac) promotes apoptosis via activation of caspases. Here we show that a low-molecular-weight Smac mimetic LBW242 induces apoptosis in multiple myeloma (MM) cells resistant to conventional and bortezomib therapies. Examination of purified patient MM cells demonstrated similar results, without significant cytotoxicity against normal lymphocytes and bone marrow stromal cells (BMSCs). Importantly, LBW242 abrogates paracrine MM cell growth triggered by their adherence to BMSCs and overcomes MM cell growth and drug-resistance conferred by interleukin-6 or insulinlike growth factor-1. Overexpression of Bcl-2 similarly does not affect LBW242-induced cytotoxicity. Mechanistic studies show that LBW242-induced apoptosis in MM cells is associated with activation of caspase-8, caspase-9, and caspase-3, followed by PARP cleavage. In human MM xenograft mouse models, LBW242 is well tolerated, inhibits tumor growth, and prolongs survival. Importantly, combining LBW242 with novel agents, including tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) or the proteasome inhibitors bortezomib and NPI-0052, as well as with the conventional anti-MM agent melphalan, induces additive/synergistic anti-MM activity. Our study therefore provides the rationale for clinical protocols evaluating LBW242, alone and together with other anti-MM agents, to improve patient outcome in MM.

Animals↗
PubMed2006

Antitumor effects of the proteasome inhibitor bortezomib in medullary and anaplastic thyroid carcinoma cells in vitro.

CONTEXT: The ubiquitin-proteasome pathway is a major pathway for degradation of intracellular proteins. Proteasome inhibitors constitute a novel class of antitumor agents with preclinical and clinical evidence of activity against hematological malignancies and solid tumors. The proteasome inhibitor bortezomib (PS-341, Velcade) has been approved by the Food and Drug Administration for the treatment of multiple myeloma and is being studied intensely in several other malignancies. Its mechanism of action is complex but appears to include the inhibition of inhibitory-kappaB degradation, which leads to inactivation of the transcriptional factor nuclear factor-kappaB (NF-kappaB). NF-kappaB has been implicated in the pathophysiology of the most aggressive forms of thyroid carcinoma, i.e. medullary and anaplastic. OBJECTIVE AND METHODS: We evaluated the effect of bortezomib on a panel of thyroid carcinoma cell lines, originating from papillary, follicular, anaplastic, and medullary carcinomas. RESULTS: Bortezomib induced apoptosis in medullary and anaplastic cell lines with IC(50) values well within the range of clinically achievable concentrations and much lower than respective IC(50) values for other solid malignancies. Bortezomib inhibited NF-kappaB activity; increased p53, p21, and jun expression; and induced caspase-dependent apoptosis. Sensitivity of thyroid carcinoma cells to bortezomib was partially decreased by overexpression of Bcl-2 or treatment with IGF-I, whereas the combination of bortezomib with chemotherapy (doxorubicin) was synergistic. CONCLUSIONS: These data provide both insights into the molecular mechanisms of antitumor activity of proteasome inhibitors and the rationale for future clinical trials of bortezomib, alone or in combination with conventional chemotherapy, to improve patient outcome in medullary and anaplastic thyroid carcinomas.

Antineoplastic Agents↗
PubMed2006

Epidermal growth factor receptor as a therapeutic target in human thyroid carcinoma: mutational and functional analysis.

CONTEXT: The epidermal growth factor receptor (EGFR), a transmembrane tyrosine kinase (TK) receptor that mediates proliferation and survival signaling, is expressed in a wide variety of normal and neoplastic tissues. EGFR inhibitors have produced objective responses in patients with non-small-cell lung carcinomas harboring activating EGFR TK domain somatic mutations. OBJECTIVE AND METHODS: Because the EGFR pathway has been reported to be important for the pathophysiology of thyroid carcinoma, we investigated the expression and mutational status of EGFR in 14 thyroid carcinoma cell lines as well as its functional role by evaluating their in vitro sensitivity to AEE788, a new dual-family EGFR/ErbB2 and vascular endothelial growth factor receptor TK inhibitor. We also evaluated the mutational status, mRNA and protein expression, as well as phosphorylation status of EGFR in a panel of thyroid carcinoma specimens. RESULTS: EGFR expression and phosphorylation in the thyroid carcinoma cell lines and tissue specimens were present but not stronger than in noncancerous thyroid tissue. EGFR TK domain mutations were detected in two of 62 histological specimens (3.2%) but not in cell lines. All thyroid carcinoma cell lines were significantly less sensitive (IC(50) at least 25-fold higher) in vitro to AEE788 than a primary culture of EGFR-mutant lung carcinoma cells. CONCLUSIONS: Thyroid carcinoma cells overall are poorly responsive to clinically relevant concentrations of AEE788 in vitro. The presence of EGFR-activating TK domain mutations may identify a small minority of thyroid cancer patients that may benefit from EGFR inhibitors, but additional preclinical evidence of efficacy is needed.

Adolescent↗
PubMed2006

Fas signaling in thyroid carcinomas is diverted from apoptosis to proliferation.

PURPOSE: The death receptor Fas is present in thyroid carcinomas, yet fails to trigger apoptosis. Interestingly, Fas has been reported to be actually overexpressed in papillary thyroid carcinomas, suggesting that it may confer a survival advantage. EXPERIMENTAL DESIGN: We investigated the expression and activation status of Fas pathway mediators in thyroid carcinoma cell lines and tumor specimens. RESULTS: All cell lines tested express Fas-associated death domain, procaspase-8, procaspase-9, and procaspase-3; resistance to Fas-mediated apoptosis could not be attributed to lack of any of these apoptosis mediators. Moreover, Fas death domain mutations were not found in our study. The proteasome inhibitors MG132 and PS-341 (bortezomib, Velcade), which lead to accumulation of the nuclear factor kappaB (NF-kappaB) inhibitor IkappaB, did not sensitize SW579 cells to Fas-mediated apoptosis, suggesting that resistance to Fas-mediated apoptosis is not due to proteasome or NF-kappaB activity. Cross-linking of Fas in vitro induced recruitment of Fas-associated death domain-like interleukin-1beta-converting enzyme inhibitory protein (FLIP) instead of procaspase-8. Inhibition of FLIP expression with a FLIP antisense oligonucleotide resulted in significant sensitization to Fas-mediated apoptosis. Fas cross-linking promoted BrdUrd incorporation; activated the mitogen-activated protein kinase/extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase, NF-kappaB, and activator protein-1 pathways in thyroid carcinoma cells in vitro; and protected cells from tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis. We also found that good prognosis papillary thyroid carcinoma specimens exhibited higher immunoreactivity for cleaved (activated) caspase-8 than poor prognosis tumors. CONCLUSIONS: In thyroid carcinomas, the proteolytic cleavage and activation of caspase-8 depends on the balance between expression levels for procaspase-8 and FLIP and correlates with favorable clinical prognosis. Fas may actually stimulate proliferation and confer a survival advantage to thyroid cancer cells.

Apoptosis↗
PubMed2006

Proteasome inhibition as a new therapeutic principle in hematological malignancies.

The intracellular concentration of proteins in both normal and tumor cells are regulated by the balance between the rates of protein synthesis vs. degradation. The ubiquitin-proteasome pathway is the main intracellular cascade for controlled degradation of proteins and has attracted in recent years major interest not only because of its biochemical complexity and the intricate regulation of its function, but also because diverse cell cycle regulators and modulators of apoptosis are subject to regulation by proteasome function, and can therefore be significantly affected by small molecule inhibitors of the proteolytic activity of the proteasome. In fact, bortezomib, the prototypic member of this class of agents, was recently approved by the U.S. Food and Drug Administration for the treatment of advanced multiple myeloma patients. This review article focuses on the exciting recent progress in the use of proteasome inhibitors, with emphasis on the bench-to-bedside research effort which provided the foundation for clinical development of bortezomib for the treatment of multiple myeloma, as well as other hematologic malignancies, such as mantle cell lymphoma.

Animals↗
PubMed2005

A novel carbohydrate-based therapeutic GCS-100 overcomes bortezomib resistance and enhances dexamethasone-induced apoptosis in multiple myeloma cells.

Human multiple myeloma is a presently incurable hematologic malignancy, and novel biologically based therapies are urgently needed. GCS-100 is a polysaccharide derived from citrus pectin in clinical development for the treatment of cancer. Here we show that GCS-100 induces apoptosis in various multiple myeloma cell lines, including those resistant to dexamethasone, melphalan, or doxorubicin. Examination of purified patient multiple myeloma cells showed similar results. Specifically, GCS-100 decreases viability of bortezomib/PS-341-resistant multiple myeloma patient cells. Importantly, GCS-100 inhibits multiple myeloma cell growth induced by adhesion to bone marrow stromal cells; overcome the growth advantage conferred by antiapoptotic protein Bcl-2, heat shock protein-27, and nuclear factor-kappaB; and blocks vascular endothelial growth factor-induced migration of multiple myeloma cells. GCS-100-induced apoptosis is associated with activation of caspase-8 and caspase-3 followed by proteolytic cleavage of poly(ADP-ribose) polymerase enzyme. Combined with dexamethasone, GCS-100 induces additive anti-multiple myeloma cytotoxicity associated with mitochondrial apoptotic signaling via release of cytochrome c and Smac followed by activation of caspase-3. Moreover, GCS-100 + dexamethasone-induced apoptosis in multiple myeloma cells is accompanied by a marked inhibition of an antiapoptotic protein Galectin-3, without significant alteration in Bcl-2 expression. Collectively, these findings provide the framework for clinical evaluation of GCS-100, either alone or in combination with dexamethasone, to inhibit tumor growth, overcome drug resistance, and improve outcome for patients with this universally fatal hematologic malignancy.

Antineoplastic Agents↗
PubMed2005

Novel histone deacetylase inhibitors in the treatment of thyroid cancer.

Histone deacetylases (HDAC) and histone acetyltransferases exert opposing enzymatic activities that modulate the degree of acetylation of histones and other intracellular molecular targets, thereby regulating gene expression, cellular differentiation, and survival. HDAC inhibition results in accumulation of acetylated histones and induces differentiation and/or apoptosis in transformed cells. In this study, we characterized the effect of two HDAC inhibitors, suberoylanilide hydroxamic acid (SAHA) and m-carboxycinnamic acid bis-hydroxamide, on thyroid carcinoma cell lines, including lines originating from anaplastic and medullary carcinomas. In these models, both SAHA and m-carboxycinnamic acid bis-hydroxamide induced growth arrest and caspase-mediated apoptosis and increased p21 protein levels, retinoblastoma hypophosphorylation, BH3-interacting domain death agonist cleavage, Bax up-regulation, down-regulation of Bcl-2, A1, and Bcl-x(L) expression, and cleavage of poly(ADP-ribose) polymerase and caspase-8, -9, -3, -7, and -2. Transfection of Bcl-2 cDNA partially suppressed SAHA-induced cell death. SAHA down-regulated the expression of the apoptosis inhibitors FLIP and cIAP-2 and sensitized tumor cells to cytotoxic chemotherapy and death receptor activation. Our studies provide insight into the tumor type-specific mechanisms of antitumor effects of HDAC inhibitors and a framework for future clinical applications of HDAC inhibitors in patients with thyroid cancer, including histologic subtypes (e.g., anaplastic and medullary thyroid carcinomas) for which limited, if any, therapeutic options are available.

Antineoplastic Agents↗
PubMed2005

Proteasome inhibitors as therapeutics.

The ubiquitin-proteasome pathway is a principle intracellular mechanism for controlled protein degradation and has recently emerged as an attractive target for anticancer therapies, because of the pleiotropic cell-cycle regulators and modulators of apoptosis that are controlled by proteasome function. In this chapter, we review the current state of the field of proteasome inhibitors and their prototypic member, bortezomib, which was recently approved by the U.S. Food and Drug Administration for the treatment of advanced multiple myeloma. Particular emphasis is placed on the pre-clinical research data that became the basis for eventual clinical applications of proteasome inhibitors, an overview of the clinical development of this exciting drug class in multiple myeloma, and a appraisal of possible uses in other haematological malignancies, such non-Hodgkin's lymphomas.

Boronic Acids↗
PubMed2005

Human retinoblastoma cells are resistant to apoptosis induced by death receptors: role of caspase-8 gene silencing.

PURPOSE: Fas ligand (FasL) and TNF-related apoptosis-inducing ligand (TRAIL)/Apo2L are members of the TNFalpha family that can trigger apoptosis in susceptible cells via respective death receptors (DRs). FasL cross-links its receptor Fas, resulting in recruitment and proteolytic activation of caspase-8, which initiates the downstream apoptotic cascade. TRAIL signals through its receptors DR4 and DR5, which can activate caspase-8 as well. This study was undertaken to investigate the functional status of the FasL and TRAIL apoptotic pathways in retinoblastoma (Rb) cells. METHODS: The human Rb cell lines Y79 and WERI-Rb1 were evaluated for their response to the Fas cross-linking antibody CH11 and recombinant TRAIL, as well as for cell surface presence and mutational status of Fas, DR4, and DR5 by flow cytometry and genomic DNA sequencing, respectively. The expression of caspase-8 and its inhibitor FLIP, as well as their recruitment to the DR signaling complex were studied by immunoblot analysis. RESULTS: Rb cells express Fas, DR4, and DR5 on their surfaces, yet were resistant to DR-mediated apoptosis. This was not due to DR mutations or secretion of the soluble decoy Fas, antiapoptotic NF-kappaB activity, or FLIP overexpression, but to the absence of caspase-8 expression. The demethylating agent 5-aza-2'-deoxycytidine restored caspase-8 expression and sensitivity to DR-mediated apoptosis. CONCLUSIONS: Rb cells are resistant to DR-mediated apoptosis because of a deficiency in caspase-8 expression secondary to epigenetic gene silencing by overmethylation. The data help delineate the apoptotic pathways in Rb cells and suggest that the combination of demethylating agents with DR-activating modalities, such as TRAIL receptor monoclonal antibodies, may benefit patients with retinoblastoma.

Apoptosis↗
PubMed2005

Proteasome inhibition as a therapeutic strategy for hematologic malignancies.

The ubiquitin-proteasome pathway is a principal intracellular mechanism for controlled protein degradation and has recently emerged as an attractive target for anticancer therapies since several cell cycle regulators and modulators of apoptosis are degraded through this pathway. The current state of the field of proteasome inhibitors and their prototypic member, bortezomib, which was recently approved by the US Food and Drug Administration for the treatment of advanced multiple myeloma, is reviewed. Particular emphasis is placed on the preclinical research data that became the basis for eventual clinical applications of proteasome inhibitors, an overview of the clinical development of this exciting drug class in multiple myeloma, and an appraisal of possible uses in other hematologic malignancies, such as non-Hodgkin's lymphomas.

Boronic Acids↗
PubMed2005

Treatment of hematologic malignancies and solid tumors by inhibiting IGF receptor signaling.

Insulin-like growth factors (IGF) and their receptors (IGF-1R) constitute a complex biologic system implicated in diverse regulatory levels of cell proliferation, viability, differentiation and metabolism. Extensive epidemiologic data have implicated the IGF/IGF-1R pathway in the establishment of human malignancies, consistent with experimental data on the role of this signaling cascade in promoting cell transformation, resistance to apoptosis, metastases and other aspects of the biology of human cancers. However, historically, the IGF/IGF-1R pathway has not been viewed as an attractive target for therapeutic intervention. The widespread IGF-1R expression in normal tissues and its close homology to the insulin receptor had led to the assumption that IGF-1R inhibition would cause unacceptable toxicities in vivo. Even though neutralizing antibodies against human IGF-1R have been efficacious against xenograft tumors, a lack of reactivity against the host rodent receptor has confounded the assessment of its therapeutic index. Furthermore, the lack of a clear understanding of the relevant significance for neoplastic cells in the function of IGF-1R versus other growth factor receptors provided an additional disincentive for the study of this pathway. However, recent reports from the authors' group and others have shown that small molecule inhibitors of tyrosine kinase activity of IGF-1R can be safely and efficaciously administered in vivo in clinically relevant orthotopic models of human neoplasias, such as multiple myeloma. This article reviews the data that validated IGF-1R as a therapeutic target for a broad spectrum of malignancies and provides in vivo proof-of-concept for the use of selective IGF-1R kinase inhibitors as primary antitumor therapy or in synergistic combination as chemosensitizers. These results have not only provided the rationale for clinical trials of small molecule IGF-1R inhibitors, but have also rekindled interest in other therapeutic modalities (e.g., monoclonal antibodies) aimed at suppressing the function of this critical pathway for tumor cell pathophysiology.

Hematologic Neoplasms↗
PubMed2004

Activin a in the regulation of corneal neovascularization and vascular endothelial growth factor expression.

Activin A, a dimeric glycoprotein that belongs to the transforming growth factor-beta superfamily, governs cellular differentiation in a wide variety of models and has been implicated in the regulation of angiogenesis. We examined the role of activin A and its downstream signaling pathway in a murine model of inflammatory corneal neovascularization induced by mechanical injury (debridement), and in vitro in corneal epithelial cells. Activin A expression increased steadily from day 2 until day 8 after mechanical debridement in vivo, paralleling vascular endothelial growth factor (VEGF) expression. Administration of recombinant activin A in mice increased the area of neovascularization, VEGF expression, and the kinase activities of p38 and p42/44 MAPKs after mechanical debridement. Systemic inhibition of activin A in vivo with a neutralizing antibody reduced the area of neovascularization, VEGF expression, and p38 and p42/44 MAPK activity, whereas administration of an isotype-matched control antibody had no effect. In vitro treatment with activin A increased VEGF secretion, as well as p38 and p42/44 MAPK activity in corneal epithelial cells, whereas concurrent administration of specific inhibitors of p38 or p42/44 MAPK abolished the stimulatory effect of activin A on VEGF production. We conclude that activin A stimulates inflammatory corneal angiogenesis by increasing VEGF levels through a p38 and p42/44 MAPK-dependent mechanism.

Activins↗
PubMed2004

Insulin-like growth factor-I plays a pathogenetic role in diabetic retinopathy.

Diabetic retinopathy is a leading cause of blindness in the Western world. Aberrant intercellular adhesion molecule-1 expression and leukocyte adhesion have been implicated in its pathogenesis, raising the possibility of an underlying chronic inflammatory mechanism. In the current study, the role of insulin-like growth factor (IGF)-I in these processes was investigated. We found that systemic inhibition of IGF-I signaling with a receptor-neutralizing antibody, or with inhibitors of PI-3 kinase (PI-3K), c-Jun kinase (JNK), or Akt, suppressed retinal Akt, JNK, HIF-1alpha, nuclear factor (NF)-kappaB, and AP-1 activity, vascular endothelial growth factor (VEGF) expression, as well as intercellular adhesion molecule-1 levels, leukostasis, and blood-retinal barrier breakdown, in a relevant animal model. Intravitreous administration of IGF-I increased retinal Akt, JNK, HIF-1alpha, NF-kappaB, and AP-1 activity, and VEGF levels. IGF-I stimulated VEGF promoter activity in vitro, mainly via HIF-1alpha, and secondarily via NF-kappaB and AP-1. In conclusion, IGF-I participates in the pathophysiology of diabetic retinopathy by inducing retinal VEGF expression via PI-3K/Akt, HIF-1alpha, NF-kappaB, and secondarily, JNK/AP-1 activation. Taken together, these in vitro and in vivo signaling studies thus identify potential targets for pharmacological intervention to preserve vision in patients with diabetes.

Animals↗
PubMed2004

The Akt pathway: molecular targets for anti-cancer drug development.

The serine/threonine kinase Akt functions intracellularly as a cardinal nodal point for a constellation of converging upstream signaling pathways, which involve stimulation of receptor tyrosine kinases such as IGF-1R, HER2/Neu, VEGF-R, PDGF-R), and an assembly of membrane-localized complexes of receptor-PI-3K and activation of Akt through the second messenger PIP(3). The integration of these intracellular signals at the level of Akt and its kinase activity, regulates the phosphorylation of its several downstream effectors, such as NF-kappa B, mTOR, Forkhead, Bad, GSK-3 and MDM-2. These phosphorylation events in turn mediate the effects of Akt on cell growth, proliferation, protection from pro-apoptotic stimuli, and stimulation of neo-angiogenesis. Because Akt and its upstream regulators are deregulated in a wide range of solid tumors and hematologic malignancies, and in view of the aforementioned biologic sequelae of this pathway, the Akt pathway is considered a key determinant of biologic aggressiveness of these tumors, and a major potential target for novel anti-cancer therapies. This review focuses on ongoing translational efforts to therapeutically target Akt and its biologic sequelae, either at the level of Akt itself or at the levels of its upstream regulators and downstream effectors. Because Akt is also important for proliferative and anti-apoptotic signaling pathways critical for normal cells, particular emphasis is placed on the fine-tuning the targeting of individual components of this pathway to maximize the therapeutic index of anti-cancer strategies based on the PI-3K/Akt pathway.

Animals↗
PubMed2004

CC-5013 (Celgene).

Celgene, in collaboration with the National Cancer Institute, is developing CC-5013, the lead compound in a series of thalidomide derivatives that inhibit TNFalpha overproduction, for the potential treatment of hematological and solid tumor cancers and inflammatory diseases.

Adjuvants, Immunologic↗