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Biomedical subjects

Georgios V Georgakis

Publications and source records attributed to Georgios V Georgakis.

14 recordsLinked to original sources
PubMed2006

The heat shock protein 90 inhibitor 17-AAG induces cell cycle arrest and apoptosis in mantle cell lymphoma cell lines by depleting cyclin D1, Akt, Bid and activating caspase 9.

Mantle cell lymphoma (MCL), a distinct type of non-Hodgkin lymphoma, is characterised by the overexpression of cyclin D1. Heat shock protein 90 (HSP90) is a molecular chaperon to proteins that regulate cell cycle and survival. 17-allylamino-17-demethoxy-geldanamycin (17-AAG), a HSP90 small molecule inhibitor, induced G(0/1) cell cycle arrest and cell death in a dose- and time-dependent manner in MCL cell lines. This effect was associated with the downregulation of cyclin D1, cdk4 and Akt, depletion of Bid, and activation of the intrinsic/mitochondrial caspase pathway. These data suggest that 17-AAG may have a potential therapeutic value in patients with MCL.

Antineoplastic Agents↗
PubMed2006

Functional expression of TRAIL receptors TRAIL-R1 and TRAIL-R2 in esophageal adenocarcinoma.

The tumour necrosis factor (TNF) related apoptosis-inducing ligand (TRAIL/Apo2L) is a member of the TNF superfamily that preferentially induces apoptosis in cancer cells, while sparing normal cells. TRAIL induces apoptosis by interacting with its receptors TRAIL-R1 and TRAIL-R2. Recently, new humanized agonistic anti-TRAIL-R1 and anti-TRAIL-R2 antibodies have been developed, and are undergoing phase I/II clinical trails. Esophageal adenocarcinoma (EA) is associated with significantly poor outcome and is rapidly increasing in incidence in the United States and Western Europe, with virtually no effective non-surgical treatment. The aim of this study was to determine whether human EA tissue express TRAIL-R1 and/or TRAIL-R2, and whether EA cell lines Bic-1 and Seg-1 expresses functional TRAIL-R1 and/or TRAIL-R2. The expression of TRAIL-R1 and TRAIL-R2 was determined in sections from 18 human EA by immunohistochemistry (IHC). Sixteen (89%) of the EA expressed TRAIL-R1 and 17 (94%) expressed TRAIL-R2. Both cell lines were found to express TRAIL-R1 and TRAIL-R2 by western blot analysis, IHC, and flow cytometry. The fully human agonistic TRAIL-R1 (HGS-ETR1) and TRAIL-R2 (HGS-ETR2) antibodies induced apoptosis in Bic-1 and Seg-1 cells in a time and dose dependent manner. Our results show that the vast majority of primary human EA express TRAIL-R1 and TRAIL-R2 and that EA cells lines express functional TRAIL-R1 and TRAIL-R2. Targeting of these receptors by agonist monoclonal antibodies may be of therapeutic value in patients with EA.

Adenocarcinoma↗
PubMed2006

Inhibition of heat shock protein 90 function by 17-allylamino-17-demethoxy-geldanamycin in Hodgkin's lymphoma cells down-regulates Akt kinase, dephosphorylates extracellular signal-regulated kinase, and induces cell cycle arrest and cell death.

PURPOSE: Heat shock protein 90 (HSP90) is a chaperone for several client proteins involved in transcriptional regulation, signal transduction, and cell cycle control. HSP90 is abundantly expressed by a variety of tumor types and has been recently targeted for cancer therapy. The objective of this study was to determine the role of HSP90 in promoting growth and survival of Hodgkin's lymphoma and to determine the molecular consequences of inhibiting HSP90 function by the small-molecule 17-allylamino-17-demethoxy-geldanamycin (17-AAG) in Hodgkin's lymphoma. EXPERIMENTAL DESIGN: HSP90 expression in Hodgkin's lymphoma cell lines was determined by Western blot and in primary lymph node sections from patients with Hodgkin's lymphoma by immunohistochemistry. Cell viability was determined by the 3-(4,5-dimethyl-thiazol-2yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. Apoptosis and cell cycle fractions were determined by flow cytometry. Expression of intracellular proteins was determined by Western blot. RESULTS: HSP90 is overexpressed in primary and cultured Hodgkin's lymphoma cells. Inhibition of HSP90 function by 17-AAG showed a time- and dose-dependent growth inhibition of Hodgkin's lymphoma cell lines. 17-AAG induced cell cycle arrest and apoptosis, which were associated with a decrease in cyclin-dependent kinase (CDK) 4, CDK 6, and polo-like kinase 1 (PLK1), and induced apoptosis by caspase-dependent and caspase-independent mechanisms. Furthermore, 17-AAG depleted cellular contents of Akt, decreased extracellular signal-regulated kinase (ERK) phosphorylation, and reduced cellular FLICE-like inhibitory protein levels (FLIP), and thus enhanced the cytotoxic effect of doxorubicin and agonistic anti-tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) death receptor antibodies. CONCLUSION: Inhibition of HSP90 function induces cell death and enhances the activity of chemotherapy and anti-tumor necrosis factor-related apoptosis-inducing ligand death receptor antibodies, suggesting that targeting HSP90 function might be of therapeutic value in Hodgkin's lymphoma.

Adaptor Proteins, Signal Transducing↗
PubMed2006

The HSP90 inhibitor 17-AAG synergizes with doxorubicin and U0126 in anaplastic large cell lymphoma irrespective of ALK expression.

OBJECTIVE: Heat shock protein 90 (HSP90) chaperones and maintains the molecular integrity of a variety of signal transduction proteins, including the nucleophosmin-anaplastic lymphoma kinase (NPM-ALK) oncogenic protein, a genetic abnormality that is frequently observed in anaplastic large cell lymphoma (ALCL) cells. Here we demonstrate that HSP90 is overexpressed in primary and cultured ALK-positive and ALK-negative ALCL cells, and we evaluate the potential role of the small molecule inhibitor of HSP90, 17-allylamino-17-demethoxygeldanamycin (17-AAG) in treating ALCL. METHODS: The antiproliferative effect of 17-AAG-cultured cells was determined by MTS assay. Apoptosis and cell-cycle arrest were determined by Annexin-V/propidium iodide and propidium iodide staining, respectively, and fluorescein-activated cell sorting analysis. Expression of HSP90 was evaluated by immunohistochemistry, and molecular changes were determined by Western blot. RESULTS: Treatment of cultured ALCL cells with 17-AAG induced cell-cycle arrest and apoptosis, irrespective of ALK expression. At the molecular level, 17-AAG induced degradation of ALK and Akt proteins, dephosphorylated extracellular signal-regulated kinase, and degraded the cell-cycle regulatory protein cyclin D1 and its cyclin-dependent kinases, CDK4 and CDK6, but had a differential effect on p27 and p53 proteins. Inhibition of extracellular signal-regulated kinase phosphorylation by the mitogen activated protein kinase inhibitor U0126 induced cell death in all ALCL cell lines, and sublethal concentration 17-AAG showed synergistic antiproliferative effects when combined with U0126 or doxorubicin. CONCLUSION: Our data demonstrate that targeting HSP90 function by 17-AAG may offer a novel therapeutic strategy for ALCL, either as single-agent activity or by combining 17-AAG with conventional or targeted therapeutic schemes.

Anaplastic Lymphoma Kinase↗
PubMed2006

Inhibition of the phosphatidylinositol-3 kinase/Akt promotes G1 cell cycle arrest and apoptosis in Hodgkin lymphoma.

Activation of the phosphatidylinositol 3-kinase (PI(3)K) pathway has been linked with tumour cell growth, survival and resistance to therapy in several cancer types. The active, phosphorylated form of Akt (pAkt) was found to be aberrantly expressed in Hodgkin lymphoma (HL)-derived cell lines and in Hodgkin-Reed-Sternberg (HRS) cells in 27 of 42 (64.3%) of primary lymph node sections of HL, indicative of PI(3)K activity. Akt phosphorylation was not associated with loss of phosphatase and tensin homologue deleted on chromosome 10 (PTEN) expression, but with its phosphorylation in HL-cell lines, suggesting that its biological function is impaired. Akt phosphorylation was further induced by CD30 ligand (CD30L), CD40L and receptor activator of nuclear factor kappa B (RANK) ligand. The PI(3)K inhibitor LY294002 demonstrated antiproliferative effects in a dose- and time-dependent manner, which was associated with Akt dephosphorylation on Thr308 and Ser473 sites and dephosphorylation of the downstream ribosomal protein S6. LY209002 induced cell cycle arrest in the G0/G1 phase and apoptosis, which were associated with upregulation of MDM2, downregulation of cyclin D1, activation of caspase 9 and poly-ADP-ribose polymerase cleavage. The Akt inhibitor QLT394 also demonstrated antiproliferative effects in a dose- and time-dependent manner, dephosphorylated ribosomal S6 and cleaved caspase 9. Collectively, these data suggest that the aberrant activation of the PI(3)K/Akt survival pathway in HRS cells is not because of loss of PTEN expression. Our data suggest that PTEN phosphorylation and activation of CD30, CD40 and RANK may play a role in activating Akt in HRS cells.

Antigens, CD↗
PubMed2006

From Rapa Nui to rapamycin: targeting PI3K/Akt/mTOR for cancer therapy.

One of the most prominent pathways explored in the area of targeted therapy is the PI3K/Akt/mTOR pathway, which plays a central role in cell survival and proliferation. Deregulation of this pathway has been implicated in the promotion of cancer cell growth and survival. Inhibition of several steps of this pathway has been shown to confer favorable antitumor activity in a variety of cancer types. This article provides a brief analysis of the PI3K/Akt/mTOR pathway, its importance in tumor pathogenesis and the current status of preclinical and clinical studies targeting signaling components of this pathway.

Antibiotics, Antineoplastic↗
PubMed2006

Hodgkin's lymphoma: molecular targets and novel treatment strategies.

The WHO classification of Hodgkin's lymphoma (HL) distinguishes between two major subtypes, classical and nodular lymphocyte predominant HL. Approximately 95% of patients with HL will have the classical HL histology, which is characterized by the presence of rare malignant Hodgkin's and Reed-Sternberg cells among an overwhelming number of benign reactive cells. In recent years, new studies have shed more light on the biological and molecular features of Hodgkin's and Reed-Sternberg cells, providing hope that new targeted therapy may be developed to enhance the cure rate and to reduce treatment-related toxicity. In this review, the current understanding of the pathology and biology of HL will be discussed, as well as the current treatment approaches for patients with classical HL. Future treatment strategies will also be discussed based on our understanding of HL biology.

Hodgkin Disease↗
PubMed2005

Expression of heat-shock protein-90 in non-Hodgkin's lymphomas.

Heat-shock protein-90 (HSP90) inhibitors are currently being used in phase I clinical trials for treating patients with a variety of neoplasms including lymphomas. Using immunohistochemical methods, we assessed for HSP90 expression in 412 cases of non-Hodgkin's lymphoma. In B-cell lymphomas, HSP90 was moderately to strongly expressed in all cases of Burkitt's lymphoma (5/5, 100%), and in subsets of follicular lymphoma (17/28, 61%), diffuse large B-cell lymphoma (27/46, 59%), nodal marginal zone B-cell lymphoma (6/16, 38%), plasma cell neoplasms (14/39, 36%), small lymphocytic lymphoma/chronic lymphocytic leukemia (3/9, 33%), mantle cell lymphoma (12/38, 32%) and lymphoplasmacytic lymphoma/Waldenstrom macroglobulinemia (3/10, 30%). HSP90 was weakly expressed in six of 14 (43%) cases of extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue. In T-cell lymphomas, HSP90 was moderately to strongly expressed in subsets of anaplastic large-cell lymphoma (14/24, 58%; 9/12 ALK+ and 5/12 ALK-), precursor-T-cell lymphoblastic leukemia/lymphoma (20/65, 31%), unspecified peripheral T-cell lymphoma (8/43, 23%) and angioimmunoblastic T-cell lymphoma (2/17, 12%). HSP90 was weakly expressed in seven of 58 (12%) cases of mycosis fungoides. We conclude that HSP90 is commonly expressed in a subset of many types of B- and T-cell lymphoma. These data suggest that many lymphoma types are suitable targets for modulation of HSP90 activity, and that HSP90 inhibitors are a potential investigational therapy for lymphoma patients.

Cell Line, Tumor↗
PubMed2005

Activity of selective fully human agonistic antibodies to the TRAIL death receptors TRAIL-R1 and TRAIL-R2 in primary and cultured lymphoma cells: induction of apoptosis and enhancement of doxorubicin- and bortezomib-induced cell death.

Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) is a death protein that preferentially kills tumour cells while sparing normal cells. TRAIL has four exclusive receptors, two of which (TRAIL-R1, TRAIL-R2) are death receptors. Both TRAIL/Apo2L and agonistic antibodies to the TRAIL death receptors are currently being explored for cancer therapy. Although the activity of TRAIL/Apo2L in a variety of haematological malignancies has been examined, the activity of anti-TRAIL receptor agonistic antibodies in primary and cultured lymphoma cells has not. Using two fully human selective agonistic monoclonal antibodies to the TRAIL death receptors TRAIL-R1 (HGS-ETR1) and TRAIL-R2 (HGS-ETR2) this study demonstrated that both monoclonal antibodies activated caspase-8 and induced cell death in five of nine human lymphoma cell lines, and induced >10% cell death in 67% and 70%, respectively, of 27 primary lymphoma cells, and >20% cell death in at least one-thirds of the samples. HGS-ETR1 and HGS-ETR2 demonstrated comparable activity in the fresh tumour samples, which was independent of TRAIL receptor surface expression, Bax, cFLIP, or procaspase-8 expression, or exposure to prior therapy. Furthermore, both antibodies enhanced the killing effect of doxorubicin and bortezomib. Our data demonstrate that HGS-ETR1 and HGS-ETR2 monoclonal antibodies can induce cell death in a variety of cultured and primary lymphoma cells, and may have therapeutic value in lymphoma.

Analysis of Variance↗
PubMed2005

Heat-shock protein 90 inhibitors in cancer therapy: 17AAG and beyond.

Heat-shock protein 90 (HSP90) has diverse functions in mammalian cells. It acts as molecular chaperone, together with several co-chaperone molecules (such as Hop, Hip, p23, cdc37, Aha, and immunophilins). HSP90 binds to its client proteins (such as steroid receptors, AKT, Bcr-Abl, Apaf-1, survivin, cyclin dependent kinases which are involved in signal transduction that regulate cell cycle, survival, and death, and promote their proper protein folding, assembly, and transportation across different cellular compartments. Failure of Hsp90 chaperone activity leads to misfolding of client proteins, which leads to ubiquitination and proteasome degradation, and this deregulating cellular homeostasis. Since tumor cells frequently overexpress the active form of HSP90, which is more susceptible to inhibition by small molecules such as geldanamycin and its analogs, HSP90 became an attractive target for cancer therapy. This paper will review the recent advances in HSP90-biology and will discuss the emerging role of the HSP90 inhibitors such as 17-allylamino-17 demethoxy-geldanamycin and other HSP-90-directed small molecules in cancer therapy.

Antineoplastic Agents↗
PubMed2004

Induction of cell cycle arrest and apoptosis by the proteasome inhibitor PS-341 in Hodgkin disease cell lines is independent of inhibitor of nuclear factor-kappaB mutations or activation of the CD30, CD40, and RANK receptors.

PURPOSE: The malignant Hodgkin and Reed-Sternberg cells of Hodgkin disease (HD) are known to constitutively express high levels of activated nuclear factor kappaB (NF-kappaB), which plays an important role in their survival. The proteasome inhibitor PS-341 has been recently shown to modulate tumor cell proliferation and survival by inhibiting NF-kappaB and modulating critical cellular regulatory proteins, but its activity in cells carrying IkappaBalpha gene mutations has not been reported previously. EXPERIMENTAL DESIGN: The activity of PS-341 in four well-characterized, HD-derived cell lines. Cell proliferation and apoptosis were determined by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxy-phenyl)-2-(4-sulfonyl)-2H-tetrazolium (MTS) and Annexin-V binding methods, respectively. Cell cycle analysis was determined by flow cytometry. Intracellular protein levels were determined by Western blot. RESULTS: PS-341 demonstrated a strong antiproliferative activity, which was irrespective of the status of mutations in IkappaBalpha and even the presence of CD30, CD40, or RANK receptor activation. This effect was attributable to the induction of apoptosis and cell cycle arrest at the G(2)-M phase. PS-341 not only inhibited nuclear localization of NF-kappaB but also activated the caspase cascade, increased p21 and Bax levels, and decreased Bcl-2 levels. Furthermore, PS-341 enhanced the effect of gemcitabine chemotherapy and potentiated the effect of tumor necrosis factor-related apoptosis-inducing ligand/APO2L and two agonistic antibodies to tumor necrosis factor-related apoptosis-inducing ligand death receptors R1 and R2. CONCLUSIONS: The in vitro activity of PS-341 against HD-derived cell lines suggests that PS-341 may have a therapeutic value for the treatment of HD.

Antibodies, Monoclonal↗
PubMed2004

Lack of c-kit (CD117) expression in CD30+ lymphomas and lymphomatoid papulosis.

c-Kit receptor (CD117) is expressed by erythroid, megakaryocytic, and myeloid precursors and mature mast cells and has been reported to be expressed in CD30+ lymphomas such as Hodgkin's disease and anaplastic large-cell lymphoma. Imatinib mesylate, a well-established inhibitor of bcr-abl tyrosine kinase, and currently used for the treatment of patients with chronic myeloid leukemia, also inhibits c-kit receptor kinase activity. In view of the possible use of imatinib as experimental therapy for patients with c-kit-positive tumors, we assessed c-kit expression in CD30+ cell lines and lymphomas. The cell lines were assessed using multiple methods (RT-PCR, flow cytometry, and Western blot). c-Kit expression was also immunohistochemically assessed in 168 CD30+ lymphomas including 87 classical Hodgkin's disease, 63 anaplastic large-cell lymphoma, and 15 cutaneous anaplastic large-cell lymphoma. We also studied 18 cases of lymphomatoid papulosis, a CD30+ lesion closely related to cutaneous anaplastic large-cell lymphoma. Neither c-kit mRNA nor protein was detected in any of the cell lines assessed. Furthermore, treatment with imatinib did not inhibit proliferation of cell lines in vitro. Using immunohistochemistry, only one of 183 (0.5%) lesions was positive for c-kit, the positive case being an ALK-negative anaplastic large-cell lymphoma. Our data demonstrate that expression of c-kit receptor is exceedingly rare among CD30+ lymphomas and lymphomatoid papulosis, suggesting that c-kit receptor is unlikely to be an appropriate target for therapeutic options such as imatinib in patients with these tumors.

Antineoplastic Agents↗