Christian Scholz

Docetaxel and Continuous-Infusion Fluorouracil Versus Epirubicin, Cisplatin, and Fluorouracil for Advanced Gastric Adenocarcinoma: A Randomized Phase II Study

PURPOSEnA combination of docetaxel and fluorouracil (DF) was evaluated in an outpatient setting and compared with epirubicin, cisplatin, and fluorouracil (ECF), which served as an internal control arm to avoid selection bias.nnnPATIENTS AND METHODSnPatients with metastatic or locally advanced gastric adenocarcinoma without prior chemotherapy were randomly assigned to receive either ECF (epirubicin 50 mg/m(2) day 1, cisplatin 60 mg/m(2) day 1, and fluorouracil 200 mg/m(2) days 1 through 21, every 3 weeks) or DF (docetaxel 75 mg/m(2) day 1, and fluorouracil 200 mg/m(2) days 1 through 21, every 3 weeks).nnnRESULTSnNinety patients were randomly assigned. Toxicity was rarely severe. Major toxic effects included diarrhea, stomatitis, and leukopenia in the DF arm and nausea, vomiting, and leukopenia in the ECF arm. Forty-three of 45 patients in each arm were assessable. In the DF arm, two patients (4.4%, intent to treat) experienced a confirmed complete tumor remission as best response, and 15 patients (33.3%) experienced a confirmed partial remission (overall response rate [ORR], 37.8%; 95% CI, 25.9% to 51.9%). Two patients (4.4%) in the ECF arm showed confirmed complete remission, and 14 (31.1%) showed confirmed partial remission (ORR, 35.6%; 95% CI, 24.8% to 48.7%). For the DF and ECF arms, the median survival was 9.5 and 9.7 months, and the median time to tumor progression 5.5 and 5.3 months, respectively.nnnCONCLUSIONnDF can be safely given in an ambulant setting. Compared with ECF, the dual combination of DF shows promising efficacy and may be an alternative treatment option that avoids cisplatin.

Arsenic trioxide triggers a regulated form of caspase-independent necrotic cell death via the mitochondrial death pathway.

Cell death is generally believed to occur either by accidental, lytic necrosis or by programmed cell death, that is, apoptosis. The initiation and execution of cell death, however, is far more complex and includes pathways like caspase-independent apoptosis or actively triggered necrosis. In this study, we investigated the mechanisms of cell death induced by arsenic trioxide (arsenite, As2O3), a clinically efficient agent in anticancer therapy. As2O3-induced cell death coincides with cytochrome c release, facilitates mitochondrial permeability transition and is sensitive to inhibition by Bcl-xL, indicating that cell demise is regulated through the mitochondrial apoptosis pathway. Nevertheless, only little caspase-3 activation was observed and As2O3-induced cell death was only weakly obstructed by the broad spectrum caspase inhibitor z-VAD-fmk. Moreover, disruption of caspase-9 or -2 failed to decrease the amount of As2O3-mediated cell death. Interestingly, As2O3-induced cell death had a predominantly necrosis-like phenotype as assessed by Annexin-V/propidium iodide staining and LDH release. Finally, blocking glutathione synthetase by buthionine sulfoximine enhanced the As2O3-mediated necrosis-like cell death without increasing caspase-3 cleavage. As2O3 does, however, not directly inhibit caspases, but appears to interfere with caspase activation. Altogether, our data clearly delineate a mode of As2O3-triggered cell death that differs considerably from that induced by conventional anticancer drugs. These findings may explain the capability of As2O3 to efficiently kill even chemoresistant tumor cells with disturbed apoptosis signaling and caspase activation, a frequent finding in malignancy.

Arsenic trioxide induces regulated, death receptor-independent cell death through a Bcl-2-controlled pathway

Arsenic trioxide (As2O3, arsenite) efficiently kills cells from various hematologic malignancies and has successfully been employed especially for the treatment of acute promyelocytic leukemia. There and in lymphoid cells, we demonstrated that As2O3 induces cell death in a caspase-2- and -9-independent fashion. Here, we address a potential role of death receptor signaling through the FADD/caspase-8 death-inducing signaling complex in As2O3-induced cell death. In detail, we demonstrate that As2O3 induces cell death independently of caspase-8 or FADD and cannot be blocked by disruption of CD95/Fas receptor ligand interaction. Unlike in death receptor ligation-induced apoptosis, As2O3-induced cell death was not blocked by the broad-spectrum caspase inhibitor z-VAD-fmk or the caspase-8-specific inhibitor z-IETD-fmk. Nevertheless, As2O3-induced cell death occurred in a regulated manner and was abrogated upon Bcl-2 overexpression. In contrast, As2O3-induced cell demise was neither blocked by the caspase-9 inhibitor z-LEHD-fmk nor substantially inhibited through the expression of a dominant negative caspase-9 mutant. Altogether our data demonstrate that As2O3-induced cell death occurs independently of the extrinsic death receptor pathway of apoptosis. Cell death proceeds entirely via an intrinsic, Bcl-2-controlled mitochondrial pathway that does, however, not rely on caspase-9.

Concurrent inhibition of PI3K and mTORC1/mTORC2 overcomes resistance to rapamycin induced apoptosis by down-regulation of Mcl-1 in mantle cell lymphoma.

Mantle cell lymphoma (MCL) is an aggressive form of Non‐Hodgkin‐lymphoma (NHL) with an ongoing need for novel treatments. Apart from the translocation t(11:14), which facilitates constitutive transcription of cyclin D1, additional aberrations are frequently observed in MCL, including a recurrent dysregulation of the phosphatidylinositol 3‐kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway. mTOR, a key component of this pathway, is pivotal for the assembly of mTOR complex (mTORC) 1 and 2. Temsirolimus, an analog of the mTOR inhibitor rapamycin, is approved for the treatment of relapsed MCL. Response rates, however, are low and response durations are short. We demonstrate that inhibition of mTORC1 by rapamycin or blocking of mTORC1 and mTORC2 in conjunction with PI3K by NVP‐BEZ235 reduces proliferation of MCL cell lines to a similar extent. However, only NVP‐BEZ235 is able to sufficiently inhibit the downstream pathway of mTOR and to mediate cell death through activation of the intrinsic apoptosis pathway. Further analysis demonstrated that the anti‐apoptotic Bcl‐2 family member Mcl‐1 plays a central role in regulation of MCL survival. While Mcl‐1 protein levels remained unchanged after coculture with rapamycin, they were down‐regulated in NVP‐BEZ235 treated cells. Furthermore, inhibition of Mcl‐1 by the BH3‐only mimetic obatoclax or down‐regulation of constitutive Mcl‐1, but not of Bcl‐2 or Bcl‐xL, by siRNA facilitated cell death of MCL cells and enhanced NVP‐BEZ235s capacity to induce cell death. Our findings may help to lay the foundation for further improvements in the treatment of MCL.

CD95/Fas-triggered apoptosis of activated T lymphocytes is prevented by dendritic cells through a CD58-dependent mechanism.

T-cell apoptosis is a mechanism regulating T-cell homeostasis. Activation renders T cells susceptible to activation-induced cell death, a process mediated through CD95 ligand/CD95 (Apo-1/Fas) ligation. The aim of this study was to test whether antigen-presenting cells can inhibit CD95/Fas-triggered activation-induced cell death. Dendritic cells (DC), which are highly effective antigen-presenting cells, were generated in vitro from human peripheral blood monocytes by culture in granulocyte-macrophage colony-stimulating factor and interleukin 4. Subsequently, DC were cocultured with activated T cells and the effect of DC on CD95/Fas-mediated apoptosis was determined. Coculture with increasing amounts of DC prevented CD95/Fas-triggered apoptosis in a dose-dependent fashion by inhibiting activation of caspase 8 and caspase 3. This protective effect of the DC on T-cell death could be blocked by 50% by adding an anti-CD58 antibody, whereas further addition of anti-CD80 (B7.1) and anti-CD86 (B7.2) led to an even more pronounced effect. Our findings suggest that DC can protect T cells from activation-induced cell death, with CD58 ligation playing a key role.

Dendritic Cells Prevent CD95 Mediated T Lymphocyte Death through Costimulatory Signals

T cell apoptosis is a mechanism regulating T cell homeostasis. Prolonged stimulation renders T cells susceptible to activation induced cell death (AICD), a process mediated through CD95 (Apo-1/Fas). While under some circumstances AICD can be prevented, little is known about molecules involved. Here, we wanted to assess whether dendritic cells (DC) have the capacity to prevent CD95-dependent AICD. T cells activated with PHA/PMA or anti-CD3 monoclonal antibody (mAb) were cocultured with increasing amounts of DC. While spontaneous T cell apoptosis amounted to 25%, the presence of an agonistic anti-CD95 antibody increased cell death to 64%. Addition of scalar amounts of DC prevented T cell apoptosis in a dose dependent fashion, where coculture of 10(5) DC/ml with 10(6) T cells/ml reduced apoptosis almost to baseline level (33%). Further addition of an anti-CD58 antibody partially abolished this protective effect. This was even more pronounced if anti-CD80 and anti-CD86 antibodies were added. Our findings suggest that dendritic cells are able to rescue T cells from AICD, with CD58 ligation playing a key role.

Retroviral B7.1 Gene Transfer in Cancer Cells Protects Cytotoxic T Cells from Deletion by “Veto” Apoptosis

It is generally accepted that T cell activation requires two distinct signals. The first signal is dependent on the ligation of the T cell receptor (TCR)/CD3 complex and the CD4 and CD8 co-receptors [1]. The second signal can be provided by cell surface molecules which mediate essential co-stimulatory signals, thereby complementing the TCR/CD3-mediated events [2, 3]. CD28 is a potent co-stimulatory molecule, and ligation of CD28 with agonistic antibodies or its natural ligands (B7.1 (CD80) and B7.2 (CD86)) synergizes with TCR-mediated signaling to initiate and maintain T cell responses [3, 4]. Recently, ligation of CD28 by agonistic antibodies was shown to prevent activation-induced cell death (AICD) by apoptosis during activation of resting T cells [5]. This was related to the upregulation of bcl-xL, a potent apoptosis-preventing member of the bcl-2 gene family. Overexpression of bcl-xL in Jurkat T cells inhibits both CD3 and CD95 (Fas/APO-1)-mediated apoptosis [5].