Biomedical subjects

R Zeidler

Publications and source records attributed to R Zeidler.

43 records · Page 3Linked to original sources

PubMed1977

Preferential hemolysis of postnatal calf red cells induced by internal alkalinization.

Red blood cells from neonatal calves, but not from adult cows, rapidly hemolyze in buffered 300 mM solutions of a variety of nonelectrolytes and amino acids. Of these compounds, sucrose is chosen to elucidate the mechanism by which this preferential hemolysis takes place. As in other mammalian red cells, both calf and cow cells are found to be impermeable to sucrose and, in an isosmolar sucrose solution, to undergo volume shrinkage caused by the net loss of chloride ions with concomitant increase in intracellular pH. To test the potential role of intracellular pH change associated with chloride loss in promoting hemolysis, intracellular pH was altered by: (a) a direct addition of fixed acid or base to sucrose solution; (b) the removal of dissolved CO(2) from sucrose solution; and (c) the addition of cells to isotonic NaHCO(3) solution in the absence of sucrose. In all cases, only calf and not cow cells underwent hemolysis. Moreover, 4-acetamido-4'-isothiocyano-2,2'-stilbene disulfonic acid, a potent anion transport inhibitor, completely protected calf cells from hemolysis and caused a nearly total inhibition of both chloride loss and intracellular alkalinization. Furthermore, the hemolytic process is closely related to the integrity of a membrane protein, the band 3 protein, which can be cleaved to varying degrees by the combined treatment of pronase and lipase. Hemolysis is progressively inhibited as the band 3 protein undergoes proteolysis, until a total inhibition of hemolysis takes place when almost all of the band 3 protein is digested into smaller protein components with a mol wt of 65,000 and 35,000 daltons. These results suggest that the intracellular alkalinization process leading to a structural instability of the membrane band 3 protein is responsible for this calf cell hemolysis.

Animals↗

PubMedDate not supplied

Induction of telomerase activity in stimulated human lymphocytes precedes expression of topoisomerase II alpha.

Telomerase activity has been demonstrated in human immortal cell lines and in tumors, whereas it is generally absent from normal tissues, with the exception of germ cells. Low levels have also been detected in blood and skin cells. In this report we describe up-regulation of telomerase activity in normal human blood lymphocytes by mitogen stimulation. After 24 h of mitogen treatment a strong induction was detectable using the PCR-based telomeric repeat amplification protocol. The level of activity remained almost constant when the cultivation lasted 72 h. By contrast, topoisomerase II alpha was induced later with a maximum expression after 48-72 h. Our data show that telomerase can be induced in normal peripheral lymphocytes prior to expression of the S-phase typical protein topoisomerase II alpha indicating that telomere elongation might be initiated before DNA replication.

Antigens, Neoplasm↗

PubMedDate not supplied

COX-inhibitors relieve the immunosuppressive effect of tumor cells and improve functions of immune effectors.

A common phenomenon in cancer patients is a suppressed cell-mediated immunity, characterized by the inability of immune effector cells to mount efficient anti-tumor responses. Immunosuppressive factors, released by the tumor, contribute to this phenomenon and thus to tolerance. Prostaglandins, catalyzed by the cyclooxygenases (COX-1 and COX-2) from arachidonic acid, are one class of these factors. Since at least one of the COX enzymes is often expressed at high level in human cancers, the enzymes were ascribed a causal role in tumor etiology and progression. Non-steroidal antiinflammatory drugs (NSAIDs) like aspirin, which block COX activity, have demonstrated their antitumor effects in preclinical and clinical trials. Pro-apoptotic and anti-angiogenic effects in tumor cells may account for this activity. In addition, by inhibiting the release of prostaglandins from the tumor and by blocking COX activity in immune effector cells, NSAIDs may also bias the function of immune cells towards a more tumoricidal phenotype. We show here that tumor cells inhibit the physiological function of immune cells, and that NSAIDs restore this function. These data contribute to an understanding of the antineoplastic effect ascribed to NSAIDs and support the prophylactic use of these drugs in high-risk patients.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMedDate not supplied

Ep-CAM--a marker for the detection of disseminated tumor cells in patients suffering from SCCHN.

Disseminated tumor cells are considered as the origin of metastases. Since the number of circulating tumor cells in the bone marrow or the peripheral blood of patients correlates well with the tumor stage, their early detection is an important feature for the identification of high risk patients. We therefore investigated the pan-carcinoma antigen Ep-CAM for its suitability to serve as a specific marker for disseminated tumor cells in patient with squamous cell carcinoma of the head and neck (SCCHN). In order to detect small numbers of tumor cells in early tumor stages, we developed and describe here a RT-PCR assay that detects a single tumor cell within 10(5) normal cells. We examined bone marrows from patients and healthy donors and demonstrate that Ep-CAM can be used as a tumor marker for the diagnosis of single tumor cells in patients with SCCHN.

Antigens, Neoplasm↗

PubMedDate not supplied

Targeting head and neck cancer by GM-CSF-mediated gene therapy in vitro.

BACKGROUND: The prognosis for patients with squamous cell carcinoma of the head and neck (SCCHN) has remained poor during the last decades, emphasizing the need for new treatment modalities. Consequently, the objective of our study was to evaluate the feasibility and efficacy of cytokine-mediated gene therapy in SCCHN in vitro. MATERIALS AND METHODS/RESULTS: The SCCHN cell line PCI-1 was transduced by lipofection with a plasmid encoding the human granulocytemacrophage colony-stimulating factor (GM-CSF). Transfection of PCI-1 resulted in the production of significant amounts of GM-CSF as tested by ELISA. Enhanced proliferation of a GM-CSF sensitive cell line, TF-1, after incubation with supernatants of GM-CSF-transduced tumor cells demonstrated the release of biological active GM-CSF from these PCI-1 cells. In addition, GM-CSF-secreting PCI-1 cells enhanced antitumor cytotoxicity of allogeneic peripheral blood mononuclear cells, as tested in 24h-MTT-cytotoxicity assays. CONCLUSIONS: Our data demonstrate the feasibility and efficacy of GM-CSF-mediated stimulation of the antitumor immune response against SCCHN in vitro and may help to define new strategies in the treatment of this malignancy.

Carcinoma, Squamous Cell↗

PubMedDate not supplied

TNFalpha contributes to the antitumor activity of a bispecific, trifunctional antibody.

Immunological cancer therapies focus on the activation of immune effector cells yielding a specific antitumor activity. Disseminated tumor cells are regarded as the origin of metastases and consequently their elimination is the central objective of adjuvant immune therapies. The use of bispecific antibodies is an approach that is regarded as promising in order to fight those disseminated tumor cells. Unfortunately, the efficiency of these antibodies is limited by the fact that they usually activate a single class of effector cell, thus not yielding optimal immune response. In addition, tumor cells may down-regulate the antibody's target molecule and escape recognition. We have recently described results with an intact bispecific molecule, BiUII, that represents a new class of intact antibodies. These antibodies, termed "triomab", provide an excellent antitumor activity in vitro, a fact that most probably is attributable to the simultaneous activation of different classes of immune effector cells. We have now investigated this antitumor activity in more detail and demonstrate here that at least a dual mechanism accounts for triomab-mediated killing of tumor cells: besides direct cell-mediated killing, triomab induces the production of TNFalpha in PBMCs at concentrations that induce apoptosis in target cells. This bystander effect may be of special interest for the clinical application of triomab in terms of killing of target antigen-negative tumor cells.

Antibodies, Bispecific↗

PubMedDate not supplied

Immune restoration in head and neck cancer patients via cyclooxygenase inhibition: an update.

Most carcinomas overexpress cyclooxygenase, especially COX-2, thus secreting large amounts of immunosuppressive prostaglandins. Epidemiological data and animal models have provided evidence that inhibition of cyclooxygenase and thus prostaglandin E2 synthesis via non-steroid antiinflammatory drugs (NSAIDs) inhibits tumor growth in vitro and in vivo. Moreover, it could be demonstrated that chemoprevention, i.e. the long-term use of NSAIDs, significantly reduced the risk of developing certain types of cancer. However, the molecular mechanisms underlying these antineoplastic effects are not entirely understood. This review focuses on prostaglandin-mediated immunosuppressive mechanisms in head and neck cancer and presents immunorestorative strategies via cyclooxygenase inhibition in vitro and in vivo with special emphasis on COX-2. A better understanding of the interaction of tumors with the immune system and how the process of carcinogenesis can be antagonized by selectively modulating the activity of specific enzymes such as COX-2 will provide the rationale for the use of NSAIDs for chemoprevention or immunoadjuvant cancer therapies.

Animals↗