Current Pharmaceutical Biotechnology - Volume 2, Issue 3, 2001

Most patients with acute myeloid leukemia (AML) respond initially to combination chemotherapy but later relapse. These patients often die from progressive disease or toxicities of further chemotherapy. At relapse, the patients blasts are usually resistant to the drugs to which the patient has been exposed and frequently to other cytotoxic agents as well. Nevertheless, a number of these patients may be salvaged and achieve remissions with allogeneic stem cell transplants. In such cases, the pre-transplant conditioning regimens do not appear to account for the entire anti-leukemic efficacy. Immunological mechanisms for blast killing appear critical. There is tissue culture, animal and clinical evidence that stimulated donor T cells can recognize and kill leukemic blasts through recognition of alloantigens, differentiation antigens or leukemia-specific antigens as targets. We will review the molecular mechanisms for the generation of anti-leukemic T cells and discuss methods to improve the specificity and intensity of anti-leukemic T cell responses in the setting of allogeneic stem cell transplants, donor lymphocyte infusions, autologous anti-leukemic T cell infusions, and vaccine use in AML patients.

Phage display is a powerful technology for selecting and engineering peptides and proteins expressed on the surface of filamentous bacteriophage. The advantages of phage display technology over other research tools and its great potential have been demonstrated by successful application of phage display in diverse fields of biomedical / clinical research. In this review we will describe some recent developments in phage display, including new expression vectors, display formats, bioselection strategies and applications in pharmaceutical biotechnology. We highlight some important applications of phage display to identify disease- and pathogen-specific biomolecules, making particular emphasis on development of phage display-derived preventive and therapeutic vaccines.

The ability to display IgE antibody fragments, allergens and peptides upon filamentous phage has increasingly been used in allergy research. This technique offers the opportunity to isolate and produce IgE antibody fragments specific for allergens. These antibody fragments can then be used to address fundamental issues regarding the development of IgE antibodies in allergic patients, at both the molecular and structural level. Random peptide display has greatly facilitated the discovery of epitopes recognized by serum IgE antibodies from allergic patients, and it is a definitive tool for investigating the IgE-epitope interaction. Whole allergens can also be displayed on phage. Selecting IgE binding phage from diverse cDNA libraries of allergens has assisted in the identification of new allergens and provided a source of purified allergens for the diagnosis of allergic diseases. Finally, phage display of antibody fragments and random peptides is currently providing a means by which the IgE antibody can be targeted as a potential treatment for allergy. This review highlights several studies which have utilized phage display methodology in the area of allergy research, and it discusses how the therapeutic potential of this approach may be exploited.

The pharmaceutical industry has recently focused on intracellular signaling as a means to integrate the multiple facets of complex disease states, such as inflammation, because these pathways respond to numerous extracellular signals and coordinate a collection of cell responses contributing to pathology. One critical aspect of intracellular signaling is regulation of key cell functions by lipid mediators, in particular the generation of a key mediator, phosphatidic acid (PA) via the hydrolysis of phosphatidylcholine by phospholipase D (PLD). Research in this field has intensified, due in part to the recent cloning and partial characterization of the two PLD isoforms in mammalian cells, and this work has contributed significantly to our understanding of events downstream of PA generation. It is these effector functions of PLD activity that make this pathway attractive as a therapeutic target while the biochemical properties of the PLD isozymes make them amenable to small molecule intervention. Recent studies indicate that PA, and its immediate metabolites diacylglycerol and lyso-PA, affect numerous cellular pathways including ligand-mediated secretion, cytoskeletal reorganisations, respiratory burst, prostaglandin release, cell migration, cytokine release, and mitogenesis. This review summarises the data implicating signaling via PLD in these cell functions, obtained from: (i) molecular analyses of PLD / effector interactions, (ii) correlation between PA production and cell responses, (iii) experimental manipulation of PA levels, (iv) inhibition of PLD regulators, and (v) direct inhibition of PA production. The utility of targeting PLD signaling for the treatment of acute/chronic inflammation and other indications is discussed in light of these data.

Thymidine phosphorylase (TP) is a key enzyme in the activating pathway of 5DFUR and capecitabine. On the other hand, TP is identical to platelet-derived endothelial cell growth factor (PD-ECGF) which is known to be an angiogenic factor. Recent studies show TP expression is increased in various malignancies compared with the surrounding normal tissues. These reports demonstrate that elevated TP expression indicates a predisposition for aggressive disease and / or poor prognosis. Therefore, it is a reasonable strategy to target TP in cancer treatment by using fluoropyrimidines including 5-fluorouracil (5FU), 5DFUR and capecitabine. TP-mediated biomodulation of fluoropyrimidines to enhance their anti-tumor effects has been investigated. TP up-regulators including cytokines, anti-tumor drugs and X-ray irradiation significantly increase cytotoxicity of fluoropyrimidines. Also, transfection of TP cDNA significantly enhances cytotoxicity of fluoropyrimidines. Biomodulation of fluoropyrimidines is clinically successful in treating some malignancies. We report a review on roles of TP in biomodulation of fluoropyrimidines.

Immuno-isolation provides a potentially safe and effective method of delivering recombinant therapeutic molecules. Its application as a drug-delivery platform for the treatment of cancer has shown promising developments recently. This review will summarize the principle and current progress of this novel therapy paradigm in oncology. In this approach, a non-autologous cell line is genetically modified to secrete a recombinant product with potential for tumor suppression. Such a cell line may be implanted without graft rejection into all patients with similar neoplastic disease. The immune protection is conferred by enclosure within immuno-isolating devices such as microcapsules whose permeability would allow passage of smaller molecules such as oxygen, nutrients and waste products as well as the desired therapeutic transgene product. However, large immune mediators such as complement, macrophages and lymphocytes responsible for graft rejection would be excluded. In this review, we will consider how this technology may be applied as a novel genetic tool for cancer treatment to deliver antibodies, cytokines, enzymes and growth factors for treatment of various types of cancer. These molecules can be delivered at low constitutive levels, thereby permitting long-term systemic delivery, maintaining biological activity over extended periods, and eliminating the costs of product purification. The current success of this strategy in cancer treatment will be reviewed in in vitro systems, in animal models of cancer, and in human clinical trials.