Cytokines and molecular therapy最新文献

Progress in medicine has solved many problems facing humanity. At the same time, however, it has also led to many new ones. There is no reason to believe that this ambivalence will cease to exist with respect to future applications of gene technology in medicine. A sober and differential assessment of the chances and risks of this new technology is therefore necessary. The present paper outlines just such an assessment. Its main conclusion is that genetic diagnostics may pose more difficult ethical and social problems than gene therapy. This may especially be the case if this diagnostic technology is routinely used for screening programs to detect widespread diseases like cancer, hypertension or diabetes in a population that is not at high risk.

Leukemic growth is determined by the balance of cell proliferation, differentiation and cell death. In vitro, the blasts of acute myelogenous leukemia (AML) proliferate under the influence of certain positive and negative regulators (cytokines). We conducted this study to determine whether cytokines could induce markers of cell death (FAS/Apo-1/CD95), of cell activation (HLA-DR) and cell adhesion (ICAM-1, CD54) in AML cell lines and primary AML samples. As inducers, tumor necrosis factor (TNF)-alpha and interferon (IFN)-gamma were chosen. At baseline, CD95 and CD54 were weakly and HLA-DR was strongly expressed. CD95 was induced by TNF in 6/12 myeloid leukemia cell lines, and by IFN in 9/12 cell lines. Taken together, CD95 was upregulated by at least one cytokine in 11/12 cell lines. HLA-DR was inducible in 10/12 cell lines, with IFN being more potent than TNF. CD54 showed the strongest induction: TNF resulted in a more than 20-fold induction in positive cell lines, and IFN resulted in a more than 20-fold induction. In primary AML samples, CD95 was induced in 14/14 samples examined, with TNF being more potent than IFN. HLA-DR expression was increased by IFN in 12/15 samples and by TNF in 11/13 samples. The inducibility of HLA-DR by IFN was inversely correlated with baseline expression. As in the cell lines, CD54 was induced in most cases of AML. In addition to the induction of surface markers by cytokines, the culture of leukemia cells with fetal calf serum increased the expression of these markers, especially CD95 and CD54. Our results demonstrate that CD95 is not downregulated when TNF binds to its receptors, but is induced in cell lines and patient samples. Despite the induction of expression of CD95 (all cases of AML and most cell lines), 7/8 myelogenous leukemia lines and 6/7 patient samples remained resistant to CD95 triggering by antibody or by CD95 ligand, which suggests a lesion in normal cell signaling. As a positive control, a T-cell line (Jurkat) with 60% to > 90% apoptotic cells after a 22 h incubation was used. The number of CD95-binding sites was not correlated with the induction of apoptosis. The resistance of most cases of AML to CD95 triggering despite inducible expression may also be related to leukemia-specific antagonists of CD95 signal transduction, and requires further investigation. Altogether, our results indicate that surface markers related to apoptosis, activation and adhesion can be induced on AML blasts, and could be relevant to treatment strategies that exploit ligand binding to these surface epitopes.

The observation that a number of genetic mutations can result in neoplastic transformation has led many investigators to speculate that gene therapy may represent a useful approach to treat cancer. Conceptually, this application of gene therapy seems quite simple: to treat cancer, restore the correctly regulated expression of the needed tumor suppressor genes inside tumor cells and revert the transformed phenotype of such cells. However, such regulated expression has been difficult to achieve in practice. Here we describe recent efforts at such restoration via a novel approach to gene therapy that involves ribozyme-mediated repair of mutant RNA transcripts.

The receptor for human interleukin-9 (hIL-9) might be a target for selective immunotherapy. It is expressed on a variety of malignant cells, including Hodgkin's lymphoma, non-Hodgkin lymphoma and acute myeloid leukemia (AML). We therefore constructed a new chimeric toxin by fusing hIL-9-cDNA to modified Pseudomonas aeruginosa exotoxin A (ETA'). The binding properties of the new recombinant protein, rhIL-9-ETA', were assessed on different cell lines expressing the hIL-9 receptor. The antitumor potency of rhIL-9-ETA' was evaluated against the Hodgkin-derived cell lines L540Cy, KM-H2 and L1236, the Burkitt lymphoma cell line Daudi, the erythroleukemia cell line K562, and the mastocytoma cell line P815-hIL9R, transfected with hIL-9 receptor cDNA. Recombinant hIL-9-ETA' exhibited potent specific cytotoxic effects against P815-hIL9R, K562 and L1236 cells, inhibiting protein synthesis by 50% (IC50) at concentrations of 0.05, 0.58 and 3 micrograms/ml respectively. The cytotoxic effect was abrogated after addition of polyclonal antibodies against the human IL-9. rhIL-9-ETA' might be of potential use against hIL-9R-expressing malignancies.

The majority of gene therapy protocols have used or plan to use retroviral vectors based upon murine leukaemia virus. These vectors are able to infect many different cell types, and the retroviral promoter, which is often used to control the expression of a therapeutic gene, is active in a wide range of different cell types. Safe and efficient gene transfer systems, whether based upon retroviruses or other agents, should deliver beneficial genes only to cells that require their therapeutic action, and these genes ideally should be expressed exclusively in such cells. In this paper, strategies for redirecting the infection spectrum of retroviral vectors in order to obtain cell-targeted gene delivery are discussed. These strategies include the engineering of the retroviral envelope protein, which, together with the availability of its cognate receptor, determines infectivity, and the use of proteins from other enveloped viruses of both retroviral and nonretroviral origin in the cell lines used to produce retroviral vector virus particles. Expression targeting can be achieved by limiting the expression of therapeutic genes to the cell type(s) of interest using promoters from genes that are normally active in these cells. This approach to targeting is illustrated using promoters from genes expressed in either the liver, the pancreas or the mammary gland as a means to limit gene expression specifically to the cell types that make up these organs. The successful utilization of new generations of targeted retroviral vectors in the clinic may well pave the way for superior gene delivery systems of the future that seek out their target cell, delivering a therapeutic gene to and expressing it only in such cells.

Nucleotide excision repair (NER) is a process required to remove DNA damage inflicted upon our skin by the short-wave bands of natural sunlight. Defective NER may result in a high risk of UV-induced skin tumors, since it occurs in patients with the inherited disorder xeroderma pigmentosum (XP). However, Cockayne's syndrome (CS) and PIBIDS (a photosensitive form of trichothiodystrophy) are also disorders with defective NER, but show no evidence of an elevated risk of cancer. In addition, many of CS and PIBIDS symptoms are difficult to explain on the basis of an NER defect only. Recent new insights into the molecular mechanisms of NER have shown additional involvements of many NER enzymes in other cellular processes. These multiple functions are likely to be the basis of the complex symptomatology of XP, CS and PIBIDS. Specific gene-targeted mouse models will probably help to solve these intricacies.

Transcription factors coordinate consitutive and inducible gene expression. They recognize and bind specific DNA sequences that are present in the regulatory regions of all genes, and thus allow transcriptional activation or repression of that given gene. Most transcription factors do not operate on their own, but form multiunit complexes consisting of homo- or heterodimers. A variety of genetic alterations observed in solid and hematologic malignancies result in gain or loss of function mutations of these molecules. As a consequence, a given transcription factor modulates its binding specificity and thus regulates the expression of a different set of target genes in the tumor cell as compared with normal cells. Alternatively, the transcription factor modulates its ability to interact with partner molecules and thus its binding specificity, its response to incoming signals or its functional activity, that is transcriptional activation or transcriptional repression of the targeted gene. Based on their functional implication in regulating gene expression and thus cellular behavior, loss or gain of function of transcription factor genes play a major role in the development or progression of tumors.

Diagnostic techniques, routinely used in clinical practice for monitoring acute leukemia patients, are able to detect only 1-5% of malignant cells. At present, two main techniques are being introduced for detection of minimal residual disease (MRD) in leukemia, namely immunological marker analysis and the polymerase chain reaction (PCR) technique with general sensitivity of 10(-4)-10(-5). Immunological marker analysis allows detection of unusual and aberrant immunophenotypes, and is usually performed by flow cytometry. PCR analysis allows detection of leukemia-specific DNA sequences, such as fusion regions of chromosome aberrations and junctional regions of rearranged immunoglogulin (Ig) genes and T-cell receptor (TcR) genes. The applicability of the immunophenotyping and PCR-mediated MRD techniques is dependent on the type of leukemia. In virtually all acute lymphoblastic leukemias, PCR analysis of Ig and TcR genes can be used, and immunophenotypic MRD detection is also possible in 70-80% of cases. In AML, immunophenotypic MRD detection can be applied in approximately 80% of cases and PCR analysis of chromosome aberrations in 25-40%. Each MRD technique has its advantages and limitations, which have to be weighed carefully to make an appropriate choice. Furthermore, standardization of the MRD techniques is needed before they are used for stratification or adaptation of treatment protocols. Finally, the clinical impact of MRD detection for the various subtypes of acute leukemias has to be established.

The cell cycle clock is the central controller of cell proliferation that governs the progress of the cell through its growth cycle, its exit from the active cycle, and its decision to differentiate. Components of the clock are found to be functioning in an aberrant fashion in many types of malignancies. Notable among these is the retinoblastoma protein, pRB, which acts to restrain proliferation in normal cells and suffers inactivation in many types of tumour cells. Its activity is controlled by D-type cyclins in various cell types. We have deleted one of these cyclins--cyclin D1--from the mouse germline and find that its absence leads to a limited range of defects including hypoplastic retinae and the inability of the mammary epithelium to respond to pregnancy-associated hormonal stimulation. Cyclin D1 is overexpressed in many human breast cancers, pointing to a highly specific association of this cell cycle clock component with mammary cell proliferation.

Several different approaches have been used successfully to document some of the molecular genetic events that play a part in colorectal tumorigenesis. This appears to be a multistep process that involves activation of oncogens as well as inactivation of tumor suppressor genes. It is important to see that, while many molecular genetic changes that occur during this process have been well documented, many other are less clear and some not yet identified at all. Studies on colorectal tumor progression are likely to continue producing new data on the initiation and progression of human tumors. An important goal of such studies is the development of molecular markers for clinical use, new prognostic markers, and diagnostic tools. The progress, in view of clinical practise, has been slow, but molecular genetic studies will contribute considerably to clinical management of cancer patients sooner or later.