Gene therapy of metastatic colon carcinoma: regression of multiple hepatic metastases by adenoviral expression of bacterial cytosine deaminase. (25/501)

Colon carcinoma accounts for 20% of deaths due to malignancies in the Western world. Once metastases occur, therapeutic options are limited, with an approximate 5-year survival of only 5%. To investigate the potential of new gene therapeutic approaches, a hepatic micrometastasis model of colon carcinoma in BALB/c mice was established. Inoculation of syngeneic MCA26 colon carcinoma cells into the spleens of 18- to 20-week-old mice resulted in the formation of multiple hepatic metastases. Selective transduction of developing hepatic metastases was demonstrated using a beta-galactosidase-expressing recombinant adenovirus. Cytosine deaminase (CD) can metabolize 5-fluorocytosine into the chemotherapeutic reagent 5-fluorouracil (5FU). The antitumoral potential of this suicide gene therapy approach was explored by systemic application of a recombinant replication-deficient adenovirus encoding for the bacterial CD gene under the control of the cytomegalovirus promoter (Ad.CMV-CD). Injection into the tail vein of tumor-bearing mice resulted in delayed tumor growth with significant reduction in hepatic metastases. The potential of this experimental approach for possible future clinical applications was evaluated by investigating adenoviral transduction efficiency, 5FU sensitivity, and 5-fluorocytosine-dependent Ad.CMV-CD toxicity in a variety of human colon cancer cell lines. Although the murine cell lines MCA26 and CC36 were highly sensitive to 5FU, the human colon cancer cell lines showed a 1-100 times higher resistance to 5FU. Specific Ad.CMV-CD toxicity correlates with 5FU toxicity. Transduction efficiency in human colon carcinoma cell lines was shown to be 10-1700 times higher compared with murine cell lines, thus compensating for 5FU resistance. In conclusion, suicide gene therapy using CD may be promising as an adjuvant treatment regimen for hepatic micrometastases of human colon carcinoma.  (+info)

Enhanced antitumoral effect of adenovirus-mediated cytosine deaminase gene therapy by induction of antigen-presenting cells through stem cell factor/granulocyte-macrophage colony-stimulating factor gene transfer. (26/501)

Suicide gene therapy has been studied intensively for the treatment of cancer. A limited antitumoral effect was obtained by intratumoral injection of adenovirus harboring Escherichia coli cytosine deaminase gene (AdCD) in tumor-bearing mice followed by continuous administration of 5-fluorocytosine (5FC). To address the drawbacks of the limited potential for the induction of antitumoral immunity by CD suicide gene therapy, we hypothesized that antigen-presenting cells (APCs) might contribute to the efficient induction of an antitumoral immune response in tumor-bearing mice undergoing suicide gene therapy. We preinjected the mice with murine stem cell factor (SCF)-encoding adenovirus (AdSCF) and murine granulocyte-macrophage colony-stimulating factor (GM-CSF)-encoding adenovirus (AdGM-CSF); after 7 days, the mice were inoculated with CT26 colon adenocarcinoma. AdCD was injected intratumorally into tumor-bearing mice followed by 5FC administration. The results showed that AdSCF/AdGM-CSF treatment could increase the number, surface molecule expression, and function of APCs efficiently. A more significant growth inhibition of established tumors and a prolongation of the survival period were observed in tumor-bearing mice after AdSCF/AdGM-CSF pretreatment in combination with AdCD/5FC therapy when compared with mice treated with AdSCF or AdGM-CSF in combination with AdCD/5FC, or AdCD/5FC alone (P < .01). Cytotoxic T-lymphocyte activity was induced efficiently after the combined therapy, and mRNA of tumor necrosis factor-alpha, interleukin-4, interferon-gamma, and interleukin-2 was present in the tumor mass after combined therapy, suggesting that a more potent antitumoral response was induced by enhanced APCs. Our results demonstrated that AdSCF/AdGM-CSF pretreatment could activate APCs, and that these APCs could present the tumor antigens released from AdCD/5FC-killed tumor cells and activate the antitumoral response of the host, thus increasing the therapeutic efficiency of suicide gene therapy.  (+info)

The metabolism of isocytidine in Escherichia coli. (27/501)

Intact cells and cell-free extracts of E. coli convert isocytidine to isocytosine and uracil. The radioactive label of 5-[(3)H]isocytidine is incorporated into RNA and, DNA of growing bacteria at a rate equal to about 1.4% of that of cytidine under similar conditions; the radioactivity is found in uridylic, cytidylic and 2'-deoxythymidylic acids, while less than 0.4% of incorporated radioactive material might be due to possible incorporation of intact isocytidine. Uridine phosphorylase and cytidine deaminase apparently do not participate in the metabolic conversion of isocytidine.5-[(3)H]isocytidine was prepared by platinum-catalyzed dehalogenation of 5-bromoisocytidine in the presence of tritium. The 5-bromo derivative was obtained from 2',3'-0- -isopropylideneisocytidine by N-bromsuccinimide bromination followed by acidic hydrolysis.  (+info)

Two approaches that increase the activity of analogs of adenine nucleosides in animal cells. (28/501)

Deamination of many analogs of adenine nucleosides results in the loss of their chemotherapeutic efficacy. Two approaches have been used in this study to overcome this problem. First, some adenine nucleotides, which are resistant to mammalian adenosine deaminase, are more toxic to animal cells than are the respective nucleosides. For toxic to animal cells than are the respective nucleosides. For example, 9-beta-D-arabinofuranosyladenine 5'-phosphate, a molecule that penetrates the cell without degradation, has a more sustained toxicity against mouse fibroblasts (L-cells) than does 9-beta-D-arabinofuranosyladenine (ara-A). Furthermore, L-cells treated with 2',3'-dideoxyadenosine 5'-phosphate are extensively killed after 48 hr, whereas 2',3'-dideoxyadenosine is almost nontoxic to L-cells. Specific inhibition of adenosine deaminase by nontoxic concentrations of erythro-9-(2-hydroxy-3-nonyl)adenine greatly potentiates the biological activity of both ara-A and 3'-deoxyadenosine (cordycepin). Simultaneous administration of cytostatic concentrations of ara-A and the inhibitor of adenosine deaminase to L-cells killed greater than 99.9 percent of cells in 36 hr. A similar concentration of ara-A plus the deaminase inhibitor also markedly extended the mean survival of mice bearing Ehrlich ascites carcinoma as compared to ara-A alone. A cytostatic concentration of cordycepin 1 x 10-4 M), administered in the presence of deaminase inhibitor, killed greater than 99.9 percent of cultured L-cells in only 8 hr. During the latter incubation, accumulation of uridine in acid-insoluble material reached a maximum after 30 min, and incorporation of thymidine into acid-insoluble material was almost totally arrested after 2 hr.  (+info)

Absence of oroticaciduria in adenosine deaminase deficiency and purine nucleoside phosphorylase deficiency. (29/501)

Orotic acid excretion was normal when tested by three methods in adenosine deaminase deficiency and purine nucleoside phosphorylase deficiency. These results do not support the speculation, based on the oroticaciduria observed by others, that the immunodeficiency in these disorders results from the inhibition of pyrimidine biosynthesis. An alternative hypothesis is discussed.  (+info)

Combined chemotherapy of murine mammary tumors by local activation of the prodrugs ifosfamide and 5-fluorocytosine. (30/501)

The success of chemotherapeutic intervention is limited because the necessary high local drug doses cannot be achieved without systemic toxicity. Application of suicide genes (SGs) and direct conversion of prodrugs (PDs) to toxic metabolites in situ by SGs may enhance the efficacy of chemotherapy. To evaluate this strategy in two murine breast cancer models, TS/A and GR, we injected cellulose sulfate capsules harboring cat kidney cells expressing the SGs cytosine deaminase and cytochrome P450 2B1 (CYP2B1) intratumorally. The PDs 5-fluorocytosine and ifosfamide were administered in 3-day intervals. The effect of in situ chemotherapy with each PD alone and the combination was analyzed over a period of 100 days. The results reveal that for TS/A tumors, the antitumoral effect mediated by CYP2B1 is more efficient than that of cytosine deaminase, whereas for GR tumors, both systems worked equally well. Furthermore, we find additive toxicity using both SG/PD systems for both TS/A and GR tumors.  (+info)

Adenosine deaminase activity in chronic lymphocytic leukemia. Relationship to B- and T-cell subpopulations. (31/501)

The level, phenotypes, and isozyme distribution of adenosine deaminase (ADA) were determined in lymphocytes from patients with chronic lymphocytic leukemia (CLL). The ADA level in lymphocytes from patients with untreated CLL was consistently lower than in lymphocytes from normal subjects. No significant differences were found in the phenotype or isozyme distribution. In untreated patients, the ADA level was inversely correlated with the lymphocyte count and the percentage of bursa-equivalent (B) cells. After therapy, a diminution in the lymphocyte count was associated with an increase of ADA activity towards normal levels. The ADA levels were slightly higher in the thymus-derived (T) than in the B lymphocytes from normal subjects. The B cells had lower activity than T cells in patients with CLL. They also had a lower activity than the B cells from normal subjects. The ADA level was 2.3-fold higher in T cells from patients with CLL than in normal T cells. The decrease in ADA levels is an anomaly that is reversible and appears to be a reflection of the proliferation of abnormal B cells in this disorder.  (+info)

Diffusion MRI detects early events in the response of a glioma model to the yeast cytosine deaminase gene therapy strategy. (32/501)

Detection of a therapeutic response early in the course of cancer treatment, before tumor growth delay or regression, is not currently possible in experimental models or clinical medicine. New interim measures of therapeutic response would be particularly useful in the development of cancer chemosensitization gene therapy by facilitating optimization of gene transfer protocols and prodrug dosing schedules. Diffusion MRI is a sensitive technique producing quantitative and noninvasive images of the apparent mobility of water within a tissue. We investigated the utility of diffusion MRI for detecting early changes associated with a refined cytosine deaminase (CD)/5-fluorocytosine (5FC) chemosensitization gene therapy paradigm in orthotopic 9L gliomas stably expressing the recently cloned S. cerevisiae CD gene. Mean tumor diffusion increased 31% within 8 days of initiating 5-FC treatment, preceding tumor growth arrest and regression. Complete regression of the intracranial tumor was observed in four of five treated animals, and recurrent tumor in the remaining animal exhibited water diffusion behavior similar to primary, untreated tumors. These results demonstrate the efficacy of the yCD/5FC strategy for glioma and suggest that increased tumor water diffusion is an indicator of active therapeutic intervention.  (+info)