Cancer research
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We examined the ability of immunization with sequential adenovirus/plasmid DNA vectors expressing human wild-type p53 to stimulate a type 1 T-cell response and induce protection against challenge from a metastatic tumor that expresses mutated murine p53. We found that tumor protection and an antigen (Ag)-specific immune response were enhanced by prior injection of Flt3 ligand (Flt3L) at a dose and schedule that significantly increased dendritic cell (DC) number and frequency. Preliminary studies using enzyme-linked immunospot and Winn assays suggested that Ag-specific CD8 cells, with their significant increase in IFN-gamma-secreting activity (Tc1 cells), were responsible for the tumor protection. ⋯ We also observed an increased frequency of IL-12 and IFN-gamma-secreting cells (but not IL-4 or IL-10) in the spleens of mice immediately after 10 days of Flt3L treatment, which was also the day of p53 priming. This observation supports the likelihood that there are multiple mechanisms of Flt3L adjuvant activity, including expansion of DC and type 1 T-cell number. Overall, these results suggest that immunization with p53 genetic sequences after in vivo expansion of DC, using Flt3L, provides a useful strategy to induce p53-specific, and protective, type 1 T-cell responses.
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Serological identification of tumor antigens by cDNA expression cloning is a technique used to isolate cDNAs encoding tumor antigens that are recognized by IgG antibodies in sera from cancer patients. It is also useful for the isolation of tumor antigens recognized by T cells. We applied this method to identify melanoma antigens recognized by the serum from a patient with a good prognosis who had T-cell-infiltrated melanoma and vitiligo. ⋯ IgG antibodies against KU-MEL-1 were detected in the sera from 9 of 26 melanoma patients and from some patients with other cancers, including brain tumor, esophageal cancer, colon cancer, and chronic myelogenous leukemia, but were not detected in sera from 30 healthy individuals. Although the IgG specific for KU-MEL-1 was not detected in sera from 12 vitiligo patients, it was detected in sera from 7 of 11 patients with Vogt-Koyanagi-Harada disease that is thought to be an autoimmune disease against melanocytes. These results suggest that KU-MEL-1 may be a useful target for the development of diagnostic and therapeutic methods for patients with various cancers, particularly with melanoma, as well as patients with autoimmune diseases against melanocytes.
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Modulation of thiol levels may alter both the efficacy and toxicity of chemotherapeutic agents. We investigated cytoenhancement, using L-buthionine-[S,R]-sulfoximine (BSO) to reduce cellular glutathione levels prior to intracarotid alkylator administration. We also evaluated chemoprotection against chemotherapy-induced systemic toxicity when the thiol agents N-acetylcysteine (NAC) and sodium thiosulfate were administered into the descending aorta to limit brain delivery. ⋯ Thus, BSO depleted brain and brain tumor glutathione but thereby increased chemotherapy-induced myelosuppression. Surprisingly, although NAC was found to readily cross the blood-brain barrier when given into the carotid artery, aortic infusion of NAC resulted in minimal exposure to the central nervous system (CNS) vasculature because of rapid clearance. As a result, aortic infusion of NAC to perfuse bone marrow and minimize myelosuppression and toxicity to visceral organs could be performed without interfering with the CNS cytotoxicity of intracarotid alkylators, even after BSO depletion of CNS glutathione.
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Comparative Study
Urea as a recovery marker for quantitative assessment of tumor interstitial solutes with microdialysis.
Microdialysis is a technique that enables measurement of extracellular concentrations of unbound analytes. A small probe with a semipermeable membrane is implanted in tissue and constantly perfused. Small analytes in the interstitial fluid diffuse into the perfusate and are collected. ⋯ There was no effect of hyperglycemia on tumor blood flow. Urea appears to be a useful low molecular weight relative recovery marker for tumor microdialysis. In combination with the determination of relative diffusivity between urea and the solute of interest, this calibration method may allow for quantitative measurements of tumor metabolites and unbound drugs.
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Immunotherapy targeting for the induction of a T-cell-mediated antitumor response in patients with renal cell carcinoma (RCC) appears to hold significant promise. Here we describe a novel RCC vaccine strategy that allows for the concomitant delivery of dual immune activators: G250, a widely expressed RCC associated antigen; and granulocyte/macrophage-colony stimulating factor (GM-CSF), an immunomodulatory factor for antigen-presenting cells. The G250-GM-CSF fusion gene was constructed and expressed in Sf9 cells using a baculovirus expression vector system. ⋯ All FP-modulated peripheral blood mononuclear cell cultures with antitumor activity showed an up-regulated CD3+CD4+ cell population. These results suggest that GM-CSF-G250 FP is a potent immunostimulant with the capacity for activating immunomodulatory DCs and inducing a T-helper cell-supported, G250-targeted, and CD8+-mediated antitumor response. These findings may have important implications for the use of GM-CSF-G250 FP as a tumor vaccine for the treatment of patients with advanced kidney cancer.