Radiation therapy for lymphoma in children.
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Adolescent↗
Biomedical subjects
J A Wolff
Publications and source records attributed to J A Wolff.
Hypothesis: naked plasmid DNA is taken up by cells in vivo by a receptor-mediated process.
Following the initial demonstration that intramuscularly-injected naked plasmid DNA (pDNA) is expressed in myofibers, it was shown that pDNA can be used for vaccination purposes. More recent studies have indicated that naked pDNA can also achieve high levels of transgene expression in vivo. This efficiency of naked pDNA expression, especially via intravascular route, is truly astounding. In this prospective review, we examine the possible mechanisms of naked pDNA uptake. The possible mechanisms; (a) large membrane disruption, (b) small membrane pores, and (c) receptor-mediated endocytosis, are considered in turn. Some recent original laboratory data relevant to these hypotheses are also presented.
Animals↗
Time course of gene expression after plasmid DNA gene transfer to the liver.
BACKGROUND: High levels of expression in hepatocytes can be achieved after intraportal delivery of plasmid DNA vectors with up to 10% of all liver cells transfected. CMV promoter-driven expression is very high on Day 1 after injection, but is diminished strongly by Day 2. Expression slowly declines after 1 week. We describe experiments aimed at elucidating the reasons for this rapid decline in transgene expression. METHODS: Histological methods were used to determine the presence and extent of liver damage and hepatocyte proliferation. Viral and liver-specific promoters were tested to study promoter shut-off, Southern blotting was performed to determine the loss of the pDNA vector over time, and several mouse models were used to study the host immunological response. RESULTS: pDNA is lost rapidly early after injection, but remains at a relatively stable copy number after Day 4. Southern blotting experiments showed that plasmid DNA could be detected for at least 12 weeks after injection (0.2 copies per genome). The early rapid decline of expression is promoter dependent. A liver-specific albumin promoter resulted in similar levels of expression on Days 1 and 7, suggesting that promoter inactivation may be responsible for the instability of CMV promoter-driven expression. The slow decline in expression levels after 1 week appears to be the result of an immune response directed against the expressed transgene. Expression was much prolonged in immunosuppressed, immunodeficient, or antigen-tolerized mice. CONCLUSION: The present data suggest that if promoter inactivation can be overcome, intravascular delivery of plasmid DNA could be a highly efficient, simple and non-toxic liver gene therapy approach. Intravascular delivery of pDNA allows for the rapid screening of novel expression vectors in vivo.
Animals↗
Caged DNA does not aggregate in high ionic strength solutions.
The assembly of DNA into compact particles that do not aggregate in physiologic salt solution occurs naturally in chromatin and viral particles but has been challenging to duplicate using artificial constructs. Cross-linking amino-containing polycations in the presence of DNA with bisimidoester cross-linker leads to the formation of caged DNA particles that are stable in salt solutions. This first demonstration of caged DNA provides insight into how natural condensation processes avoid aggregation and a promising avenue for developing nonviral gene therapy vectors.
Cross-Linking Reagents↗
Co-transplantation of plasmid-transfected myoblasts and myotubes into rat brains enables high levels of gene expression long-term.
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Animals↗
History of pediatric oncology.
Pediatric oncology emerged as a subspeciality in the United States of America following the observations in 1948 of Farber and his associates of the benefits of chemotherapy for acute leukemia. The establishment of national cooperative chemotherapy groups furthered its development. More recently, the subspeciality has been recognized by the American Board of Pediatrics. Even more recently, training programs for the subspecialty have been given accreditation. Parallel to development of the specialty in the United States has been a similar evolution of pediatric oncology in Europe.
Antineoplastic Agents↗