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In vivo modulation of N-myc expression by continuous perfusion with an antisense oligonucleotide
L Whitesell1, A Rosolen, L M Neckers
1Clinical Pharmacology Branch, National Cancer Institute, Bethesda, Maryland.
Abstract:
In this study we investigated the in vivo efficacy of continuous subcutaneous perfusion of unmodified phosphodiester oligodeoxynucleotides. The in vitro sequelae of antisense inhibition of the target gene, N-myc, have been documented and include moderate growth inhibition without effects on myc expression, loss of secretogranin I expression, and morphologic alterations. We chose to use N-myc as a model target to determine if antisense effects observed in vitro can be reproduced in vivo. N-myc-expressing human neuroectodermal tumors were grown as subcutaneous xenografts in athymic mice. Antisense and sense oligodeoxynucleotides directed against N-myc were delivered to the vicinity of the tumor by a subcutaneously implanted microosmotic pump. Antisense treatment led to loss of N-myc protein from the tumor, as well as to the loss of the neuroendocrine differentiation marker protein secretogranin I. Myc protein expression remained unaffected. Mean tumor mass was reduced by 50% in antisense-treated animals, and antisense-treated tumors morphologically resembled antisense-transfected in vitro cell cultures. These results demonstrate that regional, in vivo perfusion of an unmodified oligonucleotide specifically downregulates gene expression in human tumor xenografts with concomitant effects on tumor phenotype and growth rate that correlate well with in vitro observations.
Insights
Continuous subcutaneous perfusion of unmodified antisense oligodeoxynucleotides effectively inhibited N-myc gene expression in human tumor xenografts. This approach demonstrated significant tumor growth reduction and phenotypic changes, correlating with in vitro findings.
Area of Science:
- Molecular Biology
- Oncology
- Pharmacology
Background:
- Antisense oligodeoxynucleotides (ASOs) show promise for gene inhibition.
- In vitro studies documented antisense inhibition of N-myc, affecting cell morphology and secretogranin I expression.
- Reproducing in vitro antisense effects in vivo is crucial for therapeutic development.
Purpose of the Study:
- To investigate the in vivo efficacy of continuous subcutaneous perfusion of unmodified phosphodiester oligodeoxynucleotides.
- To determine if in vitro observed antisense effects against N-myc can be reproduced in vivo.
- To assess the impact of antisense N-myc inhibition on tumor growth and phenotype.
Main Methods:
- Human neuroectodermal tumors expressing N-myc were grown as subcutaneous xenografts in athymic mice.
- Antisense and sense oligodeoxynucleotides targeting N-myc were delivered via implanted microosmotic pumps.
- Tumor protein expression, mass, and morphology were analyzed post-treatment.
Main Results:
- Antisense treatment led to loss of N-myc protein and secretogranin I expression in tumors.
- Tumor mass was reduced by 50% in antisense-treated animals.
- Antisense-treated tumors exhibited morphological changes consistent with in vitro observations.
Conclusions:
- Regional in vivo perfusion of unmodified oligonucleotides can specifically downregulate gene expression in human tumor xenografts.
- Antisense N-myc inhibition resulted in significant tumor growth reduction and phenotypic alterations.
- In vivo antisense effects correlate well with in vitro observations, supporting its therapeutic potential.
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