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Comparison of drug effects on RNA tumor viruses and on transformed cells
Abstract:
Attempts to develop in vitro methods to test inhibitors for replication of C-type RNA tumor virus are made at two levels of the life cycle of the virus: 1) Formation of the proviral DNA, and 2) transcription and processing of viral RNA. Compounds such as rifamycin derivatives were found to be effective in interfering with the first process and compounds such as cordycepin, a nucleoside analogue, blocked effectively the second process. On the other hand, a class of known anti-tumor agents, glucocorticoids, was found to stimulate (10 fold or more) the induction of C-type virus following 5-iodo-2'-deoxyuride (IDU) treatment of murine cells. This is an intriguing example of a multi-focal action of an anti-tumor agent. We are exploring the implication of this for relapse or retransformation following successful chemotherapy in leukemic mice. Attempts are being made to develop an in vitro animal cell model for quantitative cytotoxic assays for compounds active in the above system and for comparing their effects on both normal and virus transformed cells.
Insights
Researchers explored C-type retrovirus replication inhibitors, finding rifamycin derivatives block DNA formation and cordycepin inhibits RNA processing. Glucocorticoids unexpectedly stimulated viral induction, prompting further investigation into anti-tumor agent actions.
Area of Science:
- Virology
- Molecular Biology
- Pharmacology
Background:
- C-type retroviruses are implicated in various diseases.
- Developing effective antiviral therapies requires understanding viral replication mechanisms.
- In vitro models are crucial for screening potential therapeutic compounds.
Purpose of the Study:
- To develop in vitro methods for testing inhibitors of C-type retrovirus replication.
- To investigate the effects of specific compounds on viral life cycle stages.
- To explore the impact of anti-tumor agents on viral activity.
Main Methods:
- Testing rifamycin derivatives for interference with proviral DNA formation.
- Evaluating cordycepin's effect on viral RNA transcription and processing.
- Assessing glucocorticoids' influence on C-type virus induction in murine cells treated with 5-iodo-2'-deoxyuridine (IDU).
Main Results:
- Rifamycin derivatives effectively inhibited proviral DNA formation.
- Cordycepin, a nucleoside analog, blocked viral RNA transcription and processing.
- Glucocorticoids significantly stimulated C-type virus induction (over 10-fold) in IDU-treated murine cells.
Conclusions:
- Specific compounds can target different stages of the C-type retrovirus life cycle.
- Glucocorticoids exhibit a complex, stimulatory effect on viral replication, warranting further study.
- Developing quantitative in vitro cytotoxic assays is essential for evaluating antiviral compounds and their effects on normal versus transformed cells.