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Persistence of azacytidine-induced SCEs and genomic methylation in CHO cells in vitro
P Perticone1, F Palitti, R Cozzi
1Centro di Genetica Evoluzionistica del CNR, Università La Sapienza, Rome, Italy.
Abstract:
Many carcinogenic agents are able to affect the methylation level in mammalian cells cultivated in vitro. The capacity of azacytidine (AZA) to demethylate DNA can be used to examine the relationship between the genomic methylation level and cytogenetic end-points. Here we compared the sister-chromatid exchange (SCE) level with the genomic % methylcytosine in a Chinese hamster ovary cell line in vitro after giving a single 10-microM pulse of AZA. Both parameters were followed up to 16 cell cycles after the agent was removed. While the SCE level increased starting 2 cycles from the treatment and persisted for the entire 16 cycles, the methylcytosine level, after an initial 50% decrease, approached the control value, completely returning to it after 10 cell cycles. The possibility that the persistence in the SCE increase is an inherited phenomenon is discussed.
Insights
Azacytidine (AZA) treatment in mammalian cells revealed that while DNA demethylation is transient, the increase in sister-chromatid exchange (SCE) is a persistent, potentially inherited phenomenon. This suggests a lasting impact of AZA on genomic stability.
Area of Science:
- * Molecular Biology
- * Epigenetics
- * Cytogenetics
Background:
- * Carcinogenic agents can alter DNA methylation levels in mammalian cells.
- * Azacytidine (AZA) is a known DNA demethylating agent.
- * The relationship between DNA methylation and cytogenetic endpoints requires further investigation.
Purpose of the Study:
- * To investigate the relationship between genomic methylation levels and sister-chromatid exchange (SCE) rates.
- * To determine the persistence of these changes following azacytidine (AZA) treatment in vitro.
- * To explore the potential for inherited changes in cytogenetic endpoints.
Main Methods:
- * Cultured Chinese hamster ovary (CHO) cells were treated with a single pulse of 10 µM azacytidine (AZA).
- * Sister-chromatid exchange (SCE) levels and genomic % methylcytosine were measured.
- * Both parameters were monitored for up to 16 cell cycles post-treatment.
Main Results:
- * Azacytidine (AZA) treatment caused an initial 50% decrease in methylcytosine levels.
- * Methylcytosine levels returned to control values by 10 cell cycles post-treatment.
- * Sister-chromatid exchange (SCE) levels increased by 2 cell cycles and remained elevated for the entire 16-cycle observation period.
Conclusions:
- * Azacytidine (AZA)-induced DNA demethylation is a transient effect.
- * The sustained increase in sister-chromatid exchange (SCE) suggests a lasting genomic alteration.
- * The persistence of elevated SCE levels may indicate an inherited phenomenon, impacting genomic stability long-term.
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