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Sodium arsenite disturbs mitosis and induces chromosome loss in human fibroblasts
1Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan, Republic of China.
Abstract:
Arsenite, a unique human carcinogen, induces many types of cytogenetic alterations, such as sister chromatid exchanges, chromosome aberrations, and endoreduplication in a variety of in vivo and in vitro systems. Cytogenetic alterations are frequently associated with cancer development. The purpose of this study was to explore how arsenite induces cytogenetic alterations in human skin fibroblasts (HFW). The present results show that treatment of G2-enriched HFW cells with 5 microM arsenite results in significant delay of cell cycle progression, accumulation of mitotic cells, and prolongation of mitosis. Arsenite-induced G2 and mitotic delay are accompanied by accumulation of cyclin B1 and hyperphosphorylation of cdc2 and Mos proteins. In addition to mitotic delay and prolongation, arsenite treatment also induced out-of-phase centromere separation and alterations of chromosome segregation, such as the appearance of c-metaphase, ball-metaphase, and lagged chromosomes. Unlike spindle poisons, arsenite at the dose range used did not inhibit the spindle fiber formation but conceivably deranges the spindle apparatus. By analyzing the karyotype of established subclones surviving arsenite injury, 18% (8 of 44) showed one chromosome loss, whereas all 26 subclones derived from the untreated cultures were diploid. Furthermore, most arsenite-treated clones manifest prolonged life span (86 +/- 18 population doublings) as compared to those derived from the untreated cultures (44 +/- 11 population doublings). Unfortunately, none became immortal. Collectively, treatment of the G2-enriched HFW cells with arsenite can disturb the mitotic events and subsequently induce chromosome loss.
Insights
Arsenite exposure causes significant delays in cell division and disrupts chromosome segregation in human skin fibroblasts. This can lead to chromosome loss and increased cell lifespan, contributing to cancer development.
Area of Science:
- Cell Biology
- Toxicology
- Genetics
Background:
- Arsenite is a known human carcinogen.
- Cytogenetic alterations are linked to cancer development.
- The mechanisms by which arsenite induces these alterations are not fully understood.
Purpose of the Study:
- To investigate how arsenite induces cytogenetic alterations in human skin fibroblasts (HFW).
Main Methods:
- Human skin fibroblasts (HFW) were enriched in the G2 phase of the cell cycle.
- Cells were treated with 5 microM arsenite.
- Cell cycle progression, mitotic events, and chromosome segregation were analyzed.
- Karyotype analysis of surviving subclones was performed.
Main Results:
- Arsenite treatment caused significant G2 and mitotic delay, accumulating cells in mitosis.
- Mitotic delay was associated with altered cyclin B1 and cdc2/Mos protein phosphorylation.
- Arsenite disrupted centromere separation and chromosome segregation, leading to abnormal mitotic figures.
- 18% of arsenite-treated subclones exhibited chromosome loss, unlike diploid untreated controls.
- Arsenite-treated clones showed a prolonged lifespan compared to untreated clones.
Conclusions:
- Arsenite disturbs mitotic events in human skin fibroblasts.
- Arsenite can induce chromosome loss through disruption of mitotic processes.
- These findings contribute to understanding arsenite's carcinogenic mechanisms.