Carcinogenesis, Vol 18, 657-662, Copyright © 1997 by Oxford University Press
C Diem and TM Runger
In order to study the role of DNA damage processing in the development of
cutaneous squamous cell carcinoma (SCC), we assessed the ability of six
keratinocyte cell lines from a multistage-tumor progression model to repair
three types of DNA damage: pyrimidine dimers, oxidative DNA lesions and DNA
double strand breaks (DSB). The model comprised the spontaneously
immortalized, non-tumorigenic human keratinocyte cell line HaCaT, four
different c-Ha-ras transfectants of HaCaT (non-, benign- and two
malignant-tumorigenic) and a SCC-derived cell line. Host cell reactivation
assays with UVB-treated plasmid vectors pRSVcat showed no significantly
altered repair of UVB-induced pyrimidine dimers in the tumorigenic cell
lines, compared with the non-tumorigenic lines. Using the singlet
oxygen-treated plasmids pRSVcat the Ha-ras-HaCaT- clones and the SCC-cells,
exerted a DNA repair efficiency that was not significantly different from
HaCaT cells. In order to assess the ability of the cells to ligate free DNA
ends (repair of DSB), we used a plasmid shuttle vector assay with
linearized plasmid pZ189. We found a significant increase of DNA end
joining ability in the non-tumorigenic, the benign and in one of the
malignant HaCaT-clones II-4. The malignant HaCaT-clone II-3, however,
exerted a significantly lower rate of rejoining the linearized plasmid.
This cell line also showed a highly and significantly elevated rate of
micronuclei, which reflects a pronounced chromosomal instability. The
SCC-cells exhibited a more efficient repair of DNA DSB than the HaCaT
cells. We conclude that in the examined model, progression of human
keratinocytes from the non- tumorigenic to the highly tumorigenic
phenotype, is not accompanied by a decrease in the cell's capacity to
repair UVB- and singlet oxygen- induced DNA lesions. However, an acquired
deficiency in repairing DNA double strand breaks can be one mechanism
promoting progression towards malignancy, possibly through impairing
chromosomal stability.
ARTICLES
Processing of three different types of DNA damage in cell lines of a cutaneous squamous cell carcinoma progression model
Department of Dermatology, University of Wurzburg, Germany.
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