ABSTRACT
The aim of this study was to investigate the effect of the cell differentiation status on the sensitivity to genotoxic insults. For this, we utilized the comet assay to test the DNA damage after treatment with 5 different substances with different mechanism of action in human promyelocytic HL60 cells with or without cell differentiation. A 4-hour MMS treatment induced a significant and concentration-dependent increase in DNA damage for both differentiated and undifferentiated cells, but the difference in sensitivity was only significant at the highest concentration. A 4-hour doxorubicin treatment did not induce DNA damage in differentiated HL60 cells, while it did in undifferentiated cells with its highest tested concentration. A one-hour etoposide treatment caused significant increase in DNA damage concentration dependently in both cell variants. This DNA damage was significantly higher in undifferentiated HL60 cells with several tested concentrations of etoposide. The treatment with the oxidizing substances hydrogen peroxide and potassium bromate yielded significant DNA damage induction in both undifferentiated and differentiated cells with no difference according to the differentiation status. Doxorubicin and etoposide are known to inhibit topoisomerase II. The activity of this enzyme has been shown to be higher in undifferentiated actively proliferating cells than in differentiated cells. This may be of relevance when exposures to topoisomerase-inhibiting compounds or the genotoxicity of compounds with unknown mechanism of action are assessed in routine testing.
Subject(s)
Comet Assay , HL-60 Cells/drug effects , Mutagens/toxicity , Bromides/toxicity , Cell Differentiation/drug effects , Cell Nucleus/drug effects , Cell Nucleus/ultrastructure , Cell Survival/drug effects , DNA Damage , DNA Topoisomerases, Type II , DNA, Neoplasm/drug effects , Dimethyl Sulfoxide/pharmacology , Doxorubicin/toxicity , Drug Resistance , Etoposide/toxicity , HL-60 Cells/cytology , Humans , Hydrogen Peroxide/toxicity , Methyl Methanesulfonate/toxicity , Neoplasm Proteins/antagonists & inhibitors , Oxidative Stress , Poly-ADP-Ribose Binding Proteins/antagonists & inhibitors , Potassium Compounds/toxicity , Topoisomerase II Inhibitors/toxicityABSTRACT
BACKGROUND: Vinca alkaloids are important cancer drugs belonging to the class of antimitotic agents. The most commonly used substances are vinblastine and vincristine, other compounds are vinorelbine and vinflunine. All of them are very effective drugs but their use is limited by severe side-effects including neurotoxicity and bone marrow depression. Therefore, it is very important to develop novel vinca alkaloids with similar efficacy but lower toxicity. METHODS: Here, we analyzed two new compounds, 4-chlorochablastine and 4-chlorochacristine, with regard to their biological activity. These novel compounds were applied to a leukemia cell line at clinically relevant concentrations. For comparison, the established vinca alkaloids vinblastine, vincristine, vinorelbine, and vinflunine were also tested. RESULTS: Both novel substances decreased cellular proliferation. Apoptosis was found to be increased using two different methods reflecting early and late apoptosis. Cell cycle analysis revealed a clear decrease in G1-cells and an increase in G2/M-cells indicating an arrest in mitosis. In general, 4- chlorochablastine and 4-chlorochacristine caused these effects at concentrations higher than those needed for vinblastine, vincristine, and vinorelbine, but the potency was approximately in the range of vinflunine. CONCLUSION: Taken together, the results show first indications that these novel vinca alkaloids might be effective and that they warrant further analysis.
Subject(s)
Antineoplastic Agents, Phytogenic/chemistry , Antineoplastic Agents, Phytogenic/pharmacology , Apoptosis , Cell Proliferation , Leukemia, Promyelocytic, Acute/pathology , Vinca Alkaloids/chemistry , Vinca Alkaloids/pharmacology , Cell Cycle , Humans , Leukemia, Promyelocytic, Acute/drug therapy , Tumor Cells, CulturedABSTRACT
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ABSTRACT
For mutagenicity testing, primary lymphocytes or mammalian cell lines are employed. However, the true target for carcinogenic action of mutagenic chemicals may be stem cells. Since hematopoietic cancers induced by chemical agents originate at the hematopoietic stem cell (HSC) stage and since one of the side effects of chemotherapeutic cancer treatment is the induction of secondary tumors, often leukemias, HSC may be a suitable cell system. We compared the sensitivity of HSC with the genotoxicity testing cell line TK6 for chromosomal mutations. HSC were less sensitive than TK6 cells for the genotoxic effects of the model genotoxins and chemotherapeutic agents doxorubicin, vinblastine, methyl methanesulfonate (MMS) and equally sensitive for mitomycin C (MMC). However, loss of viability after mitomycin C treatment was higher in HSC than in TK6 cells. Among the factors that may influence sensitivity for genomic damage, the generation or response to reactive oxygen species (ROS) and the effectiveness of DNA damage response can be discussed. Here we show that HSC can be used in a standard micronucleus test protocol for chromosomal mutations and that their sensitivity was not higher than that of a classical testing cell line.