Assessment of micronucleus induction in murine SCCVII cells treated with various anticancer agents

The possibility of using the cytokinesis-block micronucleus (MN) assay as a rapid test of chemosensitivity was investigated. SCCVII murine carcinoma cells growing exponentially in vitro were treated for 1 h under aerobic conditions with various concentrations of 11 anticancer agents: mitomycin C, doxorubicin, epirubicin, cisplatin, carboplatin, etoposide, vincristine, 5-fluorouracil, methotrexate, nimustine and dacarbazine. After removing the drugs, cytochalasin B (1.5 micrograms/ml) was added to block cytoplasmic but not nuclear division. At various times during culture, the proportions of binucleate cells (BNC) and multinucleate cells in the total cell population, and the mean number of micronuclei per single BNC were determined. Cell survival was also determined using the standard colony formation assay and was compared with the MN frequency. Maximal percentage of BNC was usually reached at 24-30 h of culture, except for cells treated with doxorubicin and epirubicin, in which it was reached at 30-72 h. All drugs induced formation of micronuclei and dose-response curves for MN frequency were obtained using the data at peak percentage of BNC times. For all drugs, MN frequency increased with concentration, but at the highest concentrations used (which are considered to be overly toxic) the MN frequency was rather lower. This decrease in MN frequency was largely attributable to the decrease in percent BNC. When the data at the highest concentrations of all drugs were excluded, a correlation was found between MN frequency and surviving fraction (r = 0.85). Therefore, it was concluded that the cytokinesis-block MN assay can be used to assess sensitivity of at least some tumor cells to appropriate concentrations of various chemotherapeutic agents.