The frequency of micronuclei in lung cancer cell lines and their correlation to intrinsic radiation sensitivity.

BACKGROUND: Micronuclei arise from chromosomal, acentric, fragments or whole chromosomes that are not incorporated into the daughter nuclei at mitosis. The micronuclei assay is technically simple and requires only one mitosis in order to obtain information concerning the amount of micronuclei. This study was performed to investigate whether the formation of micronuclei could be used as a marker for intrinsic radiation sensitivity in lung cancer patients. MATERIALS AND METHODS: Two human lung cancer cell lines, a non-small cell lung cancer (NSCLC) cell line (U-1810) and a small cell lung cancer (SCLC) cell line (U-1906L), were used. Radiosensitivity data on the survival fraction at 2 Gy were obtained from the clonogenic assay. Radiation was delivered as one-fraction doses: 0, 1, 2, 4, 10 and 20 Gy. After irradiation, the cells were incubated for 0, 24, 48, 60, 72 and 96 hours before fixation and staining. RESULTS: The frequency of micronuclei in U-1906L was clearly elevated after 96 hours in the 20 Gy fraction. The frequency of micronuclei reached 5.5%. For U-1810 the micronuclei had a peak clearly different than the other settings after 48 hours in the 10 Gy fraction. The frequency of micronuclei was 1.2%. CONCLUSION: Counting micronuclei is not sensitive enough for estimation of radiosensitivity in clinical doses. However, our results demonstrated a distinct difference between NSCLC and SCLC cell lines at higher doses. This difference might be due to different repair fidelity, so future studies with this assay should aim to investigate this hypothesis.