High correlation between micronuclei in lymphocytes and buccal cells in humans provides further validation of their use as biomarkers of DNA damage and cancer risks <i>in vivo</i>

Micronuclei (MN) are cellular structures containing chromosome fragments or whole chromosomes that fail to be incorporated into the main nuclei during mitosis. MN measured in lymphocytes using the cytokinesis-block method and MN in buccal cells are among the most widely used methods for measuring DNA damage in humans. However, it remains unclear whether they correlate well with each other. This has important implications regarding whether existing evidence linking MN in lymphocytes to prospective cancer risk can also be extended to MN in buccal cells, a much less invasive approach. We therefore systematically reviewed results from published studies that reported MN frequencies simultaneously in buccal cells and lymphocytes. Data were extracted from a set of 81 study groups reported in 62 publications. The overall frequency of MN in groups exposed to increased risk of DNA damage was 2.54 times higher compared to controls (95% CI: 2.06-3.01) in buccal cells and 2.43 times higher (95% CI: 1.92-2.93) in lymphocytes. Frequencies of MN in populations investigated for occupational or environmental exposure to genotoxins, various diseases, and poor nutrition/lifestyle were also compared in each study and for each tissue (lymphocytes and buccal mucosa) with frequencies in control subjects using the mean ratio (MR). Concordance between the two MN assays was evaluated by comparing MRs for primary exposure in all studies using a correlation analysis. The overall Pearson correlation index was 0.768 (0.877 for case-control studies and 0.998 for intervention studies), showing that MR estimates from the two assays were highly and significantly correlated (P < .001). The results from this investigation indicate that data obtained using the buccal MN assay reflect results obtained using the lymphocyte cytokinesis-block MN assay. This suggests that the buccal MN assay may also identify those at increased risk of tumorigenesis. Prospective studies will ultimately be required to completely verify this hypothesis.