Genotoxins induce binucleation in L5178Y and TK6 cells

Area of Science:

• Genotoxicity testing
• Cell biology
• Mutagenesis research

Background:

• Methyl methanesulphonate (MMS) was observed to induce binucleated cells with micronuclei in AHH-1 cells.
• Understanding cell line variability is crucial for accurate in vitro genotoxicity assays.

Purpose of the Study:

• To investigate the induction of binucleated cells and micronuclei by various agents in TK6 and L5178Y cell lines.
• To compare the responses of human lymphoblastoid TK6 and mouse lymphoma L5178Y cells to genotoxic agents.
• To assess the impact of cell-line specific differences on micronucleus test outcomes.

Main Methods:

• Treatment of TK6 and L5178Y cells with methyl methanesulphonate, methylnitrosourea, mitomycin C, cytosine arabinoside, colchicine, and Triton X.
• Analysis of binucleated cell formation and micronucleus incidence.
• Comparison of results between the two cell lines and consideration of p53 status.

Main Results:

• All tested genotoxins, except Triton X, induced binucleated cells in both TK6 and L5178Y lines.
• Increased micronucleus incidence in binucleated cells was observed exclusively in the TK6 cell line.
• Control cultures showed higher spontaneous binucleate formation in TK6 (2.0%) compared to L5178Y (0.5%), with more micronuclei in TK6 binucleates.
• Colchicine induced binucleates but not increased micronuclei; Triton X did not induce binucleates even at cytotoxic levels.
• Genotoxins significantly increased micronucleus frequency in mononuclear cells of both lines, validating non-cytokinesis-block micronucleus tests.

Conclusions:

• TK6 and L5178Y cell lines exhibit differential responses in micronucleus formation within binucleated cells following genotoxic insult.
• The p53 status alone may not fully explain the observed differences in genotoxic response between these cell lines.
• In vitro micronucleus tests not employing a cytokinesis block are generally reliable, as genotoxins increase micronuclei in mononuclear cells.
• Further research is needed to understand the phenomenon of micronuclei in binucleated cells, especially for weakly genotoxic agents, before including them in test results.