Reorganization of mitotic apparatus in the etoposide-treated CHO-K1 cells precedes apoptotic death

Abstract

In a culture of CHO-K1 cells, etoposide (1 h, 25 μM) has been shown to produce interphase arrest, after which the cells resume mitotic division and, after some time, are submitted to apoptotic death. Accumulation of apoptotic cells in the culture follows a gradual increase in the number of multipolar mitoses. Our findings provide the first evidence for differences in the pattern of immunofluorescent staining of multipolar mitotic spindle microtubules with antibodies to α-tubulin, acetylated α-tubulin, and tyrosinated α-tubulin in mitotic cells dividing in the period preceding apoptosis. Moreover, some parts of the multipolar mitotic spindle can differ by the presence of antigenic determinants accessible to anti-tyrosinated α-tubulin antibodies. These abnormalities of the mitotic apparatus are aggravated immediately before the increase in the number of cells submitted to apoptosis. Our data have also shown that some cells pass through at least two mitotic cycles prior to a sharp increase in the number of apoptotic cells in the cell culture.