[The reorganization of the mitotic apparatus in etoposide-treated CHO-K1 cells precedes accumulation of the apoptotic cells].

Etoposide (1 h, 25 microM) causes interphase arrest in CHO-K1 after which cells resume mitotic division and die due to apoptosis after a certain time period. Accumulation of apoptotically dying cells in the culture follows a gradual increase in the number ofmultipolar mitoses. Our findings provide the first evidence that the pattern of immunostaning for alpha-tubulin, acetylated alpha-tubulin and tyrosinated alpha-tubulin in cells dividing at various periods after etoposide treatment. Moreover, some parts of the multipolar mitotic spindle differ in the presence of antigenic determinants accessible to anti-tyrosinated alpha-tubulin antibodies. It is noteworthy that these abnormalities are aggravated just before the increase in the number of apoptotically died cells. Our findings also suggest that some cells pass through at least two mitotic cycles prior to a sharp increase in the number of apoptotically died cells in the cell culture.