Figure 1. Morphology, size and growth properties of SKOV3 cells after CPT treatment.

A. Cells were treated with CPT for 10 days, 14 days, 28 days or 21 weeks, stained with Giemsa dye and evaluated by bright field microscopy. Representative photomicrographs are shown. B. Viability of SKOV3 and SKOV3-R cells after 14 days of CPT exposure (MTT assay). C. Size (area) of attached cells (n = 285) at the indicated times. Dotted lines define three populations distinguished by size; small (S), maximum the size of untreated SKOV3 cells; medium (M), maximum twice the size of small cells; giant (G), >4-times the size of small cells. The horizontal line shows the median. D. Time course of size distributions under CPT treatment. E. Nuclear area of cells (n = 204) at the indicated times. The stacked bar graph shows the distribution of giant, medium and small nuclei on day 14. F. Effect of cyclic CPT treatment. Cells were treated with CPT (days preceded by a “+” in the Figure) followed by a CPT-free recovery phase (days preceded by a “−”), and the respective cycle was repeated as indicated in parentheses (sample size: n = 3). G. Effect of hypoxia. Cells were treated with hypoxia, CPT or both for 14 days and the fraction of giant cells was determined by flow cytometry analysis. H. Anchorage-independent growth of untreated SKOV3 cells (0d) and cells treated with CPT for 14 days or 21 weeks. Cells were embedded in a collagen matrix after this treatment and observed under a phase-contrast microscope after another 12 days (sample size: n = 3). The cell count for “14d” was 0 in each experiment.