Centrosome amplification in HCT116 tumour cells after HU treatment. (A) Centrosome abnormalities revealed by immunofluorescence microscopy detection of γ-tubulin (green) in HCT116 cells treated with HU, nuclei (blue) were stained with DAPI. The majority of HCT -wt and -p21KO cells showed normal centrosomes (arrows). Arrowheads indicate abnormal centrosomes in HCT-p53KO. (B) Histograms indicating percentages of centrosomes numbers in untreated, hydroxyurea treated (48 hours) and released (10 days) cells. (C) Presence of coalesced centrosomes (arrows, likely forming a pseudo-bipolar spindle) and supernumerary centrosomes (arrowheads, likely forming a multipolar spindle) in HCT-p53KO cells.