High-dose BIBR1532 induces telomere dysfunction in JVM13 cells. Individual telomere length was analyzed by quantitative fluorescence in situ hybridization (Q-FISH) as described previously.^28,37  The number of analyzed metaphases was between 8 and 15 (Table 4). (A) The histograms represent telomere fluorescence intensity values (TFI) of JVM13 cells treated with 80 μM BIBR1532 compared with DMSO control at indicated time points. Values represent means ± SD. (B) The presence of telomere spots was counted at individual sister chromatids. (i) Representative metaphase spread from JVM13 cells treated with 80 μM BIBR1532. (ii) Chromosome missing 2 telomere signals. (iii) Chromosome missing one telomere signal from 1 chromatid (= 3 signals). (iv) Chromosome showing 5 telomere signals. (v) Chromosome showing 6 telomere signals (end-to-end fusion). (C) Graphic summary of number of telomere spots/chromosome deviating from the normal distribution of 4 telomeres per chromosome. The values represent mean ± standard error. ^* indicates a significant difference from cells treated with DMSO (P < .05); + indicates zero events for DMSO-treated cells.