Compaction of chimeric integrin-expressing cells. Hanging drop cultures of parent MLL and chimeric integrin-expressing cells show that expression of the different chimeric integrins can markedly influence aggregate compaction. When placed in hanging drop culture, parent MLL cells tend to generate large cellular sheets. Expression of X5C2 gives rise to more compact sheets, whereas expression of X5C5 results in even more compact aggregates. Compaction of MLL-X5C5 cells can be blocked by incubation in 50 μg/ml 70 kDa fibronectin fragment (A). Quantification of aggregate compaction. Compaction was quantified and statistically analyzed by ANOVA and Tukey's MCT. ANOVA detected significant size difference within the data set (p < 0.0001). Tukey's MCT confirmed that MLL-X5C5 are more compact than MLL (p < 0.001) and MLL-X5C2 (p < 0.01). Moreover, incubation of MLL-X5C5 with 50 μg/ml 70 kDa fragment of fibronectin resulted in aggregates that were on average larger than MLL-X5C5 (p < 0.001) and MLL (p < 0.001) (B).