Figure 5. MM cell lines exhibit a deficient SAC when challenged with nocodazole.

A. Several MM cell lines were treated with nocodazole for 20 hours, and their cell cycle status after the arrest measured by conventional flow cytometry after DNA staining. Most of the MM cell lines analyzed was not as efficiently arrested in those conditions as HeLa cells. B. The indicated cell lines were arrested for up to 60 hours with nocodazole to determine if the deficient arrest was due to a slower proliferation. The increase in the time of treatment did not effectively synchronize MM1S or SJR cells. C. Cells were labeled for 30 minutes with the CellTracker Red dye, washed out the excess and placed in culture in normal medium (green line), or supplemented with nocodazole (pink line). Cell division in untreated cells made them loose staining, as indicated by the shift in the peak. When the arrest was efficient, the population did not shift (see HeLa cells). Nevertheless, part of the nocodazole treated MM1S population shifted as the control confirming that those cells had, in fact, divided even in the presence of nocodazole. On the other hand the low synchronization detected in SJR was mainly due to the low proliferation of this cell line given that even the normal population had not divided in 40 hours.