When we performed immunofluorescence staining for Plk1 and Aurora B, proteins known to regulate cytokinesis,11, 12 we found that Plk1 localized at the cytokinesis contractile ring in CLL doublets (Figure 1C), which is a hallmark of cytokinesis.11 Taken together, our results indicate that CLL cell doublets were in the cytokinesis stage of the cell cycle, specifically, after reformation of the nucleus, but before abscission and physical separation of the cytoplasm.11, 13, 14, 15, 16. The gene discussed is PLK1; the disease is B-cell chronic lymphocytic leukemia.