Clonal evolutions during long-term cultures of bone marrow from de novo acute myeloid leukaemia with trilineage myelodysplasia and with myelodysplastic remission marrow.

We previously established a long-term bone marrow culture (LTBMC) system in which novel abnormal karyotypes could emerge in vitro prior to the appearance of the same karyotypes in vivo in patients with myelodysplastic syndrome (MDS). We extended our study to examine whether acute myeloid leukaemia (AML) transformed from MDS (MDS/AML) and de novo AML with trilineage myelodysplasia (AML/TMDS) show clonal evolution in LTBMC similar to that of typical AML or MDS. We also analysed the cytogenetic changes in cultures with bone marrows from AML with myelodysplastic remission marrow (AML/MRM) as well as chronic myeloid leukaemia (CML) to compare them with typical AML with respect to the liability of clonal evolution. Among the 34 AML cases, abnormal karyotypes were newly detected in four of seven MDS/AML, three of six AML/TMDS and three of three AML/MRM. Novel abnormal karyotypes were also observed in nine out of 13 CML cases after culture. In contrast, no other abnormal karyotypes were found after culture in 18 typical AML without myelodysplasia. These findings suggest that AML/TMDS and AML/MRM are different from typical AML and are similar to MDS/AML and CML in view of their potential for disease progression from latent multiple clones. Typical AML may develop from a single abnormal clone without any subclones.