Mesenchymal stem cells in patients with chronic myelogenous leukaemia or bi-phenotypic Ph+ acute leukaemia are not related to the leukaemic clone.

BACKGROUND

Human mesenchymal stem cells (MSCs) are thought to be multipotent cells which primarily reside in the bone marrow. Besides their well-known ability to replicate as undifferentiated cells and to differentiate into diverse lineages of mesenchymal tissues, they were recently suggested to also give rise to haematopoietic and leukaemic/cancer stem cells. In this study, the relationship between MSCs and leukemic stem cells in patients with either chronic myelogenous leukaemia (CML) or the more primitive variant, Ph+ bi-phenotypic leukaemia was investigated.

PATIENTS AND METHODS

Cultured MSCs from 5 patients with CML and 3 patients with bi-phenotypic Ph+ leukaemia, all of them positive for BCP-ABL, were analysed with conventional cytogenetics, fluorescence in situ hybridisation (FISH) and polymerase chain reaction (PCR) for the presence of t(9;22) and BCR-ABL. MSCs were characterised phenotypically with surface markers (+CD73, +CD90, +CD105, -CD34, -CD45) and functionally through their potential to differentiate into both adipocytes and osteoblasts.

RESULTS

MSCs could be cultivated from seven patients. These cells were BCR-ABL negative when analysed with conventional cytogenetics and FISH. Further cytogenetic analysis revealed a normal set of chromosomes without any aberrations. Two patients were BCR-ABL-positive when analysed with PCR, probably as a result of MSC contamination with macrophages.

CONCLUSION

MSCs in patients with CML or Ph+ bi-phenotypic leukaemia are not related to the malignant cell clone.