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.