Biological Properties of Mesenchymal Stromal Cells Obtained from Paediatric Patients with B-Cell Precursor Acute Lymphoblastic Leukemia

PURPOSE: Bone Marrow-derived Mesenchymal Stromal Cells (BM-MSCs) are the main component of the bone marrow microenvironment, where they regulate differentiation, proliferation and survival of adjacent hematopoietic precursors, by cell-to-cell contact and soluble factors. In addition, it has been demonstrated that BM-MSCs play a crucial role also within the leukemic bone marrow niche by regulating disease development and progression. The purpose of our work was to isolate and characterize morphologically, phenotypically and functionally MSCs derived from paediatric patients with B-Cell-Precursor Acute Lymphoblastic Leukemia (BCP-ALL) at disease onset.

METHODS: Several BM-MSC lines have been generated from BM aspirates of Healthy Donors (HD) (n=16) as well as BCP-ALL patients (n=16) and stored at "M. Tettamanti" Res. Center. MSCs were characterized at fourth passage in terms of morphology, immunophenotype (FACS analysis) and in vitro adipogenic and osteogenic differentiation potential. Chromosomal translocations detected in leukemia cells were investigated in BCP-ALL-MSCs by fluorescence in situ hybridizations (FISH) or polymerase chain reaction (PCR). MSCs were also analysed in terms of secretoma (BioRad Protein Array).

RESULTS: Both HD-MSCs and BCP-ALL-MSCs resulted comparable in terms of morphology. They both expressed the typical MSC markers CD73, CD90 and CD105, while were negative for the hematopoietic markers CD14, CD34, CD45 and MHC-II. In addition, MSCs from all investigated BCP-ALL patients did not present the chromosomal translocations that had been detected in leukemia cells (1 patient BCR-ABL p210, 5 patients TEL-AML1). To identify possible differences, BM-MSCs isolated from HD and BCP-ALL patients were compared for their principal biological properties. We found no significant differences in terms of proliferation and differentiation into adipogeneic and osteogeneic lineages between the two different groups. Moreover, the secretome profile of BCP-ALL-MSCs and HD-MSCs resulted comparable.

CONCLUSIONS: We found that BCP-ALL-MSCs were similar in terms of morphology, phenotype and differentiation ability to HD-MSCs. Furthermore, MSCs from patients did not reveal the chromosomal translocations present in leukemia blasts. Further assays aimed at investigating MSC production of soluble molecules, migration, adhesion to different substrates and Extracellular Matrix (ECM) deposition are currently under investigation.