Abstract 16: Differential stemness properties in bone marrow-derived mesenchymal stem cells from healthy subjects and from patients with acute myeloid leukemia

Abstract

Study purpose: The imidazoquinoxaline EAPB0503, an imiquimod analogue, exhibits immunomodulatory and anti-cancer properties against several blood malignancies, including acute myeloid leukemia (AML). The bone marrow (BM) niche plays a pivotal role in normal hematopoiesis and in leukemogenesis. To characterize the molecular potency of EAPB0503 in AML, we compared its effect on the expression profile of genes involved in the function and differentiation potential of BM-derived mesenchymal stem cells (BM-MSCs) from a healthy subject and a patient with AML.

Experimental procedures: Transcriptional levels of stemness markers and genes potentially relevant to niche function were evaluated by quantitative real-time polymerase chain reaction in BM-MSCs isolated from BM aspirates of subjects undergoing BM analysis and exposed to EAPB0503. Differentiation potential was assessed in BM-MSCs exposed to EAPB0503 and induced into osteogenic differentiation using a mixture of dexamethasone, ascorbic acid and β-glycerophosphate (DAG). A colorimetric assay was used to detect early-stage osteogenic differentiation by evaluating alkaline phosphatase (ALP) activity.

Summary of results: EAPB0503 treatment induced a differential expression of functionally important marker genes between BM-MSCs from the healthy subject and the patient with AML. As such, levels of Connexin 43 (GJA1) decreased in healthy BM-MSCs and increased in AML-derived BM-MSCs following treatment with EAPB0503. In contrast, transcriptional levels of multi-drug resistance 1 (MDR1 or ABCB1) markedly increased in healthy BM-MSCs and remained stable in AML-derived BM-MSCs. Vascular Endothelial Growth Factor (VEGF) and N-cadherin (CDH2) transcriptional levels increased in AML-derived BM-MSCs, with modest changes in healthy MSCs. In addition, AML-derived BM-MSCs do not seem to respond to differentiation signals in a manner similar to healthy BM-MSCs, as shown by ALP activity.

Conclusions: These preliminary findings underscore the differential transcriptional profile in BM-MSCs derived from a healthy subject or a patient with AML. Importantly, a differential gene expression profile was also obtained in response to the therapeutic drug EAPB0503. Our preliminary findings implicate the BM niche in AML leukemogenesis and response to drugs.