Functional Characterization of Transforming Growth Factor- Signaling in Dasatinib Resistance and Pre-BCR⁺ Acute Lymphoblastic Leukemia

Simple Summary: We focus on the characterization of the transforming growth factor-beta (TGF beta) signaling pathway in B acute lymphoblastic leukemia (ALL) and in resistance to the multi-kinase inhibitor dasatinib in order to provide a better understanding of the molecular and functional mechanisms underlying leukemic transformation and the development of drug resistance. We provide evidence that TGF beta signaling is an important negative regulator of cell growth in B-cell precursor- ALL as well as in generated dasatinib-resistant ALL cells. The multi-kinase inhibitor dasatinib has been implicated to be effective in pre-B-cell receptor (pre-BCR)-positive acute lymphoblastic leukemia (ALL) expressing the E2A-PBX1 fusion oncoprotein. The TGF fi signaling pathway is involved in a wide variety of cellular processes, including embryonic development and cell homeostasis, and it can have dual roles in cancer: suppressing tumor growth at early stages and mediating tumor progression at later stages. In this study, we identified the upregulation of the TGF fi signaling pathway in our previously generated human dasatinib-resistant pre-BCR+/E2A-PBX1(+) ALL cells using global transcriptomic analysis. We confirm the upregulation of the TGF fi pathway member SMAD3 at the transcriptional and translational levels in dasatinibresistant pre-BCR+/E2A-PBX1(+) ALL cells. Hence, dasatinib blocks, at least partially, TGF beta-induced SMAD3 phosphorylation in several B-cell precursor (BCP) ALL cell lines as well as in dasatinibresistant pre-BCR+/E2A-PBX1(+) ALL cells. Activation of the TGF fi signaling pathway by TGF-beta 1 leads to growth inhibition by cell cycle arrest at the G0/G1 stage, increase in apoptosis and transcriptional changes of SMAD-targeted genes, e.g. c-MYC downregulation, in pre-BCR+/E2A-PBX1(+) ALL cells. These results provide a better understanding about the role that the TGFfi signaling pathway plays in leukemogenesis of BCP-ALL as well as in secondary drug resistance to dasatinib.