Page 172 - 2021_02-Haematologica-web

T. Yahata et al.
BCR/ABL in CML cells to barely detectable levels (Figure 4B). In addition, the overall survival of this CML-affected mice treated with IM plus the PAI-1 inhibitor was markedly extended (Figure 4C). These results are in accor- dance with our earlier experiments using genetically modified CML cell lines and BCR/ABL transduced LSK cells and indicate that inhibition of iPAI-1 activity increas- es the susceptibility of CML cells to TKI treatment.
iPAI-1 blockade induces the dislocation of CML-LSC in the BM
We then sought to identify how iPAI-1 signaling influ- ences the sensitivity of CML cells to TKI. Since the block- ade of iPAI-1 causes detachment of HSPC from the niche,17,20 we hypothesized that iPAI-1 is similarly involved in the motility of CML-LSC in the BM. In order to test this hypothesis, we examined the expression of
AB
C
D
Figure 1. TGF-β−iPAI-1 signaling is activated in chronic myeloid leukemia - leukemic stem cells. (A) Schema for experiments. (B) Representative flow cytometric pro- files of contribution of BCR/ABL-GFP+ cells to the myeloid (Mac-1+/Gr-1+) peripheral blood (PB) output post transplantation. (C) Representative flow cytometric profiles and mean fluorescent intensity (MFI) (n=6) for p-Smad3 and intracellular plasminogen activator inhibitor-1 (iPAI-1) expressions in freshly isolated BCR/ABL-GFP+ immature chronic myeloid leukemia (CML) cells in the bone marrow (BM). MFI of LSK: Lin–c-kit+Sca-1+; LS–K: Lin–c-kit+Sca–1–; LS–K–: Lin–c-kit–Sca-1–. (D) Representative flow cytometric profile and MFI for iPAI-1 expression in freshly isolated BCR/ABL-GFP+ immature CML cells in the BM of vehicle- or LY364947-treated mice (n=5). Data represent means ± standard deviation. Statistical significance was determined by Mann-Whitney unpaired t-test. P<0.001, by a Kruskal-Wallis test. TGF-β: transforming growth factor-β; BCR: breakpoint cluster region; ABL: Abelson kinase; GFP: green florescent protein; SSC: side scatter.
486
haematologica | 2021; 106(2)