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Desialylation of MM overcomes bortezomib resistance in vivo
AB
CD
EF
GH days. After treatment, cells were collected and stained with the Heca452 (A and B), CD15s (C and D), MALII (F and G), or SNA (G and H) anti- bodies or lectins. Bars repre- sent mean±Standard Error of Mean of three independent experiments. Unpaired Student’s t-test was used to determine statistical signifi- cance. *P<0.05; ** P<0.01; ***P<0.001. MFI: median
are consistent with a requirement of sialic acid for E-selectin binding. The MM1SHeca452 also showed robust adhesion and rolling on MADCAM1 under shear stress (Figure 6D-F). 3Fax-Neu5Ac pre-treatment induced a decrease in the total number of cells interacting with MADCAM1 and, in particular, decreased the number of adherent cells while increasing the number of rolling cells, suggesting a decrease in the affinity of integrin α4β7 for MADCAM1. Again, the velocity of the rolling cells was increased by 3Fax-Neu5Ac, indicating a weaker attachment (Online Supplementary Figure S4D-F). Finally, the 3Fax-Neu5Ac pre-treatment induced a reduction in the number of MM1SHeca452 cells interacting with VCAM1,
which was exclusively adhesion (Figure 6G). Indeed, rolling on VCAM1 was not observed indicating strong interactions between integrin α4β1 and VCAM1. Altogether, these data indicate that desialylation of the MM1SHeca452 cells impairs interaction (a summation of adhesion and rolling) with E-selectin, MADCAM1 and VCAM1.
3Fax-Neu5Ac treatment alters the post-translational modifications on integrin α4
Next, we examined whether 3Fax-Neu5Ac treatment decreased protein expression of integrins α4β7 or α4β1, which bind VCAM1 and MADCAM1 respectively, on
Figure 2. 3Fax-Neu5Ac treat- ment decreases sialylation in the MM1SHeca452 cell line. MM1SHeca452 cells were treated with 300 μM 3Fax-Neu5Ac or dimethyl sulfoxide (DMSO) (vehicle control) for seven
fluorescence intensity.
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