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A. Natoni et al.
MM1SHeca452 cells.29-31 Flow cytometry analysis revealed that 3Fax-Neu5Ac did not decrease α4, β1 or β7 expression (Online Supplementary Figure S5D-F). We then investigated whether 3Fax-Neu5Ac affected post-translational modifi- cations on these integrins, which in turn would result in an altered mobility on SDS-PAGE. Indeed, Western blot analysis of integrin α4 revealed a marked shift of the mature as well as the C-terminal cleavage form in response to 3Fax-Neu5Ac, suggesting an alteration of α4 post-translational modifications probably due to its desia- lylation (Figure 7A). To our knowledge, this is the first evi- dence that integrin α4 is post-translationally sialylated. The integrins β1 and β7 were not heavily affected by
3Fax-Neu5Ac pre-treatment (Figure 7B and C). Similar results were obtained in the parental MM1S cell line (Online Supplementary Figure S6A-C). Altogether, these data indicate that 3Fax-Neu5Ac primarily alters integrin α4 post-translationally, which most likely results in the observed weaker interaction of the MM cells with MAD- CAM1 and VCAM1.
Discussion
In this study, we examined whether global inhibition of sialylation could increase bortezomib sensitivity in an
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Figure 3. Effects of 3Fax-Neu5Ac pre-treatment on MM1SHeca452 xenograft mouse models. (A) Representative bioluminescence images taken at week 4.5 showing the differences in tumor burden between treatment groups. The colored scale rep- resents luminescence in radiance unit (p/sec/cm2/sr) with maximum and minimum val- ues of 2x106 and 1.5x105, respectively. Graph lines illustrate tumor burden (B), survival (C), and body weight (D) of treatment groups. Bars represent Standard Error of Mean. The two-way ANOVA was used to determine statistical significance with Tukey’s multiple comparison post-hoc testing. *P<0.05; **P<0.01; ****P<0.0001. Bort: borte- zomib
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haematologica | 2020; 105(2)