NFKB1 and myelodysplastic syndrome: To confirm the functional activation of NF-κB in mesenchymal elements in LR-MDS, we demonstrated increased phosphorylation of p65, a component of the activated NF-κB complex, in intramedullary located CD271+ mesenchymal cells (Fig. 1d) as well as in bone-lining CD271+ stromal cells (Fig. 1e, f).