Regarding Plexin-B1, bone marrow plasma and serum levels were increased in myeloma patients compared to controls (44 ± 29 ng/ml vs. 3.4 ± 0.8 ng/ml, p < 0.01 and 11 ± 20 ng/ml vs. 2.6 ± 2.7 ng/ml, p = 0.01, for bone marrow plasma, Fig. 3b, and serum, Fig. 4b, respectively). Here, PLXNB1 is linked to plasma cell myeloma.