PLXNB1 and plasma cell myeloma: Increased expressions of Sema4D and its receptor Plexin‐B1 have been evaluated in myeloma cell lines in vitro as well as in the bone marrow plasma and serum of patients diagnosed with symptomatic MM.[315] The expressions are also correlated with adverse myeloma features and enhanced bone resorption.[315] Catecholamines and their receptors are regarded as potential molecular markers of osteosarcoma progression.