S100A9 and metastasis: Next, ELISA and IHC were performed to detect the protein levels of S100A9 in NB patients (9 NB patients with bone marrow metastasis and 10 NB patients without bone marrow metastasis).The serum levels of S100A9 were higher from NB patients with bone marrow metastasis than without bone marrow metastasis (Fig. 3B).