Differences in NHE1 protein expression in normal tissue biopsies (non-malignant bone (NB); N = 5), primary tumor biopsies from metastasis-competent (MC) OS (N = 14), and from metastasis-incompetent (MI) OS (N = 9) were determined by immunohistochemistry and Western blot. This evidence concerns the gene SLC9A1 and neuroblastoma.