C-Mannosyl tryptophan is a novel biomarker for thrombocytosis of myeloproliferative neoplasms.

C-Mannosyl tryptophan (CMW), a unique glycosylated amino acid, is considered to be produced by degradation of C-mannosylated proteins in living organism. Although protein C-mannosylation is involved in the folding and secretion of substrate proteins, the pathophysiological function in the hematological system is still unclear. This study aimed to assess CMW in the human hematological disorders. The serum CMW levels of 94 healthy Japanese workers were quantified using hydrophilic interaction liquid chromatography. Platelet count was positively correlated with serum CMW levels. The clinical significance of CMW in thrombocytosis of myeloproliferative neoplasms (T-MPN) including essential thrombocythemia (ET) were investigated. The serum CMW levels of the 34 patients with T-MPN who presented with thrombocytosis were significantly higher than those of the 52 patients with control who had other hematological disorders. In patients with T-MPN, serum CMW levels were inversely correlated with anemia, which was related to myelofibrosis (MF). Bone marrow biopsy samples were obtained from 18 patients with ET, and serum CMW levels were simultaneously measured. Twelve patients with bone marrow fibrosis had significantly higher CMW levels than 6 patients without bone marrow fibrosis. Collectively, these results suggested that CMW could be a novel biomarker to predict MF progression in T-MPN.