Abundant expression of HMGB1 in human T-cell lymphotropic virus type I-infected T-cell lines and high plasma levels of HMGB1 in patients with adult T-cell leukemia

High mobility group box 1 (HMGB1) functions as a chromatin-associated nuclear protein and an extracellular signaling molecule. The concentration of HMGB1 protein and the expression of HMGB1 mRNA were analyzed by ELISA and polymerase chain reaction (PCR), respectively. The present study reports high plasma HMGB1 levels in patients with adult T-cell leukemia [ATL; which is caused by infection with human T-cell lymphotropic virus type I (HTLV-I)] compared with normal controls. In addition, HMGB1 was highly expressed in HTLV-I-infected T-cell lines compared with uninfected T-cell lines. The HTLV-I oncoprotein, Tax, induced extracellular release of HMGB1 in T cells. The results suggest that HMGB1 is a potential biomarker and a therapeutic target for ATL.