Involvement of osteopontin and its signaling molecule CD44 in clinicopathological features of adult T cell leukemia.

We previously reported that the osteopontin (OPN) gene as well as CD44 is trans-activated by the Tax protein of HTLV-1, however the synthesis of both in adult T cell leukemia (ATL) has not been described yet. Here we showed the expression of these molecules in plasma and tissue of ATL. Significant differences were found among the normal and four subtypes of 27 ATL patients in plasma levels of OPN (p=3.6×10(-6)) and soluble CD44 (p<0.001) and they were significantly related to each other (p<0.002). Also they were significantly associated with the performance status, total number of involved lesions, and lactic dehydrogenase, and inversely with lymphocyte count (p<0.01). Immunohistochemical staining of lymph-nodes and skin from 7 ATL patients using anti-OPN and anti-CD44 antibodies demonstrated that both expressions were weak/moderate in ATL cells but moderate/strong in infiltrated macrophages in 6 patients. These results demonstrate that OPN and CD44 play important roles in tumor formations and their products in plasma could be markers of the severity in ATL.