Expression of metastasis associated proteins, CD44v6 and NM23-H1, in pediatric acute lymphoblastic leukemia

Two metastasis-associated proteins, CD44v6 and NM23-H1, are expressed by normal lymphoid cells, the former serving as activation marker and the latter as a constitutive protein. CD44v6 is considered as a marker of poor prognosis of various hematological cancers but its expression was not demonstrated in childhood acute lymphoblastic leukaemia (ALL). On the other hand, NM23-H1 is considered as a differentiation inhibitory factor in various hematological cancers and as a marker of poor prognosis. Therefore we analyzed the expression of CD44v6 and NM23-H1 in the bone marrow of sixteen pediatric ALL patients using immunocytochemistry. For the first time, we have demonstrated the expression of CD44v6 protein epitopes on leukemic cells in a proportion of ALL cases (6 out of 16), primarily in the medium/high risk group (except one case), suggesting a possible association to an unfavourable outcome. On the other hand, NM23-H1 protein expression was maintained in leukaemic cells in 50% of both low and medium/high risk ALL cases. The majority of the pediatric ALL cases expressed only one of the metastasis-associated proteins (10 out of 16). This feature is similar to the observations made in several adult solid cancers. The potential of CD44v6 expression in leukaemic cells as prognosticator in pediatric ALL should be evaluated in a larger clinical trial.