BROMELAIN PROTEINASES MODULATE THE CD44 EXPRESSION ON HUMAN MOLT-4 8 LEUKEMIA AND SK-MEL-28 MELANOMA-CELLS IN-VITRO/

CD44 cell surface proteins are involved in leukocyte binding to endoth elium and the metastatic spread of tumor cells. Using flow cytometric analysis (FCMA), we investigated the effects of the proteases bromelai n, papain, trypsin, and chymotrypsin on the density of CD44 molecules present on human leukemia Molt 4/8 cells. Bromelain was found to be mo st active in reducing CD44 receptor density. In addition, the effects of the purified bromelain proteinases F4 and F9 were investigated. On Molt 4/8 cells crude bromelain and F9, with the highest proteolytical activity, were found to be most active in reducing CD44 receptor densi ty with a half maximal value of 1.9 mu g/ml and 2.3 mu g/ml, respectiv ely. On human SK-Mel 28 melanoma cells especially F9 showed a strong e ffect, with a half maximal value of 1.5 mu g/ml. The implications of t he findings are discussed with view of the reported antimetastatic act ivity of orally administrated bromelain with respect to CD44.