Abstract: The present invention is based on the finding that Gal-8 binds to carbohydrates of cell surface CD44std and CD44v and activates a chain of biological events within the cells. A specific effect exhibited was the induction of apoptosis in the CD44std and CD44v expressing cells. Thus, the present invention concerns the use of an active agent for achieving a therapeutic effect on a target cell, the therapeutic effect comprises binding of said active agent to a standard CD44 (CD44std) glycoprotein or to a CD44 variant (CD44v) expressed by said target cell, the active agent being galectin-8 (Gal-8) or a functional derivative thereof. The active ingredient may be used for the preparation of a pharmaceutical composition, for the treatment of a disease or a disorder or for diagnostic purposes.