Induction of apoptosis by ribosome-inactivating proteins and related immunotoxins

Abstract

Immunotoxins have been prepared with 3 ribosome-inactivating proteins (RIPs), namely, momordin, pokeweed anti-viral protein from seeds (PAP-S) and saporin, linked to the Ber-H2 monoclonal antibody directed against the CD30 antigen of human lymphocytes. Either the RIPs or the immunotoxins induced apoptosis in the CD30+ L540 cell line, as shown by the morphological aspects of the cells, by the DNA fragmentation visible at the electrophoresis, and by the formation of DNA breaks evidenced by 2 cytofluorometric techniques (propidium-iodide staining and fluoresceine-isothiocyanate conjugate dUTP incorporation). The AC50 (concentration causing apoptosis in 50% of the cells) is in the range 10-8 to 10-7 M in the case of pips, and 10-11 to 10-10 M in the case of the immunotoxins.