Cohen Shmuel, Cahan Rivka, Ben-Dov Eitan, Nisnevitch Marina, Zaritsky Arieh, Firer Michael A
Department of Life Sciences, Ben-Gurion University of the Negev, P. O. 653, Be'er-Sheva 84105, Israel; Department of Chemical Engineering and Biotechnology, College of Judea and Samaria, Ariel 44837, Israel.
Department of Chemical Engineering and Biotechnology, College of Judea and Samaria, Ariel 44837, Israel.
J Biol Chem. 2007 Sep 28;282(39):28301-28308. doi: 10.1074/jbc.M703567200. Epub 2007 Jul 11.
Multiple myeloma is currently an incurable cancer of plasma B cells often characterized by overproduction of abnormally high quantities of a patient-specific, clonotypic immunoglobulin "M-protein." The M-protein is expressed on the cell membrane and secreted into the blood. We previously showed that ligand-toxin conjugates (LTC) incorporating the ribosome-inactivating Ricin-A toxin were very effective in specific cytolysis of the anti-ligand antibody-bearing target cells used as models for multiple myeloma. Here, we report on the incorporation of the membrane-disruptive Cyt1Aa toxin from Bacillus thuringiensis subsp. israelensis into LTCs targeted to murine myeloma cells. Proteolytically activated Cyt1Aa was conjugated chemically or genetically through either its amino or carboxyl termini to the major peptidic epitope VHFFKNIVTPRTP (p87-99) of the myelin basic protein. The recombinant fusion-encoding genes were cloned and expressed in acrystalliferous B. thuringiensis subsp. israelensis through the shuttle vector pHT315. Both chemically conjugated and genetically fused LTCs were toxic to anti-myelin basic protein-expressing murine hybridoma cells, but the recombinant conjugates were more active. LTCs comprising the Cyt1Aa toxin might be useful anticancer agents. As a membrane-acting toxin, Cyt1Aa is not likely to induce development of resistant cell lines.