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.
多发性骨髓瘤目前是一种无法治愈的浆细胞B细胞癌症，其特征通常是患者特异性克隆型免疫球蛋白“M蛋白”异常大量过度产生。M蛋白在细胞膜上表达并分泌到血液中。我们之前表明，结合核糖体失活蓖麻毒素A毒素的配体-毒素偶联物（LTC）在用作多发性骨髓瘤模型的携带抗配体抗体的靶细胞的特异性细胞溶解中非常有效。在这里，我们报告了将来自苏云金芽孢杆菌以色列亚种的膜破坏毒素Cyt1Aa掺入靶向小鼠骨髓瘤细胞的LTC中。通过其氨基或羧基末端将经蛋白水解激活的Cyt1Aa化学或基因偶联到髓鞘碱性蛋白的主要肽表位VHFFKNIVTPRTP（p87-99）上。通过穿梭载体pHT315将重组融合编码基因克隆并在无晶体的苏云金芽孢杆菌以色列亚种中表达。化学偶联和基因融合的LTC对表达抗髓鞘碱性蛋白的小鼠杂交瘤细胞均有毒性，但重组偶联物活性更高。包含Cyt1Aa毒素的LTC可能是有用的抗癌剂。作为一种膜作用毒素，Cyt1Aa不太可能诱导耐药细胞系的产生。
