ABSTRACT
The response of most solid tumors to anticancer drugs is satisfactory, and only a few tumors such as testicular tumor and childhood leukemias, can be cured whereas most other metastatic tumors continue to have a bad prognosis. Ricin is a glycoprotein isolated from the seeds of the castor bean plant Ricinus communis and has been one of the most studied toxins for coupling to monoclonal antibodies. Ricin has a molecular weight of 65 kD consisting of two disulphide-linked chains of molecular weight 32 kD. The use of toxins is accompanied by several problems, such as toxicity— discussed above, their size and their immunogenicity. Size could be a problem, as coupling ricin and antibody could result in a substantial increase in molecular weight of the complex which may have some difficulty in penetration of tumors. Ricin A-chain, as opposed to ricin may partly overcome this problem.
