Large group of scientists from Moscow State University Department of Cell Physiology and Immunology, State Science and Research Centre of Commercial Microorganisms Genetics and Selection and New York Medical College suggests poisoning cancer cells with phytopoisons. In order to get toxins to the right place without damaging normal cells, the scientists “sewed” them to specific antibodies, which interact only with tumor cells, and obtained an immunotoxin. In this complex antibodies act as postmen, delivering a poisoned letter right to the victim’s arms: they find tumor cells and bind with them. Then immunotoxin enters the cell and kills it.
 

Many kinds of tumors have their own specific antibodies. That’s why each kind of tumor should have its own immunotoxin. Russian scientists have worked with human melanoma cell culture. Melanoma is a malignant tumor, developing from normal melanocytes (melanin (skin and eyes dark coloured pigment) producing cells). The disease appears under the influence of solar radiation and has genetic predisposition. Melanoma grows quickly and gives birth to numerous metastases. It is almost impossible to cure by surgery, chemo- and radiotherapy. However, tumor melanocytes synthesize many specific molecules (antigens), which can be targets for immunotoxins. One of such antigens, HMW, almost covers melanoma cells: one cell can carry from 100 thousand to 6 million molecules of HMW. The scientists have chosen this antigen as a target: they isolated antibodies and bound them to a toxic protein – ricin. Ricin is extracted from the castor bean seeds and its toxicity is based on damaging ribosome activity and inhibiting protein synthesis in the cell.
 

Immunotoxins were added to melanoma cell culture and to control cell culture lacking HMW antigen. To distinguish cells, which have received poisonous letters, from cells, which are indifferent to them, the culture is specially coloured. The experiment showed that tumor cells’ surface was evenly coloured, and control cells didn’t interact with immunotoxin. There’s another way to distinguish dead cells from living ones: living cells turn primrose water-soluble dye to blue crystals. In scientific experiments control cells turned blue, and tumor cells were poisoned by ricin and died.
 

According to their results the scientists concluded that the immunotoxins developed are a promising remedy for antitumoral therapy. Immunotoxin properties can be enhanced by taking potent plant toxins.