Session Speaker

Immunotoxins- as Promising Drug for Targeting Cancer- Present and Future
Rama S Verma

The conventional therapies (chemotherapy, radiation therapy and so on) used today target uncontrolled cell division, which is the most important feature of a transformed cell. The rate of tumor growth depends on factors such as (i) growth fraction – the number of cells in the tumor that are capable of proliferation, (ii) the time required to complete the cell cycle (iii) the rate at which cells within the tumor are shed. Most chemotherapeutic agents target the proliferating pool, so rapidly growing tumors respond very well. By the time of diagnosis, however, due to tumor progression, the growth fraction decreases, resulting in a poor response to chemotherapy. Conventional therapies have their own limitations, for example radiation therapy affects not only the tumor, but also the surrounding normal tissue. Most chemotherapeutic agents and radiation cause DNA damage, leading to genomic instability and a susceptibility to mutations that, again, predisposes to cancer. Cancer cells usually have specific growth factor receptors or antigens over-expressed on their surface, compared to normal cells [9]. Ligands corresponding to these receptors or antibodies raised against antigens can be conjugated to toxins, these conjugates will selectively bind to these over-expressed molecules and kill the tumor cells. Toxins used can be of microbial (diphtheria toxin, Pseudomonas exotoxin) or plant (ricin, saporin, gelonin) origin. A new generation of immunotoxins in which the cytotoxic moiety is an endogenous protein, like RNase or proapoptotic protein has also been developed. Several groups are working on detecting molecules exclusively expressed on cancer cells, which will definitely be of immense use for selective targeting. Emerging trends in immunotoxin therapy and new strategy to formulate the immunotoxin will be discussed.