Interleukin-2 and cancer treatment

The immunostimulatory activity of IL-2 has proven beneficial in the treatment of some cancer types. An effective anti-cancer agent would prove not only medically valuable, but also commercially very successful. In the developed world, an average of one-in-six deaths is caused by cancer. In the USA alone, the annual death toll from cancer stands in the region of half a million people. 

There exists direct evidence that the immune system mounts an immune response against most cancer types. Virtually all transformed cells express (a) novel surface antigens not expressed by normal cells or (b) express, at greatly elevated levels, certain antigens present normally on the cell at extremely low levels. These normal expression levels may be so low that they have gone unnoticed by immune surveillance (and thus have not induced immunological tolerance). 

The appearance of any such cancer-associated antigen should thus be capable of inducing an immune response, which, if successful, should eradicate the transformed cells. The exact elements 

Cytotoxic T cells may play a role in inducing direct destruction of cancer cells, in particular those transformed by viral infection (and who express viral antigen on their surface). In vitro studies have shown that cytotoxic T-lymphocytes obtained from the blood of persons suffering from various cancer types are capable of destroying those cancer cells. 

Although immune surveillance is certainly responsible for the detection and eradication of some transformed cells, the prevalence of cancer indicates that this surveillance is nowhere near 100 per cent effective. Some transformed cells obviously display characteristics that allow them to evade this immune surveillance. The exact molecular details of how such tumour escape is achieved remains to be confirmed, although several mechanisms have been implicated, including  

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