| Cancerous cells contain numerous mutations, qualitative and quantitative, spatial and temporal, relative to their normal, non-cancerous counterparts. At certain periods during tumour cells' growth and spread, a proportion of these are capable of being recognised by the hosts' immune system as abnormal. This has led to numerous research efforts worldwide to develop immunotherapies that harness the power of the hosts' immune system and direct it to attack the cancerous cells, thereby eliminating such aberrant cells at least to a level that is not life-threatening (1,2). The market has recognised the potential of this approach, and the cancer vaccine revenues alone are forecast at US$3 billion by 2008 (3). Numerous approaches have been taken in the quest for cancer immunotherapies, which can be classified under the five categories covered in this article: |
