Figure 1 .

Tipping the balance in colorectal cancer. A number of protumour mechanisms outweigh antitumour mechanisms and allow colorectal tumours to survive and proliferate. Gene therapy with cytokine, immunostimulatory or suicide (prodrug activating) gene transfer to tumour cells, or DNA vaccination, aims to tip the balance towards antitumour mechanisms and tumour rejection by enhancing antitumour cellular immune responses. Correction of immune deficiencies associated with the tumour could work in synergy with enhancement of antitumour immunity and many of the genes shown could apply to both sides of the balance.