11.   Recent studies have suggested an increased activity of expression of glutathione S-transferases in colonic tumour cells compared with normal non-neoplastic mucosa.

12.   For each enzyme, immunoreactivity was present in the cytoplasm of tumour cells.

13.   Immunostaining for each enzyme was present in the cytoplasm of tumour cells, although in a few cases nuclear staining was also seen for the glutathione S-transferases.

14.   With this technique the activity is limited to the tumour cells.

15.   Based on the reasoning that if tumour cells could be made to produce the herpes enzyme, ganciclovir could prevent them from copying their DNA.

16.   Viruses that entered tumour cells would force the cells to produce the enzyme while those gaining entry into normal brain cells die off.

17.   Patients in the new program will be injected with a harmless virus, stacked with a gene that will trigger tumour cells to make the potent drug interleukin.