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Figure 2 shows the effects of XMTM fusion protein expression on Thymidine kinase
(TK) mediated ganciclovir bystander killing. In this in vitro assay the ability of the
Thymidine kinase-XMTM fusion protein to penetrate co-cultured neighboring cells
deficient in Thymidine kinase is tested. The results clearly demonstrate that, in contrast to
the native TK molecule, the XMTM fusion protein has the ability to be transported from
the cells were it is expressed into the enzyme-deficient neighboring cells
ß- G al- X MTM
µM
C ontrol
Figure 1: Transport of beta-Galactosidase tetramer (mol weight 550 KDa) into epithelial cells in culture;
left cells incubated with unconjugated beta-Galactosidase, right cell incubated with beta-Galactosidase-
XMTM conjugate.
wst-1 assay (insert co-culture)
0
0.05
0.1
0.15
0.2
0.25
G
ktk
17tk
tk17
27tk
tk27
AU
0
10
25
50
Figure 2: Thymidine Kinase (TK) mediated dose-dependent ganciclovir (colored bars)
bystander killing effect on TK deficient co-cultured cells with different variants of
expressed XMTM-TK fusion protein in neighboring cells. The two left set of bars form
the control experiment, followed by experiments in which different variants of TK-
XMTM are expressed in neighboring co-cultured cells
