Abstract:
Real-time p53 activity in tumor cells was detected non-invasively both in vitro
and in vivo by bioluminescent imaging. HCT116 colon cancer cells were stably
transduced with PG13-luc, a p53 reporter with a firefly luciferase gene under
the control of 13 p53 response elements, together with a Renilla luciferase
gene under an MMLV long terminal repeat promoter. Basic conditions for both
in vivo and in vitro imaging were explored. Signals from as few as three thousand
cells in a 96-well plate were detected following addition of D-luciferin, a
substrate of firefly luciferase at a concentration of 100 μg/ml.
Bioluminescence from fifteen thousand cells with PG13-luc inoculated subcutaneously
was detected following intravenous injection of D-luciferin at a dose of 100
mg/kg. Intraperitoneal injection serves as an alternative and effective route
for D-luciferin delivery, although the maximal luminescent intensity was 4 to
10 times lower than that from intravenous injection. Bioluminescence from Renilla
luciferase constitutively expressed in tumor cells was also imaged both in vitro
and in vivo and served as an internal control to monitor the physiological state
of the cells or tumor volume. Infection of the cells with adenovirus carrying
p53 increased the bioluminescent intensity both in vitro and in vivo. Non-invasive
imaging of p53 transcriptional activity provides a practical way to monitor
the p53 response in cell culture and in animal models.