Jg. Tjuvajev et al., Imaging adenoviral-mediated herpes virus thymidine kinase gene transfer and expression in vivo, CANCER RES, 59(20), 1999, pp. 5186-5193
The feasibility of noninvasive imaging of adenoviral-mediated herpes virus
type one thymidine kinase (HSV1-tk) gene transfer and expression was assess
ed in a well-studied, animal model of metastatic colon carcinoma of the liv
er. Tumors were produced. in syngeneic BALB/c mice by intrahepatic injectio
n of colon carcinoma cells (MCA-26). Seven days later, three different dose
s (3 x 10(8), 1 x 10(8), and 3 x 10(7) plaque-forming units (pfu) of the re
combinant adenoviral vector ADV, Rous sarcoma virus (RSV)-tk bearing the HS
V1-tk gene were administered by intratumoral injection in separate groups o
f mice. Two control groups of tumor-bearing mice received intratumoral inje
ctions of the control adenoviral vector (MR) images of mice were obtained b
efore administering the virus and provided an anatomical reference of hepat
ic tumor localization Eighteen h after the virus injection, one group of an
imals was given i.v. injections of 300 mu Ci of no-carrier-added 5-[I-131]-
2'-fluoro-1-beta-D-arabinofuranosyl uracil (FIAU) and imaged 24 h later wit
h a gamma camera, In some animals, the tumors were sampled and processed fo
r histology and quantitative autoradiography (QAR), The gamma camera images
demonstrated highly specific localization of [I-131]FIAU-derived radioacti
vity to the area of ADV.RSV-Lk-injected tumors in the liver, which was conf
irmed by coregistering the gamma camera and T2-weighted MR images. There wa
s no accumulation of [I-131]FIAU-derived radioactivity in tumors that were
injected with the control vector or injection solution alone, A more precis
e distribution of radioactivity in the area of transfected tumor was obtain
ed by histological and QAR comparisons, A heterogeneous pattern of radioact
ivity distribution in transfected tumors was observed. A punctate pattern o
f radioactivity distribution was observed in peritumoral liver tissue in an
imals given injections of 3 x 10(8) and 1 x 10(8) pfu of ADV.RSV-tk but not
in animals given injections of 3 x 10(7) pfu nor in control animals, A QAR
-microscopic comparison showed that the punctate areas of radioactivity col
ocalized with cholangial ducts, The level of [I-131]FIAU-derived radioactiv
ity accumulation (HSV1-tk expression) in the transfected tumors was viral d
ose-dependent, The viral dose-dependency of radioactivity accumulation mas
more pronounced in peritumoral liver, which was confirmed by reverse transc
ription-PCR analysis. h separate group of tumor-bearing animals received di
fferent doses of ADV,RSV-tk vector followed by treatment with ganciclovir (
GCV), 10 mg/kg i.p. b.i.d. for 6 days. The ADV,RSV-tk transfected tumors si
gnificantly regressed with GCV treatment; the control tumors continued to g
row. During the GCV treatment, the levels of liver transaminases (ALT and A
ST) were significantly increased in animals that received injections of 3 x
10(8) and 1 x 10(8) pfu of ADV.RSV-tk but not in animals that received inj
ections of 3 x 10(7) pfu and in control animals, The observed liver toxicit
y confirms the results of gamma camera and QAR imaging, which demonstrated
an unwanted spread of ADV.RSV-tk vector and HSV1-tk expression in peritumor
al and remote liver tissue at higher doses. These and our previous results
indicate that noninvasive imaging of adenoviral-mediated HSV1-tk gene expre
ssion is feasible for monitoring cancer gene therapy in patients.