Gamma camera dual imaging with a somatostatin receptor and thymidine kinase after gene transfer with a bicistronic adenovirus in mice.
OBJECTIVE
To compare two systems for assessing gene transfer to cancer cells and xenograft tumors with noninvasive gamma camera imaging.


METHODS
A replication-incompetent adenovirus encoding the human type 2 somatostatin receptor (hSSTr2) and the herpes simplex virus thymidine kinase (TK) enzyme (Ad-hSSTr2-TK) was constructed. A-427 human lung cancer cells were infected in vitro and mixed with uninfected cells at different ratios. A-427 tumors in nude mice (n = 23) were injected with 1 x 10(6) to 5 x 10(8) plaque-forming units (pfu) of Ad-hSSTr2-TK. The expressed hSSTr2 and TK proteins were imaged owing to internally bound, or trapped, technetium 99m ((99m)Tc)-labeled hSSTr2-binding peptide (P2045) and radioiodinated 2'-deoxy-2'-fluoro-beta-D-arabinofuranosyl-5-iodouracil (FIAU), respectively. Iodine 125 ((125)I)-labeled FIAU was used in vitro and iodine 131 ((131)I)-labeled FIAU, in vivo. The (99m)Tc-labeled P2045 and (125)I- or (131)I-labeled FIAU were imaged simultaneously with different window settings with an Anger gamma camera. Treatment effects were tested with analysis of variance.


RESULTS
Infected cells in culture trapped (125)I-labeled FIAU and (99m)Tc-labeled P2045; uptake correlated with the percentage of Ad-hSSTr2-TK-positive cells. For 100% of infected cells, 24% +/- 0.4 (mean +/- SD) of the added (99m)Tc-labeled P2045 was trapped, which is significantly lower (P <.05) than the 40% +/- 2 of (125)I-labeled FIAU that was trapped. For the highest Ad-hSSTr2-TK tumor dose (5 x 10(8) pfu), the uptake of (99m)Tc-labeled P2045 was 11.1% +/- 2.9 of injected dose per gram of tumor (thereafter, dose per gram), significantly higher (P <.05) than the uptake of (131)I-labeled FIAU at 1.6% +/- 0.4 dose per gram. (99m)Tc-labeled P2045 imaging consistently depicted hSSTr2 gene transfer in tumors at all adenovirus doses. Tumor uptake of (99m)Tc-labeled P2045 positively correlated with Ad-hSSTr2-TK dose; (131)I-labeled FIAU tumor uptake did not correlate with vector dose.


CONCLUSIONS
The hSSTr2 and TK proteins were simultaneously imaged following dual gene transfer with an adenovirus vector.
Zinn
Kurt R
KR
Depts of Radiology, University of Alabama at Birmingham, Boshell Bldg, BDB 11, 1530 3rd Ave S, Birmingham, AL 35294-0012, USA. kurtzinn@uab.edu
Chaudhuri
Tandra R
TR
Krasnykh
Victor N
VN
Buchsbaum
Donald J
DJ
Belousova
Natalya
N
Grizzle
William E
WE
Curiel
David T
DT
Rogers
Buck E
BE
D000256:Adenoviridae / Q000235:genetics*; D000704:Analysis of Variance; D000818:Animals; D001086:Arabinofuranosyluracil / Q000031:analogs & derivatives / Q000493:pharmacokinetics; D002289:Carcinoma, Non-Small-Cell Lung; D002460:Cell Line; D015902:Gamma Cameras; D015870:Gene Expression; D015316:Genetic Therapy; D005822:Genetic Vectors; D006564:Herpesviridae / Q000235:genetics; D007457:Iodine Radioisotopes / Q000493:pharmacokinetics; D016018:Least-Squares Analysis; D008175:Lung Neoplasms; D051379:Mice; D008819:Mice, Nude; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D017481:Receptors, Somatostatin / Q000235:genetics*; D013667:Technetium / Q000493:pharmacokinetics; D013937:Thymidine Kinase / Q000235:genetics*; D014162:Transfection / Q000379:methods*; D014407:Tumor Cells, Cultured
D007457:Iodine Radioisotopes; D019275:Radiopharmaceuticals; D017481:Receptors, Somatostatin; D001086:Arabinofuranosyluracil; D013667:Technetium; D013937:Thymidine Kinase