Human breast tumor cells express multimodal imaging reporter genes.
OBJECTIVE
Human ZR75-1 cells were among the first few characterized estrogen-dependent mammary gland carcinoma cell lines and had been utilized in various studies for the pro- or antitumor effect of xenoestrogens and antiestrogens. The objective of this study was to establish a breast tumor model in ZR75-1 cells bearing multimodal reporter genes to allow noninvasive imaging of tumor growth using fluorescence and nuclear imaging platforms.


RESULTS
Enhanced green fluorescent protein (eGFP) cDNA was fused at the C-terminus with herpes simplex virus type 1 thymidine kinase (HSV1-tk) to form the fusion reporter gene (eGFP-tk). In vitro proliferation, migration, and invasion assays revealed that eGFP-tk-transfected ZR75-1 cells exhibited decreased proliferation rate, migratory activity, and invasion ability compared to the wild-type cells. The functional HSV1-tk enzymatic activity in stably transfected cells were confirmed by in vitro ganciclovir (GCV) sensitivity and [123I]2-fluoro-2-deoxy-1-beta-D-arabinofuranosyl-5-iodouracil (FIAU) accumulation assays. In vivo fluorescence and nuclear imaging were performed on nude mice bearing multiple subcutaneous xenografts established from ZR75-1-eGFP-tk and wild-type cells. Optical imaging was able to detect the green fluorescence of eGFP-tk tumor. The eGFP-tk reporter gene-specific imaging was achieved by single photon emission computed tomography (SPECT) using [123I]FIAU as a radiotracer and demonstrated decreased FIAU uptake in eGFP-tk tumor by GCV treatment. Probably due to a flare reaction after GCV treatment, micro-positron emission tomography (micro-PET) imaging using 2-deoxy-2-[18F]fluoro-D-glucose (FDG) could not demonstrate decreases in FDG uptake. However, in vitro metabolic assay also revealed that eGFP-tk cells transiently increased [3H]-deoxyglucose uptake in response to GCV treatment.


CONCLUSIONS
This study confirmed the usefulness of eGFP-tk in many applications by providing, in vitro and in vivo, the sensitive and reporter gene-specific imaging. ZR75-1-eGFP-tk cells that are ready to incorporate in various imaging platforms constitute a useful model in breast cancer research.
Lin
Kurt M
KM
Division of Medical Engineering Research, National Health Research Institutes, R1-1027, No. 35, Keyan Road, Zhunan Town, Miaoli County 350, Taiwan, Republic of China. klin@nhri.org.tw
Hsu
Ching-Han
CH
Chang
Wun-Shaing W
WS
Chen
Chiung-Tong
CT
Lee
Te-Wei
TW
Chen
Chin-Tu
CT
D000818:Animals; D001086:Arabinofuranosyluracil / Q000031:analogs & derivatives / Q000378:metabolism; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism*; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation / Q000187:drug effects; D005260:Female; D015774:Ganciclovir / Q000494:pharmacology; D017930:Genes, Reporter / Q000235:genetics*; D005822:Genetic Vectors / Q000235:genetics; D005947:Glucose / Q000378:metabolism; D006801:Humans; D051379:Mice; D008813:Mice, Inbred ICR; D008819:Mice, Nude; D049268:Positron-Emission Tomography; D013379:Substrate Specificity; D014057:Tomography, X-Ray Computed; D023041:Xenograft Model Antitumor Assays
D001086:Arabinofuranosyluracil; C043457:fialuridine; D005947:Glucose; D015774:Ganciclovir