penciclovir and Prostatic-Neoplasms

The aim of this study was to develop models that allow serial, noninvasive imaging of human prostate cancer cells in immunodeficient mice using a dedicated small animal positron emission tomography scanner (microPET).. LNCaP tumor cells were stably transduced ex-vivo with the mutant herpes simplex virus type 1 thymidine kinase (HSV-sr39tk) PET reporter gene and green fluorescent protein (GFP). The stably transduced LNCaP cells were then enriched via fluorescent cell sorting and implanted into SCID mice. Beginning 2 weeks after tumor cell inoculation, mice were repeatedly scanned by microPET performed 1 hr after tail-vein injection of approximately 200 muCi Fluorine-18 labeled penciclovir ((18)F-FHBG). PET-images were correlated to tumor size, % injected dose (ID)/g tumor tissue, PSA levels, autoradiography, and histology.. Monitoring LNCaP xenografts using microPET and our reporter gene approaches is feasible. MicroPET was capable of detecting subcutaneous tumors as small as 3 mm in diameter (approximately 0.2% ID/g). The magnitude of (18)F-FHBG-uptake in PET-images correlated with the tumor volumes and the serum PSA levels. Other non-HSV1-TK-specific tracers were also studied. While (18)F-flurodeoxyglucose ((18)F-FDG) gave poor imaging results in LNCaP cells, (11)C-acetate gave satisfactory images.. We demonstrated the feasibility of monitoring prostate cancer xenografts in a mouse model using microPET and the HSV1-sr39tk PET reporter gene/(18)F-FHBG reporter probe system. Extension of this approach may allow repetitive imaging of tumor metastases.

Topics: Acyclovir; Animals; Disease Models, Animal; Flow Cytometry; Fluorine Radioisotopes; Genetic Vectors; Green Fluorescent Proteins; Guanine; Herpesvirus 1, Human; Humans; Luminescent Proteins; Male; Mice; Mice, SCID; Neoplasm Transplantation; Prostatic Neoplasms; Thymidine Kinase; Tomography, Emission-Computed; Transduction, Genetic; Transfection; Transplantation, Heterologous; Tumor Cells, Cultured

We developed a prostate cancer tumor model capable of being noninvasively imaged using positron emission tomography (PET) based on expression of the herpes simplex virus thymidine kinase (HSV1-tk) reporter gene.. The androgen independent, metastatic prostate cancer cell lines CL1 and CL1-GFP were stably transfected with the mutant HSV1-tk gene pcDNA3.1/pCMV-sr39tk, which has increased ability to phosphorylate penciclovir. The presence of the sr39tk gene product was analyzed by Western blot analysis and relative thymidine kinase enzyme activity was assessed by a functional thymidine kinase enzyme activity assay. Subcutaneous and orthotopic CL1 and CL1-SR39 tumor xenografts were established in SCID mice. The ability to image CL1-SR39 was assessed using fluorodeoxyglucose and F-penciclovir ( F-FHBG) micro-PET (a rodent PET scanner). To investigate the systemic distribution of intratumoral sr39tk injections established CL1 tumors were transiently injected with first generation adenoviral vectors carrying the sr39tk gene under control of the strong cytomegalovirus promoter Ad-CMV-HSV1-sr39tk and imaged using micro-PET.. Transfection of sr39tk into CL1 cells was successful. CL1-SR39 thymidine kinase enzyme activity was greater than twice the activity of the glioma cell line C6-SR39 control and above the threshold necessary for micro-PET detection. Fluorodeoxyglucose micro-PET in SCID mice was positive for CL1 and CL1-SR39 tumors. Selective micro-PET of subcutaneous CL1-SR39 tumors was done using F-FHBG. Micro-PET imaging after systemic and intratumoral injection of Ad-CMV-HSV1-sr39tk revealed significant systemic transgene leakage with significant hepatic expression of sr39TK protein.. Molecular based imaging of sr39tk transfected prostate cancer tumors and adenoviral delivered HSV1-tk suicide gene therapy based on the selective conversion and intracellular trapping of F-FHBG by sr39tk is feasible. Potential applications include noninvasive monitoring of the location, duration and intensity of gene constructs, which may contribute to the safety of clinical gene therapy protocols, and noninvasive imaging of the prostate cancer xenograft response to experimental therapy.

Topics: Acyclovir; Animals; Blotting, Western; Fluorodeoxyglucose F18; Genes, Reporter; Genetic Therapy; Genetic Vectors; Guanine; Herpesvirus 1, Human; Humans; Male; Mice; Mice, SCID; Neoplasm Transplantation; Prostatic Neoplasms; Radiopharmaceuticals; Thymidine Kinase; Tomography, Emission-Computed; Transfection; Tumor Cells, Cultured