Noninvasive assessment of gene transfer and expression by in vivo functional and morphologic imaging in a rabbit tumor model.

PURPOSE: To evaluate the importance of morphology in quantifying expression after in vivo gene transfer and to compare gene expression after intra-arterial (IA) and intra-tumoral (IT) delivery of adenovirus expressing a SSTR2-based reporter gene in a large animal tumor model. MATERIALS AND METHODS: Tumor directed IA or IT delivery of adenovirus containing a human somatostatin receptor type 2A (Ad-CMV-HA-SSTR2A) gene chimera or control adenovirus (Ad-CMV-GFP) was performed in VX2 tumors growing in both rabbit thighs. Three days later, ¹¹¹In-octreotide was administered intravenously after CT imaging using a clinical scanner. ¹¹¹In-octreotide uptake in tumors was evaluated the following day using a clinical gamma-camera. Gene expression was normalized to tumor weight with and without necrosis. This procedure was repeated on nine additional rabbits to investigate longitudinal gene expression both 5 days and 2 weeks after adenovirus delivery. CT images were used to evaluate tumor morphology and excised tissue samples were analyzed to determine ¹¹¹In-octreotide biodistribution ex vivo. RESULTS: VX2 tumors infected with Ad-CMV-HA-SSTR2 had greater ¹¹¹In-octreotide uptake than with control virus (P<0.05). Intra-arterial and intra-tumoral routes resulted in similar levels of gene expression. Longitudinally, expression appeared to wane at 2 weeks versus 5 days after delivery. Areas of necrosis did not demonstrate significant uptake ex vivo. Morphology identified areas of necrosis on contrast enhanced CT and upon excluding necrosis, in vivo biodistribution analysis resulted in greater percent injected dose per gram (P<0.01) and corresponded better with ex vivo biodistribution(r = 0.72, P<0.01, Coefficient of the x-variable = .72) at 2 weeks than without excluding necrosis (P<0.01). CONCLUSION: Tumor specificity and high transgene expression can be achieved in tumors via both tumor directed intra-arterial and intra-tumoral delivery in a large animal tumor model. Using clinical machines, morphologic imaging contributes to functional imaging for quantifying SSTR2-based reporter expression in vivo.

Visualizing the prostate gland by MR imaging in young and old mice.

PURPOSE: Prostate imaging requires optimization in young and old mouse models. We tested which MR sequences and field strengths best depict the prostate gland in young and old mice; and, whether prostate MR signal, size, and architecture change with age. TECHNIQUE: Magnetic resonance imaging (MRI) of the prostate of young (2 months) and old (18 months) male nude mice (n = 6) was performed at 4.7 and 7 T and SCID mice (n = 6) at 7 T field strengths, using T1, fat suppressed T1, DWI, T2, fat suppressed T2, as well as T2-based- and proton density-based Dixon "water only" sequences. Images were ranked for best overall sequence for prostate visualization, prostate delineation, and quality of fat suppression. Prostate volume and signal characteristics were compared and histology was performed. RESULTS: T2-based-Dixon "water only" images ranked best overall for prostate visualization and delineation as well as fat suppression (n = 6, P<0.001) at both 4.7 T and 7 T in nude and 7T in SCID mice. Evaluated in nude mice, T2-based Dixon "water only" had greater prostate CNR and lower fat SNR at 7 T than 4.7 T (P<0.001). Prostate volume was less in older than younger mice (n = 6, P<0.02 nude mice; n = 6, P<0.002 SCID mice). Prostate T2 FSE as well as proton density-based and T2-based-Dixon "water only" signal intensity was higher in younger than older mice (P<0.001 nude mice; P<0.01 SCID mice) both at 4.7 and 7 T. This corresponded to an increase in glandular hyperplasia in older mice by histology (P<0.01, n = 6). CONCLUSION: T2-based Dixon "water only" images best depict the mouse prostate in young and old nude mice at 4.7 and 7 T. The mouse prostate decreases in size with age. The decrease in T2 and T2-based Dixon "water only" signal with age corresponds with glandular hyperplasia. Findings suggest age should be an important determinant when choosing models of prostate biology and disease.

Involvement of microRNA181a in differentiation and cell cycle arrest induced by a plant-derived antioxidant carnosic acid and vitamin D analog doxercalciferol in human leukemia cells.

1,25-dihydroxyvitamin D3 (1,25D) has been shown to influence differentiation, cell proliferation and cell death in cultured leukemia cells. However, its clinical use is limited by its hypercalcemic effects. An analog of 1,25D, doxercalciferol (1-D2), has anti-tumor activity, with markedly reduced calcemic effects, which makes it a potential agent for clinical treatment of AML. Previous studies suggested that the combination of 1,25D with other agents, such as plant-derived antioxidants, can have additive or synergistic anti-cancer activities in leukemia cells. Here we report that 1-D2 induced monocytic differentiation of HL60 and U937 cells, and that the antioxidant carnosic acid (CA) enhanced 1-D2 induced differentiation and cell cycle arrest. MicroRNA181a (miR181a) expression was also reduced after exposure to CA/1-D2. Since the cell cycle regulator p27Kip1 has been shown to be a target of miR181a, we modulated miR181a levels to determine if it plays a role in CA/1-D2 induced differentiation and cell cycle arrest in AML cells. We found that transfection of antisense miR181a potentiated CA/1-D2-induced cell differentiation, while the transfection of precursor of miR181a partially inhibited the effect of CA/1-D2 on the differentiation. These findings imply that miR181a has a role in CA/1-D2- induced differentiation and cell cycle arrest of HL60 and U937 cells, and shows a broader participation of miR181a in cell cycle control in leukemia cells.