Citation Details

Journal Article

FMT; OsteoSense; ProSense bone mineralization; bone turnover markers; molecular imaging; bisphosphonates; in vivo imaging

Abstract: FRFP binds to mineral at osteoblastic, osteoclastic, and quiescent surfaces, with accumulation likely modulated by vascular delivery. In vivo visualization and quantification of binding can be accomplished noninvasively in animal models through optical tomographic imaging.

Introduction: The development of near-infrared optical markers as reporters of bone metabolism will be useful for early diagnosis of disease. Bisphosphonates bind differentially to osteoblastic and osteoclastic surfaces depending on choice of side-chain and dose, and fluorescently tagged bisphosphonates provide a convenient way to visualize these sites. This study examines the ability of a fluorescently labeled pamidronate imaging probe to bind to regions of bone formation and resorption in vivo.

Materials and Methods: In vitro binding of a far-red fluorescent pamidronate (FRFP) to mineral was assessed using intact and demineralized dentine slices. In vivo, FRFP binding was studied in three models: developing neonatal mouse, bone healing after injury, and metastasis-induced osteolysis and fracture. 3D fluorescence molecular tomographic (FMT) imaging was used to visualize signal deep within the body.

Results: FRFP binding to bone depends on the quantity of mineral present and can be liberated from the bone during decalcification. In vivo, FRFP binds to surfaces of actively forming bone, as assessed by alkaline phosphatase staining, surfaces undergoing active resorption, as noted by scalloped bone border and presence of osteoclasts, and to quiescent surfaces not involved in formation or resorption. Binding is likely modulated by vascular delivery of the imaging agent to the exposed mineral surface and total quantity of surface exposed.FMT imaging is capable of visualizing regions of bone formation because of a large volume of labeled surface, but like radiolabeled bone scans, cannot discriminate pure osteolysis caused by metastasis.

Conclusions: FRFP may function as a local biomarker of bisphosphonate deposition to assess interplay between drug and cellular environment or may be combined with other imaging agents or fluorescent cells for the noninvasive assessment of local bone metabolism in vivo.

Journal Article

valves; stenosis; inflammation; atherosclerosis; hypercholesterolemia; imaging; ProSense; OsteoSense

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Journal Article

Acetyl-CoA Carboxylase; Apoptosis; Autophagy; Bioware; Cell Death; Cell Proliferation; Drug Evaluation, Preclinical; Fatty Acids; Humans; Macrolides; Male; Neoplasms; Palmitic Acid; PC-3M-luc; Phospholipids; Prostatic Neoplasms; Tumor Cells, Cultured

Development and progression of cancer is accompanied by marked changes in the expression and activity of enzymes involved in the cellular homeostasis of fatty acids. One class of enzymes that play a particularly important role in this process are the acetyl-CoA carboxylases (ACC). ACCs produce malonyl-CoA, an intermediate metabolite that functions as substrate for fatty acid synthesis and as negative regulator of fatty acid oxidation. Here, using the potent ACC inhibitor soraphen A, a macrocyclic polyketide from myxobacteria, we show that ACC activity in cancer cells is essential for proliferation and survival. Even at nanomolar concentrations, soraphen A can block fatty acid synthesis and stimulate fatty acid oxidation in LNCaP and PC-3M prostate cancer cells. As a result, the phospholipid content of cancer cells decreased, and cells stopped proliferating and ultimately died. LNCaP cells predominantly died through apoptosis, whereas PC-3M cells showed signs of autophagy. Supplementation of the culture medium with exogenous palmitic acid completely abolished the effects of soraphen A and rescued the cells from cell death. Interestingly, when added to cultures of premalignant BPH-1 cells, soraphen A only slightly affected cell proliferation and did not induce cell death. Together, these findings indicate that cancer cells have become dependent on ACC activity to provide the cell with a sufficient supply of fatty acids to permit proliferation and survival, introducing the concept of using small-molecule ACC inhibitors as therapeutic agents for cancer.

Journal Article

Animals; Bioware; Carcinoma; Estradiol; Humans; Male; Mice; Mice, Inbred BALB C; Mice, Nude; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; PC-3M-luc; Phosphorylation; Prostatic Neoplasms; Radiation-Sensitizing Agents; Subcutaneous Tissue; Transplantation, Heterotopic; Tumor Cells, Cultured; Xenograft Model Antitumor Assays

2-Methoxyestradiol (2ME2) is an endogenous estradiol metabolite that inhibits microtubule polymerization, tumor growth, and angiogenesis. Because prostate cancer is often treated with radiotherapy, and 2ME2 has shown efficacy as a single agent against human prostate carcinoma, we evaluated 2ME2 as a potential radiosensitizer in prostate cancer models. A dose-dependent decrease in mitogen-activated protein kinase phosphorylation was observed in human PC3 prostate cancer cells treated with 2ME2 for 18 h. This decrease correlated with in vitro radiosensitization measured by clonogenic assays, and these effects were blocked by the expression of constitutively active MEK. Male nude mice with subcutaneous PC3 xenografts in the hind leg were treated with 2ME2 (75 mg/kg) p.o. for 5 days, and 2 Gy radiation fractions were delivered each day at 4 h after drug treatment. A statistically significant super-additive effect between radiation and 2ME2 was observed in this subcutaneous model, using analysis of within-animal slopes. A PC-3M orthotopic model was also used, with bioluminescence imaging as an end point. PC-3M cells stably expressing the luciferase gene were surgically implanted into the prostates of male nude mice. Mice were given oral doses of 2ME2 (75 mg/kg), with radiation fractions (3 Gy) delivered 4 h later. Mice were then imaged weekly for 4 to 5 weeks with a Xenogen system. A significant super-additive effect was also observed in the orthotopic model. These data show that 2ME2 is an effective radiosensitizing agent against human prostate cancer xenografts, and that the mechanism may involve a decrease in mitogen-activated protein kinase phosphorylation by 2ME2.

Journal Article

Animals; Bioware; Cell Line, Tumor; Cell Movement; Cell Proliferation; Gene Expression Regulation, Neoplastic; GRB2 Adaptor Protein; Humans; Mice; Mice, SCID; Microscopy, Fluorescence; Neoplasm Metastasis; Neoplasm Transplantation; PC-3M-luc; Protein Binding; Protein Structure, Tertiary; Tetrazolium Salts; Thiazoles

Metastasis, the primary cause of death in most forms of cancer, is a multistep process whereby cells from the primary tumor spread systemically and colonize distant new sites. Blocking critical steps in this process could potentially inhibit tumor metastasis and dramatically improve cancer survival rates; however, our understanding of metastasis at the molecular level is still rudimentary. Growth factor receptor binding protein 2 (Grb2) is a widely expressed adapter protein with roles in epithelial cell growth and morphogenesis, as well as angiogenesis, making it a logical target for anticancer drug development. We have previously shown that a potent antagonist of Grb2 Src homology-2 domain-binding, C90, blocks growth factor-driven cell motility in vitro and angiogenesis in vivo. We now report that C90 inhibits metastasis in vivo in two aggressive tumor models, without affecting primary tumor growth rate. These results support the potential efficacy of this compound in reducing the metastatic spread of primary solid tumors and establish a critical role for Grb2 Src homology-2 domain-mediated interactions in this process.