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1.  Radiolabeled Antibodies in Prostate Cancer: A Case Study Showing the Effect of Host Immunity on Antibody Bio-distribution 
Nuclear medicine and biology  2014;42(4):375-380.
Human tumors xenografted in immunodeficient mice are crucial models in nuclear medicine to evaluate the effectiveness of candidate diagnostic and therapeutic compounds. However, little attention has been focused on the biological profile of the host model and its potential effects on the bio-distribution and tumor targeting of the tracer compound under study. We specifically investigated the dissimilarity in bio-distribution of 111In-DTPA-5A10, which targets free Prostate Specific Antigen (fPSA), in two animal models.
In vivo bio-distribution studies of 111In-DTPA-5A10 were performed in immunodeficient BALB/c-nu or NMRI-nu mice with subcutaneous (s.c.) LNCaP tumors. Targeting-specificity of the tracer was assessed by quantifying the uptake in (a) mice with s.c. xenografts of PSA-negative DU145 cells as well as (b) BALB/c-nu or NMRI-nu mice co-injected with an excess of non-labeled 5A10. Finally, the effect of neonatal Fc-receptor (FcRn) inhibition on the bio-distribution of the conjugate was studied by saturating FcRn-binding capacity with nonspecific IgG1.
The inherent biological attributes of the mouse model substantially influenced the bio-distribution and pharmacokinetics of 111In-DTPA-5A10. With LNCaP xenografts in BALB/c-nu mice (with intact B and NK cells but with deficient T cells) versus NMRI-nu mice (with intact B cells, increased NK cells and absent T cells), we observed a significantly higher hepatic accumulation (26±3.9 versus 3.5±0.4 %IA/g respectively), and concomitantly lower tumor uptake (25±11 versus 52±10 %IA/g respectively) in BALB/c-nu mice. Inhibiting FcRn by administration of nonspecific IgG1 just prior to 111In-DTPA-5A10 did not change tumor accumulation significantly.
We demonstrated that the choice of immunodeficient mouse model importantly influence the bio-distribution of 111In-DTPA-5A10. This study further highlighted important considerations in the evaluation of preclinical tracers, with respect to gaining information on their performance in the translational setting. Investigators utilizing xenograft models need to assess not only radiolabeling strategies, but also the host immunological status.
PMCID: PMC4472383  PMID: 25577038
2.  Contemporary approaches for imaging skeletal metastasis 
Bone Research  2015;3:15024-.
The skeleton is a common site of cancer metastasis. Notably high incidences of bone lesions are found for breast, prostate, and renal carcinoma. Malignant bone tumors result in significant patient morbidity. Identification of these lesions is a critical step to accurately stratify patients, guide treatment course, monitor disease progression, and evaluate response to therapy. Diagnosis of cancer in the skeleton typically relies on indirect bone-targeted radiotracer uptake at sites of active bone remodeling. In this manuscript, we discuss established and emerging tools and techniques for detection of bone lesions, quantification of skeletal tumor burden, and current clinical challenges.
PMCID: PMC4502405  PMID: 26273541
3.  Prostate Specific Kallikrein-related Peptidases and Their Relation to Prostate Cancer Biology and Detection; Established Relevance and Emerging Roles 
Thrombosis and haemostasis  2013;110(3):484-492.
The kallikreins are a family of serine proteases with a range of tissue-specific and essential proteolytic functions. Among the most well-studied are the prostate tissue specific KLK2 and KLK3 genes and their secreted protease products, hk2 and PSA. Members of the so-called classic kallikreins, these highly active trypsin-like serine proteases play established roles in human reproduction. Both hK2 and PSA expression is regulated by the androgen receptor, whose activity has a fundamental role in prostate tissue development and progression of disease. This feature, combined with the ability to sensitively detect different forms of these proteins in blood and biopsies, result in a crucially important biomarker for the presence and recurrence of cancer. Emerging evidence has begun to suggest a role for these kallikreins in critical vascular events. This review discusses the established and developing biological roles of hK2 and PSA, as well as the historical and advanced use of their detection to accurately and non-invasively detect and guide treatment of prostatic disease.
PMCID: PMC4029064  PMID: 23903407
4.  Quantitative imaging of disease signatures through radioactive decay signal conversion 
Nature medicine  2013;19(10):1345-1350.
In the era of personalized medicine there is an urgent need for in vivo techniques able to sensitively detect and quantify molecular activities. Sensitive imaging of gamma rays is widely used, but radioactive decay is a physical constant and signal is independent of biological interactions. Here we introduce a framework of novel targeted and activatable probes excited by a nuclear decay-derived signal to identify and measure molecular signatures of disease. This was accomplished utilizing Cerenkov luminescence (CL), the light produced by β-emitting radionuclides such as clinical positron emission tomography (PET) tracers. Disease markers were detected using nanoparticles to produce secondary Cerenkov-induced fluorescence. This approach reduces background signal compared to conventional fluorescence imaging. In addition to information from a PET scan, we demonstrate novel medical utility by quantitatively determining prognostically relevant enzymatic activity. This technique can be applied to monitor other markers and facilitates a shift towards activatable nuclear medicine agents.
PMCID: PMC3795968  PMID: 24013701
Activatable probes; Molecular imaging; Nanoparticles; Cerenkov luminescence
5.  Cerenkov imaging - a new modality for molecular imaging 
Cerenkov luminescence imaging (CLI) is an emerging hybrid modality that utilizes the light emission from many commonly used medical isotopes. Cerenkov radiation (CR) is produced when charged particles travel through a dielectric medium faster than the speed of light in that medium. First described in detail nearly 100 years ago, CR has only recently applied for biomedical imaging purposes. The modality is of considerable interest as it enables the use of widespread luminescence imaging equipment to visualize clinical diagnostic (all PET radioisotopes) and many therapeutic radionuclides. The amount of light detected in CLI applications is significantly lower than other that in other optical imaging techniques such as bioluminescence and fluorescence. However, significant advantages include the use of approved radiotracers and lack of an incident light source, resulting in high signal to background ratios. As well, multiple subjects may be imaged concurrently (up to 5 in common bioluminescent equipment), conferring both cost and time benefits. This review summarizes the field of Cerenkov luminescence imaging to date. Applications of CLI discussed include intraoperative radionuclide-guided surgery, monitoring of therapeutic efficacy, tomographic optical imaging capabilities, and the ability to perform multiplexed imaging using fluorophores excited by the Cerenkov radiation. While technical challenges still exist, Cerenkov imaging has materialized as an important molecular imaging modality.
PMCID: PMC3477724  PMID: 23133811
Cerenkov radiation; PET; optical imaging; fluorescence

Results 1-5 (5)