ImmunoPET Imaging of αβ Expression Using an Engineered Anti-αβ Cys-diabody Site-Specifically Radiolabeled with Cu-64: Considerations for Optimal Imaging with Antibody Fragments.

Purpose: Increased expression of the αβ integrin correlates with advanced tumor grade and poor clinical outcome, identifying αβ as a prognostic indicator and an attractive target for molecular imaging. This work investigated the ability of a disulfide-stabilized [Cu]NOTA-αβ cys-diabody to image αβ expression in vivo using a nu/nu mouse model bearing human melanoma xenografts and positron-emission tomography.

Procedures: Small-animal positron emission tomography (PET) imaging, quantitative ROI analysis, and ex vivo biodistribution were conducted to ascertain tumor uptake and organ distribution of the [Cu]NOTA-αβ cys-diabody.

Development and characterization of an αvβ6-specific diabody and a disulfide-stabilized αvβ6-specific cys-diabody.

Introduction: This work describes the development and characterization of two antibody fragments that specifically target the α(v)β(6) integrin, a non-covalent diabody and a disulfide-stabilized cys-diabody. The diabodies were analyzed for their ability to bind both immobilized and cell surface-bound α(v)β(6). Radiolabeling was done using non-site-specific and site-specific conjugation approaches with N-succinimidyl 4-[(18)F]fluorobenzoate ([(18)F]-SFB) and the bifunctional chelator 1,4,7-triazacyclononane-triacetic acid maleimide (NOTA-maleimide) and copper-64 ([(64)Cu]), respectively.

Modeling truncated AR expression in a natural androgen responsive environment and identification of RHOB as a direct transcriptional target.

Recent studies identifying putative truncated androgen receptor isoforms with ligand-independent activity have shed new light on the acquisition of androgen depletion independent (ADI) growth of prostate cancer. In this study, we present a model system in which a C-terminally truncated variant of androgen receptor (TC-AR) is inducibly expressed in LNCaP, an androgen-dependent cell line, which expresses little truncated receptor. We observed that when TC-AR is overexpressed, the endogenous full length receptor (FL-AR) is transcriptionally downmodulated.

Establishment of clonal MIN-O transplant lines for molecular imaging via lentiviral transduction & in vitro culture.

As the field of molecular imaging evolves and increasingly is asked to fill the discovery and validation space between basic science and clinical applications, careful consideration should be given to the models in which studies are conducted. The MIN-O mouse model series is an established in vivo model of human mammary precancer ductal carcinoma in situ with progression to invasive carcinoma. This series of transplant lines is propagated in vivo and experiments utilizing this model can be completed in non-engineered immune intact FVB/n wild type mice thereby modeling the tumor microenvironment with biological relevance superior to traditional tumor cell xenografts.

In vivo Cerenkov luminescence imaging: a new tool for molecular imaging.

Cerenkov radiation is a phenomenon where optical photons are emitted when a charged particle moves faster than the speed of light for the medium in which it travels. Recently, we and others have discovered that measurable visible light due to the Cerenkov effect is produced in vivo following the administration of β-emitting radionuclides to small animals. Furthermore, the amounts of injected activity required to produce a detectable signal are consistent with small-animal molecular imaging applications.

New covalent capture probes for imaging and therapy, based on a combination of binding affinity and disulfide bond formation.

We describe the synthesis and development of new reactive DOTA-metal complexes for covalently targeting engineered receptors in vivo, which have superior tumor uptake and clearance properties for biomedical applications. These probes are found to clear efficiently through the kidneys and minimally through other routes, but bind persistently in the tumor target. We also explore the new technique of Cerenkov luminescence imaging to optically monitor radiolabeled probe distribution and kinetics in vivo.

Male germ cell-associated kinase, a male-specific kinase regulated by androgen, is a coactivator of androgen receptor in prostate cancer cells.

Androgen receptor (AR) is a ligand-induced transcriptional factor, which plays an important role in the normal development of prostate as well as in the progression of prostate cancer. Numerous coactivators, which associate with AR and function to remodel chromatin and recruit RNA polymerase II to enhance the transcriptional potential of AR, have been identified. Among these coactivators, few are protein kinases.

Characterization of a novel androgen receptor mutation in a relapsed CWR22 prostate cancer xenograft and cell line.

CWR22 has been a valuable xenograft model for the study of prostate cancer progression from an androgen-dependent tumor to one that grows in castrated animals. Herein, we report the identification and characterization of a novel androgen receptor (AR) mutation occurring in a relapsed tumor (CWR22R-2152) and in the CWR22Rv1 cell line established from it. The mutation was not detected in the original, hormone-dependent CWR22 xenograft, indicating that this change occurred during the progression to androgen independence.