Development and Characterization of an Antibody-Labeled Super-Paramagnetic Iron Oxide Contrast Agent Targeting Prostate Cancer Cells for Magnetic Resonance Imaging

Abstract

In this study we developed, characterized and validated in vitro a functional superparagmagnetic iron-oxide based magnetic resonance contrast agent by conjugating a commercially available iron oxide nanoparticle, Molday ION Rhodamine-B Carboxyl (MIRB), with a deimmunized mouse monoclonal antibody (muJ591) targeting prostate-specific membrane antigen (PSMA). This functional contrast agent is intended for the specific and non-invasive detection of prostate cancer cells that are PSMA positive, a marker implicated in prostate tumor progression and metastasis. The two-step carbodiimide reaction used to conjugate the antibody to the nanoparticle was efficient and we obtained an elemental iron content of 1958±611 per antibody. Immunofluorescence microscopy and flow cytometry showed that the conjugated muJ591:MIRB complex specifically binds to PSMA-positive (LNCaP) cells. The muJ591:MIRB complex reduced cell adhesion and cell proliferation on LNCaP cells and caused apoptosis as tested by Annexin V assay, suggesting anti-tumorigenic characteristics. Measurements of the T2 relaxation time of the muJ591:MIRB complex using a 400 MHz Innova NMR and a multi-echo spin-echo sequence on a 3T MRI (Achieva, Philips) showed a significant T2 relaxation time reduction for the muJ591:MIRB complex, with a reduced T2 relaxation time as a function of the iron concentration. PSMA-positive cells treated with muJ591:MIRB showed a significantly shorter T2 relaxation time as obtained using a 3T MRI scanner. The reduction in T2 relaxation time for muJ591:MIRB, combined with its specificity against PSMA+LNCaP cells, suggest its potential as a biologically-specific MR contrast agent.

In Vivo 3T Magnetic Resonance Imaging Using a Biologically Specific Contrast Agent for Prostate Cancer: A Nude Mouse Model

“…This study expands on our previous work [21] by treating prostate-tumour-induced mice with an antibody-labeled contrast agent. In this previous work, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) spectroscopy were used to characterize the muJ591:MIC6 conjugate and to confirm the presence of organic matter (antibody) and iron nanoparticles.…”

“…In a previous study, we developed a functional antibodylabeled MRI contrast agent complex that bound to live cells and was detected in a clinical 3T MRI [21]. Abdolahi et al [22] proposed and tested a similar J591:SPIO conjugate that targeted PSMA-positive prostate cancer cells in vitro.…”

“…Taylor and Sillerud [23] reported the use of paclitaxel-loaded PSMA-targeted iron platinum micelles as an MRI contrast agent, showing that this agent caused tumour volume to significantly decrease compared to paclitaxel alone. In our previous work we showed that a muJ591:SPIO conjugate worked as an MRI contrast agent while reducing cell proliferation and causing apoptosis [21].…”

Double-receptor-targeting multifunctional iron oxide nanoparticles drug delivery system for the treatment and imaging of prostate cancer

“…These superparamagnetic IONPs are used as contrast agents for clinical diagnostics with magnetic resonance imaging (MRI). [35][36][37] Here, we report the development of a multifunctional drug delivery system that can be tracked by MRI. This system utilizes the overexpression of LHRH-R and uPAR on PCa cells to selectively and preferentially deliver the chemotherapeutic paclitaxel (PTX) into the tumor.…”

Prostate cancer radiotherapy: potential applications of metal nanoparticles for imaging and therapy

“…42 While normal prostate epithelium tissue expresses alternative cytosolic splice variants of PSMA, the transmembrane form is significantly elevated levels in CaP tissue, and has been shown to increase with Gleason grade. 43 Importantly, this mechanism for CaP tumour selectivity is not restricted to the primary tumour, with lymph node and bone metastatic deposits in the castrate-resistant setting also exhibiting elevated PSMA expression. 38, 44 Tse et al 45 have recently developed an antibody (J591)-iron oxide conjugate designed to target an extracellular epitope of PSMA, with the aim of developing a superior CaP-MRI contrast agent.…”