Development and characterization of an antibody-labeled super-paramagnetic iron oxide contrast agent targeting prostate cancer cells for magnetic resonance imaging.

David Bates,Michael Campbell,Laura Curiel,Ingeborg Zehbe,Suraj Abraham,Roberto Furlan

doi:10.1371/journal.pone.0097220

David Bates, Michael Campbell + Show 4 more

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https://doi.org/10.1371/journal.pone.0097220

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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.

Highlights

In the last 10 years, the incidence of prostate cancer has steadily risen, remaining the second most common cancer diagnosed in men worldwide
We developed a functional super-paramagnetic iron oxide (SPIO)-based MR contrast agent that attaches to prostate-specific membrane antigen (PSMA) receptors for MR imaging of prostate cancer cells
The presence of the iron was confirmed by a fast T2 relaxation time obtained by Nuclear Magnetic Resonance (NMR) analysis at 400 MHz, which was 12.960.7 ms for the muJ591:Molday ION Rhodamine-B Carboxyl (MIRB) complex and 10.260.6 for the muIgG:MIRB complex

Summary

Introduction

In the last 10 years, the incidence of prostate cancer has steadily risen, remaining the second most common cancer diagnosed in men worldwide. In Canada alone, it accounts for roughly 27% of newly diagnosed cancers in 2012 [1]. Prostate tumour growth and spread are often very slow and remain undetected at early stages of the cancer. Current detection and treatment planning heavily relies on the use of prostate specific antigen (PSA)-expressing cells. The low specificity of this test has led to overtreatment of early and less aggressive cancer and under-treatment of indolent but aggressive cancer, leading to high morbidity [2]. Current treatments have high morbidity and possible posttreatment relapses, which compromise the patient’s quality of life and survival [3,4]

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