Cysteine-specific 89Zr-labeled anti-CD25 IgG allows immuno-PET imaging of interleukin-2 receptor-α on T cell lymphomas

Abstract

IntroductionPositron emission tomography (PET) using radiolabeled Abs as imaging tracer is called immuno-PET. Immuno-PET can verify therapeutic Ab delivery and can noninvasively quantify global levels of target expression in tumors of living subjects. The interleukin-2 receptor α chain (IL-2Rα; CD25) is a promising target for immune therapy and radioimmunotherapy of lymphomas. Immuno-PET could facilitate this approach by visualizing CD25 expression in vivo.MethodsWe prepared 89Zr-anti-CD25 IgG specifically labeled to sulfhydryl moieties by maleimide-deferoxamine conjugation.Results and DiscussionCD25(+) SUDHL1 human T-cell lymphoma cells showed high anti-human 89Zr-CD25 IgG binding that reached 32-fold of that of CD25(-) human lymphoma cells and was completely blocked by excess unlabeled Ab. In SUDHL1 tumor-bearing nude mice, pharmacokinetic studies demonstrated exponential reductions of whole blood and plasma activity following intravenous 89Zr-anti-CD25 IgG injection, with half-lives of 26.0 and 23.3 h, respectively. SUDHL1 tumor uptake of 89Zr-CD25 IgG was lower per weight in larger tumors, but blood activity did not correlate with tumor size or blood level of human CD25, indicating minimal influence by circulating soluble CD25 protein secreted from the lymphoma cells. 89Zr-CD25 IgG PET allowed high-contrast SUDHL1 lymphoma visualization at five days. Biodistribution studies confirmed high tumor 89Zr-CD25 IgG uptake (8.7 ± 0.9%ID/g) that was greater than blood (5.2 ± 1.6%ID/g) and organ uptakes (0.7 to 3.5%ID/g). Tumor CD25-specific targeting was confirmed by suppression of tumor uptake to 4.3 ± 0.2%ID by excess unlabeled CD25 IgG, as well as by low tumor uptake of 89Zr-labeled IgG2a isotype control Ab (3.6 ± 0.9%ID). Unlike CD25(+) lymphocytes from mouse thymus that showed specific uptake of anti-mouse 89Zr-CD25 IgG, EL4 mouse lymphoma cells had low CD25 expression and showed low uptake. In immunocompetent mice bearing EL4 tumors, anti-mouse 89Zr-CD25 IgG displayed low uptakes in normal organs as well as in the tumor. Furthermore, the biodistribution was not influenced by Ab blocking, indicating that specific uptake in nontumor tissues was minimal. 89Zr-CD25 IgG immuno-PET may thus be useful for imaging of T-cell lymphomas and noninvasive assessment of CD25 expression on target cells in vivo.

The Improved Antigen Uptake and Presentation of Dendritic Cells Using Cell-Penetrating D-octaarginine-Linked PNVA-co-AA as a Novel Dendritic Cell-Based Vaccine

“…The most common adult hematologic malignancy is lymphoma, including B-cell and T-cell lymphomas. While the survival rate for patients with B-cell lymphoma has significantly improved with the molecular-targeted drug Rituximab, the prognosis for T-cell lymphoma remains poor due to frequent treatment resistance and relapse [ 21 ]. Therefore, this study evaluated the anti-tumor effect of a dendritic cell-based vaccine using EL4, a T-cell lymphoma cell line, as an experimental model.…”

Imaging Very Late Antigen-4 on MOLT4 Leukemia Tumors with Cysteine Site-Specific 89Zr-Labeled Natalizumab Immuno-Positron Emission Tomography

“…Natalizumab was sitespecifically conjugated with deferoxamine−maleimide on sulfhydryl residues using previously reported methods. 28 Briefly, 2 mg of the Ab underwent reduction at cysteine sites by reaction with 100 mM TCEP in a 1:100 molar ratio (final concentration, 3.7 mM) for 20 min at room temperature (RT). The reduced Ab was diluted in 0.1 M sodium phosphate containing 150 mM NaCl and 1 mM ethylene diamine tetraacetic acid (EDTA) and conjugated with 56.4 μL of 2 mM deferoxamine−maleimide (molar ratio, 1:60) at RT for 60 min.…”

“…Natalizumab was site-specifically conjugated with deferoxamine–maleimide on sulfhydryl residues using previously reported methods . Briefly, 2 mg of the Ab underwent reduction at cysteine sites by reaction with 100 mM TCEP in a 1:100 molar ratio (final concentration, 3.7 mM) for 20 min at room temperature (RT).…”