Abstract 4289: MRI-guided intra-arterial delivery of SPIO-labeled natural killer cells to hepatocellular carcinoma
Authors: Sheu Alexander Y. , Zhang Zhuoli , Li Weiguo , Omary Reed A. , Larson Andrew C. 
Published: August 2012

Abstract
Adoptive immunotherapy with natural killer (NK) lymphocytes is a promising approach for treatment of HCC; however, intravenous (IV) infusion may lead to insufficient NK dose delivery to tumors. Also, quantification of intra-tumoral NK delivery may be crucial to optimize therapy or to predict response. We hypothesize that: a) transcatheter intra-arterial (IA) infusion allows for targeted delivery of NK cells to HCC and b) iron oxide labeling methods allow for visualization of IA NK delivery with MRI. 4.0×106 NK-92 cells (ATCC; Manassas, VA) were labeled overnight with 10 pg/cell of Texas Red iron oxide nanoparticles (GENOVIS AB, Sweden) using 4.5 mg/ml protamine sulfate as a transfection agent. Cell viability was measured using a cell counter, and labeling efficacy was measured by fluorescence microscopy with DAPI and by Prussian blue iron staining. With IACUC approval, 6 Sprague-Dawley rats were implanted with 4.0×106 McA-RH7777 HCC cells divided between the left lateral and median lobes to simulate a metastatic tumor. After 8 days of tumor growth, a 24G catheter (Terumo Medical Co., Somerset, NJ) was placed in the proper hepatic artery via laparotomy, and digital subtraction angiography (DSA) confirmed placement. 7.0T MRI scanner (Bruker, Billerica, MA) was used for T2*W scans pre- and post- NK infusion. T2* measurements in tumor and normal liver were compared pre- and post-infusion using paired t-test. Livers were harvested for Prussian blue histology to confirm NK delivery; percentage of cells in a high-powered (20×) field identified as NK (%HPF) were compared between tumor and normal tissues. NK cell viability was &gt;90% before and after labeling. Labeling efficacy was &gt;95%. DSA confirmed successful catheter placement in each animal. Transcatheter NK infusions led to significant reductions in tumor T2* (mean±SD: pre 11.6±0.7 msec, post 9.8±1.1 msec, p=0.04) but no significant reductions in normal liver T2* (mean±SD: pre 7.5±0.1 msec, post 7.6±0.3 msec, p=0.36) during intra-procedural MRI scans. Histologic %HPF measurements were significantly higher in tumor (1.51%) than surrounding normal liver tissues (0.06%) (p&lt;0.01). Transcatheter infusion permitted selective delivery of NK cells to HCC. The intra-hepatic distribution of iron oxide labeled NK cells was quantitatively visualized with MRI. We will perform studies in the future to assess relationships between therapeutic outcomes and the delivered NK dose, comparing IV and IA administration routes. Clinicians could one day use these methods to adjust patient-specific therapeutic regimens during adoptive immunotherapies for the treatment of HCC. In vivo quantification of the delivery of therapeutic agents is a powerful concept that offers the potential to address many unmet needs in both pre-clinical and translational research settings.
Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4289. doi:1538-7445.AM2012-4289