Immunotargeting of Integrin α₆β₄ for Single-Photon Emission Computed Tomography and Near-Infrared Fluorescence Imaging in a Pancreatic Cancer Model

Abstract

To explore suitable imaging probes for early and specific detection of pancreatic cancer, we demonstrated that α6β4 integrin is a good target and employed single-photon emission computed tomography (SPECT) or near-infrared (NIR) imaging for immunotargeting. Expression levels of α6β4 were examined by Western blotting and flow cytometry in certain human pancreatic cancer cell lines. The human cell line BxPC-3 was used for α6β4-positive and a mouse cell line, A4, was used for negative counterpart. We labeled antibody against α6β4 with Indium-111 (111In) or indocyanine green (ICG). After injection of 111In-labeled probe to tumor-bearing mice, biodistribution, SPECT, autoradiography (ARG), and immunohistochemical (IHC) studies were conducted. After administration of ICG-labeled probe, in vivo and ex vivo NIR imaging and fluorescence microscopy of tumors were performed. BxPC-3 tumor showed a higher radioligand binding in SPECT and higher fluorescence intensity as well as a delay in the probe washout in NIR imaging when compared to A4 tumor. The biodistribution profile of 111In-labeled probe, ARG, and IHC confirmed the α6β4 specific binding of the probe. Here, we propose that α6β4 is a desirable target for the diagnosis of pancreatic cancer and that it could be detected by radionuclide imaging and NIR imaging using a radiolabeled or ICG-labeled α6β4 antibody.

Radioimmunotherapy of pancreatic cancer xenografts in nude mice using 90Y-labeled anti-α6β4 integrin antibody

“…Furthermore, we observed previously that BxPC-3 tumors show decreased radiosensitivity and abundant cancer-associated stroma, and most of the blood vessels in these tumors are surrounded by the stromal tissue [26] which could lead to the reduced penetration of macromolecules, such as IgG [27]. In comparison with 111 In-TSP-A01 uptake in BxPC-3 tumor [26], the uptake of our new antibody, 111 In-ITGA6B4, in same tumor was superior [17]. In vivo activity of 90 Y-ITGA6B4 may be predicted from a biodistribution surrogate, 111 In-ITGA6B4, because 111 In- and 90 Y-labeled antibodies, proteins, and peptides are biologically similar [28].…”

“…Additionally, overexpression of α 6 β 4 in different types of cancer was associated with poor prognosis [21]. Previously, we proposed α 6 β 4 as a potential target for pancreatic cancer imaging and showed the specific accumulation of ITGA6B4 in α 6 β 4 overexpressing tumor [17]. Here, we labeled anti-α 6 β 4 antibody with β-emitting radionuclide 90 Y and reconfirmed, using PET imaging, that this antibody ( 90 Y-ITGA6B4) accumulates in tumor.…”

“…According to ELISA results, our ITGA6B4 antibody was strongly reacts with human α 6 β 4 antigen but its cross-reactivity to murine α 6 β 4 antigen is negligible (Supplementary Figure 1). We labeled it with indium-111 ( 111 In) for single-photon emission computed tomography (SPECT) and with the near-infrared (NIR) fluorophore indocyanine green (ICG) for NIR fluorescence imaging [17]. SPECT and NIR imaging demonstrated that α 6 β 4 -expressing tumors exhibited good uptake of these probes.…”

Molecular Imaging of Pancreatic Duct Adenocarcinoma Using a Type 2 Cannabinoid Receptor-Targeted Near-Infrared Fluorescent Probe

“…Much effort has been spent on exploring highly specific molecular target of PDAC to improve the diagnosis and treatment of this dismal disease in the past decade. However, long blood circulation times and suboptimal tumor accumulation constrained their potential clinical application [34] , [35] ; effective therapy has only been shown in few examples in experimental pancreatic tumor models, including nanomedicines targeting the epidermal growth factor, integrin α v β 3 receptor, and transferrin receptor [36] , [37] , [38] , [39] . In this study, we demonstrate that an NIR probe (NIR760-XLP6) specifically binds to CB 2 R in PANC-1 cells and tumors and led to high imaging contrast (3.2-fold in vivo and 50-fold ex vivo) with minimal uptake in organs.…”

Utilizing High Resolution Ultrasound to Monitor Tumor Onset and Growth in Genetically Engineered Pancreatic Cancer Models

“…Therefore, the exact detection of tumor onset and tumor size is an essential prerequisite for preclinical study logistics and therapy monitoring. In general, several approaches like magnetic resonance imaging (MRI) 6 , computed tomography scanning 7,8,9 or high resolution ultrasound can be employed to conduct tumor screening and therapy…”