Molecular Imaging of Pancreatic Cancer with Antibodies

Intraoperative Imaging in Hepatopancreatobiliary Surgery

Hepatopancreatobiliary surgery belongs to one of the most complex fields of general surgery. An intricate and vital anatomy is accompanied by difficult distinctions of tumors from fibrosis and inflammation; the identification of precise tumor margins; or small, even disappearing, lesions on currently available imaging. The routine implementation of ultrasound use shifted the possibilities in the operating room, yet more precision is necessary to achieve negative resection margins. Modalities utilizing fluorescent-compatible dyes have proven their role in hepatopancreatobiliary surgery, although this is not yet a routine practice, as there are many limitations. Modalities, such as photoacoustic imaging or 3D holograms, are emerging but are mostly limited to preclinical settings. There is a need to identify and develop an ideal contrast agent capable of differentiating between malignant and benign tissue and to report on the prognostic benefits of implemented intraoperative imaging in order to navigate clinical translation. This review focuses on existing and developing imaging modalities for intraoperative use, tailored to the needs of hepatopancreatobiliary cancers. We will also cover the application of these imaging techniques to theranostics to achieve combined diagnostic and therapeutic potential.

Recent advances in estrogen receptor-targeted probes conjugated to BODIPY dyes

Estrogens, is a class of steroid hormones associated with the occurrence and development of breast cancer, that bind to estrogen receptors (ER). The development of BODIPY-based fluorescent ligands for the ER has continued to gain tremendous attention over the past 20 years. This review focuses on the synthesis methods, optical properties, and biological activity of BODIPY fluorescent probes conjugated to ER ligands. These will provide new strategy for designing fluorescent probes for targeting estrogen receptors.

Recent advances in understanding pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is an intractable cancer and a leading cause of cancer deaths worldwide. Over 90% of patients die within 1 year of diagnosis. Deaths from PDAC are increasing and it remains a cancer of substantial unmet need. A number of factors contribute to its poor prognosis: namely, late presentation, early metastases and limited systemic therapy options because of chemoresistance. A variety of research approaches underway are aimed at improving patient survival. Here, we review high-risk groups and efforts for early detection. We examine recent developments in the understanding of complex molecular and metabolic alterations which accompany PDAC. We explore artificial intelligence and biological targets for therapy and examine the role of tumour stroma and the immune microenvironment. We also review recent developments with respect to the PDAC microbiome. It is hoped that current research efforts will translate into earlier diagnosis, improvements in treatment and better outcomes for patients.

Sensitive and selective detection of Mucin1 in pancreatic cancer using hybridization chain reaction with the assistance of Fe3O4@polydopamine nanocomposites

Pancreatic cancer is characterized as the worst for diagnosis lacking symptoms at the early stage, which results in a low overall survival rate. The frequently used techniques for pancreatic cancer diagnosis rely on imaging and biopsy, which have limitations in requiring experienced personnel to operate the expensive instruments and analyze the results. Therefore, there is a high demand to develop alternative tools or methods to detect pancreatic cancer. Herein, we propose a new strategy to enhance the detection sensitivity of pancreatic cancer cells both in biofluids and on tissues by combining the unique property of dopamine coated Fe₃O₄ nanoparticles (Fe₃O₄@DOP NPs) to specifically quench and separate free 6-carboxyfluorescein (FAM) labeled DNA (H₁-FAM/H₂-FAM), and the key feature of hybridization chain reaction (HCR) amplification. We have determined the limit of detection (LOD) to be 21 ~ 41 cells/mL for three different pancreatic cancer cell lines. It was also discovered that the fluorescence intensity of pancreatic cancer cells was significantly higher than that of HPDE-C7 and HepG-2 cells (control cell lines), which express lower MUC1 protein. Moreover, the HCR amplification system was used to identify the cancer cells on pancreatic tissue, which indicated the versatility of our strategy in clinical application. Therefore, the presented detection strategy shows good sensitivity, specificity and has great potential for the diagnosis of pancreatic cancer.

Multimodal molecular imaging evaluation for early diagnosis and prognosis of cholangiocarcinoma

Cholangiocarcinoma (CCA) is an aggressive and lethal malignancy with limited therapeutic options. Despite recent advances in diagnostic imaging for CCA, the early diagnosis of CCA and evaluation of tumor invasion into the bile duct and its surrounding tissues remain challenging. Most patients with CCA are diagnosed at an advanced stage, at which treatment options are limited. Molecular imaging is a promising diagnostic method for noninvasive imaging of biological events at the cellular and molecular level in vivo. Molecular imaging plays a key role in the early diagnosis, staging, and treatment-related evaluation and management of cancer. This review will describe different methods for molecular imaging of CCA, including nuclear medicine, magnetic resonance imaging, optical imaging, and multimodal imaging. The main challenges and future directions in this field are also discussed.

18F-labeled Dimer-Sansalvamide A Cyclodecapeptide: A Novel Diagnostic Probe to Discriminate Pancreatic Cancer from Inflammation in a Nude Mice Model

Early detection of pancreatic cancer has been a long-standing challenge. Inflammatory mass is the main source of false-positive findings in ¹⁸F-labeled fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography / computed tomography (PET/CT). Heat shock protein 90 (Hsp90) is an established biomarker overexpressed in pancreatic cancer. We modified a Dimer-Sansalvamide A cyclodecapeptide by conjugating it with the bifunctional chelator NOTA (1,4,7-triazacyclononane-1,4,7-trisacetic acid), yielding ¹⁸F-NOTA-Dimer-Sansalvamide A cyclodecapeptide (¹⁸F-NOTA-Dimer-San A). The binding specificity of the probe was confirmed by in vitro cell uptake assays in Hsp90-positive PL45 pancreatic cancer cells. Hsp90 expression was imaged via MicroPET in pancreatic cancer xenografts and inflammation in mice. All of the mice received an intravenous injection of ¹⁸F-NOTA-Dimer-San A, and images were acquired at 1 and 2 hour time points. The novel probe demonstrated prominent tumor uptake in the pancreatic cancer xenografts (4.00 ± 0.88 %ID/g, 5.80 ± 0.94 %ID/g), and the inflammatory thigh showed minimal uptake (0.85 ± 0.01 %ID/g, 1.50 ± 0.20 %ID/g) at 1 and 2 hours after injection, respectively. The activity accumulation between the two groups was significantly different (P < 0.05), and the biodistribution data was consistent with the images. Moreover, immunohistochemistry (IHC) confirmed that the expression of Hsp90 was positive in PL45 pancreatic cancer but negative in the muscles next to the tumor and inflammatory muscles. We concluded that ¹⁸F-NOTA-Dimer-San A PET might allow non-invasive imaging for Hsp90 expression in tumors and has the potential to discriminate pancreatic cancer from inflammatory mass.

Overview and Future Perspectives on Tumor-Targeted Positron Emission Tomography and Fluorescence Imaging of Pancreatic Cancer in the Era of Neoadjuvant Therapy

BACKGROUND

Despite recent advances in the multimodal treatment of pancreatic ductal adenocarcinoma (PDAC), overall survival remains poor with a 5-year cumulative survival of approximately 10%. Neoadjuvant (chemo- and/or radio-) therapy is increasingly incorporated in treatment strategies for patients with (borderline) resectable and locally advanced disease. Neoadjuvant therapy aims to improve radical resection rates by reducing tumor mass and (partial) encasement of important vascular structures, as well as eradicating occult micrometastases. Results from recent multicenter clinical trials evaluating this approach demonstrate prolonged survival and increased complete surgical resection rates (R0). Currently, tumor response to neoadjuvant therapy is monitored using computed tomography (CT) following the RECIST 1.1 criteria. Accurate assessment of neoadjuvant treatment response and tumor resectability is considered a major challenge, as current conventional imaging modalities provide limited accuracy and specificity for discrimination between necrosis, fibrosis, and remaining vital tumor tissue. As a consequence, resections with tumor-positive margins and subsequent early locoregional tumor recurrences are observed in a substantial number of patients following surgical resection with curative intent. Of these patients, up to 80% are diagnosed with recurrent disease after a median disease-free interval of merely 8 months. These numbers underline the urgent need to improve imaging modalities for more accurate assessment of therapy response and subsequent re-staging of disease, thereby aiming to optimize individual patient's treatment strategy. In cases of curative intent resection, additional intra-operative real-time guidance could aid surgeons during complex procedures and potentially reduce the rate of incomplete resections and early (locoregional) tumor recurrences. In recent years intraoperative imaging in cancer has made a shift towards tumor-specific molecular targeting. Several important molecular targets have been identified that show overexpression in PDAC, for example: CA19.9, CEA, EGFR, VEGFR/VEGF-A, uPA/uPAR, and various integrins. Tumor-targeted PET/CT combined with intraoperative fluorescence imaging, could provide valuable information for tumor detection and staging, therapy response evaluation with re-staging of disease and intraoperative guidance during surgical resection of PDAC.

METHODS

A literature search in the PubMed database and (inter)national trial registers was conducted, focusing on studies published over the last 15 years. Data and information of eligible articles regarding PET/CT as well as fluorescence imaging in PDAC were reviewed. Areas covered: This review covers the current strategies, obstacles, challenges, and developments in targeted tumor imaging, focusing on the feasibility and value of PET/CT and fluorescence imaging for integration in the work-up and treatment of PDAC. An overview is given of identified targets and their characteristics, as well as the available literature of conducted and ongoing clinical and preclinical trials evaluating PDAC-targeted nuclear and fluorescent tracers.

Pancreatic cancer in 2021: What you need to know to win

Pancreatic cancer is one of the solid tumors with the worst prognosis. Five-year survival rate is less than 10%. Surgical resection is the only potentially curative treatment, but the tumor is often diagnosed at an advanced stage of the disease and surgery could be performed in a very limited number of patients. Moreover, surgery is still associated with high post-operative morbidity, while other therapies still offer very disappointing results. This article reviews every aspect of pancreatic cancer, focusing on the elements that can improve prognosis. It was written with the aim of describing everything you need to know in 2021 in order to face this difficult challenge.

c-Met-targeted near-infrared fluorescent probe for real-time depiction and dissection of perineural invasion and lymph node metastasis lesions in pancreatic ductal adenocarcinoma xenograft models

Pancreatic ductal adenocarcinoma (PDAC), a fatal malignant tumour, has a high postoperative recurrence rate, mainly due to the difficulty of discerning occult lesions, including those related to perineural invasion (PNI) and lymph node metastasis (LNM). Cellular mesenchymal-epithelial transition factor (c-Met), an excellent imaging marker, is aberrantly expressed in the majority of PDACs. Thus, we plan to utilize a c-Met-targeted near-infrared fluorescent (NIRF) probe for real-time visualization and dissection of PDAC, and corresponding PNI and LNM lesions. Immunohistochemistry showed c-Met expression in PDAC, PNI and LNM reached 94.3% (100/106), 88.3% (53/60), and 71.4% (25/35), respectively, and its expression in PNI and LNM was significantly correlated with that in primary PDAC (r = 0.66, p < 0.0001 and r = 0.44, p < 0.01, respectively). SHRmAb-IR800 was successfully synthesized using an anti-c-Met antibody and a NIRF dye. The in vitro targeting ability of SHRmAb-IR800 was higher in CFPAC1 cells (c-Met positive) than in Miapaca-2 cells (c-Met negative) (p < 0.05). In vivo NIRF imaging of CFPAC1 subcutaneous tumours demonstrated higher accumulation of SHRmAb-IR800 than the control probe (p < 0.05). The signal-to-background ratio (TBR) of an orthotopic PDAC tumour was 3.38 ± 0.46, and imaging with SHRmAb-IR800 facilitated the resection of metastatic lesions with sensitivity and specificity values of 93.3% (56/60) and 87.1% (27/31), respectively. Furthermore, tiny PNI and LNM lesions in xenograft models were detected by NIRF imaging, with TBRs measuring 2.59 ± 0.19 and 2.88 ± 0.72, respectively. Therefore, the clinical translation of this probe might shed new light on NIRF-guided pancreatectomy and improve the surgical prognosis of PDAC patients.

Therapeutic Application of Monoclonal Antibodies in Pancreatic Cancer: Advances, Challenges and Future Opportunities

Pancreatic cancer remains as one of the most aggressive cancer types. In the absence of reliable biomarkers for its early detection and more effective therapeutic interventions, pancreatic cancer is projected to become the second leading cause of cancer death in the Western world in the next decade. Therefore, it is essential to discover novel therapeutic targets and to develop more effective and pancreatic cancer-specific therapeutic agents. To date, 45 monoclonal antibodies (mAbs) have been approved for the treatment of patients with a wide range of cancers; however, none has yet been approved for pancreatic cancer. In this comprehensive review, we discuss the FDA approved anticancer mAb-based drugs, the results of preclinical studies and clinical trials with mAbs in pancreatic cancer and the factors contributing to the poor response to antibody therapy (e.g. tumour heterogeneity, desmoplastic stroma). MAb technology is an excellent tool for studying the complex biology of pancreatic cancer, to discover novel therapeutic targets and to develop various forms of antibody-based therapeutic agents and companion diagnostic tests for the selection of patients who are more likely to benefit from such therapy. These should result in the approval and routine use of antibody-based agents for the treatment of pancreatic cancer patients in the future.

Tailor-Made Nanomaterials for Diagnosis and Therapy of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest cancers worldwide due to its aggressiveness and the challenge to early diagnosis and treatment. In recent decades, nanomaterials have received increasing attention for diagnosis and therapy of PDAC. However, these designs are mainly focused on the macroscopic tumor therapeutic effect, while the crucial nano-bio interactions in the heterogeneous microenvironment of PDAC remain poorly understood. As a result, the majority of potent nanomedicines show limited performance in ameliorating PDAC in clinical translation. Therefore, exploiting the unique nature of the PDAC by detecting potential biomarkers together with a deep understanding of nano-bio interactions that occur in the tumor microenvironment is pivotal to the design of PDAC-tailored effective nanomedicine. This review will introduce tailor-made nanomaterials-enabled laboratory tests and advanced noninvasive imaging technologies for early and accurate diagnosis of PDAC. Moreover, the fabrication of a myriad of tailor-made nanomaterials for various PDAC therapeutic modalities will be reviewed. Furthermore, much preferred theranostic multifunctional nanomaterials for imaging-guided therapies of PDAC will be elaborated. Lastly, the prospects of these nanomaterials in terms of clinical translation and potential breakthroughs will be briefly discussed.

Diagnosis of Pancreatic Ductal Adenocarcinoma by Immuno-Positron Emission Tomography

Diagnosis of pancreatic ductal adenocarcinoma (PDAC) by current imaging techniques is useful and widely used in the clinic but presents several limitations and challenges, especially in small lesions that frequently cause radiological tumors infra-staging, false-positive diagnosis of metastatic tumor recurrence, and common occult micro-metastatic disease. The revolution in cancer multi-"omics" and bioinformatics has uncovered clinically relevant alterations in PDAC that still need to be integrated into patients' clinical management, urging the development of non-invasive imaging techniques against principal biomarkers to assess and incorporate this information into the clinical practice. "Immuno-PET" merges the high target selectivity and specificity of antibodies and engineered fragments toward a given tumor cell surface marker with the high spatial resolution, sensitivity, and quantitative capabilities of positron emission tomography (PET) imaging techniques. In this review, we detail and provide examples of the clinical limitations of current imaging techniques for diagnosing PDAC. Furthermore, we define the different components of immuno-PET and summarize the existing applications of this technique in PDAC. The development of novel immuno-PET methods will make it possible to conduct the non-invasive diagnosis and monitoring of patients over time using in vivo, integrated, quantifiable, 3D, whole body immunohistochemistry working like a "virtual biopsy".

Aptamer Generated by Cell-SELEX for Specific Targeting of Human Glioma Cells

The most prevalent primary brain tumors are gliomas, which start in the glial cells. Although there have been significant technological advances in surgery and radio-chemotherapy, the prognosis and survival of patients with malignant gliomas remain poor. For routine diagnosis of glioma, computed tomography and magnetic resonance imaging primarily depend on anatomical changes and fail to detect the cellular changes that occur early in the development of malignant gliomas. Therefore, it is urgent to find effective molecular diagnostic tools to detect early stages of malignant gliomas. Currently, cell-based Systematic Evolution of Ligands by EXponential enrichment (cell-SELEX) technology is one effective tool to obtain DNA or RNA aptamers capable of differentiating the molecular signatures among different types of cell lines. Using cell-SELEX, we generated and characterized an aptamer, termed S6-1b, that can distinguish the molecular differences between glioma cell line SHG44 and human astrocytes. Under the conditions of 4 and 37 °C, respectively, the dissociation constants of aptamer-cell interaction were both measured in the low nanomolar range. The aptamer S6-1b also exhibited excellent selectivity, making it suitable for use in a complex biological environment. Furthermore, the aptamer can effectively target glioma cells for in vivo fluorescence imaging of tumors. The target type of aptamer S6-1b was identified as a cell membrane protein. Our work indicates that aptamer S6-1b has diagnostic and therapeutic potential to specifically deliver imaging or therapeutic agents to malignant gliomas.

ImmunoPET/NIRF/Cerenkov multimodality imaging of ICAM-1 in pancreatic ductal adenocarcinoma

PURPOSE

We dual-labeled an intercellular adhesion molecule-1 (ICAM-1) monoclonal antibody (mAb) and evaluated its effectiveness for lesion detection and surgical navigation in pancreatic ductal adenocarcinoma (PDAC) via multiple noninvasive imaging approaches, including positron emission tomography (PET), near-infrared fluorescence (NIRF), and Cerenkov luminescence imaging (CLI).

METHODS

ICAM-1 expression in PDAC cell lines (BxPC-3 and AsPC-1) was assessed via flow cytometry and immunofluorescent staining. An ICAM-1 mAb labeled by IRDye 800CW and radionuclide zirconium-89 (denoted as [⁸⁹Zr]Zr-DFO-ICAM-1-IR800) was synthesized. Its performance was validated via in vivo comparative PET/NIRF/CLI and biodistribution (Bio-D) studies in nude mice bearing subcutaneous BxPC-3/AsPC-1 tumors or orthotopic BxPC-3 tumor models using nonspecific IgG as an isotype control tracer.

RESULTS

ICAM-1 expression was strong in the BxPC-3 and minimal in the AsPC-1 cell line. Both multimodality imaging and Bio-D data exhibited more prominent uptake of [⁸⁹Zr]Zr-DFO-ICAM-1-IR800 in BxPC-3 tumors than in AsPC-1 tumors. The uptake of [⁸⁹Zr]Zr-DFO-IgG-IR800 in BxPC-3 tumors was similar to that of [⁸⁹Zr]Zr-DFO-ICAM-1-IR800 in AsPC-1 tumors. These results demonstrate the desirable affinity and specificity of [⁸⁹Zr]Zr-DFO-ICAM-1-IR800 compared to [⁸⁹Zr]Zr-DFO-IgG-IR800. Orthotopic BxPC-3 tumor foci could also be clearly delineated by [⁸⁹Zr]Zr-DFO-ICAM-1-IR800. An intermodal match was achieved in the ICAM-1-targeted immunoPET/NIRF/CLI. The positive expression levels of ICAM-1 in BxPC-3 tumor tissue were further confirmed by immunohistopathology.

CONCLUSION

We successfully developed a dual-labeled ICAM-1-targeted tracer for PET/NIRF/CLI of PDAC that can facilitate better diagnosis and intervention of PDAC upon clinical translation.

Current status of targeted microbubbles in diagnostic molecular imaging of pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is often associated with a poor prognosis due to silent onset, resistance to therapies, and rapid spreading. Most patients are ineligible for curable surgery as they present with advanced disease at the time of diagnosis. Present diagnostic methods relying on anatomical changes have various limitations including difficulty to discriminate between benign and malignant conditions, invasiveness, the ambiguity of imaging results, or the inability to detect molecular biomarkers of PDAC initiation and progression. Therefore, new imaging technologies with high sensitivity and specificity are critically needed for accurately detecting PDAC and noninvasively characterizing molecular features driving its pathogenesis. Contrast enhanced targeted ultrasound (CETUS) is an upcoming molecular imaging modality that specifically addresses these issues. Unlike anatomical imaging modalities such as CT and MRI, molecular imaging using CETUS is promising for early and accurate detection of PDAC. The use of molecularly targeted microbubbles that bind to neovascular targets can enhance the ultrasound signal specifically from malignant PDAC tissues. This review discusses the current state of diagnostic imaging modalities for pancreatic cancer and places a special focus on ultrasound targeted-microbubble technology together with its clinical translatability for PDAC detection.

Detecting Early Pancreatic Cancer: Current Problems and Future Prospects

The number of patients with pancreatic cancer (PC) is currently increasing in both Korea and Japan. The 5-year survival rate of patients with PC 13.0%; however, resection with minimal invasion (tumor size: ≤10 mm) increases the 5-year survival rate to 80%. For this reason, early detection is essential, but most patients with early-stage PC are asymptomatic. Early detection of PC has been reported to require screening of high-risk individuals (HRIs), such as those with a family history of PC, inherited cancer syndromes, intraductal papillary mucinous neoplasm, or chronic pancreatitis. Studies on screening of these HRIs have confirmed a significantly better prognosis among patients with PC who were screened than for patients with PC who were not screened. However, to date in Japan, most patients with early-stage PC diagnosed in routine clinics were not diagnosed during annual health checks or by surveillance; rather, PC was detected in these patients by incidental findings during examinations for other diseases. We need to increase the precision of the PC screening and diagnostic processes by introducing new technologies, and we need to pay greater attention to incidental clinical findings.

Toward the Clinical Development and Validation of a Thy1-Targeted Ultrasound Contrast Agent for the Early Detection of Pancreatic Ductal Adenocarcinoma

Early detection of pancreatic ductal adenocarcinoma (PDAC) represents the most significant step toward the treatment of this aggressive lethal disease. Previously, we engineered a preclinical Thy1-targeted microbubble (MBThy1) contrast agent that specifically recognizes Thy1 antigen overexpressed in the vasculature of murine PDAC tissues by ultrasound (US) imaging. In this study, we adopted a single-chain variable fragment (scFv) site-specific bioconjugation approach to construct clinically translatable MBThy1-scFv and test for its efficacy in vivo in murine PDAC imaging, and functionally evaluated the binding specificity of scFv ligand to human Thy1 in patient PDAC tissues ex vivo.

MATERIALS AND METHODS

We recombinantly expressed the Thy1-scFv with a carboxy-terminus cysteine residue to facilitate its thioether conjugation to the PEGylated MBs presenting with maleimide functional groups. After the scFv-MB conjugations, we tested binding activity of the MBThy1-scFv to MS1 cells overexpressing human Thy1 (MS1Thy1) under liquid shear stress conditions in vitro using a flow chamber setup at 0.6 mL/min flow rate, corresponding to a wall shear stress rate of 100 seconds, similar to that in tumor capillaries. For in vivo Thy1 US molecular imaging, MBThy1-scFv was tested in the transgenic mouse model (C57BL/6J - Pdx1-Cre; KRas; Ink4a/Arf) of PDAC and in control mice (C57BL/6J) with L-arginine-induced pancreatitis or normal pancreas. To facilitate its clinical feasibility, we further produced Thy1-scFv without the bacterial fusion tags and confirmed its recognition of human Thy1 in cell lines by flow cytometry and in patient PDAC frozen tissue sections of different clinical grades by immunofluorescence staining.

RESULTS

Under shear stress flow conditions in vitro, MBThy1-scFv bound to MS1Thy1 cells at significantly higher numbers (3.0 ± 0.8 MB/cell; P < 0.01) compared with MBNontargeted (0.5 ± 0.5 MB/cell). In vivo, MBThy1-scFv (5.3 ± 1.9 arbitrary units [a.u.]) but not the MBNontargeted (1.2 ± 1.0 a.u.) produced high US molecular imaging signal (4.4-fold vs MBNontargeted; n = 8; P < 0.01) in the transgenic mice with spontaneous PDAC tumors (2-6 mm). Imaging signal from mice with L-arginine-induced pancreatitis (n = 8) or normal pancreas (n = 3) were not significantly different between the two MB constructs and were significantly lower than PDAC Thy1 molecular signal. Clinical-grade scFv conjugated to Alexa Fluor 647 dye recognized MS1Thy1 cells but not the parental wild-type cells as evaluated by flow cytometry. More importantly, scFv showed highly specific binding to VEGFR2-positive vasculature and fibroblast-like stromal components surrounding the ducts of human PDAC tissues as evaluated by confocal microscopy.

CONCLUSIONS

Our findings summarize the development and validation of a clinically relevant Thy1-targeted US contrast agent for the early detection of human PDAC by US molecular imaging.

Recent progress in the molecular imaging of therapeutic monoclonal antibodies

Therapeutic monoclonal antibodies have become one of the central components of the healthcare system and continuous efforts are made to bring innovative antibody therapeutics to patients in need. It is equally critical to acquire sufficient knowledge of their molecular structure and biological functions to ensure the efficacy and safety by incorporating new detection approaches since new challenges like individual differences and resistance are presented. Conventional techniques for determining antibody disposition including plasma drug concentration measurements using LC-MS or ELISA, and tissue distribution using immunohistochemistry and immunofluorescence are now complemented with molecular imaging modalities like positron emission tomography and near-infrared fluorescence imaging to obtain more dynamic information, while methods for characterization of antibody's interaction with the target antigen as well as visualization of its cellular and intercellular behavior are still under development. Recent progress in detecting therapeutic antibodies, in particular, the development of methods suitable for illustrating the molecular dynamics, is described here.

Early Detection in a Mouse Model of Pancreatic Cancer by Imaging DNA Damage Response Signaling

Despite its widespread use in oncology, the PET radiotracer 18F-FDG is ineffective for improving early detection of pancreatic ductal adenocarcinoma (PDAC). An alternative strategy for early detection of pancreatic cancer involves visualization of high-grade pancreatic intraepithelial neoplasias (PanIN-3s), generally regarded as the noninvasive precursors of PDAC. The DNA damage response is known to be hyperactivated in late-stage PanINs. Therefore, we investigated whether the SPECT imaging agent 111In-anti-γH2AX-TAT allows visualization of the DNA damage repair marker γH2AX in PanIN-3s in an engineered mouse model of PDAC, to facilitate early detection of PDAC. Methods: Genetically engineered KPC (KRasLSL.G12D/+; p53LSL.R172H/+; PdxCre) mice were imaged with 18F-FDG and 111In-anti-γH2AX-TAT. The presence of PanIN/PDAC as visualized by histologic examination was compared with autoradiography and immunofluorescence. Separately, the survival of KPC mice imaged with 111In-anti-γH2AX-TAT was evaluated. Results: In KPC mouse pancreata, γH2AX expression was increased in high-grade PanINs but not in PDAC, corroborating earlier results obtained from human pancreas sections. Uptake of 111In-anti-γH2AX-TAT, but not 111In-IgG-TAT or 18F-FDG, within the pancreas correlated positively with the age of KPC mice, which correlated with the number of high-grade PanINs. 111In-anti-γH2AX-TAT localizes preferentially in high-grade PanIN lesions but not in established PDAC. Younger, non-tumor-bearing KPC mice that show uptake of 111In-anti-γH2AX-TAT in the pancreas survive for a significantly shorter time than mice with physiologic 111In-anti-γH2AX-TAT uptake. Conclusion:111In-anti-γH2AX-TAT imaging allows noninvasive detection of DNA damage repair signaling upregulation in preinvasive PanIN lesions and is a promising new tool to aid in the early detection and staging of pancreatic cancer.

Multiple Carcinomas and Intraepithelial Neoplasms in a Case of Familial Pancreatic Cancer: Rapid Morphological Changes in the Pancreatic Cyst and Pathological Lesions Undetected by Clinical Images

A 69-year-old woman with a family history of pancreatic cancer was referred because of imaging changes of a pancreas cyst. Magnetic resonance cholangiopancreatography showed a faintly dilated main pancreatic duct and a pancreas body cyst that had changed rapidly over the past year. Computed tomography demonstrated an emerging enhancing lesion in the pancreatic cyst. Endoscopic ultrasonography revealed an irregular-margined, heterogeneous-echoic pancreatic mass, without findings of early chronic pancreatitis. She underwent distal pancreatectomy. A histologic examination of the resected specimen revealed invasive adenocarcinoma with numerous multicentric foci of pancreatic intraepithelial neoplasia (PanIN), including high-grade PanIN, apparently separate from the main cancer.

An Innovation for Treating Orthotopic Pancreatic Cancer by Preoperative Screening and Imaging-Guided Surgery

PURPOSE

Pancreatic cancer is still associated with a poor outcome and low patient quality of life, which are mainly attributed to the late detection and requirement of distal pancreatectomy with extended resection of pancreatic tumors. Therefore, novel strategies for early screening and precise tumor resection are urgently needed. In this study, we evaluated the feasibility of a low-density lipoprotein receptor (LDLR)-targeted small-molecule contrast agent (peptide-22-Cy7) for early screening with photoacoustic tomography and near-infrared (NIR) imaging as guided surgical navigation to achieve precise resection.

PROCEDURE

Normal pancreatic cells (HPDE6-C7) and cancer cells (PANC-1) were respectively used in the in vitro targeting evaluations. The ability of peptide-22-Cy7 for preoperative in vivo pancreatic tumor detection was investigated in a mouse orthotopic pancreatic cancer model (n = 10) using photoacoustic tomography; 18 tumor-bearing mice were further divided into three groups for different treatments. After intravenous injection of peptide-22-Cy7, surgical navigation was conducted through laparotomy. Histopathological analysis was used to further confirm the tumor area and the state of surgical margins.

RESULTS

Flow cytometry demonstrated that peptide-22 is highly specific to pancreatic cancer cells, with a fluorescence intensity of approximately 87.3 %. Orthotopic pancreatic tumors with a size of 4 mm could be accurately detected by photoacoustic tomography. Surgical navigation effectively achieved R0 resection and minimized the range of resection, which led to increased body weight of the mice following surgery.

CONCLUSION

Overall, our newly developed targeted contrast agent facilitated the accurate positioning and resection of pancreatic tumors. Photoacoustic tomography and optical imaging-guided surgical navigation may be a novel direction for improving the survival, quality of life, and disease management of pancreatic cancer patients.

Molecular imaging in the second near-infrared window

In the past decade, noticeable progress has been achieved regarding fluorescence imaging in the second near-infrared (NIR-II) window. Fluorescence imaging in the NIR-II window demonstrates superiorities of deep tissue penetration and high spatial and temporal resolution, which are beneficial for profiling physiological processes. Meanwhile, molecular imaging has emerged as an efficient tool to decipher biological activities on the molecular and cellular level. Extending molecular imaging into the NIR-II window would enhance the imaging performance, providing more detailed and accurate information of the biological system. In this progress report, selected achievements made in NIR-II molecular imaging are summarized. The organization of this report is based on strategies underlying rational designs of NIR-II imaging probes and their applications in molecular imaging are highlighted. This progress report may provide guidance and reference for further development of functional NIR-II probes designed for high-performance molecular imaging.

Early Detection of Pancreatic Cancer: Opportunities and Challenges

Most patients with pancreatic ductal adenocarcinoma (PDAC) present with symptomatic, surgically unresectable disease. Although the goal of early detection of PDAC is laudable and likely to result in significant improvement in overall survival, the relatively low prevalence of PDAC renders general population screening infeasible. The challenges of early detection include identification of at-risk individuals in the general population who would benefit from longitudinal surveillance programs and appropriate biomarker and imaging-based modalities used for PDAC surveillance in such cohorts. In recent years, various subgroups at higher-than-average risk for PDAC have been identified, including those with familial risk due to germline mutations, a history of pancreatitis, patients with mucinous pancreatic cysts, and elderly patients with new-onset diabetes. The last 2 categories are discussed at length in terms of the opportunities and challenges they present for PDAC early detection. We also discuss current and emerging imaging modalities that are critical to identifying early, potentially curable PDAC in high-risk cohorts on surveillance.

Nanobodies: New avenues for imaging, stabilizing and modulating GPCRs

The family of G protein-coupled receptors (GPCRs) is the largest class of membrane proteins and an important drug target due to their role in many (patho)physiological processes. Besides small molecules, GPCRs can be targeted by biologicals including antibodies and antibody fragments. This review describes the use of antibodies and in particular antibody fragments from camelid-derived heavy chain-only antibodies (nanobodies/VHHs/sdAbs) for detecting, stabilizing, modulating and therapeutically targeting GPCRs. Altogether, it becomes increasingly clear that the small size, structure and protruding antigen-binding loops of nanobodies are favorable features for the development of selective and potent GPCRs-binding molecules. This makes them attractive tools to modulate GPCR activity but also as targeting modalities for GPCR-directed therapeutics. In addition, these antibody-fragments are important tools in the stabilization of particular conformations of these receptors. Lastly, nanobodies, in contrast to conventional antibodies, can also easily be expressed intracellularly which render nanobodies important tools for studying GPCR function. Hence, GPCR-targeting nanobodies are ideal modalities to image, stabilize and modulate GPCR function.

Click Chemistry as a Tool for Cell Engineering and Drug Delivery

Click chemistry has great potential for use in binding between nucleic acids, lipids, proteins, and other molecules, and has been used in many research fields because of its beneficial characteristics, including high yield, high specificity, and simplicity. The recent development of copper-free and less cytotoxic click chemistry reactions has allowed for the application of click chemistry to the field of medicine. Moreover, metabolic glycoengineering allows for the direct modification of living cells with substrates for click chemistry either in vitro or in vivo. As such, click chemistry has become a powerful tool for cell transplantation and drug delivery. In this review, we describe some applications of click chemistry for cell engineering in cell transplantation and for drug delivery in the diagnosis and treatment of diseases.

Translational molecular imaging in exocrine pancreatic cancer

Effective treatment for pancreatic cancer remains challenging, particularly the treatment of pancreatic ductal adenocarcinoma (PDAC), which makes up more than 95% of all pancreatic cancers. Late diagnosis and failure of chemotherapy and radiotherapy are all too common, and many patients die soon after diagnosis. Here, we make the case for the increased use of molecular imaging in PDAC preclinical research and in patient management.

In vivo near infrared fluorescence imaging and dynamic quantification of pancreatic metastatic tumors using folic acid conjugated biodegradable mesoporous silica nanoparticles

Cancer metastasis is one of the biggest challenges in cancer treatments since it increases the likelihood that a patient will die from the disease. Therefore, the availability of techniques for the early detection and quantification of tumors is very important. We have prepared cyanine 7.5 NHS ester (Cy_7.5) and folic acid (FA) conjugated biodegradable mesoporous silica nanoparticles (bMSN@Cy_7.5-FA NPs) (~100 nm) for visualizing tumors in vivo. The fluorescence spectra revealed that the emission peak of bMSN@Cy_7.5-FA NPs had a red-shift of 1 nm. Confocal immunofluorescent images showed that bMSN@Cy_7.5-FA NPs had an excellent targeting ability for visualizing cancer cells. In vivo fluorescence imaging has been conducted using an orthotopic model for pancreatic cancer within 48 h, and the fluorescence intensity reached a maximum at a post injection time-point of 12 h, which demonstrated that the use of bMSN@Cy_7.5-FA NPs provides an excellent imaging platform for tumor precision therapy in mice.

"Albumin Hitchhiking" with an Evans Blue Analog for Cancer Theranostics

Although ¹⁷⁷Lu-DOTA-TATE was recently approved in Europe for the treatment of certain neuroendocrine tumors, continued development and optimization has been ongoing to further improve the therapeutic efficacy of somatostatin receptor 2 targeted peptide receptor radionuclide therapy, as well as reducing the renal toxicity. In this work, the use of an Evans blue analog for “albumin hitchhiking” resulted in significant improvement in both the imaging performance and therapeutic efficacy of radiolabeled octreotate, as well as reducing the toxicity since much less radioactivity was used for therapy. Upon clinical translation, such “albumin hitchhiking” could make significant impact in the near future for cancer patient management.

Targeted Molecular Imaging of Pancreatic Cancer with a Miniature Endoscope

It is highly desirable to develop novel approaches to improve patient survival rate of pancreatic cancer through early detection. Here, we present such an approach based on photoacoustic and fluorescence molecular imaging of pancreatic tumor using a miniature multimodal endoscope in combination with targeted multifunctional iron oxide nanoparticles (IONPs). A novel fan-shaped scanning mechanism was developed to minimize the invasiveness for endoscopic imaging of pancreatic tumors. The results show that the enhancements in photoacoustic and fluorescence signals using amino-terminal fragment (ATF) targeted IONPs were ~four to six times higher compared to that using non-targeted IONPs. Our study indicates the potential of the combination of the multimodal photoacoustic-fluorescence endoscopy and targeted multifunctional nanoparticles as an efficient tool to provide improved specificity and sensitivity for pancreatic cancer detection.

EUS and related technologies for the diagnosis and treatment of pancreatic disease: research gaps and opportunities-Summary of a National Institute of Diabetes and Digestive and Kidney Diseases workshop

A workshop was sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases to address the research gaps and opportunities in pancreatic EUS. The event occurred on July 26, 2017 in 4 sessions: (1) benign pancreatic diseases, (2) high-risk pancreatic diseases, (3) diagnostic and therapeutics, and (4) new technologies. The current state of knowledge was reviewed, with identification of numerous gaps in knowledge and research needs. Common themes included the need for large multicenter consortia of various pancreatic diseases to facilitate meaningful research of these entities; to standardize EUS features of different pancreatic disorders, the technique of sampling pancreatic lesions, and the performance of various therapeutic EUS procedures; and to identify high-risk disease early at the cellular level before macroscopic disease develops. The need for specialized tools and accessories to enable the safe and effective performance of therapeutic EUS procedures also was discussed.

Generation and evaluation of antibody agents for molecular imaging of CD44v6-expressing cancers

AIM

The aim of this study was to generate and characterize scFv antibodies directed to human CD44v6, as well as to radiolabel and evaluate top candidates in vitro and in vivo for their potential use in CD44v6-targeted molecular imaging in cancer patients.

MATERIALS AND METHODS

Phage display selections were used to isolate CD44v6-specific scFvs. A chain shuffling strategy was employed for affinity maturation based on a set of CD44v6-specific first-generation clones. Two second-generation scFv clones were then chosen for labeling with 111In or 125I and assessed for CD44v6-specific binding on cultured tumor cells. In vivo uptake and distribution was evaluated in tumor-bearing mice using a dual tumor model. Finally, a proof-of-concept small animal PET-CT study was performed on one of the candidates labeled with 124I.

RESULTS

Two affinity-matured clones, CD44v6-scFv-A11 and CD44v6-scFv-H12, displayed promising binding kinetics. Seven out of eight radiolabeled conjugates demonstrated CD44v6-specific binding. In vivo studies on selected candidates demonstrated very advantageous tumor-to-organ ratios, in particular for iodinated conjugates, where 125I-labeled scFvs exhibited favorable kinetics and tumor-to-blood ratios above five already at 24 hours p.i.. The small animal PET-CT study using 124I-labeled CD44v6-scFv-H12 was in line with the biodistribution data, clearly visualizing the high CD44v6-expressing tumor.

CONCLUSION

The single chain fragments, CD44v6-scFv-A11 and CD44v6-scFv-H12 specifically bind to CD44v6, and the radiolabeled counterparts provide high tumor-to-blood ratios and fast clearance from organs and blood. We conclude that radioiodinated CD44v6-scFv-A11 and CD44v6-scFv-H12 possess features highly suitable for stringent molecular imaging.

Future trends and emerging issues for nanodelivery systems in oral and oropharyngeal cancer

Oral cancer is a prevalent cancer type on a global scale, whose traditional treatment strategies have several drawbacks that could in the near future be overcome through the development of novel therapeutic and prognostic strategies. Nanotechnology provides an alternative to traditional therapy that leads to enhanced efficiency and less toxicity. Various nanosystems have been developed for the treatment of oral cancer, including polymeric, metallic, and lipid-based formulations that incorporate chemotherapeutics, natural compounds, siRNA, or other molecules. This review summarizes the main benefits of using these nanosystems, in parallel with a particular focus on the issues encountered in medical practice. These novel strategies have provided encouraging results in both in vitro and in vivo studies, but few have entered clinical trials. The use of nanosystems in oral cancer has the potential of becoming a valid therapeutic option for patients suffering from this malignancy, considering that clinical trials have already been completed and others are currently being developed.

Investigation into the Biological Impact of Block Size on Cathepsin S-Degradable HPMA Copolymers

N-(2-Hydroxypropyl)methacrylamide (HPMA) copolymers have been studied as an efficient carrier for drug delivery and tumor imaging. However, as with many macromolecular platforms, the substantial accumulation of HPMA copolymer by the mononuclear phagocyte system (MPS)-associated tissues, such as the blood, liver, and spleen, has inhibited its clinical translation. Our laboratory is pursuing approaches to improve the diagnostic and radiotherapeutic effectiveness of HPMA copolymers by reducing the nontarget accumulation. Specifically, we have been investigating the use of a cathepsin S (Cat S)-cleavable peptidic linkers to degrade multiblock HPMA copolymers to increase MPS-associated tissue clearance. In this study, we further our investigation into this area by exploring the impact of copolymer block size on the biological performance of Cat S-degradable HPMA copolymers. Using a variety of in vitro and in vivo techniques, including dual labeling of the copolymer and peptide components, we investigated the constructs using HPAC pancreatic ductal adenocarcinoma models. The smaller copolymer block size (S-CMP) demonstrated significantly faster Cat S cleavage kinetics relative to the larger system (L-CMP). Confocal microscopy demonstrated that both constructs could be much more efficiently internalized by human monocyte-differentiated macrophage (hMDM) compared to HPAC cells. In the biodistribution studies, the multiblock copolymers with a smaller block size exhibited faster clearance and lower nontarget retention while still achieving good tumor targeting and retention. Based on the radioisotopic ratios, fragmentation and clearance of the copolymer constructs were higher in the liver compared to the spleen and tumor. Overall, these results indicate that block size plays an important role in the biological performance of Cat S-degradable polymeric constructs.

ImmunoPET and Near-Infrared Fluorescence Imaging of Pancreatic Cancer with a Dual-Labeled Bispecific Antibody Fragment

Dual-targeted imaging agents have shown improved targeting efficiencies in comparison to single-targeted entities. The purpose of this study was to quantitatively assess the tumor accumulation of a dual-labeled heterobifunctional imaging agent, targeting two overexpressed biomarkers in pancreatic cancer, using positron emission tomography (PET) and near-infrared fluorescence (NIRF) imaging modalities. A bispecific immunoconjugate (heterodimer) of CD105 and tissue factor (TF) Fab' antibody fragments was developed using click chemistry. The heterodimer was dual-labeled with a radionuclide (⁶⁴Cu) and fluorescent dye. PET/NIRF imaging and biodistribution studies were performed in four-to-five week old nude athymic mice bearing BxPC-3 (CD105/TF^+/+) or PANC-1 (CD105/TF^-/-) tumor xenografts. A blocking study was conducted to investigate the specificity of the tracer. Ex vivo tissue staining was performed to compare TF/CD105 expression in tissues with PET tracer uptake to validate in vivo results. PET imaging of ⁶⁴Cu-NOTA-heterodimer-ZW800 in BxPC-3 tumor xenografts revealed enhanced tumor uptake (21.0 ± 3.4%ID/g; n = 4) compared to the homodimer of TRC-105 (9.6 ± 2.0%ID/g; n = 4; p < 0.01) and ALT-836 (7.6 ± 3.7%ID/g; n = 4; p < 0.01) at 24 h postinjection. Blocking studies revealed that tracer uptake in BxPC-3 tumors could be decreased by 4-fold with TF blocking and 2-fold with CD105 blocking. In the negative model (PANC-1), heterodimer uptake was significantly lower than that found in the BxPC-3 model (3.5 ± 1.1%ID/g; n = 4; p < 0.01). The specificity was confirmed by the successful blocking of CD105 or TF, which demonstrated that the dual targeting with ⁶⁴Cu-NOTA-heterodimer-ZW800 provided an improvement in overall tumor accumulation. Also, fluorescence imaging validated the PET imaging, allowing for clear delineation of the xenograft tumors. Dual-labeled heterodimeric imaging agents, like ⁶⁴Cu-NOTA-heterodimer-ZW800, may increase the overall tumor accumulation in comparison to single-targeted homodimers, leading to improved imaging of cancer and other related diseases.

Endoscopic Ultrasound and Related Technologies for the Diagnosis and Treatment of Pancreatic Disease - Research Gaps and Opportunities: Summary of a National Institute of Diabetes and Digestive and Kidney Diseases Workshop

A workshop was sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases to address the research gaps and opportunities in pancreatic endoscopic ultrasound (EUS). The event occurred on July 26, 2017 in 4 sessions: (1) benign pancreatic diseases, (2) high-risk pancreatic diseases, (3) diagnostic and therapeutics, and (4) new technologies. The current state of knowledge was reviewed, with identification of numerous gaps in knowledge and research needs. Common themes included the need for large multicenter consortia of various pancreatic diseases to facilitate meaningful research of these entities; to standardize EUS features of different pancreatic disorders, the technique of sampling pancreatic lesions, and the performance of various therapeutic EUS procedures; and to identify high-risk disease early at the cellular level before macroscopic disease develops. The need for specialized tools and accessories to enable the safe and effective performance of therapeutic EUS procedures also was discussed.

DNA nanomaterials for preclinical imaging and drug delivery

Besides being the carrier of genetic information, DNA is also an excellent biological organizer to establish well-designed nanostructures in the fields of material engineering, nanotechnology, and biomedicine. DNA-based materials represent a diverse nanoscale system primarily due to their predictable base pairing and highly regulated conformations, which greatly facilitate the construction of DNA nanostructures with distinct shapes and sizes. Integrating the emerging advancements in bioconjugation techniques, DNA nanostructures can be readily functionalized with high precision for many purposes ranging from biosensors to imaging to drug delivery. Recent progress in the field of DNA nanotechnology has exhibited collective efforts to employ DNA nanostructures as smart imaging agents or delivery platforms within living organisms. Despite significant improvements in the development of DNA nanostructures, there is limited knowledge regarding the in vivo biological fate of these intriguing nanomaterials. In this review, we summarize the current strategies for designing and purifying highly-versatile DNA nanostructures for biological applications, including molecular imaging and drug delivery. Since DNA nanostructures may elicit an immune response in vivo, we also present a short discussion of their potential toxicities in biomedical applications. Lastly, we discuss future perspectives and potential challenges that may limit the effective preclinical and clinical employment of DNA nanostructures. Due to their unique properties, we predict that DNA nanomaterials will make excellent agents for effective diagnostic imaging and drug delivery, improving patient outcome in cancer and other related diseases in the near future.

Pancreatic cancer: yesterday, today and tomorrow

Pancreatic cancer is one of our most lethal malignancies. Despite substantial improvements in the survival rates for other major cancer forms, pancreatic cancer survival rates have remained relatively unchanged since the 1960s. Pancreatic cancer is usually detected at an advanced stage and most treatment regimens are ineffective, contributing to the poor overall prognosis. Herein, we review the current understanding of pancreatic cancer, focusing on central aspects of disease management from radiology, surgery and pathology to oncology.

Maghemite-human serum albumin hybrid nanoparticles: towards a theranostic system with high MRI r2* relaxivity

Human Serum Albumin (HSA) is the most abundant plasma protein in human blood, and therefore, it is the material of choice for the development of particulate formulations due to its biodegradable and biocompatible nature. Over the last decade, HSA nanoparticles (NPs) have been prepared mostly using desolvation techniques and evaluated as promising drug carriers. In addition, controlling the particle size has become a primary concern while formulating such nanoparticulate systems. Since many of these HSA-based carrier systems have often demonstrated batch-to-batch fabrication variability, significant efforts have been made to develop and characterize HSA-based NPs featuring a robust and controllable particle size, by using a desolvation/cross-linking-type Divinyl Sulfone (DVS)-mediated nanofabrication method. For this purpose and for global multi-parameter fabrication process optimization, a statistically significant Design of Experiment (DoE, MINITAB® 17 DoE software) methodology has been successfully implemented. It aimed to disclose an optimal set of HSA NP fabrication conditions in order to afford highly reproducible and stable 23.05 ± 5.3 nm-sized DoE-globally optimized core HSA NPs. Due to the use of bifunctional DVS as a cross-linker for the preparation of such DoE-optimized HSA NPs, their surface contains a variety of free functional groups which are available for further second step functional modifications. Moreover, related hybrid organic/inorganic nanosystems consisting of DoE-optimized HSA NPs that encapsulated hydrophilic (NH₄)₂Ce(IV)(NO₃)₆ (Ceric Ammonium Nitrate - CAN) modified γ-Fe₂O₃ NPs (CAN-maghemite or CAN-γ-Fe₂O₃ NPs), which enable medical imaging using magnetic resonance imaging (MRI), have also been fabricated and characterized. The resulting hybrid magnetic NPs are a quite powerful T₂* contrast agent (r₂* of 482 mM^-1 s^-1), which may be used as a powerful dual phase platform for both therapeutic (drug delivery) and diagnostic imaging (MRI) applications.

ImmunoPET Imaging of Insulin-Like Growth Factor 1 Receptor in a Subcutaneous Mouse Model of Pancreatic Cancer

The role of insulin-like growth factor-1 receptor (IGF-1R) in cancer tumorigenesis was established decades ago, yet there are limited studies evaluating the imaging and therapeutic properties of anti-IGF-1R antibodies. Noninvasive imaging of IGF-1R may allow for optimized patient stratification and monitoring of therapeutic response in patients. Herein, this study reports the development of a Zirconium-89 (⁸⁹Zr)-labeled anti-IGF-1R antibody (⁸⁹Zr-Df-1A2G11) for PET imaging of pancreatic cancer. Successful chelation and radiolabeling of the antibody resulted in a highly stable construct that could be used for imaging IGF-1R expressing tumors in vivo. Western blot and flow cytometry studies showed that MIA PaCa-2, BxPC-3, and AsPC-1 pancreatic cancer cell lines expressed high, moderate, and low levels of IGF-1R, respectively. These three pancreatic cancer cell lines were subcutaneously implanted into mice. By employing the PET imaging technique, the tumor accumulation of ⁸⁹Zr-Df-1A2G11 was found to be dependent on the level of IGF-1R expression. Tumor accumulation of ⁸⁹Zr-Df-1A2G11 was 8.24 ± 0.51, 5.80 ± 0.54, and 4.30 ± 0.42 percentage of the injected dose (%ID/g) in MIA PaCa-2, BxPC-3, and AsPC-1-derived tumor models at 120 h postinjection, respectively (n = 4). Biodistribution studies and ex vivo immunohistochemistry confirmed these findings. In addition, ⁸⁹Zr-labeled nonspecific human IgG (⁸⁹Zr-Df-IgG) displayed minimal uptake in IGF-1R positive MIA PaCa-2 tumor xenografts (3.63 ± 0.95%ID/g at 120 h postinjection; n = 4), demonstrating that ⁸⁹Zr-Df-1A2G11 accumulation was highly specific. This study provides initial evidence that our ⁸⁹Zr-labeled IGF-1R-targeted antibody may be employed for imaging a wide range of malignancies. Antibodies may be tracked in vivo for several days to weeks with ⁸⁹Zr, which may enhance image contrast due to decreased background signal. In addition, the principles outlined in this study can be employed for identifying patients that may benefit from anti-IGF-1R therapy.