Specific tumor labeling enhanced by polyethylene glycol linkage of near infrared dyes conjugated to a chimeric anti-carcinoembryonic antigen antibody in a nude mouse model of human pancreatic cancer

Abstract

Abstract. Labeling of metastatic tumors can aid in their staging and resection of cancer. Near infrared (NIR) dyes have been used in the clinic for tumor labeling. However, there can be a nonspecific uptake of dye by the liver, lungs, and lymph nodes, which hinders detection of metastasis. In order to overcome these problems, we have used two NIR dyes (DyLight 650 and 750) conjugated to a chimeric anti-carcinoembryonic antigen antibody to evaluate how polyethylene glycol linkage (PEGylation) can improve specific tumor labeling in a nude mouse model of human pancreatic cancer. The conjugated PEGylated and non-PEGylated DyLight 650 and 750 dyes were injected intravenously into non-tumor-bearing nude mice. Serum samples were collected at various time points in order to determine serum concentrations and elimination kinetics. Conjugated PEGylated dyes had significantly higher serum dye concentrations than non-PEGylated dyes (p ¼ 0.005 for the 650 dyes and p < 0.001 for the 750 dyes). Human pancreatic tumors subcutaneously implanted into nude mice were labeled with antibody-dye conjugates and serially imaged. Labeling with conjugated PEGylated dyes resulted in significantly brighter tumors compared to the non-PEGylated dyes (p < 0.001 for the 650 dyes; p ¼ 0.01 for 750 dyes). PEGylation of the NIR dyes also decreased their accumulation in lymph nodes, liver, and lung. These results demonstrate enhanced selective tumor labeling by PEGylation of dyes conjugated to a tumor-specific antibody, suggesting their future clinical use in fluorescence-guided surgery.

Development and Evaluation of a Fluorescent Antibody-Drug Conjugate for Molecular Imaging and Targeted Therapy of Pancreatic Cancer

“…Images were obtained at the time points indicated, with fixed exposure times where noted. Signal intensity and specificity are clearly illustrated, and are consistent with previous reports demonstrating in vivo CEA detection, particularly with fluorescently labeled antibodies [ 72 – 81 ]. In addition to fixed exposure times, automatic exposures were obtained for the 600-640nm excitation on the dorsal side of mice in group 3, and the average exposure time at different points in the study is plotted in Fig 10 .…”

“…In addition, a majority of paclitaxel ADCs previously reported couple paclitaxel to antibodies which also exhibit some cytotoxic effects [ 56 – 59 ]. Although CEA is an effective target for immunofluorescent diagnostics (Figs 3 – 5 ) and visualization of tumors [ 66 – 81 ], we have demonstrated that CEA antibodies alone do not contribute to cytotoxicity ( Fig 6 ), likely due to the fact that CEA is not necessary for cell survival [ 60 , 61 ]. Further, drug-free antibody control samples (α-CEA-680, IgG-680) exhibited no decrease in cell survival even after prolonged incubation times ( Fig 5 ).…”

“…There also exists an impressive body of work demonstrating the biomarker’s efficacy as a cancer imaging and diagnostic tool, ranging from radio-labeled CEA antibodies [ 66 – 71 ] to the use of fluorescent labels [ 72 – 79 ]. More recent work has demonstrated the improved optical performance and physiological stability of PEGylated, NIR dyes coupled to CEA-specific antibodies for highly effective molecular imaging of tumors [ 80 , 81 ].…”

Tumor-Specific Labeling of Pancreatic Cancer Using a Humanized Anti-CEA Antibody Conjugated to a Near-Infrared Fluorophore

“…Despite the initial fluorescence at the liver, the signal rapidly decreases after 12 hours and returns close to baseline near 48 hours and beyond. The addition of polyethylene glycol (PEG) groups or attachments of the fluorophore in a conformation that may mask the hydrophobic moieties, could be approaches to improve this issue which will be addressed in future work (28).…”

Current status and future perspectives of fluorescence-guided surgery for cancer

“…Conjugation of molecules with polyethylene glycol (PEG), known as PEGylation, affects the biodistribution of the molecule and is widely used in pharmacology [22]. Maawy et al demonstrated that PEGylation of two NIR antibody-dye conjugates increased the half-life, favorably altered biodistribution, and significantly increased the tumor to background contrast in liver and lung lesions [23]. PEGylated dyes had significantly lower accumulation in the liver when compared to non-PEGylated dyes, and this enabled high contrast imaging of metastatic tumor lesions of the liver [24].…”