Necrosis binding of Ac-Lys0(IRDye800CW)-Tyr3-octreotate: a consequence from cyanine-labeling of small molecules

• Published in: EJNMMI research Vol. 11; no. 1; p. 47
• Main Authors: Stroet, Marcus C. M., Dijkstra, Bianca M., Dulfer, Sebastiaan E., Kruijff, Schelto, den Dunnen, Wilfred F. A., Kruyt, Frank A. E., Groen, Rob J. M., Seimbille, Yann, Panth, Kranthi M., Mezzanotte, Laura, Lowik, Clemens W. G. M., de Jong, Marion
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 10.05.2021; Springer Nature B.V; SpringerOpen
• Subjects: 800CW-TATE; Antibodies; Binding; Cardiac Imaging; Contrast agents; Fluorescence; Fluorescent molecular probes; Imaging; Infrared imaging; Labeling; Medicine; Medicine & Public Health; Molecular fluorescence-guided surgery; Molecular structure; Necrosis; Necrosis-avidity; Nuclear Medicine; Oncology; Original Research; Orthopedics; Paraffins; Peptides; Radiology; Somatostatin receptor subtype 2; Surgery; Tumors; Necrosis-avidity; 800CW-TATE; Somatostatin receptor subtype 2; Molecular fluorescence-guided surgery; Fluorescent molecular probes
• ISSN: 2191-219X; 2191-219X
• DOI: 10.1186/s13550-021-00789-4

Background There is a growing body of nuclear contrast agents that are repurposed for fluorescence-guided surgery. New contrast agents are obtained by substituting the radioactive tag with, or adding a fluorescent cyanine to the molecular structure of antibodies or peptides. This enables intra-operative fluorescent detection of cancerous tissue, leading to more complete tumor resection. However, these fluorescent cyanines can have a remarkable influence on pharmacokinetics and tumor uptake, especially when labeled to smaller targeting vectors such as peptides. Here we demonstrate the effect of cyanine-mediated dead cell-binding of Ac-Lys 0 (IRDye800CW)-Tyr 3 -octreotate (800CW-TATE) and how this can be used as an advantage for fluorescence-guided surgery. Results Binding of 800CW-TATE could be blocked with DOTA 0 -Tyr 3 -octreotate (DOTA-TATE) on cultured SSTR 2 -positive U2OS cells and was absent in SSTR 2 negative U2OS cells. However, strong binding was observed to dead cells, which could not be blocked with DOTA-TATE and was also present in dead SSTR 2 negative cells. No SSTR 2 -mediated binding was observed in frozen tumor sections, possibly due to disruption of the cells in the process of sectioning the tissue before exposure to the contrast agent. DOTA-TATE blocking resulted in an incomplete reduction of 61.5 ± 5.8% fluorescence uptake by NCI-H69-tumors in mice. Near-infrared imaging and dead cell staining on paraffin sections from resected tumors revealed that fluorescence uptake persisted in necrotic regions upon blocking with DOTA-TATE. Conclusion This study shows that labeling peptides with cyanines can result in dead cell binding. This does not hamper the ultimate purpose of fluorescence-guided surgery, as necrotic tissue appears in most solid tumors. Hence, the necrosis binding can increase the overall tumor uptake. Moreover, necrotic tissue should be removed as much as possible: it cannot be salvaged, causes inflammation, and is tumorigenic. However, when performing binding experiments to cells with disrupted membrane integrity, which is routinely done with nuclear probes, this dead cell-binding can resemble non-specific binding. This study will benefit the development of fluorescent contrast agents.