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Updated: Jan 3, 2026
Computed Tomography-guided Time-domain Diffuse Fluorescence Tomography in Small Animals for Localization of Cancer Biomarkers
Published on: July 17, 2012
TOPKi-NBD: a fluorescent small molecule for tumor imaging
Giacomo Pirovano1, Sheryl Roberts1, Thomas Reiner2,3,4
1Department of Radiology, Memorial Sloan Kettering Cancer Center, 1275 York Avenue, New York, NY, 10065, USA.
Purpose:
OTS514 is a highly specific inhibitor targeting lymphokine-activated killer T cell-originated protein kinase (TOPK). A fluorescently labeled TOPK inhibitor could be used for tumor delineation or intraoperative imaging, potentially improving patient care.
Methods:
Fluorescently labeled OTS514 was obtained by conjugating the fluorescent small molecule NBD to the TOPK inhibitor. HCT116 colorectal cancer cells were used to generate tumors in NSG mice for in vivo studies. Images were generated in vitro using confocal microscopy and ex vivo using an IVIS Spectrum.
Results:
OTS514 was successfully conjugated to a fluorescent sensor and validated in vitro, in vivo, and ex vivo. The labeling reaction led to TOPKi-NBD with 67% yield and 97% purity after purification. We were able to test binding properties of TOPKi-NBD to its target, TOPK, and compared them to the precursor inhibitor. EC50s showed similar target affinities for TOPKi-NBD and the unlabeled OTS514. TOPKi-NBD showed specific tumor uptake after systemic administration and was microscopically detectable inside cancer cells ex vivo. Blocking controls performed with an excess of the unlabeled OTS514 confirmed specificity of the compound. Overall, the results represent a first step toward the development of a class of TOPK-specific fluorescent inhibitors for in vivo imaging and tumor delineation.
Conclusions:
TOPK has the potential to be a new molecular target for cancer-specific imaging in a large variety of tumors. This could lead to broad applications in vitro and in vivo.
Insights
A new fluorescently labeled TOPK inhibitor, TOPKi-NBD, shows promise for cancer imaging. This TOPK-specific compound demonstrates effective tumor uptake and detection, paving the way for improved tumor delineation and intraoperative imaging.
Area of Science:
- Biochemistry
- Molecular Imaging
- Oncology
Background:
- Lymphokine-activated killer T cell-originated protein kinase (TOPK) is a potential molecular target in various cancers.
- Developing targeted imaging agents can significantly improve cancer diagnosis and treatment planning.
Purpose of the Study:
- To develop and validate a fluorescently labeled inhibitor of TOPK (lymphokine-activated killer T cell-originated protein kinase) for potential use in tumor imaging.
- To assess the specificity, tumor uptake, and detectability of the fluorescent TOPK inhibitor in vitro, in vivo, and ex vivo models.
Main Methods:
- Conjugation of the TOPK inhibitor OTS514 with a fluorescent molecule (NBD) to create TOPKi-NBD.
- In vitro, in vivo (using HCT116 colorectal cancer xenografts in NSG mice), and ex vivo imaging studies.
- Confocal microscopy, IVIS Spectrum imaging, and binding affinity assays (EC50) were employed.
Main Results:
- TOPKi-NBD was synthesized with high yield (67%) and purity (97%).
- The fluorescent inhibitor exhibited comparable target affinity to the parent compound OTS514.
- Specific tumor uptake and intracellular detection of TOPKi-NBD were observed in vivo and ex vivo, confirmed by blocking studies.
Conclusions:
- The development of TOPKi-NBD represents a significant advancement in creating TOPK-specific fluorescent imaging agents.
- TOPK is a viable molecular target for developing novel cancer-specific imaging agents with broad in vitro and in vivo applications.
