Presented at the annual meeting of the Israeli Neurological Association, December 2nd-3th 2003, Tel-Aviv
Background: Current methods for clinical imaging of brain tumors provide mainly anatomical data on the size and location of the lesion, while not providing data on its functional aspects at the cellular level, such as the viability of the tumor cells and their sensitivity to therapeutic agents. Such aspects are important for tumor staging and for the design and monitoring of treatment. Aposense is a novel small organic molecule developed for clinical functional imaging of apoptosis. Upon systemic administration, Aposense performs selective detection of and uptake to apoptotic cells in vivo. Aposense has been demonstrated as a non-invasive tool for functional imaging of cell death in vivo in various animal models, such as cancer, cerebrovascular stroke and myocardial infarction. We now report the application of Aposense for functional assessment of brain tumors.
Objective: To test the ability of Aposense to label apoptotic brain tumor cells and to monitor the effect of anti-cancer treatment in vivo in brain glioma in mice.
Methods: C6-glioma cells were injected into the right caudate nucleus of mice. Tumors were allowed to grow for 8-9 days, wherein animals were subjected to treatment, being either irradiation alone or a combined treatment of irradiation and chemotherapy. One to three days later, mice were injected intravenously with fluorescent-labeled Aposense. Two hours later, animals were sacrificed and their brains subjected to histopathological assessment. Fluorescent microscopy was performed to detect the ApoSenseTM molecule within the tissue, while parallel hematoxylin and eosin (H&E) staining and TUNEL were performed for verification that the Aposense-stained cells were indeed apoptotic cells.
Results: Aposense specifically and selectively labeled cells undergoing cell death within the glioma tumor, while not binding to viable tumor cells or normal brain tissue. Labeling by Aposense was at the single-cell level, and was correlated with the H&E and TUNEL staining. Aposense labeling within the tumors was detected only in animals subjected to the anti-cancer treatments, reflecting specific tumor cell death in response to therapy. The percentage of mice responding to the radiotherapy was low (30%). Nevertheless, Aposense was able to accurately detect all these responders and distinguish them from the non-responders.
Conclusions: Aposense is a useful tool for selective and specific labeling in vivo of glioma cells undergoing apoptosis, allowing monitoring of tumor response to therapy. Future radio-labeled Aposense would allow non-invasive real time functional imaging of cell death within brain tumors, thus improving clinical staging of tumors, monitoring the effect of treatment, and evaluation of novel therapeutic strategies