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TMOD-22. AKALUC BIOLUMINESCENCE OFFERS SUPERIOR SENSITIVITY TO TRACK IN VIVO GBM EXPANSION


 Longitudinal tracking of tumor growth using non-invasive bioluminescence imaging (BLI) is a key approach for in vivo cancer studies, but the current method of firefly luciferase (Fluc) BLI has quantitative limitations, as it is only suited for detection of tumors of considerable sizes at advanced stage, typically in the order of >105 cells. Recently, Akaluciferase (Akaluc) has been developed as an alternative BLI system that offers higher signal strength and better light penetration of tissue due to its red-shifted emission. Here, we established Akaluc BLI as a new sensitive method for in vivo tracking of glioblastoma (GBM) expansion in intracranial transplant models. In multiple GBM cell lines, including the frequently used U87MG and GL261, as well as patient-derived glioma stem cells (GSC), we demonstrate that Akaluc-expressing GBM cells produced more than 50-times brighter BLI signals in vitro and up to 100-fold higher signal intensities in vivo over Fluc-expressing counterparts. The higher sensitivity of Akaluc BLI permits early in vivo detection of intracranial GBM transplants starting as early as 4 hours after implantation and with as little as 5,000 transplanted GSC. We also reveal a prolonged engraftment period in intracranial GSC transplants before wide dissemination into host brain parenchyma. Akaluc BLI is also advantageous for longitudinal monitoring of therapeutic effects of chemoradiation for GBM and detection of early phase of tumor relapse. Thus, Akaluc BLI offers an important addition to the tool box for cancer research. SIGNIFICANCE: The high sensitivity of Akaluc bioluminescence is a significant improvement for the non-invasive tracking of tumors in preclinical cancer studies, including detection of small incipient tumors and micro-metastasis.