Abstract
Introduction. 5-Aminolevulinic Acid (5-ALA) is a precursor of heme synthesis. A metabolite, protoporphyrin IX (PpIX), selectively accumulates in neoplastic tissue including glioblastoma. Presurgical administration of 5-ALA forms the basis of fluorescence-guided resection (FGR) of glioblastoma (GBM) tumors. However, not all gliomas accumulate sufficient quantities of PpIX to fluoresce, thus limiting the utility of FGR. We therefore developed an assay to determine cellular and pharmacological factors that impact PpIX fluorescence in GBM. This assay takes advantage of a GBM cell line engineered to express yellow fluorescent protein. Methods. The human GBM cell line U87MG was transfected with a YFP expression vector. After treatment with a series of 5-ALA doses, both PpIX and YFP fluorescence were measured. The ratio of PpIX to YFP fluorescence was calculated. Results. YFP fluorescence permitted the quantification of cell numbers and did not interfere with 5-ALA metabolism. The PpIX/YFP fluorescence ratio provided accurate relative PpIX levels, allowing for the assessment of PpIX accumulation in tissue. Conclusion. Constitutive YFP expression strongly correlates with cell number and permits PpIX quantification. Absolute PpIX fluorescence alone does not provide information regarding PpIX accumulation within the cells. Our research indicates that our PpIX/YFP ratio assay may be a promising model for in vitro 5-ALA testing and its interactions with other compounds during FGR surgery.
Highlights
Glioblastoma multiforme (GBM) is the most common and aggressive primary malignant brain tumor
A valuable tool to achieve gross total resection and thereby increase progression-free survival is the use of 5-Aminolevulinic Acid (5-ALA) for fluorescence-guided resection (FGR) [2]. 5-ALA is a substrate of the heme biosynthesis pathway and is the source of carbon for porphyrin synthesis [3]
protoporphyrin IX (PpIX) fluorescence was compared between the eleven 5-ALA concentrations (0.0, 0.10, 0.20, 0.39, 0.78, 1.56, 3.13 6.25, 12.5, 25.0, and 50.0 mM) and the ten different time points (0, 8, 16, 24, 32, 40, 48, 56, 64, and 72 hours) using a two-way repeated measures analysis of variance (ANOVA)
Summary
Glioblastoma multiforme (GBM) is the most common and aggressive primary malignant brain tumor. Not all brain tumors accumulate sufficient quantities of PpIX to make the use of 5-ALA advantageous during surgery [5, 6], and it is not fully understood how 5-ALA might affect other physiological processes. At this time, it is unknown if prescribed medications of tumor patients or if drugs given to patients just prior to/during surgery interfere with 5-ALA synthesis and/or PpIX accumulation. It is unknown if prescribed medications of tumor patients or if drugs given to patients just prior to/during surgery interfere with 5-ALA synthesis and/or PpIX accumulation
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
