Kinetics of porphyrin fluorescence accumulation in pediatric brain tumor cells incubated in 5-aminolevulinic acid.
BACKGROUND
Fluorescence-guided surgery with 5-aminolevulinic acid (5-ALA) enables more complete resections of tumors in adults. 5-ALA elicits accumulation of fluorescent porphyrins in various cancerous tissues, which can be visualized using a modified neurosurgical microscope with blue light. Although this technique is well established in adults, it has not been investigated systematically in pediatric brain tumors. Specifically, it is unknown how quickly, how long, and to what extent various pediatric tumors accumulate fluorescence. The purpose of this study was to determine utility and time course of 5-ALA-induced fluorescence in typical pediatric brain tumors in vitro.


METHODS
Cell cultures of medulloblastoma [DAOY and UW228], cPNET [PFSK] atypical teratoid rhabdoid tumor [BT16] and ependymoma [RES196] were incubated with 5-ALA for either 60 minutes or continuously. Porphyrin fluorescence intensities were determined using a fluorescence-activated cell sorter (FACS) after 1, 3, 6, 9, 12 and 24 hours. C6 and U87 cells served as controls.


RESULTS
All pediatric brain tumor cell lines displayed fluorescence compared to their respective controls without 5-ALA (p < 0.05). Sixty minutes of incubation resulted in peaks between 3 and 6 hours, whereas continuous incubation resulted in peaks at 12 hours or beyond. 60 minute incubation peak levels were between 52 and 91 % of maxima achieved with continuous incubation. Accumulation and clearance varied between cell types.


CONCLUSIONS
We demonstrate that 5-ALA exposure of cell lines derived from typical pediatric central nervous system (CNS) tumors induces accumulation of fluorescent porphyrins. Differences in uptake and clearance indicate that different application modes may be necessary for fluorescence-guided resection, depending on tumor type.
Department of Neurosurgery, University Hospital, Albert-Schweitzer-Campus 1, Gebäude A1, D-48149, Münster, Germany, Michael.Schwake@ukmuenster.de.
Michael
M
Schwake
Dennis
D
Günes
Michaela
M
Köchling
Angela
A
Brentrup
Juliane
J
Schroeteler
Marc
M
Hotfilder
Michael C
MC
Fruehwald
Walter
W
Stummer
Christian
C
Ewelt
D000622:Aminolevulinic Acid / Q000494:pharmacology*; D001932:Brain Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D002648:Child; D004806:Ependymoma / Q000378:metabolism*; D005453:Fluorescence; D006801:Humans; D008527:Medulloblastoma / Q000378:metabolism*; D017319:Photosensitizing Agents / Q000378:metabolism*; D011166:Porphyrins / Q000378:metabolism*; D018335:Rhabdoid Tumor / Q000378:metabolism*
D017319:Photosensitizing Agents; D011166:Porphyrins; D000622:Aminolevulinic Acid