Quantitative Modulation of PpIX Fluorescence and Improved Glioma Visualization

Area of Science:

• Oncology
• Biochemistry
• Surgical Technology

Background:

• 5-Aminolevulinic acid (5-ALA) induced Protoporphyrin IX (PpIX) fluorescence aids high-grade glioma surgical resection but suffers from variable tumor expression and interpretation.
• The epidermal growth factor receptor (EGFR) expression varies across different glioblastoma (GBM) cell lines, potentially influencing 5-ALA induced PpIX fluorescence.

Purpose of the Study:

• To investigate if pharmacological agents can increase 5-ALA induced PpIX fluorescence in different GBM cell lines with varying EGFR expression.
• To evaluate methods for quantitatively measuring PpIX concentration and its potential as an intraoperative surgical adjunct.

Main Methods:

• Analyzed 5-ALA induced PpIX fluorescence in three GBM cell lines using flow cytometry, fluorescence microplate reader, and confocal microscopy.
• Treated cells with tin protoporphyrin IX (SnPP), deferoxamine (DFO), and genistein to block PpIX breakdown or influence its transport.
• Developed a Qp9-microscope for quantitative PpIX concentration measurement and compared results with ex vivo tumor biopsy analysis.

Main Results:

• All tested GBM cell lines showed increased 5-ALA induced fluorescence after treatment with SnPP, DFO, or genistein, despite differing baseline fluorescence.
• The Qp9-microscope generated quantitative PpIX concentration maps of tumor samples, correlating with ex vivo measurements, though extraction methods yielded lower values.

Conclusions:

• Pharmacological augmentation of PpIX signal in GBM cell lines is achievable, offering a potential strategy to enhance fluorescence-guided surgery.
• Quantitative PpIX mapping using the Qp9-microscope shows feasibility for surgical guidance, warranting further validation against tumor tissue analysis for intraoperative application.