Highly malignant tumor cells accumulate less PpIX and enhanced cell dormancy increases PpIX accumulation

Area of Science:

• Biomedical Engineering
• Oncology
• Photochemistry

Background:

• 5-Aminolevulinic acid photodynamic diagnosis (ALA-PDD) detects cancer by fluorescence from protoporphyrin IX (PpIX) in tumor cells.
• False negatives in ALA-PDD occur when tumor cells accumulate low PpIX levels.
• Understanding PpIX accumulation factors is crucial for improving ALA-PDD sensitivity.

Purpose of the Study:

• To identify factors influencing 5-Aminolevulinic acid (ALA)-induced PpIX accumulation in tumor cells.
• To characterize tumor cells based on their differential PpIX accumulation levels.

Main Methods:

• Tumor cells were sorted into high and low PpIX accumulation groups using Fluorescence-Activated Cell Sorting (FACS).
• Cellular characteristics, including malignancy markers, transporter activity, iron metabolism, proliferation, and glucose metabolism, were compared between the groups.

Main Results:

• Tumor cells with low PpIX accumulation exhibited higher malignancy, indicated by RANKL expression.
• Differences in PpIX efflux transporter activity and iron insertion into the porphyrin ring were observed.
• Tumor cells with high PpIX accumulation showed characteristics of dormancy, including low proliferation and suppressed glucose metabolism.

Conclusions:

• Tumor cells with low PpIX accumulation are associated with high tumor grade.
• Low PpIX accumulation correlates with low cell dormancy.
• These findings provide insights into optimizing ALA-PDD for more accurate cancer diagnosis.