BACKGROUND: Since the ATP-binding cassette transporter ABCG2 plays a 
physiologically significant role of porphyrin efflux from living cells, the 
expression of ABCG2 may influences the efficacy of photodynamic therapy (PDT). 
In this study, we evaluated the effect of gefitinib, a potent ABCG2 inhibitor, 
on 5-aminolevulinic acid (5-ALA)-PDT in brain tumor cell lines in vitro.
MATERIALS AND METHODS: Four human glioma cell lines (U87MG, U118MG, A172, and 
T98G) and a malignant meningioma cell line (IOMM-Lee) were incubated with 
gefitinib (0.01-1.0μM) before incubation with 5-ALA (1mM). The effects gefitinib 
on intracellular protoporphyrin IX (PpIX), mRNA and protein expression of ABCG2, 
and PDT were evaluated, in vitro.
RESULTS: At concentrations of 0.1μM or higher, gefitinib enhanced intracellular 
levels of PpIX in a dose-dependent manner in all those cell lines. Gefitinib 
decreased mRNA and plasma membrane protein expression of ABCG2, and efficiently 
enhanced the effect of 5-ALA-PDT in malignant brain tumor cells.
CONCLUSION: Gefitinib can inhibit ABCG2-mediated PpIX efflux from malignant 
brain tumor cells to increase the intracellular PpIX and thereby enhance the PDT 
effect.