Mangostin enhances efficacy of aminolevulinic acid-photodynamic therapy against cancer through inhibition of ABCG2 activity

Background: Aminolevulinic acid-photodynamic therapy (ALA-PDT) is gaining attention as a potential method for treating select cancers due to its high specificity and low side effect feature. ALA enters cancer cells and accumulate as protoporphyrin IX (PpIX), which will then trigger phototoxicity following light irradiation. However, it is reported that some cancer cells have reduced efficacy of ALA-PDT due to high expression of ABCG2, a transporter involved in the PpIX efflux. In this study, we evaluated the effect of mangostin, a natural compound containing anti-tumor property, on the efficacy of ALA-PDT against cancer and the mechanism involved.Methods: We utilized TMK1 gastric cancer cell line, which has high ABCG2 expression, to evaluate the PpIX accumulation and phototoxicity exerted by ALA and mangostin co-addition.Results: We found that co-addition of ALA and mangostin significantly increase the phototoxicity and PpIX accumulation in TMK1 cells. We also investigated the effect of mangostin on porphyrinheme pathway enzymes and ABCG2 and found that the addition of mangostin reduce the activity of ABCG2, reducing PpIX efflux.Conclusion: These findings suggest that mangostin enhances the efficacy of ALA-PDT in cancer through inhibition of ABCG2 activity.