Differential sensitivity in cell lines to photodynamic therapy in combination with ABCG2 inhibition.

•Compartmentalisation of PpIX in oesophageal OE19 adenocarcinoma cells protected cells from porphyrin phototoxicity.•The ABCG2 inhibitor Ko-143 incubation reversed PpIX compartmentalisation in OE19 cells and restored phototoxicity.•The type and concentration of porphyrin isomers detected differed between the four cell lines examined.