ABCG2 and breast carcinoma: Previously, we have shown that VP can be effluxed by ATP‐binding cassette (ABC) drug transporters (breast cancer resistance protein, ABCG2; and P‐glycoprotein, P‐gp), reducing PDT efficacy.[18] Using a human breast cancer cell line MCF‐7, and its sub‐lines ABCG2‐overexpressing MCF‐7 MX100 and or P‐gp‐overexpressing MCF‐7 TX400,[18, 32] we found that NanoVP remains a substrate of ABCG2 and P‐gp (Figure S11, Supporting Information).