AX11890, an inhibitor of overexpressed enzyme, KIAA1363, in some breast cancers, was conjugated with a benzo[a]phenothiazinium photosensitizer to develop a tumor micro-environment-responsive photosensitizer NBS-L-AX. In normal cells, the special geometry of NBS-L-AX causes the fluorescence and photodynamic therapeutic (PDT) effect of NBS-L to be quenched. In cancer cells, when allowed to interact with the enzyme KIAA1363, the geometry of NBS-L-AX changes such that it becomes fluorescent and photodynamically active. Thus, the material of NBS-L-AX serves as an activated imaging and PDT treatment agent for breast cancers. In addition, NBS-L-AX also shows a selective inhibition effect against breast cancer cells.