ALA 4 ALA derivatives 4 Aminolevulinic Acid 4 Aminolevulinic acid 4 Animals 4 Apoptosis 4 Cell Survival 4 Mice 4 Microscopy, Fluorescence 4 PDT 4 Photochemotherapy 4 Photodynamic therapy 4 Photosensitizing Agents 4 Tumor Cells, Cultured 4 aminolevulinic acid 4 aminolevulinic acid hexyl ester 4 aminolevulinic acid methyl ester 4 animal cell 4 apoptosis 4 article 4 cell death 4 cell viability 4 concentration response 4 cytotoxicity 4 drug diffusion 4 mouse 4 nonhuman 4 photodynamic therapy 4 photosensitization 4 phototoxicity 4