NQO1 and cancer: Small-molecule tumor-selectivetheranostic fluorescent probes canbe activated in the tumor microenvironment through various mechanisms.These probes are sensitive to factors like low pH, overexpressed (bio)moleculesin cancer cells (e.g., GSH), redox imbalances (e.g., H2S, ROS), enzymes activated or enhanced under hypoxia (e.g., DT-diaphorase,azo-reductase, nitro-reductase), as well as other enzymes with increasedexpression levels in cancerous tissues (e.g., esterases, proteases),and combinations thereof.