A Review on the Design, Synthesis, and Structure-activity Relationships ofBenzothiazole Derivatives against Hypoxic Tumors

There has been a growing body of studies on benzothiazoles and benzothiazole derivatives as strong and effective anti-tumor agents against lung, liver, pancreas, breast, and brain tumors. Due to the highly proliferative nature of the tumor cells, the oxygen levels get lower than that of normal tissues in the tumor microenvironment. This situation is called hypoxia and has been associated with increased ability for carcinogenesis. For the drug design and development strategies, the hypoxic nature of the tumor tissues has been exploited more aggressively. Hypoxia itself acts as a signal initiating system to activate the pathways that eventually lead to the spread of the tumor cells into the different tissues, increases the rate of DNA damage, and eventually ends up with more mutation levels that may increase the drug resistance. As one of the major mediators of hypoxic response, hypoxia-inducible factors (HIFs) have been shown to activate angiogenesis, metastasis, apoptosis resistance, and many other protumorigenic responses in cancer development. In the current review, we will be discussing the design, synthesis, and structureactivity relationships of benzothiazole derivatives against hypoxic tumors such as lung, liver, pancreas, breast, and brain as potential anti-cancer drug candidates. The focus points of the study will be the biology behind carcinogenesis and how hypoxia contributes to the process, recent studies on benzothiazole and its derivatives as anti-cancer agents against hypoxic cancers, conclusions, and future perspectives. We believe that this review will be useful for researchers in the field of drug design during their studies to generate novel benzothiazole-containing hybrids against hypoxic tumors with higher efficacies.