HPGDS and cancer: Some of the conventional anti-cancer drugs, such as chlorambucil [29,61,62,63], cyclophosphamide [29,63], melphalan [29,62,63,64], carmustine [29,55,62], cisplatin [65], busulfan [66], and thiotepa [29,63,67], are also substrates for GSTs and can be directly inactivated through conjugation reaction with glutathione (Table 1).