HMOX1 and cancer: HO-1 expression is also induced by exposure to cytotoxic chemotherapies (CCTs) (105, 106) and provides a mechanism of resistance to CCTs such as; etoposide, doxorubicin, gemcitabine and cisplatin (45, 106–108), as well as other classes of anti-cancer drugs such as sapatinib, a pan-Her family kinase inhibitor (109).