HIF1A and cancer: Long puzzling has been why the highly oxygen sensitive ‘hypoxia-inducible transcription factor’ HIF1α is inactivated by both the, until now thought very differently acting, ‘microtubule binding’ anti-cancer taxanes such as paclitaxel and the anti-cancer DNA intercalating topoisomerases such as topotecan or doxorubicin, as well as by frame-shifting mutagens such as acriflavine [36,37].