HIF1A and neoplasm: Cardenolides like uscharin, calotropin, calactin, 2′‐oxovoruscharin, 19‐dihydrocalactin, 19‐dihydrocalotoxin, 15‐β hydroxy uscharin, asclepin and calotropagenin have been known to inhibit Na+/K+ATPase and HIF‐1α activity, which are important for tumour metastasis.