MCF7 and MDA-MB-231 cells were treated with oleandrin and culture supernatants were collected 0, 4, 8, 12, 24, and 48 h after treatment. A Secreted HMGB1 was detected by ELISA. B ATP secretion was detected by chemiluminescence assay. Data were acquired from three independent experiments. *p < 0.05, **p < 0.01 vs. 0 h cells. C Cell supernatants were collected and concentrated at 0, 24, and 48 h after oleandrin treatment. At the same time cell lysates were collected. The expression of HSP70 and HSP90 were detected by western blotting.