Figure 2: Effects of corosolic acid and oleanolic acid on STAT3 activation and cell proliferation in the tumor cells. U373 cells were incubated with the indicated concentrations of corosolic acid or oleanolic acid for three hours, after which the phosphorylated STAT3, STAT3, and -actin expression was determined using a Western blot analysis (a). Glioblastoma cells (U373 cells) and osteosarcoma cells (Saos2 cells, HSOS-1 cells, and LM8 cells) were incubated with the indicated concentrations of corosolic acid and oleanolic acid for 24 hours, after which the degree of cell proliferation was determined using a WST-8 assay (b). Ovarian carcinoma cells, SKOV3 and RMG-1 cells, were incubated with 10 μM of anticancer drugs (ADR: adriamycin; CDDP: cisplatin) during incubation with or without corosolic acid (20 μM) for 24 hours, after which the cell viability was determined using a WST-8 assay (c). The data are presented as the mean SD. *, ** versus control.