Curcumin pre-treatment effectively lowers the cisplatin dose needed for inhibiting growth of cisplatin resistant A2780CP ovarian cancer cells. (A) Design of treatment method for curcumin sensitization followed by cisplatin treatment. Cisplatin resistant ovarian cancer cells (A2780CP) were either treated with curcumin or cisplatin alone for 48 hrs, or pre-treated with curcumin for 6 hrs followed by cisplatin for an additional 42 hrs. (B) Curcumin pre-treatment followed by cisplatin exposure decreases cell proliferation at lower doses of cisplatin. A2780CP cells were treated with either 2.5-40 μM of curcumin (CUR) or cisplatin (CIS) alone for 48 hrs or pre-treated with 10 or 20 μM curcumin for 6 hrs followed by 2.5-40 μM of cisplatin treatment for 42 hrs (CUR + CIS). Cell proliferation was determined by MTS assay and normalized to control cells treated with appropriate amounts of vehicle (DMSO or DMSO-PBS). Data represent mean ± SE of 6 repeats for each treatment and the experiment was repeated three times. (C) Phase contrast microscopic analysis reveals curcumin sensitization to cisplatin. Phase contrast images of A2780CP cells treated with vehicle (DMSO, control), 2.5 μM CIS for 48 hrs, 20 μM CUR for 48 hrs, and 20 μM CUR for 6 hrs followed by 2.5 μM CIS for 42 hrs. Bar equals 100 microns.