Dose response relationship of combination treatment of doxycycline with platinum compounds. 2 × 104 HT 29 cells/ml were treated in the wells of 24 well plates with cisplatin or oxaliplatin with and without 10 μg/ml of doxycycline for 24 hours. The cytotoxicity was assessed with Alamar blue assay according to the manufacturer's instructions. Data are depicted as means of six experiments ± standard deviation. (p = 0.84 for cisplatin and p = 0.95 for oxaliplatin experiments).