Figure 3

Doxycycline treatment enhances cytolytic capacity of CIK cells. (a) Initial tests determined the cytotoxicity of different treatments against different cell lines. Cells were treated with doxycycline (1; 10; 20 or 40 μgml⁻¹) or PXD101 (0.625 μM) for 24 h before. Cytotoxicity was determined as level of lactate dehydrogenase released into the medium relative to media alone (0% cytotoxicity), or lysed cells (100%). Doxycycline treatment did not result in significantly increased cytotoxicity (*P<0.05) for any cell lines or concentrations tested). (b) CIK mediated killing of selected cell lines. Human CIK cells (hCIK) were mixed with the indicated target tumor cells at the indicated effector:target ratios (between 5:1 and 100:1) which had or had not been treated with 1 μgml⁻¹ doxycycline for 24 h prior to the assay. Target cell survival was determined after 4 h by LDH assay as before.