TSA and ionizing radiation treated HCT116 cells increase surface levels of 41BBL protein more than OX40L protein. (A, B and F) OX40L, and (C, D and G) 41BBL protein expression on the surface of HCT116 cells was evaluated by flow cytometry. (E) Cells were untreated (0Gy) or treated with 10Gy radiation (IR). (H) In separate experiments HCT116 cells were untreated (DMSO) or treated with either TSA (250 nM). After 48 hr, cells were collected and stained with PE-labeled antibody to either OX40L and 41BBL. Control cell staining with a non-specific isotype control antibody was less than 5% positive. Isotype control staining is shown as the gray filled histogram and protein specific staining is shown as black line histogram for the FACS plot data graphed in E and H. Dotted line histogram in F and G indicates specific protein expression in untreated cells. Values shown on histograms are for treated cells and untreated and treated values are displayed graphically in H for comparison. Experiments were repeated three times with similar results.