Inhibition of clonogenicity of the CER variants with a combination treatment. We added Celecoxib (10 µM) or the DMSO solvent (as a control) along with different concentrations of doxorubicin or paclitaxel (taxol) at day 1. A and B, SUM149-CER cells (passage 5) were plated at 7,500 cells per 10 cm dish in a low FBS (0.5%) medium as described in Materials and Methods and stained at day 25. C and D, BSC60-CER cells (passage 4) were plated at 7,500 cells per 10 cm dish in medium with normal amount of FBS (10%) and stained at day 13. Comparison of the plates showed that 1) the CER variants are inhibited with celecoxib in this assay, and 2) celecoxib cooperates with the chemotherapy drugs to inhibit clonogenicity.