T47D:A18/PKCα cells are resistant to 4-OHT and RAL in 2D and 3D cell culture. DNA and Matrigel™ colony formation assays were performed as described in materials and methods. Cells were grown in the presence of vehicle (DMSO, 0.1%), E2 (10-9M), 4-OHT (10-7M) or RAL (10-7M) with media changes every three days. A. T47D:A18/neo cells. B. T47D:A18/PKCα cells. RFU, relative fluorescence units. C. Quantification of T47D:A18/PKCα colonies. Graphs are representative of at least three independent experiments and error bars represent SEM. *P < 0.05 compared to vehicle; by one-way ANOVA followed by Bonferroni’s post-test. D. Photographic representation of T47D:A18/PKCα colonies. Total magnification: 6X.