Effect of combined MAPK inhibition on long-term melanoma cultures. M238 and M792, two MAPK inhibitor-sensitive cell lines, were chronically exposed to 500nM of Vemurafenib (V), SCH722984 (E) or combination (V + E) in 96-well plates. A. Schematic. For each cell line, 20,000 cells/well were plated on 96-well plates. The following day, all cells on the plate were treated with 500nM of each drug or combination. Fresh media containing the appropriate inhibitor(s) was added weekly. When cells in several wells were confluent, viable cells were quantified by MTS assay and cell numbers were determined by comparing with a standard curve of known cell numbers. B. Microscopic imaging of treated M238 cells photographed at 14 days (top) or 44 days (bottom) of treatment. C. Quantitative analysis of viable cells for M792 at 44 days (V) or 84 days (E and V + E). D. Quantitative analysis of viable cells for M238 at 44 days (V), 140 days (E) or 280 days (V + E). The percentage of wells with 1–1,000 (white), 2,000-3,999 (tan), 4,000-5,999 (yellow), 6,000-7,999 (orange), 8,000-9,999 (red) and >10,000 (brown) viable cells are shown. Data are representative of triplicate independent experiments.