Enzastaurin-treated (0.5 and 1 μM) or untreated MM. 1S cells were exposed to bortezomib (0.5 and 1 mM), lenalidomide (0.5 and 2 nM), and melphalan (0.5 and 2 μM). Proliferation was measured using [³H]-thymidine uptake during the last 10 hours of 48-hour cultures. FA indicates the fraction of cells with growth affected in drug-treated versus untreated cells. CI indicates the combination index. CI<1 synergism, CI=0.9-1.1 additive effects. The results shown are representative of 3 independent experiments performed in quadruplicate.