Low-dose enzastaurin enhances cytotoxicity of low-dose bortezomib, lenalidomide, and melphalan. Enzastaurin-treated (1 μM) or untreated MM.1S cells were exposed to bortezomib (1 nM), lenalidomide (2 μM), and melphalan (2 μM). MTT cleavage was measured during the last 4 hours of 48-hour cultures. Values represent the mean ± SD absorbance of quadruplicate cultures.