Lack of protection from DMC by IL-6 and IGF-1. RPMI8226 and 8226/Dox40 MM cells were cultured in regular growth medium with or without exogenously added human IL-6 (25 ng/mL) and IGF-1 (200 ng/mL). DMC at various concentrations was added for 72 hours, and MTT assays were performed as described in “Materials and methods.” Shown are the mean values of n equal to 8, plus or minus SE.