Seliciclib overcomes the protective effects conferred by BMSCs on MM cells via down-regulation of Mcl-1 transcription. MM 1.S cells were cultured in the presence of BMSCs. (A) Seliciclib resulted in inhibition of DNA synthesis of MM cells in the presence of BMSCs at 24 hours in a dose-dependent manner. Data represent the mean ± standard deviation of triplicate cultures. (B) Mcl-1 and pSTAT3 protein expression were both up-regulated in the coculture system and were inhibited by increasing doses of seliciclib for 6 hours. (C) Repression of Mcl-1 transcription was similarly noted by RT-PCR after 6 hours of exposure to seliciclib.