CD81 and neoplasm: The expression levels of BCL-2 (P < 0.01), clCasp3 (P = 0.04), Ki-67 (P = 0.04) and CD81 which has been associated with chemoresistant MM tumor cells [47] (P < 0.01), were significantly higher in RRMM than in NDMM samples (Fig. 1B) consistent with a more aggressive disease.