Figure 1 showed that there was correlation between IL-6 and TNFα level in bone marrow aspirate samples of patients. We examined whether TNFα could be the stimulator that releases IL-6 from multiple myeloma cells. In U266 cells, IL-6 secretion was markedly increased in response to TNFα, whereas other MM cell lines did not show drastic IL-6 secretion. As shown in Figure 2, IL-6 concentration was 1.5 folds higher in TNFα-treated U266 cells compared with untreated cells. However, induction of IL-6 by TNFα treatment was not detected in IM9 cells. Here, TNF is linked to plasma cell myeloma.