['To investigate the mechanism of interleukin 6 (IL-6) overexpression in multiple myeloma(MM).', 'Human myeloma cells(KM3) and bone marrow stromal cells(BMSCs) were fixed by paraformaldehyde. KM3 cells and BMSCs (fixed and non-fixed) were co-cultured in 10%FCS-RPMI1640. IL-6 activity in the supernatant was determined by B9 cell proliferation test.', 'Both non-fixed myeloma cells and BMSCs could automatically secret IL-6, while the fixed cells did not. Co-cultures of fixed one with non-fixed the other of either kind of the cells could significantly increase the IL-6 activity in the supernatants. The promoting effect on IL-6 production was greater in BMSCs from MM patients than that in BMSCs from normal controls.'] Are [ Both myeloma cells and bone marrow stromal cells involved in the overproduction of interleukin 6 in multiple myeloma ]?