| Induction of Multilineage Markers in Human Myeloma Cells and Their Down-Regulation by Interleukin 6
Abstract
Human primary myeloma cells are well known to be heterogeneous with regard to morphology and surface phenotype.We
confirmed the heterogeneous expression of such multilineage markers as CD33, CD7, CD56, CD4, and CD86 in primary
myeloma cells from 20 patients with multiple myeloma and in 8 human myeloma cell lines. CD33 expression in the Liu01 cell
line, a subclone of U266 cells, and in vitamin D3–treated ILKM3 cells, correlated with a monocytoid morphology featuring convoluted
nuclei and with increased C/EBPa expression.CD56+ myeloma cells from some myeloma patients and the CD56+ (but
not the CD56–) myeloma cell lines expressed neuronal cell markers, such as neuron-specific enolase and b-tubulin III. CD7
expression in Liu01 cells and forskolin-stimulated U266 cells coincided with the presence of large cytoplasmic granules, and
these cells featured increased expression of perforin messenger RNA and significant natural killer cell activity. Interleukin 6
(IL-6), a growth factor for myeloma cells, down-regulated CD33, CD7, or CD56 expression in primary myeloma cells, as well
as in Liu01 cells. Therefore, these data suggest that human myeloma cells are capable of inducing the expression of multilineage
markers and that IL-6 can down-regulate such expression. |