Primary tumor cells of myeloma patients induce interleukin-6 secretion in long-term bone marrow cultures

Abstract

Long-term bone marrow cultures (LTBMC) from patients with multiple myeloma (MM) and normal donors were analyzed for immunophenotype and cytokine production. Both LTBMC adherent cells from myeloma and normal donor origin expressed CD10, CD13, the adhesion molecules CD44, CD54, vascular cell adhesion molecule 1, very late antigen 2 (VLA-2), and VLA- 5, and were positive for extracellular matrix components fibronectin, laminin, and collagen types 3 and 4. LTBMC from myeloma patients and normal donors spontaneously secreted interleukin-6 (IL-6). However, levels of IL-6 correlated with the stage of disease; highest levels of IL-6 were found in LTBMC from patients with active myeloma. To identify the origin of IL-6 production, LTBMC from MM patients and normal donors were cocultured with BM-derived myeloma cells and cells from myeloma cell lines. IL-6 was induced by plasma cell lines that adhered to LTBMC such as ARH-77 and RPMI-8226, but not by nonadhering cell lines U266 and FRAVEL. Myeloma cells strongly stimulated IL-6 secretion in cocultures with LTBMC adherent cells from normal donors and myeloma patients. When direct cellular contact between LTBMC and plasma cells was prevented by tissue-culture inserts, no IL-6 production was induced. This implies that intimate cell-cell contact is a prerequisite for IL-6 induction. Binding of purified myeloma cells to LTBMC adherent cells was partly inhibited by monoclonal antibodies against adhesion molecules VLA-4, CD44, and lymphocyte function-associated antigen 1 (LFA-1) present on the plasma cell. Antibodies against VLA-4, CD29, and LFA-1 also inhibited the induced IL-6 secretion in plasma cell-LTBMC cocultures. In situ hybridization studies performed before and after coculture with plasma cells indicated that LTBMC adherent cells produce the IL-6. These results suggest that the high levels of IL-6 found in LTBMC of MM patients with active disease are a reflection of their previous contact with tumor cells in vivo. These results provide a new perspective on tumor growth in MM and emphasize the importance of plasma cell-LTBMC interaction in the pathophysiology of MM.

Abnormal cytokine production by bone marrow stromal cells of multiple myeloma patients in response to RPMI8226 myeloma cells

“…The induction of IL-6 in BMSCs from myeloma patients and normal donors by myeloma tumor cell lines has already been described by other authors [ 28 ]. It has been found that BMSCs of MM patients produce more IL-6 than those of healthy controls.…”

Aloperine executes antitumor effects against multiple myeloma through dual apoptotic mechanisms

“…The bone marrow microenvironment promotes MM proliferation and growth via the secretion of IL-6. IL-6 is a major growth factor and antiapoptotic cytokine for MM cells [ 32 ]; the importance of IL-6 as an autocrine growth factor for MM cells is widely accepted [ 24 ]. In the current experiment, aloperine overcame the proliferative effects of IL-6, IGF-I, and BMSCs, suggesting that aloperine could be efficacious in treating MM.…”

“…The purity of the MM cells was confirmed to be >90% via flow cytometric analysis using an anti-CD138 antibody (Miltenyi). CD138-negative mononuclear cells were also used to establish long-term BMSC cultures, as described previously [ 24 ]. BMSCs were obtained from MM patients and used between the third and fifth passages for all experiments.…”

A major role for Mcl-1 antiapoptotic protein in the IL-6-induced survival of human myeloma cells

“…Thus, these cell lines have kept the major characteristic of primary myeloma cells whose survival is strictly dependent on the addition of exogenous IL-6 (Klein et al, 1989;Gu et al, 2000). In patients with multiple myelome (MM), IL-6 is largely produced by bone marrow stromal cells, indicating a paracrine stimulation of tumor cell survival by their environment (Portier et al, 1991;Uchiyama et al, 1993;Lokhorst et al, 1994).…”

“…Human myeloma cells (HMCL) survive and proliferate in close contact with bone marrow stromal cells (Klein et al, 1989;Uchiyama et al, 1993;Lokhorst et al, 1994). Interleukin-6 (IL-6) is one of the survival factors delivered by stromal cells.…”