Cancer and the Microenvironment

Abstract

We have investigated the interaction between tumor cells and specific cells in their microenvironment using myeloma as a model. The role of myeloma-induced osteoclastogenesis in the disease was studied ex vivo. Myeloma plasma cells freshly purified from patients' bone marrow attracted committed osteoclast (OC) precursors (n ‫؍‬ 9; P < 0.01) and in 22 experiments directly induced their differentiation to multinucleated, boneresorbing OCs (P < 0.00002) in a receptor activator of nuclear factor-B ligand-mediated mechanism that was inhibited by the receptor activator of nuclear factor-B (RANK-Fc) in 13 experiments by 71 ؎ 12% (P < 0.008). In contrast, myeloma cells did not induce differentiation of peripheral blood mononuclear cells. Myeloma plasma cells cocultured with OCs retained their viability and proliferative activity for >13 weeks. After 14 days in coculture, the plasma cells from 29 patients had higher viability (P < 2 ؋ 10 ؊6 ), fewer apoptotic cells (P < 4 ؋ 10 ؊15 ), and a higher bromodeoxyuridine labeling index (P < 0.0006) than controls. Physical contact between OCs and myeloma cells was required for these effects to take place. No differences were observed between OCs from healthy donors and those from myeloma patients. Blocking interleukin 6 activity, while reducing survival of myeloma cells, had no effect on their proliferative activity. These results support data obtained from animal models and clinical observations on the essential role of the microenvironment in tumor sustenance and progression.

Chondroitin Synthase 1 Is a Key Molecule in Myeloma Cell-Osteoclast Interactions

“…Osteoclast Serum-free Co-culture-It has been reported that in co-culture with myeloma cells, osteoclasts support survival and sustained proliferation of freshly purified primary myeloma cells for extended time periods and that this effect requires contact between myeloma cells and osteoclasts (10). Here we present confirmation of these results (Figs.…”

“…MM PCs were isolated using CD138 immunomagnetic bead selection and the autoMACs automated separation system (Miltenyi Biotec, Auburn, CA). Purity of MM PC preparations was determined by CD38/CD45 flow cytometry to be routinely 95% (10).…”

“…After removal of non-adherent cells, 95% of the remaining cells are multinucleated osteoclast (OC) and their precursors. Osteoclasts generated in these culture are multinucleated, TRAP-and vitronectin receptor-positive, and form resorption pits on mineralized discs; details have been described previously (10).…”

“…The data using the severe combined immunodeficient-human (SCID-hu) animal model indicate that osteoclasts, cells responsible for the breakdown of bone, facilitate survival and growth of myeloma cells (4 -7). Furthermore, it has been recently found that sustained survival and proliferation of purified primary myeloma cells in ex vivo cultures can be supported by osteoclasts alone in a contact-dependent manner (10).…”

Interference with nuclear factor kappa B and c-Jun NH2-terminal kinase signaling by TRAF6C small interfering RNA inhibits myeloma cell proliferation and enhances apoptosis

“…These experiments, however, were performed in the absence of the BM microenvironment, known to rescue MM cells from cell death and contribute to the growth of the malignant cells (Pagnucco et al, 2004;Yaccoby et al, 2004;Vincent and Mechti, 2005). To assess the ability of TRAF6C siRNA to interfere with the growth of MM cells within the protective BM microenvironment, 8226/ GFP myeloma cells were transfected with siTRAF6C or siGAPDH and injected into the femoral BM of irradiated mice.…”