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Myeloma is a unique hematologic malignancy that exclusively homes in the bone marrow and induces massive osteoclastic bone destruction presumably by producing cytokines that promote the differentiation of the hematopoietic progenitors to osteoclasts (osteoclastogenesis). It is recognized that neighboring bone marrow stromal cells influence the expression of the malignant phenotype in myeloma cells. This study examined the role of the interactions between myeloma cells and neighboring stromal cells in the production of osteoclastogenic factors to elucidate the mechanism underlying extensive osteoclastic bone destruction. A murine myeloma cell line 5TGM1, which causes severe osteolysis, expresses alpha(4)beta(1)-integrin and tightly adheres to the mouse marrow stromal cell line ST2, which expresses the vascular cell adhesion molecule-1 (VCAM-1), a ligand for alpha(4)beta(1)-integrin. Co-cultures of 5TGM1 with primary bone marrow cells generated tartrate-resistant acid phosphatase-positive multinucleated bone-resorbing osteoclasts. Co-cultures of 5TGM1 with ST2 showed increased production of bone-resorbing activity and neutralizing antibodies against VCAM-1 or alpha(4)beta(1)-integrin inhibited this. The 5TGM1 cells contacting recombinant VCAM-1 produced increased osteoclastogenic and bone-resorbing activity. The activity was not blocked by the neutralizing antibody to known osteoclastogenic cytokines including interleukin (IL)-1, IL-6, tumor necrosis factor, or parathyroid hormone-related peptide. These data suggest that myeloma cells are responsible for producing osteoclastogenic activity and that establishment of direct contact with marrow stromal cells via alpha(4)beta(1)-integrin/VCAM-1 increases the production of this activity by myeloma cells. They also suggest that the presence of stromal cells may provide a microenvironment that allows exclusive colonization of myeloma cells in the bone marrow. (Blood. 2000;96:1953-1960)

Osteolytic bone destruction and its complications, bone pain, pathologic fractures, and hypercalcemia, are a major source of morbidity and mortality in patients with multiple myeloma. The bone destruction in multiple myeloma is due to increased osteoclast (OCL) activity and decreased bone formation in areas of bone adjacent to myeloma cells. The mechanisms underlying osteolysis in multiple myeloma in vivo are unclear. We used a human plasma cell leukemia cell line, ARH-77, that has disseminated growth in mice with severe combined immunodeficiency (SCID) and expresses IgG kappa, as a model for human multiple myeloma, SCID mice were irradiated with 400 rads and mice were injected either with 10(6) ARH-77 cells intravenously (ARH-77 mice) or vehicle 24 hours after irradiation. Development of bone disease was assessed by blood ionized calcium levels, x-rays, and histology. All ARH-77, but none of control mice that survived irradiation, developed hind limb paralysis 28 to 35 days after injection and developed hypercalcemia (1.35 to 1.46 mmol/L) a mean of 5 days after becoming paraplegic. Lytic bone lesions were detected using x-rays in all the hypercalcemic mice examined. No lytic lesions or hypercalcemia developed in the controls. Controls or ARH-77 mice, after developing hypercalcemia, were then killed and bone marrow plasma from the long bones were obtained, concentrated, and assayed for bone-resorbing activity. Bone marrow plasma from ARH-77 mice induced significant bone resorption in the fetal rat long bone resorption assay when compared with controls (percentage of total 45Ca released = 35% +/- 4% v 11% +/- 1%). Histologic examination of tissues from the ARH-77 mice showed infiltration of myeloma cells in the liver and spleen and marked infiltration in vertebrae and long bones, with loss of bony trabeculae and increased OCL numbers. Interestingly, cultures of ARH-77 mouse bone marrow for early OCL precursors (colony-forming unit-granulocyte-macrophage [CFU-GM]) showed a threefold increase in CFU-GM from ARH-77 marrow versus controls (185 +/- 32 v 40 +/- 3 per 2 x 10(5) cell plated). Bone-resorbing human and murine cytokines such as interleukin-6 (IL-6), IL-1 alpha or beta, TGF-alpha, lymphotoxin, and TNF alpha were not significantly increased in ARH-77 mouse sera or marrow plasma, compared with control mice, although ARH-77 cells produce IL-6 and lymphotoxin in vitro. Conditioned media from ARH-77 cells induced significant bone resorption in the fetal rat long bone resorption assay when compared with untreated media (percentage of total 45Ca released = 22% +/- 2% v 11% +/- 1%). This effect was not blocked by anti-IL-6 or antilymphotoxin (percentage of total 45Ca released = 19% +/- 1% and 22% +/- 1%, respectively). Thus, we have developed a model of human multiple myeloma bone disease that should be very useful to dissect the pathogenesis of the bone destruction in multiple myeloma.

Chromosomes have been studied in cultures of nucleated peripheral blood cells in 30 patients with myeloma. Both unstimulated cultures and cultures stimulated by phytohemagglutinin (PHA) were examined in all cases. Mitoses were observed in 13 unstimulated cultures of peripheral blood from 12 cases, providing evidence for the presence of circulating abnormal cells in these patients. In 19 stimulated cultures of peripheral blood from 17 cases, abnormal mitoses were present, seven of these included abnormalities involving a chromosome of group 13-15. In five cases, a large acrocentric chromosome was observed similar to that previously described in some cases of myeloma. In eight cases, chromosome studies were also carried out on bone marrow to allow comparison of methods. Examination of stimulated peripheral blood cells was found to be the better method. Marked aneuploidy was not a feature of the results. No correlation was found between the cytogenetic abnormalities and previous treatment, disease stage, further progression of the disease, or serum and urinary protein abnormalities. The results are discussed, particularly with reference to technical factors influencing the frequency of demonstrable chromosome abnormalities in these cases and the relative merits of examination of peripheral blood and bone marrow.