Mouse anti-human interleukin-6 receptor monoclonal antibody inhibits proliferation of fresh human myeloma cells in vitro

Humanized anti-interleukin-6 receptor monoclonal antibody induced apoptosis of fresh and cloned human myeloma cells in vitro

We investigated the effect of anti-IL-6 receptor monoclonal antibody (hPM1) on the in vitro proliferation of cloned and freshly isolated myeloma cells from 20 patients with advanced stage multiple myeloma (MM). Humanized PM1 significantly inhibited the growth of a myeloma cell line in a dose-dependent manner and inhibited more than 30% of the proliferation of fresh myeloma cells in 10 of the 19 cases. Flow cytometric analysis using annexin V and 7AAD showed that hPM1 induced apoptosis of myeloma cells. These observations suggest the possibility of using hPM1 for treating some patients with MM whose growth depends on IL-6.

Safety and kinetic properties of a humanized antibody to human interleukin-6 receptor in healthy non-human primates

A monoclonal antibody, hPM-1, was constructed by grafting the complementarity determining regions to human interleukin-6 (IL-6) receptor, raised in mouse, onto a human antibody backbone (humanized antibody). It is expected to be useful as a therapeutic agent for IL-6-related diseases such as multiple myeloma. To investigate the toxicological and kinetic properties of hPM-1 preliminarily, normal cynomolgus monkeys, which showed cross-reactivity with hPM-1, were intravenously administered with hPM-1 at doses of 0 (vehicle), 4 or 40 mg/kg once a week for 13 weeks. Upon toxicological examination, there were no changes in clinical signs, food consumption, body weights, urinalyses, body temperatures, electrocardiograms, hematological and biochemical parameters including blood platelet counts, serum levels of immunoglobulin G and C-reactive protein, and pathological findings. In a kinetic study, serum concentrations of hPM-1 showed a linearity between doses of 4 and 40 mg/kg. The serum concentrations, even at a dose of 4 mg/kg, were maintained at a high enough level to inhibit the IL-6 functions throughout the period of the study. Concentrations of hPM-1 in bone marrow were almost equal to those in serum. The antibodies against hPM-1 were detected only in one of four monkeys receiving hPM-1. This study suggests that blockage of the IL-6 receptor by hPM-1 does not induce any influence on a healthy living body, and hPM-1 is not toxic under the conditions of this investigation.

New Xenograft Model of Multiple Myeloma and Efficacy of a Humanized Antibody Against Human Interleukin-6 Receptor

A new xenograft model of multiple myeloma (MM), where growth is strongly regulated by interleukin-6 (IL-6), was established in severe combined immunodeficiency (SCID) mice. In this model, endogenous IL-6 from SCID mice was ineffective at eliciting growth of the established human MM cell line KPMM2; these cells achieved autonomous growth through their autocrine secretion of IL-6. The etiopathology in this disease model is consistent with that of human MM. When greater than 3 × 106 KPMM2 cells were injected intravenously (IV), tumors developed in all mice and were predominantly localized in their bone marrow. Tumors were also apparent in the lymph nodes, but absent from other organs. Immunostaining of cell surface antigen (CD38) showed that more than 40% of bone marrow cells in femur were of myeloma origin in the advanced stage of tumor progression (day 37). Histologic analysis of these mice show that bone marrow was largely occupied by plasmablastic cells and bones had developed osteolytic lesions at multiple sites. Concurrently, there was a decrease in bone density throughout the body and a significant increase in ionized plasma calcium. M-protein was detected in the serum within 10 days after transplantation, which correlated with the tumor progression. Between 30 and 40 days after the transplantation, mice presented with a rapid and severe loss of body weight, hind leg paralysis, and fatigue. Subsequently, the mice died within a week. A single IV injection of 0.2 mg humanized anti–IL-6 receptor antibody (hPM1) into mice on the day after tumor transplantation substantially suppressed the elevation of serum M-protein and development of the tumor-associated abnormalities and significantly increased in the life span of tumor-bearing mice. Our data show the usefulness of this model to analyze the pathologic role of IL-6 in MM and the efficacy of targeting the IL-6 receptor in IL-6–dependent KPMM2 cells.

New Xenograft Model of Multiple Myeloma and Efficacy of a Humanized Antibody Against Human Interleukin-6 Receptor

A new xenograft model of multiple myeloma (MM), where growth is strongly regulated by interleukin-6 (IL-6), was established in severe combined immunodeficiency (SCID) mice. In this model, endogenous IL-6 from SCID mice was ineffective at eliciting growth of the established human MM cell line KPMM2; these cells achieved autonomous growth through their autocrine secretion of IL-6. The etiopathology in this disease model is consistent with that of human MM. When greater than 3 × 106 KPMM2 cells were injected intravenously (IV), tumors developed in all mice and were predominantly localized in their bone marrow. Tumors were also apparent in the lymph nodes, but absent from other organs. Immunostaining of cell surface antigen (CD38) showed that more than 40% of bone marrow cells in femur were of myeloma origin in the advanced stage of tumor progression (day 37). Histologic analysis of these mice show that bone marrow was largely occupied by plasmablastic cells and bones had developed osteolytic lesions at multiple sites. Concurrently, there was a decrease in bone density throughout the body and a significant increase in ionized plasma calcium. M-protein was detected in the serum within 10 days after transplantation, which correlated with the tumor progression. Between 30 and 40 days after the transplantation, mice presented with a rapid and severe loss of body weight, hind leg paralysis, and fatigue. Subsequently, the mice died within a week. A single IV injection of 0.2 mg humanized anti–IL-6 receptor antibody (hPM1) into mice on the day after tumor transplantation substantially suppressed the elevation of serum M-protein and development of the tumor-associated abnormalities and significantly increased in the life span of tumor-bearing mice. Our data show the usefulness of this model to analyze the pathologic role of IL-6 in MM and the efficacy of targeting the IL-6 receptor in IL-6–dependent KPMM2 cells.

A possible growth factor role of IL-6 in neuroectodermal tumours

Preliminary data have shown that IL-6 may act as an autocrine growth factor to control proliferation. We further characterised the role of IL-6 in tumour growth as an autocrine/paracrine growth factor in neuroectodermal tumours. We evaluated the production and secretion of IL-6 by seven human melanoma, five neuroblastoma and one glioblastoma cell lines. Moreover, we determined their IL-6-dependent growth in serum free-medium or under minimal growth-supplement conditions: IL-6 dependent growth was observed in two non-IL-6 producing melanoma and in one neuroblastoma cell lines. In addition, expression of IL-6 mRNA and peptide was increased by retinoic acid. The data support the hypothesis that IL-6 contributes to neuroectodermal tumour growth, even though it shows a less potent effect than other reported growth factor such as IGF-II.

The influence of interleukin-6 on the growth of human esophageal cancer cell lines

We reported that human esophageal cancer cell lines (ECC) (YES-1, -2, -3, -4, -5, and -6) produced interleukin-6 (IL-6). We, therefore, investigated the growth effects ([3H]thymidine uptake assay and direct cell count) of IL-6 on these ECC. IL-6 receptor (R) and GP-130 mRNA were detected in all the ECC, using reverse transcriptase-polymerase chain reaction (RT-PCR) assay, and IL-6R was detected in one (YES-3) by immunohistochemical staining. IL-6, anti-IL-6 monoclonal antibody (mAb), or anti-IL-6R mAb caused no reproducible enhancement or suppression of [3H]thymidine uptake by all six ECC. Direct cell count also revealed that the growth enhancement or suppression by IL-6, anti-IL-6 mAb, or anti-IL-6R mAb was relatively small. Particularly, there was no significant sensitivity of YES-3 cells, which definitely produce IL-6 and express IL-6R for IL-6, anti-IL-6 mAb, or anti-IL6R mAb. These results suggest that some esophageal cancers may produce IL-6 and express IL-6R. However, no major interactions between IL-6 and the growth of human esophageal cancer cell lines were detected in this study.