Recombinant human erythropoietin (rHuEpo) has been used successfully in the treatment of cancer-related anemia. Clinical observations with several patients with multiple-myeloma treated with rHuEpo has shown, in addition to the improved quality of life, a longer survival than expected, considering the poor prognostic features of these patients. Based on these observations, we evaluated the potential biological effects of rHuEpo on the course of tumor progression by using murine myeloma models (MOPC-315-IgAλ₂and 5T33 MM-IgG_2b). Here we report that daily treatment of MOPC-315 tumor-bearing mice with rHuEpo for several weeks induced complete tumor regression in 30–60% of mice. All regressors that were rechallenged with tumor cells rejected tumor growth, and this resistance was tumor specific. The Epo-triggered therapeutic effect was shown to be attributed to a T cell-mediated mechanism. Serum Ig analysis indicated a reduction in MOPC-315 λ light chain in regressor mice. Intradermal inoculation of 5T33 MM tumor cells followed by Epo treatment induced tumor regression in 60% of mice. The common clinical manifestation of myeloma bone disease in patients with multiple-myeloma was established in these myeloma models. Epo administration to these tumor-bearing mice markedly prolonged their survival and reduced mortality. Therefore, erythropoietin seems to act as an antitumor therapeutic agent in addition to its red blood cell-stimulating activity.

Synthetic peptides and their respective antibodies have been used in order to map the alpha-bungarotoxin binding site within the alpha subunit of the acetylcholine receptor. By using antibodies to a synthetic peptide corresponding to residues 169-181 of the alpha subunit, we demonstrate that this sequence is included within the 18-kDa toxin binding fragment previously reported. Furthermore, the 18-kDa fragment was also found to bind a monoclonal antibody (5.5) directed against the cholinergic binding site. Sequential proteolysis of the acetylcholine receptor with trypsin, prior to Staphylococcus aureus V8 protease digestion, resulted in a 15-kDa toxin binding fragment that is included within the 18-kDa fragment but is shorter than it only at its carboxyl terminus. This 15-kDa fragment therefore initiates beyond Asp-152 and terminates in the region of Arg-313/Lys-314. In addition, experiments are reported that indicate that in the intact acetylcholine receptor, Cys-128 and/or Cys-142 are not crosslinked by disulfide bridges with any of the cysteines (at positions 192, 193, and 222) that reside in the 15-kDa toxin binding fragment. Finally, the synthetic dodecapeptide Lys-His-Trp-Val-Tyr-Tyr-Thr-Cys-Cys-Pro-Asp-Thr, which is present in the 15-kDa fragment (corresponding to residues 185-196 of the alpha subunit) was shown to bind alpha-bungarotoxin directly. This binding was completely inhibited by competition with d-tubocurarine.

Erythropoietin (EPO) primarily regulates red blood cell formation, and EPO serum levels are increased on hypoxic stress ( e.g. , anemia and altitude). In addition to anemia, recent discoveries suggest new therapeutic indications for EPO, unrelated to erythropoiesis. We investigated the skeletal role of EPO using several models of overexpression (Tg6 mice) and EPO administration (intermittent/continuous, high/low doses) in adult C57B16 female mice. Using microcomputed tomography, histology, and serum markers, we found that EPO induced a 32%‐61% trabecular bone loss caused by increased bone resorption (+60%‐88% osteoclast number) and reduced bone formation rate (‐19 to ‐74%; P < 0.05 throughout). EPO targeted the monocytic lineage by increasing the number of bone monocytes/macrophages, preosteoclasts, and mature osteoclasts. In contrast to the attenuated bone formation in vivo , EPO treatment in vitro did not inhibit osteoblast differentiation and activity, suggesting an indirect effect of EPO on osteoblasts. However, EPO had a direct effect on preosteoclasts by stimulating osteoclastogenesis in isolated cultures (+60%) via the Jak2 and PI3K pathways. In summary, our findings demonstrate that EPO negatively regulates bone mass and thus bears significant clinical implications for the potential management of patients with endogenously or therapeutically elevated EPO levels.—Hiram‐Bab, S., Liron, T., Deshet‐Unger, N., Mittelman, M., Gassmann, M., Rauner, M., Franke, K., Wielockx, B., Neumann, D., Gabet, Y. Erythropoietin directly stimulates osteoclast precursors and induces bone loss. FASEB J. 29, 1890‐1900 (2015). www.fasebj.org

To investigate which parts of the acetylcholine receptor are involved in the initiation and development of myasthenia gravis (MG), peptides representing different sequences of the human acetylcholine receptor alpha-subunit were synthesized. These peptides were tested for their ability to stimulate T cells of myasthenic patients and healthy control patients in proliferation assays and to bind to sera antibodies. Three of eight peptides discriminated significantly between the two groups in the proliferation assay, as well as in their ability to bind to serum antibodies. HLA-DR3 and DR5 were associated with proliferative responses to specific AChR peptides in the group of myasthenics. Acetylcholine receptor epitopes that might play a specific role in myasthenia gravis thus were demonstrated.