Canine B-cell lymphoma (CBL) is an incurable, spontaneous lymphoid malignancy constituting an accurate animal model for testing novel therapeutic strategies in human medicine. Resources of available species-specific therapeutic monoclonal antibodies (mAbs) targeting CBL are scarce. The aim of the present study was to evaluate the therapeutic potential of mAb B5, specific for the dog leukocyte antigen DR (DLA-DR) and its antibody-drug conjugate with methotrexate (B5-MTX). B5 induced caspase-dependent apoptosis of DLA-DR-expressing canine B cell lymphoma/CLBL1 and CLB70 leukemia lines, but not the GL-1 line not expressing DLA-DR. The cytotoxicity of B5-MTX to sensitive cells was further potentiated by a payload of MTX, but without any substantial off-target effects. The infusion of B5 and B5-MTX in a murine model of disseminated, advanced canine lymphoma, mediated >80% and >90% improvement in survival, respectively, and was well tolerated by the animals. Interestingly, the concentrations of soluble DLA-DR (sDLA-DR) antigens present in the blood serum of tumor-bearing mice were found proportional to the tumor burden. On this basis, sDLA-DR levels were evaluated as a potential biomarker using samples from canine lymphoma patients. In summary, the action of B5 and B5-MTX holds promise for further development as an alternative/complementary option for the diagnosis and treatment of canine lymphoma.

Emery–Dreifuss muscular dystrophy type 1 (EDMD1) is a rare genetic disease caused by mutations in the EMD gene, which encodes the nuclear envelope protein emerin. Despite understanding the genetic basis of the disease, the molecular mechanism underlying muscle and cardiac pathogenesis remains elusive. Progress is restricted by the limited availability of patient-derived samples; therefore, there is an urgent need for human-specific cellular models. In this study, we present the generation and characterization of induced pluripotent stem cell (iPSC) lines derived from EDMD1 patients carrying EMD mutations that lead to truncated or absent emerin, together with iPSCs from healthy donor. The patient-specific iPSCs exhibit stable karyotypes, maintain appropriate morphology, express pluripotency markers, and demonstrate the ability to differentiate into three germ layers. To model EDMD1, these iPSCs were differentiated into myogenic progenitors, myoblasts, and multinucleated myotubes, which represent all stages of myogenesis. Each developmental stage was validated by the presence of stage-specific markers, ensuring the accuracy of the model. We present the first iPSC-based in vitro platform that captures the complexity of EDMD1 pathogenesis during myogenesis. This model can significantly contribute to understanding disease mechanisms and develop the targeted therapeutic strategies for EDMD1.

Emery-Dreifuss muscular dystrophy type 1 (EDMD1) is a rare genetic disease caused by mutations in the EMD gene, which encodes the nuclear envelope protein emerin. Despite understanding the genetic basis of the disease, the molecular mechanism underlying muscle and cardiac pathogenesis remains elusive. Progress is restricted by the limited availability of patient-derived samples, therefore there is an urgent need for human-specific cellular models. In this study, we present the generation and characterization of induced pluripotent stem cell (iPSC) lines derived from EDMD1 patients carrying EMD mutations that lead to truncated or absent emerin, together with iPSCs from healthy donor. The patient-specific iPSCs exhibit stable karyotypes, maintain appropriate morphology, express pluripotency markers and demonstrate the ability to differentiate into three germ layers. To model EDMD1, these iPSCs were differentiated into myogenic progenitors, myoblasts and multinucleated myotubes, which represent all stages of myogenesis. Each developmental stage was validated by the presence of stage-specific markers, ensuring the accuracy of the model. We present the first iPSC-based in vitro platform that captures the complexity of EDMD1 pathogenesis during myogenesis. This model can significantly contribute to understanding disease mechanisms and develop the targeted therapeutic strategies for EDMD1.