Multiple Myeloma is a tumor of the bone marrow, induced by B cells and the malignant proliferation of abnormal plasma cells. It is therefore defined as plasmocytoma and belongs to the group of B cell Non-Hodgkin-lymphomas.
Usually plasma cells, which migrated into the lymphatic system, produce functional antibodies. During Multiple Myeloma abnormal cells secrete dysfunctional antibodies or antibody fragments, so called para-proteins. This overproduction of monoclonal antibodies leads on the one hand to reduced production of normal, functional antibodies and thus to a immunodeficiency of the patient. On the other hand it causes a build-up of proteins within the blood and organs, which results in dysfunctionalities and loss of function of organs like the kidneys.
The origin of the malignant tumor cells from the bone marrow leads to the indirect activation of so called osteoclasts. These specialized cells resorb the bones and release a high amount of calcium into the blood (“hypercalcemia”). Massive instability of the bone structure and disordered creation of red and white blood cells are then consequences of osteoclast activation.
The conventional therapies of Multiple Myeloma are dependent on the stages of disease. Stages can be determined by calcium and red blood cell counts within the blood, osteoclast infestation of the bones as visible in X-ray and concentration of para-proteins in the blood and urine. Therapy usually starts with unspecific, anti-inflammatory drugs (eg. glucocorticoids). As disease progresses, a cyclic chemotherapy and local radiation for increased osteolysis is applied.
Stem cell transplantations (autologous, even allogenic) are a promising approach and therapy of choice, especially for young, physically stable patients.
Recent development in the field of characterization of the cause and signal pathways of Multiple Myeloma allow for improved drug-based, conventional therapies. Nevertheless, the mean 5-year survival rate after diagnosis is less than 29 %. The generation of new therapeutics and therapy approaches is thus of utmost social and scientific importance.
The task of EMI
To circumvent the pitfalls of conventional therapies, we cooperate with the university Würzburg/Giessen (Prof. Gattenlöhner) and the university de Barcelona to create innovative, selective targeting therapies: Typical surface proteins of the malignant cells of Multiple Myeloma are targeted by highly specific antibodies. The discrimination between affected and normal plasma cells allows the selective use of therapeutically relevant substances, such as apoptosis-inducing or proliferation-inhibiting toxins.
Within this project the Phage-Display method is used to select plasmocytoma-specific, recombinant antibody fragment, so called scFv (single chain variable fragment).
As source for the selection we utilized the human antibody library HAL7/8, kindly provided by Prof. Dr. Stefan Dübel (TU Braunschweig, Germany).
This project aims particularly at the selection of MM-specific, internalizing antibodies, to be able to generate therapeutic antibody derivatives. In a first step, the antibody libraries were depleted using mononuclear cells of the peripheral blood (depletion step), to avoid cross reactivity to healthy blood cells. The stable and effective binding of the scFv antibodies to internalizing surface proteins is the main criterion for the selection. During the selection rounds in Phage-Display, this was realized by elution of surface bound phages and attaining internalized phages by lysis after a temperature shift from 4°C to 37°C.
An accumulation of MM-specific phage antibodies was already shown after three combined selection rounds (depletion and positive selection) using polyclonal ELISA. In the next steps, we want to test mononuclear binders with respect to their reproducible binding activity in ELISA and flow cytometry. On phage as well as on protein level we apply very strict, standardized quality controls. After extensive characterization and evaluation of the selected antibody fragments, we initiate their Functionalization with possible therapeutic substances.