Monoclonal antibody-based immunotherapy has been widely used as a strategy to treat cancer. Successful treatment of B-cell lymphoma with the monoclonal antibody (mAb) Rituximab (RTX) in combination with chemotherapy has increased the survival of patients and minimized the side effects of the treatment. However, many patients do not react to the treatment with RTX or gain resistance quickly. Thus, strategies to enhance the tumor cell killing and improve the response rates of mAb-based immunotherapy are a fundamental goal. In this study, I use four different B-cell lymphoma cell lines grown into 3D structures, called spheroids, as a model organism. Those spheroids, which are closer to the in vivo situation of B-cell lymphoma in patients compared to conventional in vitro 2D cell cultures, in combination with RTX, are tested for the activation of effector functions to eliminate tumor cells and compared to experiments conducted in the same cell lines in 2D cell cultures. Moreover, the therapeutic mAb RTX is only approved by the FDA in an IgG1 isotype form. Here, I test different isotype forms of RTX on their efficacy to kill cancer cells by the complement system and also by the activation of monocytes to engulf them in the process of phagocytosis. Interestingly, the IgG3 isotype form of RTX can induce both effector functions most efficiently while the IgG1 isotype form, used in clinical approaches, is only second most efficient in eradicating cancer cells. In addition, when grown into spheroids, the efficacy of both effector functions is reduced compared to 2D cell cultures. Furthermore, the efficacy of the complement system to kill the different B-cell lymphoma cell lines was directly correlated with the expression of the complement regulatory surface protein CD59. By blocking CD59, the efficacy of the complement system could be partially enhanced when cells were treated in 2D cell cultures but not when grown into 3D spheroids. In addition, the antibody-dependent phagocytosis (ADP) of cancer cells by monocytes might correlate with the expression of the RTX target surface protein CD20. Also, the previous incubation of B-cell lymphoma cells with a chemotherapy agent can enhance the efficacy of ADP by presumably providing an “eat me” signal to the effector cells. In summary, this work shows that the outcome of a treatment with RTX in B-cell lymphoma patients could be improved by the detection of the specific features of the cancer cells, for example the expression of CD59 and CD20 and the structure of the tumor. Moreover, the different isotypes of RTX can activate effector functions in different intensities. The IgG3 isotype form might be able to overcome resistance or lack of reaction to the treatment in B-cell lymphoma patients but further experiments will be needed to investigate these possibilities.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:uu-444518 |
| Date | January 2021 |
| Creators | Heilig, Juliane |
| Publisher | Uppsala universitet, Mikrobiologi, Uppsala universitet, Mikrobiologi och immunologi, Uppsala universitet, Institutionen för biologisk grundutbildning |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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