Cancer Immunotherapy : A Preclinical Study of Urinary Bladder Cancer
Abstract: Bacillus Calmette Guérin (BCG), or attenuated Mycobacterium bovis, is the gold standard of immunotherapy in the clinic to treat superficial bladder cancer. However, setbacks remain due to a high recurrence rate, side effects, and BCG-refractory disease. In this thesis, we explored the use of novel immunotherapeutic agents such as CpG oligodeoxynucleotides (CpG ODNs) or synthetic ODNs containing unmethylated CpG dinucleotides. Since unmethylated CpG motifs are predominant in bacterial but not vertebrate DNA, they function as a “danger signal” leading to a potent immune response.To be able to test various immunotherapeutic agents, we optimized subcutaneous (s.c.), metastatic, and orthotopic models using the murine bladder-49 (MB49) cancer cell line. In the orthotopic model, we show that poly-L-lysine promotes MB49 attachment to the bladder leading to 100% tumor take. In addition, Clorpactin (sodium oxychlorosene) potently enhances adenoviral transduction in the bladder.Utilizing the MB49 model, we compare CpG ODNs with BCG and demonstrate the increased efficacy of CpG ODNs which could cure both s.c. and aggressive orthotopic bladder cancer. In our model, type B ODNs were most optimal and the antitumor response required T cells in order to induce regression and tumor-specific immunity. We also combined CpG ODNs with adenoviral vectors (Ad) expressing the immunostimulatory molecules CD40L, TRANCE, lymphotactin, IL2 or IL15. However, we show that CpG ODNs are effective as a monotherapy and adenoviral vectors did not enhance the effect.AdCD40L was also used to genetically modify human dendritic cells (DCs). AdCD40L-transduced DCs not only had a higher and prolonged expression of the Th1 cytokine IL12 compared to TNFα-matured DCs, but CD40L-activated DCs could also resist the suppressive effects of IL10 and TGFβ. Since TNFα is commonly used in clinical DC vaccination protocols and because tumors often secrete immunosuppressive cytokines, these data have important implications for optimizing cancer immunotherapy.
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