Bacteriomimetic Nanoparticles for Immunotherapy against Breast Cancer

Short description: Immunotherapy represents a potential and innovative means to combat cancer. It essentially harnesses the body’s immune system to fight against cancer. Previous literature suggests that cancer vaccines designed against a specific tumor antigen have been efficiently utilized to trigger immune responses against tumor cells. Despite the preliminary evidence in animal models, low immunogenicity is one of the major hurdles in the development of vaccines in humans. In order to surmount this obstacle, several approaches including the use of an “ideal” tumor antigen, appropriate delivery techniques, immune boosting strategies with co-stimulatory molecules are being explored. Purpose: The purpose of this study was to develop “bacteriomimetic nanoparticles” to enhance adaptive cell-mediated immune responses (CD4+ and CD8+ T cell responses) against tumor antigen as a therapeutic option for cancer treatment. Materials and Methods: NPs were prepared by modified solid/oil/water solvent evaporation method using an ultrasonic processor UP200H system (Hielscher Ultrasonics GmbH, Germany). We used membrane preparations of the 4T1 mouse mammary cancer cell line as a tumor antigen and CpG ODN’s as a “bacteriomimetic” stimulant. Fourteen days before tumor challenge BALB/c female mice (6-8 weeks) were pre-immunized with CpG followed by secondary immunization using respective NPs encapsulated with the membrane antigen preparation. Subsequently, mice (n=5) were challenged subcutaneously (SC) with 105 tumor cells and the primary tumor size was monitored using vernier caliper and bioluminiscence imaging (Caliper Life Sciences Inc., MA, USA). Mice were sacrificed on day fourteen after tumor challenge; spleen cells were used for flow cytometric analysis and primary tumor tissue was used to evaluate effect of NP immunization on tumor growth, survival as well as the immune response (CD4+ and CD8+ T cell) via immunohistochemistry. Results: We found significant reduction in progression of tumor growth in mice immunized with CpG coated NPs containing tumor antigen (CpG-NP-Tag). Histological analysis confirmed that tumors in CpG-NP-Tag mice were relatively well differentiated and of lower grade in contrast to CpG-Blank tumors. Immunofluorescence (IF) data further revealed that CpG-NP-Tag tumors had lesser proliferation and higher apoptotic activity. Tumor CD4+ and CD8+T cell infiltration as well as T cell response in spleen was found be higher in CpG-NP-Tag NP immunized mice as compared to the controls (CpG-NP-Blank and NP-Tag). Conclusions: Primary tumor size, IHC, IF and flow cytometry analysis indicate that CpG-NP-Tag NPs were successfully employed to boost the immune response against tumor cells.