CANCER IMMUNOTHERAPY: TARGETED CELLULAR VEHICLE-MEDIATED IMMUNOGENE THERAPY AND DENDRITIC CELL-BASED VACCINE

Abstract

Cancer immunotherapies have provided treatments and improvement in quality of life of many cancer patients. The available treatments using cytokines and antibodies, in spite of their clinical effects, are still hindered by their toxic effects, half-life and efficacies. In this project, we are interested in the developments of immunotherapy using stem cell vehicles to deliver immunogene products and DC-based vaccination approach. Targeted immuno-gene therapy approach using stem cell delivery vehicle is based on the inherent tumor tropism of stem cells. Endothelial progenitor cells (EPCs) is particularly attractive, not only due to their intrinsic tumor tropism but also their involvement in cancer angiogenesis. However, collecting sufficient amount of EPCs is one of the challenging issues critical for effective clinical translation of this new approach. In this study, we sought to explore whether human induced pluripotent stem (iPS) cells could be used as a reliable and accessible cell source to generate uniform human EPCs with cancer gene therapy potential. We showed that using an embryoid body formation method CD133+CD34+ EPCs could be efficiently derived from human iPS cells. The generated EPCs expressed endothelial markers such as CD31, Flk1 and VE-cadherin but not the CD45 hematopoietic marker. Subsequently, we showed that intravenously injected iPS cell-derived EPCs migrated towards orthotopic and lung metastatic tumors in the mouse 4T1 breast cancer model, and injection of the EPCs alone did not escalate the tumor growth and metastatic progression. Most importantly, systemic injection of EPCs transduced with baculovirus encoding the potent DC co-stimulatory molecule CD40 ligand could impede the tumor growth, leading to prolonged survival of the tumor bearing mice. Therefore, our findings suggest that human iPS cell-derived EPCs could potentially serve as tumor-targeted cellular vehicles for anticancer gene immunotherapy. Most of the available cancer treatments, including chemotherapy and radiation therapy while proven effective in reducing the tumor burden, failed to eradicate cancer stem cells (CSCs). With their self-renewal and differentiation capability, CSCs are capable to reestablish tumor mass resulting in the relapse of tumors in patients. By utilizing baculovirus zinc-finger technology, we have reprogrammed human glioma and colorectal cancer cell line into CSC-like cells. We generated whole tumor lysates by free-thaw-cycles technique from these enriched CSCs and used them to pulse PBMC-derived dendritic cells (DCs). We showed that we could obtain functional DCs that were capable of stimulating naive T cells into cytotoxic T lymphocytes and the stimulated CTLs were capable of producing IFNgamma cytokine in a CSC-like antigen-specific manner. Our findings suggest that DC-based immunotherapy approach can be used to target CSC-like cell population.