In order to develop immunotherapies against common cancers, such as ovarian, breast, and colon cancer, we have developed chimeric antibody/T- cell receptor genes which combine variable regions from mAb with T-cell signaling chains. Previously, we demonstrated that T-cells transduced with chimeric receptor genes are redirected to recognize new targets. Over the past year, we have developed methods to produce transduced T- cells on a large-scale in order to utilize this strategy in a clinical trial for ovarian cancer patients, which should begin soon. In addition, we have designed chimeric receptors against colon cancer, and have demonstrated their ability to function in primary T-cells. This should lead to a clinical trial for metastatic colon cancer in the near future. We have also transduced hematopoietic stem cells with chimeric receptor genes, and have demonstrated that mice reconstituted with the gene- modified bone marrow cells exhibit decreased tumor growth when challenged with tumor cells expressing the corresponding antigens. Transducing hematopoietic stem cells with chimeric receptor genes may allow the continuous in vivo production of lymphocytes, macrophages, neutrophils, and NK cells directed against the tumor. By utilizing gene transfer into hematopoietic cells, we have also developed a novel method to gene modify dendritic cells. Although primary, mature dendritic cells are difficult to gene modify, we reasoned that hematopoietic stem cells might be gene modified followed by in vitro differentiation into dendritic cells. We have demonstrated that this novel technique can generate dendritic cells expressing foreign genes. We have shown that the MART-1 melanoma antigen can be expressed by dendritic cells, and that these cells could stimulate MART-specific T-cells, as well as the generation of specific T-cells from resting lymphocytes. This technique may allow us to raise specific T-cells against common tumors and may also provide a novel method to actively immunize patients against known tumor antigens, by utilizing dendritic cells transduced with antigen or cytokine genes.
