| Cancers remain difficult to treat due to heterogeneity of the cancer cells themselves as well as the diversity of cells that contribute to the environment in which the cancer grows. Success in eliminating these aberrant cells can be achieved upon recognition of the cancerous cells by sufficiently activated cytotoxic T cells. However, the environment containing the tumor uses many different mechanisms to ensure a highly immunosuppressive environment, therefore inhibiting any T cells that could react. By using retroviral vectors for expression of Chimeric Antigen Receptors in T cells, we can induce sufficient T cell signaling upon encountering an antigen of choice. By targeting antigens expressed by cancerous cells, these genetically engineered T cells can receive sufficient signaling and mount a robust T cell mediated illumine response to eliminate tumor. However, it is difficult to select a single antigen with specificity for the cancerous cells and not for normal cells. Therefore, we attempted to split T cell activation and co-stimulation signals by supplying CD3ζ activation signals upon binding of one antigen by one receptor and supplying co-stimulation signals CD28 and 4-1BB upon binding of a second antigen by an additional receptor. By splitting the induction of these signaling pathways, we can successfully supply all three signals upon binding both antigens. Depending on the strength of the CD3ζ activation signal supplied, carefully titered cytotoxicity and cytokine secretion can be achieved. This allows for the selective eradication of cancerous cells expressing both antigens, but reduces any immune response to cells expressing either antigen alone. Attempts were made to use human embryonic stem cells to generate mature T cells. We used fluorescent reporters for live imaging of these cells in order to determine how these cells develop to give rise to hematopoietic lineages. We discovered that only embryonic and fetal types of hematopoietic cells were generated with an inability to produce mature T cells with current technology. By using mature T cells and by supplying sufficient T cell signaling upon binding a combination of antigens, we demonstrate the ability to generate potent T cell mediated immune responses against cancerous cells expressing two antigens. |
