While TIL Therapy is effective, melanoma samples cannot be obtained for TIL production from all patients and, in some cases, TIL cannot be isolated from the resected tumor. Engineered T cells are being used increasingly for patients from whom TIL are not available. Two general approaches involving engineered T cells are being used clinically. Both involve the use of autologous peripheral blood T cells; one involves gene transfer of high affinity T cell receptors (TCR) and the other gene transfer of chimeric antibody-T cell receptors (CAR) [6
Patients with melanoma have been treated with T cells engineered using recombinant retroviral vectors to express HLA-2 restricted high affinity T cell receptors (TCRs) specific for melanoma antigens MART-1 and gp100 [7
]. While patients treated with these engineered autologous cells have had objective clinical responses, some patients have experienced autoimmune responses due to the destruction of normal melanocytes in the skin, eyes and ears [8
]. Another adoptive cellular therapy approach utilizing engineered T cells involves the use of TCRs specific for cancer testis antigens that are expressed by fetal tissue and cancer, but not by adult cells, such as NY-ESO-1. NY-ESO-1 is expressed by 10 to 50% of metastatic melanomas, 80% of synovial cell sarcomas and breast, prostate, thyroid and ovarian cancers [6
]. TCRs specific for NY-ESO-1 have been used to treat patients with melanoma and sarcoma and have resulted in objective clinical responses in 5 of 11 melanoma patients and 4 of 6 synovial sarcoma patients [9
]. Protocols are also being developed that involve gene transfer of vectors encoding IL-12 and MAGE-A3 specific TCRs.
Another approach involves the transduction of autologous T cells to express CARs made up of the variable region a tumor specific antibody fused to an intracellular signaling domain capable of activating T cells. Typically, a CAR is comprised of an extracellular scFv portion of a monoclonal antibody and an intracellular CD3 zeta chain in tandem with a co-stimulatory signaling domain, such as CD28. In addition, some CARs include other stimulatory factors such as 4-1BB or OX-40, alone or in combination with CD28 [6
]. Since CARs have the specificity of a monoclonal antibody, they are not HLA restricted and they can be used to treat any patient whose tumor expresses the antigen to which the monoclonal antibody is directed. Autologous T cells engineered to express anti-CD19 CAR have been effective in treating patients with lymphoma and chronic lymphocytic leukemia (CLL) [10
]. CD19 CAR T cell adoptive therapy has resulted in dramatic clinical responses which have been associated with in vivo expansion and long term persistence of the engineered T cells. Some patients have experienced tumor lysis syndrome and prolonged depletion of B cells is common.
A clinical protocol that uses the autologous T cells expressing CAR specific for the folate receptor -alpha (FRα)[14
] is being developed by University of Pennsylvania investigators in cooperation with the National Cancer Institute (NCI) Cancer Immunotherapy Trial Network (CITN). FRα is over expressed on the surface of epithelial malignancies including ovarian, breast, renal, colorectal, lung, and other solid cancers, but its expression is limited on normal tissue. The protocol involves adoptive cell therapy with genetically engineered autologous T cells given to patients with ovarian cancer following lymphodepletion alone or followed by the administration of recombinant IL-7 and was rationalized by the established role for IL-7 in maintaining T cell memory and homeostasis, as well as initial observations by Powell et al. that transferred tumor antigen-specific T cells dramatically up-regulate the IL-7 receptor immediately after infusion [15