4-1BB and CD28 Signaling Plays a Synergistic Role in Redirecting Umbilical Cord Blood T Cells Against B-Cell Malignancies

Umbilical cord blood (UCB) T cells can be redirected to kill leukemia and lymphoma cells by engineering with a single-chain chimeric antigen receptor (CAR) and thus may have general applications in adoptive cell therapy. However, the role of costimulatory molecules in UCB T-cell activation and effector functions in context with CAR remains elusive. To investigate the effect of costimulatory molecules (4-1BB and CD28) on UCB T cells, we transduced UCB T cells with lentiviral vectors expressing Green Fluorescent Protein (GFP) and CAR for CD19 containing an intracellular domain of the CD3 zeta chain and either a 4-1BB (UCB-19BB zeta) or a CD28 intracellular domain (UCB-1928 zeta), both (UCB-1928BB zeta), or neither (UCB-19 zeta). We found that UCB-19BB zeta and UCB-28BB zeta T cells exhibited more cytotoxicity to CD19(+) leukemia and lymphoma cell lines than UCB-19 zeta and UCB-1928 zeta, although differences in secretion of interleukin-2 and interferon-g by these T cells were not evident. In vivo adoptive transfer of these T cells into intraperitoneal tumor-bearing mice demonstrated that UCB-19BB zeta and UCB-1928BB zeta T cells mounted the most potent antitumor response. The mice adoptively transferred with UCB-1928BB zeta cells survived longer than the mice with UCB-19BB zeta. Moreover, UCB-1928BB zeta T cells mounted a more robust antitumor response than UCB-19BB zeta in a systemic tumor model. Our data suggest a synergistic role of 4-1BB and CD28 costimulation in engineering antileukemia UCB effector cells and implicate a design for redirected UCB T-cell therapy for refractory leukemia.