Inhibition of JAK/STAT signaling sustain stem-like exhausted CD8+ T lymphocytes with enhanced antitumor effects

Abstract

Abstract T-cell exhaustion and reduced memory potential is an obstacle to successful adoptive cell therapy (ACT) of cancer. Ex-vivo expansion protocols require sustained TCR and cytokine stimulation that limit ACT efficacy and long-term persistence. We have shown that IL-2 and IL-15, JAK-STAT dependent-cytokines used in ACT expansion protocols, induce CD8+ T-cell exhaustion both in vitro and in vivo following chronic viral infection. We hypothesized that blocking JAK-STAT signaling during ex-vivo expansion protocols will limit T-cell exhaustion and sustain stemness of adoptively transferred cells. In the current study, we mimicked current ex-vivo expansion protocols using purified murine T-cells stimulated by tumor antigens in the presence of IL-2 or IL-15 and evaluated the impact of adding distinct inhibitors of the JAK-STAT pathway on expanded T cells. We observed that JAK-STAT inhibitors reduced CD8+ T-cell exhaustion and increased the number of Ly108+ TCF1+ stem-like progenitors. The reduction in T-cell exhaustion was observed by decreased expression of exhaustion markers, changes in specific transcription factors, and increased expression of effector cytokines using flow cytometry. Adoptive transfer of ex-vivo expanded T-cells to tumor-bearing mice indicated that CD8+ T-cells expanded in the presence of JAK-STAT inhibitor significantly reduced tumor size and increased mice survival after ACT. RNA-seq analysis identified a reduced exhaustion signature in JAK/STATi treated T-cells. These results suggest that targeting JAK-STAT signaling sustains potent antitumor reactivity of adoptive-transferred cells and may enhance the ex-vivo generation of stem-like progenitor CD8+ T cells for long-term survival in the host.