Targeted calcium influx boosts cytotoxic T lymphocyte function in the tumour microenvironment

Adoptive cell transfer utilizing tumour-targeting cytotoxic T lymphocytes (CTLs) is one of the most effective immunotherapies against haematological malignancies, but significant clinical success has not yet been achieved in solid tumours due in part to the strong immunosuppressive tumour microenvironment. Here, we show that suppression of CTL killing by CD4 + CD25 + Foxp3 + regulatory T cell (Treg) is in part mediated by TGFβ-induced inhibition of inositol trisphosphate (IP 3 ) production, leading to a decrease in T cell receptor (TCR)-dependent intracellular Ca 2+ response. Highly selective optical control of Ca 2+ signalling in adoptively transferred CTLs enhances T cell activation and IFN-γ production in vitro , leading to a significant reduction in tumour growth in mice. Altogether, our findings indicate that the targeted optogenetic stimulation of intracellular Ca 2+ signal allows for the remote control of cytotoxic effector functions of adoptively transferred T cells with outstanding spatial resolution by boosting T cell immune responses at the tumour sites. Regulatory T cells (Tregs) promote immune suppression in the tumour. Here, the authors show that Tregs suppress cytotoxic T lymphocyte (CTL) activity by impairing Ca 2+ signalling and that adoptive transfer of CTLs engineered with an optogenetic control of Ca 2+ overcome the immune suppression at the tumour site.