Alizée J Grimm

Abstract Expansion of antigen-experienced CD8 + T cells is critical for the success of tumour-infiltrating lymphocyte (TIL)-adoptive cell therapy (ACT) in patients with cancer 1 . Interleukin-2 (IL-2) acts as a key regulator of CD8 + cytotoxic T lymphocyte functions by promoting expansion and cytotoxic capability 2,3 . Therefore, it is essential to comprehend mechanistic barriers to IL-2 sensing in the tumour microenvironment to implement strategies to reinvigorate IL-2 responsiveness and T cell antitumour responses. Here we report that prostaglandin E2 (PGE 2 ), a known negative regulator of immune response in the tumour microenvironment 4,5 , is present at high concentrations in tumour tissue from patients and leads to impaired IL-2 sensing in human CD8 + TILs via the PGE 2 receptors EP2 and EP4. Mechanistically, PGE 2 inhibits IL-2 sensing in TILs by downregulating the IL-2Rγ c chain, resulting in defective assembly of IL-2Rβ–IL2Rγ c membrane dimers. This results in impaired IL-2–mTOR adaptation and PGC1α transcriptional repression, causing oxidative stress and ferroptotic cell death in tumour-reactive TILs. Inhibition of PGE 2 signalling to EP2 and EP4 during TIL expansion for ACT resulted in increased IL-2 sensing, leading to enhanced proliferation of tumour-reactive TILs and enhanced tumour control once the cells were transferred in vivo. Our study reveals fundamental features that underlie impairment of human TILs mediated by PGE 2 in the tumour microenvironment. These findings have therapeutic implications for cancer immunotherapy and cell therapy, and enable the development of targeted strategies to enhance IL-2 sensing and amplify the IL-2 response in TILs, thereby promoting the expansion of effector T cells with enhanced therapeutic potential.

Abstract Cancer-specific TCF1 + stem-like CD8 + T cells can drive protective anticancer immunity through expansion and effector cell differentiation 1–4 ; however, this response is dysfunctional in tumours. Current cancer immunotherapies 2,5–9 can promote anticancer responses through TCF1 + stem-like CD8 + T cells in some but not all patients. This variation points towards currently ill-defined mechanisms that limit TCF1 + CD8 + T cell-mediated anticancer immunity. Here we demonstrate that tumour-derived prostaglandin E2 (PGE 2 ) restricts the proliferative expansion and effector differentiation of TCF1 + CD8 + T cells within tumours, which promotes cancer immune escape. PGE 2 does not affect the priming of TCF1 + CD8 + T cells in draining lymph nodes. PGE 2 acts through EP 2 and EP 4 (EP 2 /EP 4 ) receptor signalling in CD8 + T cells to limit the intratumoural generation of early and late effector T cell populations that originate from TCF1 + tumour-infiltrating CD8 + T lymphocytes (TILs). Ablation of EP 2 /EP 4 signalling in cancer-specific CD8 + T cells rescues their expansion and effector differentiation within tumours and leads to tumour elimination in multiple mouse cancer models. Mechanistically, suppression of the interleukin-2 (IL-2) signalling pathway underlies the PGE 2 -mediated inhibition of TCF1 + TIL responses. Altogether, we uncover a key mechanism that restricts the IL-2 responsiveness of TCF1 + TILs and prevents anticancer T cell responses that originate from these cells. This study identifies the PGE 2 –EP 2 /EP 4 axis as a molecular target to restore IL-2 responsiveness in anticancer TILs to achieve cancer immune control.

ovarian tumors in vivo, offering rational combinatorial therapies for HRD cancers.