PD‐1‐induced T cell exhaustion is controlled by a Drp1‐dependent mechanism
Luca Simula, Ylenia Antonucci, Giorgia Scarpelli, Valeria Cancila, Alessandra Colamatteo, Simona Manni, Biagio De Angelis, Concetta Quintarelli, Claudio Procaccini, Giuseppe Matarese, Claudio Tripodo, Silvia Campello
Abstract
Programmed cell death‐1 (PD‐1) signaling downregulates the T‐cell response, promoting an exhausted state in tumor‐infiltrating T cells, through mostly unveiled molecular mechanisms. Dynamin‐related protein‐1 (Drp1)‐dependent mitochondrial fission plays a crucial role in sustaining T‐cell motility, proliferation, survival, and glycolytic engagement. Interestingly, such processes are exactly those inhibited by PD‐1 in tumor‐infiltrating T cells. Here, we show that PD‐1 pos CD8 + T cells infiltrating an MC38 (murine adenocarcinoma)‐derived murine tumor mass have a downregulated Drp1 activity and more elongated mitochondria compared with PD‐1 neg counterparts. Also, PD‐1 pos lymphocytic elements infiltrating a human colon cancer rarely express active Drp1. Mechanistically, PD‐1 signaling directly prevents mitochondrial fragmentation following T‐cell stimulation by downregulating Drp1 phosphorylation on Ser616, via regulation of the ERK1/2 and mTOR pathways. In addition, downregulation of Drp1 activity in tumor‐infiltrating PD‐1 pos CD8 + T cells seems to be a mechanism exploited by PD‐1 signaling to reduce motility and proliferation of these cells. Overall, our data indicate that the modulation of Drp1 activity in tumor‐infiltrating T cells may become a valuable target to ameliorate the anticancer immune response in future immunotherapy approaches.